crab biodiversity from arukkattuthurai to pasipattinam...

INDIAN J MAR SCI VOL 43(4), APRIL 2014676

Crab biodiversity from Arukkattuthurai to Pasipattinam,south east coast of India

D. Varadharajan & P. Soundarapandian

Faculty of Marine Sciences, Centre of Advanced Study in Marine Biology,

Annamalai University, Parangipettai-608 502, Tamil Nadu, India.

[E-Mail: [email protected]]

Received 30 July 2012; revised 14 January 2013

Coastal environment provides a greater range of habitats and thus potentially supports greater biodiversity. Beforestarting to produce seeds in a hatchery and culture them in ponds, thorough knowledge about their distribution in natureis important. So the present study is aimed to know the biodiversity of crabs from Arukkattuthurai to Pasipattinam.Totally 79 individual crab species were recorded belonging to 21 families from all 10 stations. Maximum crab specieswere recorded belonging to the family Portunidae than others families and also the maximum number of crab species163 were recorded in Mallipattinam (station5) and minimum 69 species in Pasipattinam (station10). Occurrence of crabspecies in different stations were in the following order; Mallipattinam (163) > Sethubavachatram (161) > Manamelkudi(127) > Pointcalimere (117) > Muthupettai (116) > Jegathapattinam (110) > Kattumavadi (101) > Arukkattuthurai (92)> Adirampattinam (85) > Pasipattinam (69). Crabs were collected plenty during summer and monsoon than pre-monsoonand post-monsoon. The crabs belonging to families viz., Calappidae, Portunidae, Potamidae, Grapsidae, Sesarmidaeand Ocypodidae were obtained almost all seasons.

[Keywords: Crabs, Family, Portunidae, Distribution, Abundance]

Introduction

Biodiversity is important for human survival andeconomic interests and for the environmental purposeand stability. India’s marine and coastal ecosystemsconstitute an important natural resource, sincemillions of people dependent on them for theirlivelihoods. This rich biodiversity has a significantrole in the maintenance of the ecosystem. Crustaceansare visibly a remarkable group of organisms with along evolutionary history and prominent adaptability.The decapod crabs are mostly active animals withcomplex behaviour patterns. Southern coast of TamilNadu has a very narrow continental shelf, with highsalinity, a rocky shore and strong wave action. Itincludes mangroves, sandy beaches, mudflats, coralreefs and seagrass beds1,2. Detailed study on decapodcrab fauna was already made in Indian seas bydifferent workers3,4,5,6,7,8. Habitat destruction,pollution, over exploitation and new species

introduction are identified as main threat tobiodiversity9. India, a mega biodiversity country,definitely needs conservation strategy to save thebiodiversity. Although, the crabs are caughtthroughout the year at various regions of the coast,the main season varies from place to place10. In thepresent study an attempt has been made on thebiodiversity of crabs from Arukkattuthurai toPasipattinam south east coast of India.

Materials and Methods

The present study was carried out for one yearfrom January 2010 to December 2010 fromArukkattuthurai to Pasipattinam, south east coast ofIndia. Ten different stations were selected for thepresent study viz., Arukkattuthurai (Station1),Pointcalimere (or) Kodikkarai (Station2), Muthupettai(Station3), Adirampattinam (Station4), Mallipattinam(Station5), Sethubavachatram (Station6),

Indian Journal of Geo-Marine SciencesVol. 43(4), April 2014, pp. 676-698

677VARADHARAJAN & DARAPANDIAN : CRAB BIODIVERSITY FROM ARUKKATTUTHURAI TO PASIPATTINAM

Kattumavadi (Station7), Manamelkudi (Station8),Jegathapattinam (Station9) and Pasipattinam(Station10). Crabs were collected by using FRB boatsin different depths (up to 25 m) and 40–50 mm netwas used (Length 80–100 m, Breadth 1.0-1.5 m).Apart from collection a regular visit was made indifferent fishing sites, landing centres and sell points.The number of crabs that belonging to differentspecies were recorded and identified up to specieslevel using the taxonomic keys of11,12,13,14.

Results

In the present study totally 79 crab species wererecorded belonging to 21 families. Family Aethridaewas represented by single genera consists(Cryptopodia) of a species C. fornicata. FamilyCalappidae was represented by 2 genera (Calappaand Matuta) consists of 4 species which includesC. lophos (Plate1a

1), C. gallus (Plate1a

2), M. lunaris

(Plate1a3) and M. planipes (Plate1a

4). Family

Carpillidae was represented by a genera (Carpilius)consists of a species C. maculates (Plate1a

5). Family

Dorippidae was represented by 3 genera(Dorippoides, Dorippe and Ethusa) consists of 3species which includes D. facchino (Plate1a

6),

D. quadridens (Plate1a7) and E. indica. The family

Leucosiidae was represented by two genera(Oreophorus and Arcania) consists of 2 species whichincludes O. reticulates and A. septemspinosa(Plate1a

8). The family Hymenosomatidae was

represented by only one genera (Elamena) consistsof a species E. cristatipes. Family Majidae wasrepresented by 3 genera (Hyastenus, Doclea andAchaeus) consists of 3 species which includesH. gracilirostris, D. gracilipes and A. lacertosus. Thefamily Parthenopidae was represented by 2 genera(Parthenope and Platylambrus) consists of 2 specieswhich includes P. echinatus and P. prensor. The familyPilumnidae was represented by only one genera


The family Xanthidae was represented by 4 genera(Paractaea, Leptodius, Zozymodes and Demania)consists of 4 species which includes P. neospeciosa,L. exaratus, Z. cavipes and D. buccalipes. The familyOziidae was represented by only one genera (Ozius)consists of a species O. rugulosus. The familyGrapsidae was represented by 7 genera (Grapsus,Metopograpsus, Metaplax, Leucosia, Philyra, Dromiaand Plagusia) consists of 9 species which includesGrapsus albolineatus, G. strigosus, M. messor,M. maculatus, M. distincta, L. pubescens, P. globosa,D. dormia and P. depressa tuberculata. The familySesarmidae represented by 2 genera (Sesarma andNanosesarma) consists of 5 species which includesS.brockii, S. (Chiromantes) bidens, S. (Parasesarma)plicatum, S. tetragonum and N. batavicum. FamilyOcypodiae was represented by 3 genera (Uca,Ocypoda and Dotilla) consists of 6 species whichincludes U. annulipes, U.lactea, U.vocans,O. platytarsis, O. macrocera and D.myctiroides.Family Macrophthalmidae was represented by onlyone genera (Macrophthalmus) consists of 2 specieswhich includes M. convexus and M. depressus. Thefamily Gecarcinidae was represented by only onegenera (Cardisoma) consists of a species C. carnifex.Family Diogenidae was represented by 2 genera(Clibanarius and Dardanus) consists of 4 specieswhich includes C. longitarsus, C. arethusa,C. olivaceus and D. megistos. Family Paguridae wasrepresented by only one genera (Spiropagurus) consistof a species S. spirifer (Table 1).

Maximum crab species recorded in the presentstudy was belonging to the family Portunidae thanothers families and also the maximum 79 species wererecorded in Mallipattinam (station5) and minimum42 species in Pasipattinam (station10). Theoccurrence of crab species in different stations werein the following order; Mallipattinam (163) >Sethubavachatram (161) > Manamelkudi (127) >Pointcalimere (117) > Muthupettai (116) >Jegathapattinam (110) > Kattumavadi (101)>Arukkattuthurai (92) > Adirampattinam (85)>Pasipattinam (69) (Table 1). In the present studymaximum crabs were collected during summer andmonsoon than pre-monsoon and post-monsoon. The

(Pilumnopeus) consists of a species P. vespertilio(Plate1a

9). Family Portunidae was represented by 5

genera (Scylla, Portunus, Podophthalmus, Charybdisand Thalamita) consists of 24 species which includesScylla tranquebarica (Plate1a

10), S.serrata (Plate1a

11),

Portunus sanguinolentus (Plate1a12

), P. pelagicus(Plate1a

13), P.gladiator (Plate1a

14), P. hastatoides

(Plate1a15

), P.trituberculatus (Plate1a16

),Podophthalmus vigil (Plate1a

17), C.affinis (Plate1a

18),

C.feriata (Plate1a19

), C.natator (Plate1a20

),C. (Goniosoma) lucifera (Plate1a

21), C. (Goniohellenus)

truncata (Plate1a22

), C. hellerii (Plate1a23

),C. granulata (Plate1a

24), C. rostrata, C. japonica,

C. miles, C. variegata, C.hoplites, T. picta ,T. chaptali,T. crenata and T. sima. The family Potamidae wasrepresented by 3 genera (Sartoriana, Spiralotelphusaand Potamon) consists of 3 species which includesS. spinigera, S. hyhrodroma and P. fluviatile. Thefamily Trapeziidae was represented by only onegenera (Trapezia) consists of a species of T. cymodoce.


Table 1—Checklist of crab species recorded during the study in different stations

S. No Species Stations & (No/m2)

Family 1 2 3 4 5 6 7 8 9 10

1 Cryptopodia fornicate (Fabricius, 1781) Aethridae + + + + + + + + + +

2 Calappa lophos (Herbst, 1782) Calappidae + + + + + + + + + +

3 C. gallus (Herbst, 1803) + + + + + + + + + +

4 Matuta lunaris (Forskal, 1775) + + + + + + + + + +

5 M.planipes (Fabricius, 1798) + + * + + + + + * *

6 Carpilius maculatus (Linnaeus, 1758) Carpillidae + + + + + + + + + +

7 Dorippoides facchino (Herbst, 1785) Dorippidae + + + + + + + + + +

8 Dorippe quadridens (Fabricius, 1793) + + + + + + + + + +

9 Ethusa indica (Alcock,1894) * + * * + + * + * *

10 Oreophorus reticulatus (Adams & White, 1849 ) Leucosiidae * + * * + + * + * *

11 Arcania septemspinosa (Fabricius, 1787) + + + + + + + + + +

12 Elamena cristatipes (Gravely, 1927) Hymenosoma-tidae + + + + + + + + + +

13 Hyastenus gracilirostris (Miers, 1879) Majidae + + + + + + + + + +

14 Doclea gracilipes (Stimpson,1857) + + + + + + + + + +

15 Achaeus lacertosus (Stimpson, 1858) + + + + + + + * + +

16 Parthenope echinatus (Herbst, 1790) Parthenopidae + + + + + + + + + +

17 Platylambrus prensor (Herbst, 1803) + + + + + + + + + +

18 Pilumnus vespertillio (De Man, 1887) Pilumnidae * * * * + + + + + *

19 Scylla tranquebarica (Fabricius, 1798) Portunidae + + + + + + + + + +

20 S. serrata (Forskal, 1775) + + + + + + + + + +

21 Portunus sanguinolentus (Herbst, 1783) + + + + + + + + + +

22 P. pelagicus (Linnaeus, 1758) + + + + + + + + + +

23 P. gladiator (Fabricius, 1798) + + + + + + + + + +

24 P. hastatoides (Fabricius, 1798) * * + + + + + * * *

25 P. trituberculatus (Miers, 1876) + + + + + + + + + *

26 Podophthalmus vigil (Fabricius, 1798) * + + + + + + + + +

27 Charybdis affinis (Milne Edwards,1861) * * * + + + + + * *

28 C. feriata (Linnaeus, 1758) + + + + + + + + + +

29 C. natator (Herbst, 1794) + + + + + + + + + +

30 C. (Goniosoma) lucifera (Fabricius,1798) * * * + + + + + * *

31 C. (Goniohellenus) truncata (Fabricius, 1798) + + + + + + + + + +

32 C. hellerii (A. Milne Edwards, 1867) + + + + + + + + + +

33 C. granulata (De Haan, 1835) + + + + + + + + + +

34 C. (Goniosoma) rostrata (A. Milne Edwards,1861) * + + + + + + + * *

35 C. japonica (A. Milne Edwards, 1861) + + + + + + + * * *

36 C. miles (De Haan, 1835) + + + + + + + + + +

37 C. variegata (Fabricius, 1798) + + + + + + + + + *

38 C. (Goniohellenus) hoplites (Wood Mason,1877) + + + + + + + + + +

39 Thalamita picta (Stimpson, 1858) + + + + + + + + + +


40 T. chaptali (Audouin, 1826) * + + + + + + * * *

41 T. crenata (Ruppell, 1830) + + + + + + + + + +

42 T. sima (Milne Edwards,1834) + + + + + + + + + +

43 Sartoriana spinigera (Wood Manson,1871) Potamidae * + * + + + + + + *

44 Spiralotelphusa hyhrodroma (Herbst,1794) + + + + + + + + + +

45 Potamon fluviatile (Herbst, 1785) + + + + + + + + + +

46 Trapezia cymodoce (Herbst, 1801) Trapeziidae * + + + + + + * * *

47 Paractaea neospeciosa (Deb, 1989) Xanthidae * + + + + + + + + +

48 Leptodius exaratus ( H. Milne Edwards, 1834) + + + + + + + + + +

49 Zozymodes cavipes (Dana, 1852) * + * * + * + * + *

50 Demania buccalipes (Alcock, 1898) * + * * + + * + * *

51 Ozius rugulosus ( Stimpson, 1858) Oziidae * + * * + + * * * *

52 Grapsus albolineatus ( Lamarck, 1818) Grapsidae + + + + + + + + + +

53 G.strigosus (Herbst, 1799) + + + + + + + + + *

54 Metopograpsus messor (Forskal, 1775) * + + + + + + + * +

55 M.maculatus (Milne-Edwards, 1853) + + * + + + + + + *

56 Metaplax distincta (H. Milne Edwards, 1852) * + * + + + * + + *

57 Leucosia pubescens (Miers, 1877) + + * + + + + + + +

58 Philyra globosa (De Man, 1888) + + + + + + * * * *

59 Dromia dormia (Linnaeus, 1763) + + + + + + + + + *

60 Plagusia depressa tuberculata (Lamarck, 1818) + + + + + + + + + +

61 Sesarma brockii ( De Man, 1887) Sesarmidae + + + + + + + + + +

62 S. (Chiromantes) bidens (De Haan, 1835) + + + + + + * + + *

63 S. (Parasesarma) plicatum (Latreille, 1806) + + + + + + + + + +

64 S. tetragonum (Fabricius, 1798) + + * + + + + + + +

65 Nanosesarma batavicum (Moreira, 1903) + + + + + + + + + +

66 Uca annulipes ( H. Milne Edwards, 1937 ) Ocypodidae + + + + + + + + + +

67 U. lactea (De Haan, 1835) + + + + + + * + + +

68 U. vocans (Linnaeus, 1758) + + + + + + + + + +

69 Ocypode ceratophthalmus (H. Milne-Edwards,1852) * + * + + + * + * *

70 O. macrocera ( H. Milne-Edwards, 1852) + + + + + + + + + +

71 Dotilla myctiroides (H. Milne Edwards, 1852) + + + + + + + + + +

72 Macrophthalmus convexus (Stimpson, 1858) Macrophthal-midae+ + + + + + + + + +

73 M. depressus * + * + + + * + * *

74 Cardisoma carnifex (Herbst, 1796) Gecarcinidae + + + + + + + + + +

75 Clibanarius longitarsus (De Haan, 1849) Diogenidae + + + + + + + + + +

76 C. arethusa (De Man, 1888) * * * * + + * + + +

77 C. olivaceus (Henderson, 1915) * + + + + + + + + +

78 Dardanus megistos (Herbst, 1804) * * * * + + + + + *

79 Spiropagurus spirifer (Stimpson, 1858) Paguridae + + + + + + + + + *

Total 92 117 85 116 163 161 101 127 110 69

(+present and *absent) [Arukkattuthurai (1), Pointcalimere (2), Muthupettai (3), Adirampattinam (4), Mallipattinam(5), Sethubavachatram (6), Kattumavadi (7), Manamelkudi (8), Jegathapattinam (9) and Pasipattinam (10) ].


Table 3—Crab species evenness, diversity, richness and index

Index Stations

1 2 3 4 5 6 7 8 9 10

Pielou’s evenness J 0.9703 0.9775 0.9573 0.9672 0.9626 0.957 0.9726 0.9632 0.9531 0.975

Shannon -Wienner’s 5.6106 5.8875 5.56007 5.8887 5.9008 5.8668 5.8143 5.8013 5.6077 5.5036diversity(H)

Margalef’s(D) Diversity 4.6437 4.9508 4.546 4.9302 5.1218 5.0867 4.8139 4.9283 4.7221 4.412index

Margalef’s(D) Species 11.9421 13.4392 12.3799 14.0946 13.546 13.579 13.434 13.2117 12.339 11.5726Richness(SR)

Simpson’s Index(D) 0.977 0.9816 0.9741 0.9805 0.9809 0.9799 0.9801 0.9793 0.9755 0.9754

crabs belonging to the families viz., Calappidae,Portunidae, Potamidae, Grapsidae, Sesarmidae andOcypodidae were obtained almost all the seasons(Table 2).

The pielou’s evenness of crabs was maximum inPointcalimere (0.9775) and minimum inJegathapattinam (0.9531). Shannon Wiennersdiversity was maximum in Mallipattinam (5.9008)

and minimum in Pasipattinam (5.5036). Margalef’sdiversity index was maximum in Mallipattinam(5.1218) and minimum in Pasipattinam (4.412).Margalef ’s species richness was maximum inAdirampattinam (14.0946) and minimum inPasipattinam (11.5776). Simpson index wasmaximum in Pointcalimere (0.9816) and minimumin Muthupettai (0.9741) (Table 3).

Table 2—Abundance of crabs in different seasons.

S.No Family Postmonsoon Summer Premonsoon Monsoon

1 Aethridae - + + +

2 Calappidae + + + +

3 Carpillidae - + + +

4 Dorippidae + + - +

5 Leucosiidae + - - +

6 Hymenosomatidae - - + +

7 Majidae + + - +

8 Parthenopidae - - + +

9 Pilumnidae + + - -

10 Portunidae + + + +

11 Potamidae + + + +

12 Trapeziidae - + - +

13 Xanthidae - + + +

14 Oziidae + - - +

15 Grapsidae + + + +

16 Sesarmidae + + + +

17 Ocypodidae + + + +

18 Macrophthalmidae - + + -

19 Gecarcinidae - + + +

20 Diogenidae - + + -

21 Paguridae - + + -

(+ present and - absent)


a1. C. lophos a2. C. gallus

a3 . M. lunaris a4. M. planipes

a5. C. maculatus a

6. D. fecchino

a7. D. quadridens a8. A. septemspinosa

a9. P. vespertillio a10. S. tranquebarica

a11

. S. serrata a12

. P. sanguinolentusa13. P. pelagicus a14. P. gladiator

a15. P. hastatoides a16. P. trituberculatus

a17

. P. vigil a18

. C. affinis

a19. C. feriata a20. C. natator

a21. C. lucifera a22. C. truncata

a23

. C. helleri a24

. C. granulata

Plate 1. Crab species recorded during the study indifferent stations

Discussion

Crabs are one of the fascinating groups inDecapoda. They have developed a successfulrelationship between the environment and thebiological mechanisms involved in evolutionaryprocess15. They are filter feeders, sand cleaners, mud,plant and carrion feeders, predators, commensals andparasites16. Some are temporary swimmers but mostof them are walking bottom dwellers. Some evenclimbing tress and construct burrows on land17. Outof about 640 species of marine crabs so far recordedfrom Indian waters only 15 species are edible, whichinhabit the coastal waters and adjoining brackishwater environments, support commercialfisheries18,19,20. The marine water ecosystems such asestuaries, backwaters, saltwater lakes, mangroves etc.,which form the nursery grounds of crabs, areincreasingly encroached by various purposes.

Crustaceans are well known for their hard,calcified exoskeleton, but some regions showflexibility, indicating a different structure andcomposition. The domed elbow crab C. fornicatacollected on a sandy area near seagrasses belongingto the family Aethridae. Carapace creamy-beige incolour; carapace sub-pentagonal; branchial, cardiac

and gastric regions strongly elevated; posterior margincurved laterally; pterygostomial ridge absent;ambulatory legs hidden under carapace; the crab hasdomed body covers spindly walking legs. This isrecorded summer, pre-monsson and monsson andabsent during post-monsoon seasons. In the presentstudy it was collected almost all the stations.

Box crabs belonging to the family Calappidaeare morphologically and ecologically diverse groupin shallow water. Colour of C. lophos in dorsal surfacewas uniform tan overall; with rows of widely spacedspots on posterior surface. Cheliped carpus and palmwith purple spots and thick lines on outer surface,clypeiform expansions well-developed; cheliped palmwith generally smooth outer surface and prominentgranulate ridge running subparallel to lower margin.This species available almost all the stations of thepresent study. C. gallus chelipeds and carapacemottled yellowish-red and grayish-brown; carapaceconvex;clypeiform processes well developed; marginsgranular with low triangular teeth; cheliped outersurfaces granulate on lower third and with roundedtubercles on upper two-thirds. Furthermore, the crabshigher on the beach are larger than the crabs found intidal pools near the low tide mark21. Some crabscollected in gastropods empty shells, whose shellsthey may then acquire22. It is more active at night andis rarely seen day time by visitors. Since it is usuallyburied in the sediments23. This crab was collected notonly almost all the seasons of a year but also allstations of the present study.

The carapace of spotted moon crab M. lunariswith lots of little maroon dots all over the upper partof the body, their paddle-like legs and all legs flattenedare for swimming and digging. Most probablyomnivorous, they forage for small fish, worms andother animals, its inhabitants on sandy to muddy openareas, sand flats near mangroves, but often associatedwith them, sandy silty shores, especially nearseagrasses24. It breeds from September to March witha peak in November25 . It is more active at night andis rarely seen in daytime, it’s normally burrow justbelow the surface during the day. This speciescollected almost all the stations of the present study.


Flower moon crab M. planipes inhabitant’s shallowsandy beach between high and low tide marks to adepth of 10-15 metres. Carapace rounded with 2 long,well developed lateral spines; anterolateral marginsunevenly serrated. Outer surface of palm with strongoblique ridge. Carapace with reticulating brown linesforming small rings anteriorly and larger loopsposteriorly. This crab was not only collected almostall the seasons of a year but almost all the stations ofthe present study.

Spotted reef crab C. maculatus is cream to pinkground color, with 11 large red spots on dorsal surfaceof carapace: 3 on median region, 2 on posterior region,2 on anterolateral region and 4 around orbits. It hasfour blunt spines between the eyes. Maximum wascollected in pre-monsoon, summer and minimum wascollected in monsoon. This species available almostall the stations of the present study. The leaf portercrab D. facchino is narrow V-shaped notch is foundbetween the tips of the frontal teeth; in the youngmale the second to the fourth segments of the abdomenis each armed with three small tubercles; velvety incolor. This species available almost all the stationsof the present study.

The association of the crab D. quadridens withsea anemone is well known. Carapace is sculptured;carpus of cheliped with distinct spinules and hairs onupper surface; palm of chela smooth; flexible hairs.This species available almost all the stations of thepresent study. E. indica carapace was longer thanbroad, its surface with granules, chelipeds unequal,fingers of large chelae with teeth; second and thirdpereiopods naked. The crab belonging to dorippidaefamily is a scavenger, eating any dead plants oranimals that it comes across. Because of the transportbehaviour with sea anemones, it is more active at nighttime. At this time, there are few predators above thewater that can spot them in the dark. So at night, itswims with the leaf under it, to hide from aquaticpredators below. If it senses danger from above,however, it will quickly flip under the leaf. Duringthe day, it often hides under the leaf, half buried inthe sand or mud. Maximum was collected in post-monsoon, summer and minimum was collected in

monsoon and absent in pre-monsoon. This speciesavailable almost all the stations except stations 2, 5& 8 of the present study.

O. reticulates belonging to the family Leucosiidaewas collected in silty, sandy areas near seagrasses.They are usually buried under the sand, they feed onsmall animals in the muds. Its dorsal surface ofcarapace with network of granules and depressions,branchial crests indistinct, median longitudinal ridgevery distinctly separated from rest of carapace byfossae on dorsal surface of carapace. This speciesavailable in stations 2, 5, 6 & 8 but absent in otherstations. A. septemspinosa carapace is finely granularin irregular patches, front slightly projected, with 2lobes, separated by the median V-shaped notch.Middle of the lateral margin with a slender sharpspine. Postero-lateral and posterior margins with 5spines. Chelipeds are symmetrical and slender, carpussmall, fingers and ambulatory legs slender. Meruswith granules on its dorsal surface, dactylus fringedwith small setae. These two species were observedmaximum in Post-monsoon and minimum in monsoonseasons. A. septemspinosa recorded almost all stationsof the present study. The carapace of E. cristatipes isflat, weakly calcified. Carapace pyriform withrounded front. The walking legs are flattened.Dactylus is curved. They do not bear hairs. They werecollected in estuarine areas. Maximum was in pre-monsoon and minimum in monsoon. This speciesavailable almost all the stations of the present study.

Majidae crabs are commonly known as the spidercrabs. They were collected from the bottom of theintertidal area that can be both sand and mud. Crabscollected in seaweed are covered with long hookedhairs, which allow the crab to snip off living piecesof algae and attach them to the hairs. A decoratedseaweed crab with algae, sponges and other marinegrowths is excellently camouflaged. It only gives itselfaway when it moves. Young crabs are found inintertidal areas that have more of seagrass andseaweeds26,27,28. H. gracilirostris carapace issubpyriform, hardly at all setose, with numerous sharptubercles spinules. Especially noticeable are threespinules, longitudinally arranged in the middle line


on the gastric region; carapace, are very slender andhave nearly straight fingers. This species availablealmost all the stations of the present study. Both sexesof D. gracilipes, was collected at all sampling stationsof the present study. It lives among rocks encrustedwith weeds. Carapace is discoid, second pair of legsthree to four times longer than length of carapace;single series of tubercles or spines down middle ofcarapace, the legs covered by fur is dark green; thelast two segments of the legs have a reddish tinge.Carapace of A. lacertosus is smooth, without tuberclesor spines, regions generally ill defined exceptbranchial and cardiac ones, rostrum deeply dividedby a V-shaped notch, rostral spines very short,rounded apically. Basal antennal article unarmed andcheliped of adult male long. Maximum was recordedin post-monsoon and summer and minimum wasrecorded in monsoon. A. lacertosus was collectedalmost all the stations of the present study.

P. echinatus is a tiny, slow moving crab look likebits of dirt and junk among seaweeds look verycarefully to find them. Elbow crabs are commonlyseen in Palk bay shores among seagrasses andseaweeds. They are predators of small creatures. Inturn, they are eaten by many animals higher up in thefood chain. Maximum was recorded in pre-monsoonand minimum was in monsoon. This species availablealmost all the stations of the present study. Thecommon hairy crab P. vespertillio was collected inthe plant mudstone area. It is sluggish in its habits. Itis smooth patch can be found near the base of thefinger of the large hand, carapace as broad as long,convex in the anterior half and depressed in theposterior half; surface thickly covered with darkbrown setae some ones golden-yellow colored setae(hair) of various lengths, chelipeds asymmetrical, withlong setae; merus covered with granules and shortpubescence on the outer surface. Maximum wascollected in post-monsoon and minimum in summer.This species recorded only in the stations from 5 to9. But absent in other stations of the present study.

Carapace of the mud crab S. serrata is usuallydeep green to olive green; cheliped palm green topurplish on outer surface, often with reticulate pattern,last legs with reticulate pattern in both sexes; carapace

frontal teeth prominent, acute, cheliped carpus with2 distinct spiniform, spines on outer surface; palmwith 2 distinct distal dorsal spines and spine at carpalarticulation. This species was recorded almost all thestations of the present study. Carapace ofS. tranquebarica is usually dark green to black green,cheliped palm green to purple in life, outer surfacewith reticulate pattern; only males last legs withreticulate pattern present; carapace frontal teethobtuse, usually rounded; cheliped palm with sharp,but never spiniform, dorsodistal granules; carpus with2 distinct spiniform; spines on outer surface. Theportunid swimming crabs have a broad carapace andflattened hind legs which form swimming paddles andsometimes digging spades. None of the portunidscome out onto the shore, but they do enter shallowwater to hunt for live food. This species availablealmost all the stations of the present study. Colour ofP. pelagicus males is blue purple dorsally withirregular white lines and spots, especially posteriorly;chelipeds and legs especially bright blue with whiteand some ones yellowish reticulations. Femalesmottled dull green and white. Carapace broad, 2.3times as wide as long; front 4-lobed, medians shorterthan laterals, cheliped merus with 3 spines on anteriorborder and 1 distal spine on outer border. This speciesavailable almost all the stations of the present study.P. sanguinolentus colour is overall greenish; posteriorhalf of the carapace with three, large, white-borderedblood-red spots. Carapace more than twice as broadas long; front 4-lobed; last anterolateral spinedistinctly larger than preceding spines and directedlaterally. Cheliped merus outer border unarmed. Theywere collected almost all seasons of a year and alsoall stations of the present study.

P. gladiator colour is mottled light and darkbrown, carapace relatively narrow, about 1.3–1.5times wider than long; covered with close-packedgranulated patches with a fine pubescence among thegranules; cheliped merus with 4 anterior spines and2 posterior spines. Penultimate segment of maleabdomen with straight of faintly convex margins. Thisspecies available almost all the stations of the presentstudy. P. hastatoides overall pale tan, carapace broad,about twice as broad as long front with 4 lobes;cheliped merus robust, with 2 spines on posterior


border. P5 merus poster distal margin with 3 or 4serrations but without spine. Anterolateral angle ofthird maxilliped merus strongly produced. Thisspecies available only in stations from 3 to 7. Butabsent in other stations of the present study. Thecarapace colour of P. trituberculatus is olive greenwith scattered white spots posteriorly, cheliped andlast leg dark brown-green with white spots. First threeambulatory legs bluish distally, carapace twice as wideas long; front with 3 teeth, median longer than laterals;last anterolateral spine distinctly larger than precedingspines and directed laterally. Cheliped merus with 4spines on anterior border and 1 distal spine on outerborder. This species available almost all the stationsof the present study.

Colour of P. vigil is overall greenish brown.Cheliped merus green, remainder dark red-maroon,eyestalks simple, without pterygoid expansions.Carapace about 2.5 times as wide as long, front entire,deflexed. Cheliped palm with spinule on inner distalsurface. Now it has been under high exploitation,breeds almost was intense in October and January29,absent and poor in summer seasons, peak abundanceof pre-monsoon season. This species available almostall the stations of the present study. Smooth shelledswimming crab C. affinis has a hexagonal, concavecarapace with a yellowish-grey colour. It is availableseasonally, because of peaked in summer andpre-monsoon seasons30. This species available onlyin the stations 4 to 8 of the present study. C. feriatarefers to the red cross on the carapace, colour on thecarapace brownish with purplish tinge andconspicuous yellow markings, central one resemblinga cross; chelipeds purplish brown, spotted withyellow, tips light brownish pink. Three spine onanterior borders of arm, across on the carapace, broadon carapace, slightly convex and smooth, length muchless than its width, Fingers as long as the palm,chelipeds stout, asymmetrical, denticles on theproximal half. Mostly collected in muddy bottoms,mangrove marshes and coastal mouths in estuarineenvironments31. It’s available throughout the yearbecause of continuous breeding activities with twopeak breeding seasons, one during October–

November and another one during May-June,25. Thisspecies available almost all the stations of the presentstudy.

Colour of the ridged swimming crab of C. natatoris dorsal pubescence light brown; granules, ridges andmargins of carapace maroon. Cheliped mottledmaroon and light brown. Carapace surface convex,uniformly covered with dense short setae; Chelipedsstrongly granular, pubescent; P5 propodus posteriormargin serrated. Large adults, small juvenileswimming crabs are also hidden among the seagrassand seaweed and other nooks and crannies. Theseactive crabs come in all kinds of colours, the collectedspecies was orangish red overall, with ridges oncarapace and legs dark and reddish brown. Malesoutnumbered females in the catch by almost two toone, but females were more abundant in catchesduring June-July, possibly because of increasedfeeding activity prior to the main spring spawningperiod. Female had two spawning peaks, a major peakin spring and a secondary peak in autumn32. Thisspecies available almost all the stations of the presentstudy. C. truncata is blunt-toothed crab collected inmuddy bottoms and seagrass areas, transverse ridgesof carapace faint. A large red impermanent spot oneither branchial region. Chelipeds not much morethan twice the length of the carapace, their uppersurface more or less granular, their under surface withsmooth-worn squamiform markings. It was intensivebreeders and peak season in summer and pre-monsoon. This species available almost all the stationsof the present study. Spiny hands crabs of C. helleriiwas collected in soft bottom, carapace and thechelipeds dark green and are fully covered with purpleon upper. Spine on the posterior margin of the carpusof the fifth leg separates this crab from other speciesof Charybdis33 and by the presence of the diagnosticspine on the carpus of the swimming leg33. Mostly inthese crabs can avoid the common types of fishinggear. While the considerable crab trapping usingthroughout the year of collections34,35,36. This speciesavailable almost all the stations of the present study.

Colour of C. granulata is drab gray-green, mottledwith dull maroon. Cheliped fingers dark maroon,


carapace surface convex, covered unevenly withdense short setae, chelipeds strongly granular,pubescent; P5 propodus posterior margin serrated,merus posterior margin with sub distal spine. It wascollected in the burrows of adult individuals whereverseagrass areas36 , its also intensive breeders and peakseason in summer and pre-monsoon. This speciesavailable almost all the stations of the present study.Colour of C. rostrata carapace is brownish purple;chelipeds creamy to brownish chocolate colored,carapace about four-fifth as long as broad, more orless convex with granular ridges; front prominent andcut into six teeth, the middle two teeth remarkablylarger and bluntly pointed; Chelipeds nearly smooth,less than twice as long as the carapace; handssix-costate and inflated in the male but not so inflatedin the female; fingers longer than the palm in thesmaller cheliped and as long as the palm of majorcheliped. Sixth segment of male abdomen broaderthan long, gently curved and convergent at the sides.There are predominantly found at the lower intertidallevel and in the adjacent sub tidal, but frequently alsoon rocky sea shore37. This species available all thestations except stations 1, 8 & 9 of the present study.Colour of C. japonica is overall drab green dorsally.Cheliped fingers maroon and blue. Ambulatory legsgreen with purplish tinge, carapace pilose; with6 triangular frontal teeth, medians inclined slightlylaterad; with finely granular protogastric ridges,mesogastric, metagastric and epibranchial ridges.Cheliped merus with 3 spines on inner border;propodus with 5 dorsal spines. This species absent instations 8 to 10. But present in other stations of thepresent study. The colour of C. miles carapace andambulatory legs are pale orange-pink. Chelipedsmottled orange and white, carapace surface convex,with dense short setae; with 6 sharp frontal teeth; inneroribital lobe sharp; surface with protogastric ridges,mesogastric, epibranchial and metagastric ridges andchelipeds elongate. This species available almost allthe stations of the present study.

The colour of C. variegata is overall light sandwith light brown mottling, carapace surface pilose;with 6 frontal teeth, medians triangular, projectinganteriorly beyond sub medians, laterals separated

from sub medians by V-shaped notch, Chelipedsfinely pubescent. It was collected near seagrass mudarea, the carapace densely pubescent, granulate inpostfrontal area, transverse granular lines onprotogastric and mesogastric regions, chelipedscovered with large granules and some onessquamiform markings; merus with 3 strong spines andnumerous granules on anterior border, posteriorborder granulate. Mostly collected in summer andpremonsoon and the breeding activities areseasonally38. This species available almost all thestations of the present study. Thalamita sp preferredwet water saturated soil beds and mangroveecosystems39. T. picta could be collected on the shore,color on the crabs red and white, carapace closelybeset with fine hairs only missing at ridges, uppersurface of cheliped palm with 2 spines on anteriorand posterior borders, posterior border of propodusof swimming leg with about 5-7 spines, breedingactivity from summer and pre-monsoon and peaks inthe months of February, March and September15. Thisspecies available almost all the stations of the presentstudy. T. chaptali colour is overall dark olive greenwith blackish mottling, carapace surface sparselypilose; cheliped palm smooth, with 5 dorsal spines;outer surface with costa on lower half extending ontopollex; fingers with simple tips. Basal antennalsegment smooth, without spines or tubercles and thisis found to be seasonal being available only duringsummer and pre-monsoon season, it was intensivebreeds almost throughout the year, except in summerin the month of March, April and pre-monsoon in themonth of September. This study is in agreement withthe earlier study of 40 in Portonovo coast. This speciesrecorded only the stations from 2 to 7. The colour ofT. crenata is overall dark brownish green; chelipedfingers maroon, carapace surface smooth, sparselypilose; all anterior carapace ridges present, Basalantennal segment granulate. Cheliped palm uppersurface bearing 5 spines, outer surface smooth withsingle ridge running to pollex, inner surface smooth.This species available almost all the stations of thepresent study. T. sima carapace is covered denselywith short hairs, 3 pairs of gastric ridges, basalantennal joint with a smooth, short and curved crest.


Upper surface of cheliped palm with 1 spine onanterior and 2 on posterior borders, posterior borderof propodus without spines, hand of cheliped withsquamiform markings (except in juveniles), male firstpleopod with flared tip. Swimming crabs werecommonly seen in all seashores. They are particularlyactive at night, but are often also out and about duringthe day. Besides the large adults, small juvenileswimming crabs are also hidden among the seagrassand seaweed. They eat fish, worms, other crustaceans,snails and clams. They may also nibble on seaweed.It is breeds almost throughout the year41, peaks insummer in the months of January, March and pre-monsoon in the months of August and September,absent in April and July42. This species availablealmost all the stations of the present study.

The crabs belonging to family Potamidae werecollected near inshore of coastal areas. The carapaceof S. spinigera is physiognomy and the diagnosticspine on the dorsal sub distal part of the chelipedmerus. This species recorded all stations except 1, 3& 10. S. hydrodroma carapace is strongly convex,cervical groove distinct but appears superficial; itdisappears behind the post-orbital tresis and orbithorned. The notch-lateral borders of carapace stronglyconvex, cristiform and smooth, postero-lateral bordersill defined. Three terminal segments of the maleabdomen are slightly narrower in comparison to thebasal segment. This species available almost all thestations of the present study. The shape of P. fluviatileis roughly square, with the reduced abdomen tuckedbeneath the thorax. The thorax bears five pairs of legs,the first of which is armed with large claws, the malesbeing normally larger than females. The crabs wereavailable maximum in pre-monsoon and monsoon andminimum in post-monsoon and summer seasons. Thecrab P. fluviatile was available almost all the stationsof the present study.

The common name of T. cymodoce is red coralcrab or orange coral crab. The colour of carapace ispurplish to brownish blue, with transverse row oforange-red spots. Cheliped dactylus black on distaltwo-thirds. Carapace dorsal surface with transverserow of orange-red spots; anterolateral margins nearly

straight. Thoracic sternites 2 and 3 separated byconspicuous suture. Cheliped propodus withconspicuous tomentum, dorsal margin keel-like andare adapted to a specific existence with seagrass,where they find protection among branches ofseagrass. The extensive ecological distribution ofthese crabs parallels the dispersal of the corals withwhich they are habitually associated. The crab feedson the mucus produced by the coral, gathering thesewith the minute comb-like structures at the tips oftheir feet. Maximum was recorded in summer andminimum was recorded in monsoon. This speciesrecorded in the stations of 2 to 7 and absent in otherstations.

The crabs belonging to the family Xanthidae areessentially herbivorus, normally grazing on plantorigin and coral growing near their place and on foundwhich drifted into their hiding place. Several seem tobe widely dispersed without reference to anyparticular environment within a given area, wanderingat random and seeking concealment under seagrass,stones or in crevices of dead. Convinced species ofParactaea, Leptodius, Zozymodes and Demania aretypical of the shoreline, often concealing themselvesunder stones in the intertidal zone. These forms, whichlive in moist environments but out of water forconsiderable periods of time, are highly tolerant offresh water, surviving heavy downpours of rainwithout apparent ill effects.

The carapace of P. neospeciosa is broadly ovalin shape. The entire carapace is divided very cleanlyinto regional and subregional convex lobules. Infemale chelipeds are equal, stout, the lobules on outersurfaces of wrists and on upper edge of hands aredistinctly outlined and one granular longitudinal linepresent on the middle of outer surface of palms. Lowerhalf of palms are granular; base of dactylus is alsogranular. Tips of the fingers are pointed. This speciesabsent in station 1 but recorded all other stations ofthe present study. The colour of L. exaratus is overallpale dirty brown, carapace regions projecting, rugoseand separated by deep grooves; with 4 anterolateralteeth behind outer orbital angle. This crab wasavailable almost all the stations of the present study.


Z. cavipes has carapace surface with irregularrugosities composed of granules often arranged inshort transverse groups or striae; anterolateral marginswith 4 short, narrow teeth each intervened by smallertooth. Cheliped carpus and propodus deeply pittedand eroded. This species represented only in stations2, 5, 7 & 9.

D. buccalipes carapace and chelipeds coveredwith large depressed tubercles; carapace aboutseven-ninth as long as broad. The characteristictubercles have everywhere a worn appearance,especially in the middle of the carapace and on thechelipeds and the ischium of the external maxillipeds.Dorsal crest of the arm and of the meropodites of thelegs have each become a row of berry like teeth andthe serrated crest and granular ridges of thecarpopodites and propodites of the legs have becomemerely low rough elevations. Bright and distinctivecolor pattern of this species is characteristic of manyknown poisonous species and is an indirectconfirmation of their toxicity. These crabs areavailable all seasons except post-monsoon. Thisspecies available only in stations 2, 5, 6 & 8 of thepresent study.

Oziidae crab O. rugulosus was collected near theseagrass mud area and identified by its carapacethickly covered with fine granules and pits, but theposterior half of the dorsal surface is almost smoothto the unaided eye, antero lateral border rather faintlydivided into 5 lobes, of which the first two are broadand rounded and the last three are bluntly acuminate.Legs stout, the last three joints. It is more active atnight, but even so, very quick to scuttle back intohiding when disturbed. Maximum was recorded inpost-monsoon and minimum was recorded inmonsoon. This species obtained only in stations 2, 5& 6 of the present study.

Grapsidae crab, G. albolineatus is circular shapein dark with a pattern of light spots in bands at thelower portion of the body. Short small flattenedpincers. Very long walking legs tipped with pointyclaws. With these legs, the crab clings tightly so itdoesn’t get washed away in the waves and can

scramble quickly among slippery rocks. Colours seenrange from reddish to bluish and greenish. It is ascavenger and also eats seaweeds. It is more active atnight and seldom seen during daylight. This speciesavailable almost all the stations of the present study.The colour of G. strigosus is dark reddish brown andwhite, carapace depressed, naked, smooth betweenthe ridges, branchio-cardiac groove indistinct,external surface of cheliped palm smooth, bearing twoindistinct ridges, finger tips coloured dark tan orbrown. Inferior distal extremity of last pair ofambulatory legs serrate. Male abdomen with sixthsegment equal to or shorter than fifth. Male firstpleopod straight and very stout. This species absentonly in station 10 and present all other stations of thepresent study. The carapace of M. messor legs arebrownish green and irregularly mottled. Clawsbrownish red with clearer tips. Male abdomen withsixth somite shorter than fifth somite. This mangrovecrab can be found in belt mangroves43 and on rockyshores44. This species absent in stations 1 & 9 andpresent all other stations of the present study.M. maculates morphological colour of dark bottle-green, the claws in some adult males are a brilliantviolet, in others bright orange, dull in the female; thelegs are striped with alternate light and dark bands,carapace being seven-eighths as long as broad, withmarkedly convergent sides and the absence oftransverse markings on the post-frontal region. Thefingers of the chelipeds are much longer than theupper border of the palm. Except in the last pair oflegs, the greatest breadth of the meropodites isdecidedly less than half their length. The terminalmale abdominal segment has a three-lobedappearance. This species only absent in 3 & 10 andrecorded all other stations of the present study. Pebblecrab L. pubescens is a rounded and colour is shinyolive green, chelipeds and legs with brownish bands.It is distinguished by the sharply hexagonal carapace.Long legs; Pterygostomian convex. The maleabdomen consists of three segments. Maximum wasrecorded in summer and minimum was recorded inpost-monsoon. This crab absent only in the station 3and recorded all other stations of the present study. P.


globosa is smoky bluish brown above, the bluedeepest on the carapace. Carapace smooth, its regionshardly defined. Epistome projects beyond the front,which hardly pubscent. Sixth abdominal tergumsmooth. Maximum was recorded in monsoon andminimum in post-monsoon. This species present instations 1 to 6 and absent in all other stations of thepresent study.

Large crab or sponge crab D. dormia has browncolour, white or pink claws tip. Dome shaped carapacemuch wider than long, strongly convex, antero-lateralborders armed with four teeth, covered with thick andrough hair; Short conical lateral spines, chelipedsmassive, outer face of palm inflated, inner superiormargin with four tubercles. This species availablealmost all the stations of the present study. Tidal spraycrab P. depressa tuberculata colour is reddish brownor light reddish, dotted with blood red, tuberclesbordered with blackish haris having gray extremities;blood-red spots on legs; underside of body yellowish,chelipeds with purplish spots and stripes, this crab isdistinguished by the absence of a true front, so thatthe antennular fossae are visible in a dorsal view asdeep clefts in the anterior border of the carapace. Theregions of the carapace are distinct, and covered withflat pearly or squamiform tubercles. The antero-lateralborders are cut into four teeth. The chelipeds aremassive and have tubercles on the upper surface ofthe palm and finger arranged in longitudinal rows.They live in sandy, muddy and sea grass areas andare often found buried in the soft bottom during day.Maximum was recorded in summer and monsoon andminimum was recorded in post-monsoon. This speciesavailable almost all the stations of the present study.

The Grapsidae crabs mostly collected in largenumber in seashores. They may be distinguished bytheir broad fronts, short eyes and almost square shapedcarapace. Mostly grapsids have equal sized chelae(claws), unless one has been broken off and isregrowing. The male grapsids usually have muchlarger chelae than females of the same species. Thefactors such as low salinity and temperature possiblephysical changes in the substrate composition andavailability of maximum organic materials during

post-monsoon and monsoon seasons may be attributedfor greater abundance in seasons and categorized themas permanent inhabitant seasonal immigrant andcasual visitors45. They were recorded in intertidalareas and feeding strategies of scavengers and willeat almost anything, plant origin, such as seagrassand seaweed46. This species available almost all thestations of the present study.

S.brockii is a tree climbing species from coastalmangroves. It is commonly found underneath the barkof dead trunks or inside hollow trees in mangroves.Carapace quadrate to longitudinally rectangular,lateral margins parallel to subparallel or gentlydivergent posteriorly. Cheliped merus with expandedfoliaceous distal margin, lined with prominent sharpspines and teeth. Chelae with stridulating structure;male telson slightly longer than wide; all somites free.Maximum was recorded in post-monsoon andmonsoon and minimum was recorded in pre-monsoon.It was recorded throughout the year including lowsaline of monsoon47. This species available almostall the stations of the present study.

Colour of S. bidens is flattened deep redand brown shell with protruding eye stalks and2 equal-sized orange to bright red claws. Carapacesubquadrate, surface almost flat, covered with finepiles and the ridges of the postero-lateral surface alsofurnished with piles. Merus of the chelipeds short,prismatic, with a strong subdistal spine on its innerborder. Carpus convex, rugose, the inner- distal anglebluntly rounded. First pleopod of the male straight,the distal chitinous process bent ventrally outwards.Abdomen triangular; telson semicircular distally.Males are more brightly coloured than females.Females also have a different shaped abdomen, onlyvisible on the underside. Maximum was recorded inmonsoon and minimum was recorded in pre-monsoon.This species available almost all the stations of thepresent study.

Carapace of S. plicatum is broader than long, thedorsal surface moderately convex and uneven butgenerally naked and glabrous. Eyestalk relativelyshort. Chelipeds of female smaller than those of males,granulate than that of males, without pectinated crests;


tubercles on upper surface of movable finger notprominent. Walking legs medium sized, flattenedmerus relatively wide that of second walking leg.Merus of ambulatory legs is almost twice as long asbroad. This species available almost all the stationsof the present study. S. tetragonum is a square shapedparallel lateral side with one acute tooth behind outerorbital spine. All the regions especially the gastricwell defined, whole dorsal surface covered with tuftsof hairs, longer and thicker anteriorly. In male,chelipeds stouter and more sharply rugose on outersurface than in females. Maximum was recorded inpre-monsoon and summer and minimum was recordedin post-monsoon. This species available almost allthe stations of the present study. S. batavicum has itscarapace, square, deep, broader than long; lateralsides slightly convergent posteriorly and without teethbehind the outer orbital angle. Small transverse rowsof setae present on carapace. Chelipeds in male equal,outer sides of arm and wrist rugose. Patch of longthick hairs present at the finger cleft in all males. Infemales no dent on dactylus present and few long hairson finger cleft. Anterior edge of carpus and propodusdensely setose. Moveable finger of male chelaedifferentiate the species. This crabs collected inmangrove, intertidal and muddy substratum.Maximum was recorded in monsoon and minimumwas recorded in pre-monsoon. This species availablealmost all the stations of the present study.

The crabs belonging to family Grapsidae andOcypodidae were the principal forms, whichparticipate a very important role in recycling thenutrients enhancing the role of decayed plant materialsand litter processing48. Colour of U. annulipes inenlarged pincer is usually pink, sometimes nearlywhite. The body is often black with blue or whitestripes; the male fiddler crab’s enlarged pincer has aridge of bumps on inside or the ‘palm’ of the pincer.Outer side is smooth and does not have a triangulardepression. Movable upper finger extends past theimmobile lower finger. This small crab with anenlarged pincer that is smooth is sometimes seen onsome of the Indian shores. Sandy, silty shores nearthe low water mark, often near mangroves. Thisspecies available almost all the stations of the presentstudy.

The carapace of U. lactea is white or gray black.Major cheliped white. Carapace front broad;anterolateral margin almost straight, major chelipedof male without longitudinal groove on outer surfaceof pollex and dactylus. This species available almostall the stations of the present study. Immobile lowerfinger U. vocans is orange or yellow and has a longgroove on the outside. Body colours and patterns vary,some greenish, others greyish. Male fiddler crab’senlarged pincer has a bumpy outer face. Tips of thepincers are flattened and sabre-like. O. ceratophthalmuscan be distinguished from other related crabs by theeyestalks extending beyond the eyes into long points,which are longer in males and shorter in females andjuveniles. Crabs have a box-shaped body, across thecarapace, with darker markings towards the rear inthe shape. They were collected in sandy beaches andsand flats in front of mangroves. This species presentin stations 2, 4, 5, 6 & 8 and absent in all other stationsof the present study. Carapace of O. macrocera has acarapace faint reddish-chestnut color. Chelipeds arered at the base with red spine and the outer surface ofthe large claw is bright orange. The walking legs arefrenching grey in color. carapace square, deep,strongly convex from before backwards andmoderately so from side to side; surface covereduniformly with bubble like small granules; chelipednot pointed but expanded and blunt, length ofstridulating ridge on inner side of palm, more thanhalf of the breadth of larger palm, this ridge consistsof striae only, hairs scanty. This species availablealmost all the stations of the present study. D.myctiroides across the carapace, and they arecharacterised by the presence of “gas windows” onthe merus of the legs; in Dotilla, these windows arealso present on the thoracic sternites. Sand bubblercrabs live in burrows in the sand, where they remainduring high tide. When the tide is out, they emergeon to the surface of the sand and scour the sand forfood, forming it into inflated pellets, which cover thesand. However in moist, semi-fluid and unstablesubstrate, it rotates in the sand creating pellets anduses it to seal the opening roof. It was collected in allstations and maximum was recorded in pre-monsoonand minimum in post-monsoon and totally absent in


monsoon season. This species available almost all thestations of the present study.

The other groups of shore crabs are belonging tothe family Ocypodidae. They are mostly in tall eyed,with the bases of their eyes close together at the frontof the carapace. Ocypodid crabs were collected liveon sandy beaches, mudflats and in mangrove swamps.They are active burrowers and many live incolonies49,23. Density of these crab are high comparedto other brachyurans50,51. Diet includes algae, tiny crabpellets and freeze dried plankton and shrimp. It isconsists as a main food items for a large number offauna, being responsible for an important part of themacrobenthic production in the intertidal zone. Maleghost crabs and especially the fiddler crabs haveunequal sized chelae52. Uca sp mostly collectedintertidal mud flat area 53. Population of U. annulipes,U. lactea and U. vocans inhabitant area between highwater neap and low water neap before the onset ofmonsoon seasons. Migration Uca sp during monsoonseason to distance of twenty five meter away fromthe pre-monsoon habitat54. It is also suggests thatreproduction is continuous, a very common patternin tropical brachyurans. Major peaks of spawningoccur during the summer and subsequently declinein winter55,56.

Macropthalmus sp were collected mostly in lowtides, normally the population density of this specieswas not much as found in their family Calappidae.Colour of the M. convexus carapace is slate purplewith maroon spots. Ambulatory legs gray-lilac; dactylidark pink, carapace broadest anteriorly, surface finelygranulate except frontal, protogastric and mesogastricregions; eyestalks not extending beyond apices ofouter orbital angle. Cheliped palm about 2.5 times aslong as high, merus of first three ambulatory legsdorsally setose. Maximum was recorded in summerand minimum was recorded in pre-monsoon. Thisspecies available almost all the stations of the presentstudy. Sediment may play a role as an appropriatehabitat for the dominant species M.-depressus, thecolour of the crab is greyish carapace broader thanlong, tooth at anterolateral angle of carapace truncateand square cut; surface of palm of male smooth;carapace studded with minute granules not always

plainly visible to the naked eye, its length in the maleabout two-thirds of its breadth; eyestalks slender,hardly curved, the eyes reach almost to the end of theorbital trenches; the chelipeds and legs are unarmedexcept for a small sub-terminal denticle on the anteriorborder of the meropodites of the first three pair oflegs. Maximum was recorded in summer andminimum was recorded in pre-monsoon. They werecollected in sediment of the undisturbed and thelogging areas both silty clay in the mangrove andshore sediment. This species absent in stations 1, 3,7, 9 & 10 and present all other stations of the presentstudy.

C. carnifex is found in coastal regions of PalkStrait57,58. Species is large dull, dark reddish brownwith a deep transversely oval carapace with roundedsides to allow for the expanded gill chambers. Bothsexes were collected however larger males thechelipeds are conspiculously unequal and largefemales have rather unequal chelipeds. The crabscollected in near mangroves and its burrows undercoconut trees and dried mud59,60. They areoccasionally seen above ground during the daytime33.Maximum was recorded in summer and pre-monsoonand minimum was recorded in monsoon. This speciesavailable almost all the stations of the present study.

The hermit crabs belonging to family Diogenidaeand Paguridae were recorded in varies places in wood,shells61,62 and seagrass meadows. In Diogenidae, theleft chela that is enlarged instead of the right, becausein contrast to most other hermit crabs. The presenceof crabs in gastropod shells, the crabs to occupyvirtually all suitable shells. The cephalothorax colourof C. longitarsus is green-brown with darker brownmottling and patches with dark sub medial linesposteriorly. Ocular peduncles dorsally olive green,ventrally very pale green or cream. Shield longer thanbroad. Chelipeds sub equal, right slightly longer andmore robust, similar in armature; dorsomesial marginof palms each with row of 4 spines, dorsal surfaceswith 1 or 2 irregular rows. This species availablealmost all the stations of the present study. Thecarapace colour of C. arethusa is white or light grey;eyestalks, antennules, antennae, chelipeds and legsdeep orange red with black tipped fingers of chelipedsand dactyli, eyestalks shorter than antennular


peduncles; ophthalmic scale narrow, pointed at tipand close together; numerous tufts of setae on gastricregion and behind cervical groove; antennal aciclereaching about one-third last antennal segment; a fewconical spinules with blunt tips on hand and virist;dactylus of third pair of legs of same length aspropodus; propodite with flattened outer surface; butdevoid of superior external carina. This speciesrepresented only in stations 5, 6, 8, & 10 of the presentstudy. The colour of C. olivaceus carapace and legsare green in color, 3 red lines, 1 on the dorsal sideand 2 on the lateral sides are present on eyestalks. Onthe merus and carpus of walking legs brownish darkspots are seen. Formalin preserved specimens areyellowish with the chelipeds and other legs red incolor, eyestalks as long as the antennular pedunclesas but distinctly longer than the anterior border ofthe carapace. Chelipeds sub-equal and similar. Thiscrab absent only in station 1 and present all otherstations of the present study.

The carapace colour of D. megistos is brightred-orange with numerous white spots ringed withblack. Ocular peduncles bright red-orange with fewtiny darker red spots. Antennular and antennalpeduncles red-orange. Chelipeds and ambulatory legsbright red-orange with numerous white spots ringedwith black. Setae generally dark red, ocular pedunclesmoderately long and slender; corneas only veryslightly dilated, setose and weakly spinose. Chelipedsand ambulatory legs, especially three distal segmentseach thickly covered with tufts of long bristles andcorneous-tipped spines. Chelipeds grossly unequaland left larger. These crabs are available all seasonsexcept post-monsoon and monsoon. This crabrepresented only in stations 5 to 9 of the present study.

S. spirifer is overall brownish-orange, shieldbroader than long; rostrum broadly subtriangular.Chelipeds slender, similar, of equal length or rightslightly larger; chela with marginal fringe of longsetae; Dactyls of ambulatory legs each with row oflong setae on dorsal margins; male left sexual tubestout, long, coiled and lateral margins each with fewprominent spines. Paguridae crabs found twoaggregations on the beach at low tide, one close to

the forest edge near the high tide mark and the otherapproximately 10 m from the tree line near the lowtide mark, with few crabs in between 63. Accordinglydifferent habitats such as seagrass, seaweed andmangroves compared hermit crabs mostly collectedand abundance in gastropod shells64, as well as thegastropod shells can be limiting resources to hermitcrab populations65. So many studies previouslydiscussed shell occupation by hermit crabs65,66. Thehermit crabs abundance can be influenced byphysico-chemical conditions, for instance selectingheavier shells in areas of high water turbulence andwave action65. Maximum was recorded in summerand minimum was in pre-monsoon and absent inpost-monsoon and monsoon. This crab was recordedalmost all stations except station 10 of the presentstudy.

Fiddler crabs approximately 100 species of semiterrestrial marine crabs which make up the genus Uca.Hermit crabs 1100 species are decapod crustaceansof the super family Paguroidea. The infraorderBrachyura contains 6,793 species in 93 families, asmany as the remainder of the Decapoda. Freshwatercrabs more than 1,280 species that comprises thelargest group within the Brachyura67,68 reported 254species of crabs belonging to 120 genera whichrepresented 24 families. A total number of 990 speciesof marine brachyuran crabs belonging to 281 generaand 36 families are found in Indian waters14. In thepresent study totally 21 families represented by 79crab species were recorded. The species contributionsof different families were in the following order;Aethridae 1, Calappidae 4, Carpillidae 1, Dorippidae3, Leucosiidae 2, Hymenosomatidae 1, Majidae 3,Parthenopidae 2, Pilumnidae 1, Portunidae 24,Potamidae 3, Trapeziidae 1, Xanthidae 4, Oziidae 1,Grapsidae 9, Sesarmidae 5, Ocypodidae 6,Macrophthalmidae 2, Gecarcinidae 1, Diogenidae 4and Paguridae1. This study agreement with earlierstudies along Indian coast by69 recorded 27 speciesof crabs belonging to the three families Portunidae,Ocypodidae, and Grapsidae Alcock8,70 in his‘Materials for a Carcinological Fauna of India’described 35 species of portunids, 13 species ofocypodids and 24 species of grapsoids from the


Andaman and Nicobar Islands. Brachyuran fauna ofthe Maldive and Laccadive Archipelagos wereinitiated by8,70 who recorded 43 species of crabsbelonging to 9 families. Subsequently,71,72,73,74,75

reported 191 species of crabs including 27 alreadydescribed by76 which brought up the total record fromthis region to 207 species.65 were reported crabsbelonging to Portunidae, Ocypodidae, Grapsidae andMictyridae and described 29 species besides few newrecords from Andaman and Nicobar islands18.reported 68 species coming under 14 families ofbrachyuran crabs along Parangipettai coast. The crabsalong Pitchavaram mangrove represented byCalappidae 3, Dromidae 2, Dorippidae 1,Geocarcinidae1, Goneplacidae 2, Grapsidae 11,Leucosiidae 7, Majidae 1, Ocypodidae 9,Parthenopidae 4, Pinnotheridae 2, Portunidae 30 andXanthidae 4 was recorded by46,77 reported 29 speciesof crabs from Pulicate Lake. Totally 105 speciesbelonging to 16 families coming under 56 generawhich includes, Calappidae 5, Dromidae 2,Dorippidae 2, Goneplacidae 1, Grapsidae 2,Leucosiidae 11, Majidae 13, Ocypodidae 2,Parthenopidae 4, Portunidae 23, Xanthidae 8,Carpillidae 3, Menippidae 1, Zosiminae 7, ETisinae1,Chlorodinae 6, Cymoinae 2, Actaeinae 2, Pilumnidae3, Trapeziidae 4, Aethrinae 1 and Plaguiidae 2reported by78 from Gulf of Mannar.79 reported 18species of crabs in Sundarbans,80 recorded 18 speciesin Pazhaiyar and Parangipettai coast.81 reported 16species of crabs in Cuddalore coast.82 reported 34species of crabs in Mudasalodai and 32 species inNagapattinam coats.83 obtained 12 species in Keralacoast and84 recorded 38 species in Pichavaranmangroves.85 recorded 43 species of crabs belongingto family Dromidae (1), Dorippidae (1), Leucosidae(9), Calappidae (5), Matutidae (2), Majidae (2),Parthenopidae (2), Portunidae (16), Xanthidae (3),Graspidae (1) and Corystidae (1) was reported in trawlby catch in Kerala coast. Forty six species of crabsbelonging to the family Portunidae, Podaphthalmidae,Ocypodidae, Sesarmidae, Dromidae and Dorippidaewere reported in five different stations of Pichavarammangrove by86,87 recorded 9 species of crabs inPondicherry coast and88 recorded 67 species of crabs

in Gulf of Mannar.89 Among 57 species of crabsbelonging to 37 genera and 11 families were recordedfrom three lakes, such as Chilka, Pulicat andVembanad Lake. List of species following familiesin Calappidae (3), Leucosiidae (3), Hymenosomatidae(3), Majidae (1) Portunidae (10), Pilumnidae (2),Gecarcinidae (1), Grapsidae (15), Pinnotheridae (1),Ocypodidae (16), Gecarcinidae (2). Similarly 36species of crabs were recorded in Pichavarammangrove environment by90. Recently91 were reportedcrabs in Cuddalore coast. Totally 13 families wererecorded coming under 31 genera which representedCalappidae (6), Carpillidae (2), Corytidae (1),Dromidae (2), Dorippidae (2), Grapsidae (2),Goneplacidae (1), Leucosiidae (6), Majidae (6),Ocypodidae (2), Portunidae (23) and Xanthidae (8).

In the present study maximum crabs werecollected during summer and monsoon thanpre-monsoon and post-monsoon. The crabs belongingto families viz., Calappidae, Portunidae, Potamidae,Grapsidae, Sesarmidae and Ocypodidae wereobtained almost all seasons. Some scientist alreadyreported that the crabs abundant maximum inmonsoon92,85 post-monsoon, summer and minimumin monsoon and pre-monsoon35,93.

Each and every substrate is preferred by a specificcommunity of animals that are often limited to thathabitat, a behavioral response such as modifiedfeeding habits94. Burrowing activity of crabs inmangroves, seagrass and salt marshes may stronglyaffect the substratum landscape95. Loss of habitat isthe primary cause of species loss96. Among the, mostproductive plant communities, providing habitat andfood for a variety of crustaceans97,98. Seagrass bedshave a very high productivity rate and contributesignificantly to the total primary production of inshorewaters. Its serve as a number of important functionsin inshore areas. They are significant source of foodfor many organisms both by direct grazing and detritusfeeding and have usually been considered theprincipal and optimal nursery grounds for manydecapod species 99,100,101. On the seashore a very largenumber of different species of crabs (Ocypodiae,Sesarmidae, Portunidae) are found, but most of them


are smaller in size and therefore rarely for humanconsumption. Perhaps the only shore crabs still caughtin great numbers are the mangrove associated crabswhich occurs in the mangrove and throughout themuddy bottom of intertidal and subtidal zones ofcoastal regions.

The natural population of crustaceans whichsupport commercial fisheries is damaged in severalways by the activities of modern man. Various kindsof human activities adversely affecting the crustaceanfauna and their resources have been pointed out by102, 103,104.Trampling by careless visitors also has an impact onlocal populations. Overwhelming value ofbiodiversity as an indication of environment healthand for the functioning of ecosystems105,106. Estimationof biodiversity values in monetary terms helps topromote and justify conservation actions at the publicpolicy and decision making level and is essential todefine the optimal level of conservation. Valuesperceived by decision makers influence their choiceswith regard to the management of biological resourcesand socially optimal decisions require the fullvaluation of costs and benefits of the options underconsideration107. Human impacts and the most generalexplanation to reduction of coastal plants is excessivenutrient enrichment108,109. Effluent disposal110 andchanges in land use pattern are other importantanthropogenic disturbances that threaten crabpopulations and loss of biodiversity as evident inrecent years111 and the multifarious activities of mancausing damages to the natural habitat ofcrustaceans102,112 are potential threats to thebiodiversity of this important group. Loss ofbiodiversity is regularly identified as one of thegreatest environmental risks facing mankind as aresult of anthropogenic disturbances. Legislation hasbeen proposed to preserve biodiversity andgovernments have been urged to approach this issue.An international treaty for the conservation ofbiodiversity has been negotiated113. Theseenvironmental and biological conditions are amongseveral factors that invoke a number of questionsincluding anthropological stresses and environmentalchanges. Speculation on the newest stress is that itwill occur due to global warming114. A superior

understanding of the structure and functioning of theseagrass, seaweed and mangrove ecosystems arehighly important for formulating strategies forconservation of these valuable ecosystems.

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crab biodiversity from arukkattuthurai to pasipattinam...

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