Estuarine, Coastal and Shelf Science (1987) 24,265-278

Macrofauna Associated with the Sponge Verongiaaerophoba intheNorthAegean Sea

H. E. Voultsiadou-Koukoura”, A. Koukoura9 and A. Eleftherioub “Department of Zoology, University of Thessaloniki, Thessaloniki, Greece and bMarine Laboratory, PO Box 101, Victoria Road, Aberdeen AB98DB, U.K.

Received 21 October 1985 and in revised form 22 April 1986

Keywords: sponges; fauna1 association; macrofauna; diversity index; density; biomass; Aegean sea

The macrofaunal organisms associated with the sponge Verongia aerophoba were investigated at a number of stations along the Chalkidiki Peninsula. The high diversity fauna consisting of 104 episponge and intrasponge species included 34 species which are reported for the first time associated with sponges. This fauna was not specific to V. aerophoba but consisted of organisms reported from other sponge species and different substrata. However because of its high stability it was classified as a distinct community. Examination of the elements of the fauna in relation to sponge size showed no correlation between the volume of the host and the density, diversity and biomass of the associated fauna. Polychaetes and crustaceans were the dominant taxa both in abundance and biomass. Small amphipods and decapods were the most abundant organisms, clearly favoured by the small diameter of the canals which excluded the larger polychaetes. The fauna1 diversity of the associates in the different sampling stations appear to be influenced by physical and biotic parameters. Investigation of the possible factors influencing fauna1 diversity showed that diversity was inversely pro- portional to the degree of exposure and proportional to the amount of total cover of vegetation in the vicinity of me sponge.

Introduction

Recent studies have established that numerous representatives of the major animal phyla have been found in an endobiotic or epibiotic association with sponges. Most of the relevant information is scattered over a couple of hundred works of which only a few are concerned exclusively with the fauna associated with different species of sponge. The relevant bibliography on the subject has been reviewed more or less comprehensively by Arndt (1933), Bacescu (1971), Sara & Vacelet (1973), Rutzler (1975) and Lauckner (1980).

The species Verongia aerophoba (Schmidt, 1862) is an upright branching form emerg- ing from a small base attached to a hard substratum. The extremities of the finger-like branches are flat, the centre being occupied by a canal running the entire length of the branches. The organisms associated with the sponge are found either inhabiting these

265

0272-7714/87/020265 + 14 $03.00/O 0 1987 Academic Press Inc. (London) Limited

266 H. E. Voultsiadou-Koukoura et al.

--- “11

ESSALONIKI

Figure 1. Map of Chalkidiki Peninsula showing the location of the sampling stations (only samples from stations indicated in the text have been considered in the present

paper).

canals or at the outer surface of the sponge, usually between the branches, and they have been little studied. Some information can be found in Sube (1970), Vacelet (1971) and Lauckner (1980) but most emphasis has been on the symbiotic association of this sponge with the blue-green alga Aphanocupsafeld~nani. Sube (1970) reports the occurrence of the copepod Entomolepis udriue in the canals of V. uerophobu, Zavodnik (1976) observed the frequent presence of the ophiuroid Ophiothrix frugilis and Koukouras et al. (1979) provided preliminary information on the macrofauna associated with this species. Furthermore Bergquist (1978) and Lauckner (1980) reported in this species the presence of substances with antibiotic properties.

This study is part of a general programme investigating fauna1 and sponge associations and recording possible similarities or differences in the seven species of sponges found in the same habitat along the Chalkidiki Peninsula in the northern Aegean Sea. From these comparisons it may be possible to establish whether the morphological characteristics influence or determine the composition of this association. In this part the composition of the fauna associated with Verongiu uerophobu is reported and an attempt is made to describe its community structure.

Materials and methods

Of the 21 sampling stations established in the summer of 1975 on the coast of Chalkidiki Peninsula in the northern Aegean Sea (Figure l), 11 (nos 1,3-8,13, 14,17 and 21) were

Macrofauna associated with a sponge 267

TABLE 1. Volume (u) of the sponge samples, number of species (N,,), density (NJ and biomass (B) of the associated fauna

Stations 1 3 4 5 6 7 8 13 14 17 21

L’(cm’J 576 5550 235 2080 3956 700 412 4330 1750 290 450

‘x’\p 33 29 18 28 28 12 13 54 38 9 11 v 150 127 80 130 403 86 37 555 242 21 26

B (9) 3.56 2.20 5.77 3.48 12.53 11.94 0.81 11.65 7.58 0.69 1 58

selected for the collection of specimens of Verongia aerophoba. All the specimens were collected by SCUBA diving or by snorkelling in depths ranging from 3-5 m. At each sampling station one or more individuals with a well developed branching growth were retained. The sponge was enclosed in a plastic bag by the diver, its base removed from the substratum with a knife, the bag being immediately sealed after removal. Organisms attached to the sponge base were not included. The volume of the sponges was measured by means of water displacement. The individuals were cut into l-2 cm fragments chiefly along the canal length and placed in containers where careful washing removed the associ- ated fauna. Examination under the microscope of the sponge fragments ensured the removal of any remaining animals. The water contained in the plastic bag, the sample container and in the sponge tissue from each sample was sieved through 1 mm mesh. The extracted fauna was separated into groups, identified, counted and weighed, providing a crude biomass estimate, after the superficial moisture had been removed by filter paper. The methods used by Guille (1970) were applied to assess the degree of affinity between samples from different stations, to estimate the biological indices of the species and to describe the association between host and its inhabitants. It should be noted, however, that the use of percentages in expressing similarity, minimizes the effect of differences in the volume of individual sponges in each sample. The estimation of the species diversity of each station was carried out by the application of the formulae of Margalef & Shannon-Weiner (Dajoz, 1975).

All the samples were collected from areas which belong to the zone of the wider assemb- lage of the photophilic soft algae (Peres, 1982). It should be made clear that although it was possible to separate the endofauna from the epifauna associated with each sponge nevertheless the total fauna has been considered as one entity in this association.

Results

Eleven samples of sponge of a total volume of 20,329 cm3 were examined and a total of 1857 individuals belonging to 104 species was recovered. Table 1 gives details of the volume of the sponge sample, the number of species, the abundance and the biomass of the individuals at each sampling station. Information on the abundance and biomass of the main taxonomic groups is given in Table 2.

The method applied by Guille (1970) in the study of soft-sediment benthic assemblages was used to describe the assemblage of organisms associated with a certain species of sponge. The samples were thus considered as equivalent although the sizes, expressed by volume, were different. This approximation was considered acceptable because the different degree of exploitation of both internal and external space by the various

TABL

E 2.

Den

sity

(Ni)

and

biom

ass

(Bin

g

wet

weigh

t) of

th

e m

ain

taxa

as

socia

ted

with

I’e

mng

ia

aero

phob

a

Isop

oda

Polyc

haet

a Ta

naid

acea

Stn

N,

B(g)

N,

B

M

Amph

ipod

a

N,

B k)

Echi

no-

Deca

poda

G

astro

poda

Bi

valvi

a de

rmat

a O

ther

s

N B(

g)

N,

B(g)

Ni

B

k) Ni

B(

g)

Ni

B k)

1 76

1.

477

6 0.

002

20

0.00

9 29

1.

390

1 0.

001

7 0.

347

7 0,

315

4 0,

020

3 25

1,

105

- -

63

0.11

1 31

0.

656

4 0.

262

3 0,

042

- -

1 0.

025

4 14

4,

613

- -

36

0.03

9 25

0.

552

2 0.

546

- -

- -

3 0,

020

5 6

0,11

1 -

- 50

0.

251

51

I.208

13

0.

939

2 0.

607

3 0,

130

5 0,

232

6 8

0.28

6 2

0.06

1 18

0 0,

241

184

4.64

1 13

6.

963

1 0.

041

14

0,28

4 1

0.01

4 7

- -

- 52

0,

133

22

5.37

2 11

6.

182

- 1

0.25

2 -

- 8

4 0.

161

1 <O

.OOl

12

0.

003

17

0,48

3 -

- 3

0.15

9 -

- 13

42

2,

058

10

0.06

2 29

6 0.

245

140

4.39

2 10

0.

813

6 0.

641

49

3.42

0 2

0,01

7 14

21

0,

573

- -

71

0.05

6 12

8 2.

368

14

4.24

2 5

0.11

9 1

0.20

8 2

0,01

5 17

1

<O.O

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11

0.

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7 0.

631

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7 0.

273

- 8

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2 6

0.17

9 -

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1.02

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l 20

4 10

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20

0,

125

799

1.19

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68

19

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1.

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84

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5 18

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343

- Macrofauna associated with a sponge 260

14

13

7

6

3

4

5

17

E

2’

14 13

58

71 1691 -

42

11 - 24

Figure 2. Trellis diagram showing aRmity (in “,) between sponge samples from different stations (station numbers indicated in horizontal and vertical axes).

% 60 I

0 4 17 8 21 1 7 14 5 6 13 3 StatIons

235 290 412 450 576 700 1750 2060 3956 4330 5550 cm3

-V

Figure 3. Mean fauna1 affinity of sponge samples from different stations in relation to the total sponge volume. Sponge samples arranged in a gradient of increasing volume.

organisms is substantially different, especially when the samples originated from widely separated areas. This was emphasized by the lack of correlation between the size of sponge and the number of species or individuals associated with it. Table 1 shows that small volume samples can have a larger number of species and individuals than samples of a larger volume. Furthermore the trellis diagram shown in Figure 2, calculating the index of affinity for pairs of samples, confirms the above contention that samples irrespective of volume might show a higher degree of affinity than samples of the same volume.

Moreover the average affinity value of small volume samples as indicated in Figure 3 can be as high as that of large volume sponge samples. With the exception of samples from

270 H. E. Voultsiadou-Koukoura et al.

stations 1, 14 and 21 the average affinity ranged between 4@554,,. Overall the affinity values between pairs of sponge samples were high (Figure 2). In 21 pairs of sponge samples (38”,, of the total) affinity was greater than 30?;, and in as many other pairs ranged between 30-50°, . In the remaining pairs of samples (229,) of the total) it ranged between 15-309, and only in one sample was it less than 15?,, . The very high affinity between sponge samples is due to the overwhelming dominance of the amphipod Colomastixpusilla and the other five preferential species as shown in Table 3. The low affinity between sponge samples from station 21 and the rest of the stations is due to the absence of Colomastix and the small numbers of the rest of the preferential species.

Assessment of the importance of different species in their association with this sponge species was carried out by calculating the different indices (Guille, 1970) of this associ- ation and the community dominants are listed in Table 3. This includes classification of these species, their presence (P) and frequency of their appearance (F), their biological index (Zb) as well as the mean (D,) and cumulative dominance (D,). The total number of species which constituted the fauna1 association are listed in decreasing order of abundance in Table 4.

‘Host’ specific species were not found; all the species in Table 4 have been found in other sponge species as well as on other substrata.

The first six species shown in Table 3 were considered as preferential species because of their high cumulative dominance (66.4”“). A large proportion of this percentage (30.4”,,) was due to the presence of large numbers of the amphipod Colomastix pusilla which had the highest index value. All six species can be classified as constant species (F> 50”,,) deriving from different locations in the sponge; the first three are intra-sponge, the following three are epi-sponge.

Of the 29 accompanying species, four can be classified as constant, 21 are common (50*,, <F< lo”,) and four are rare (F< loo,,). In the latter category is included the only fish species, Knipowitschia caucasica, three individuals of which were found between the branches of the sponge at station 5. Of the accompanying species 15 were intra-sponge and 14 epi-sponge. A similar proportion exists for the accessory species of which 33 were intra-sponge and 36 epi-sponge.

Figure 4 gives the percentage contribution of the different taxa to the total number of samples. Numerically the crustaceans were dominant [Figure 4(a)] representing 78.5O, of the total, of which amphipods (43.096) and decapods (34.4O/,) were the most important. Polychaetes (1 l.O?,,) were less important while echinoderms were represented only by Ophiothrixfragilis living between the branches of the sponge. The biomass [Figure 4(b)] was dominated by the crustaceans (37.5O,) mostly because of the presence of large decapods. Gastropods and polychaetes accounted for 32g”,, and 17.2O,,, respectively, while other taxa accounted for smaller weights.

The proportional representation of the three main taxa (amphipods, polychaetes, decapods) in all sponge samples in shown in Figure 5. Amphipods were numerically more abundant than polychaetes, the only exceptions being at stations 1 and 21 where poly- chaetes were most important (669, and 3306, respectively). These two stations had also the lowest mean affinity values (Figure 3). Amphipods were numerically dominant but because of their size their contribution to the total biomass was consistently lower than 2Oq;, occasionally less than 10:/b. Of the other two groups, decapods were more important than polychaetes in most samples.

To calculate the fauna1 diversity in the samples the Margalef and Shannon-Weiner equations were used. These two indices were selected because, while Margalef’s index

TABL

E 3.

Lib

t of

sp

onge

co

mm

unity

do

mina

nts,

ranke

d ac

cord

ing

to

their

biolog

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index

va

lue

(see

text

for

detai

ls)

Spec

ies

1 2

3

Clas

sifica

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gical

Mean

Cu

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ce

index

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mina

nce

dom

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e

4 5

6 7

8 9

10

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1,

D,

DC

Colo

nras

tix

pusi

lla

8 1

Alph

eus

dent

ipes

4

Leuc

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e sp

inica

rpu

1 3

Cata

pagu

roid

es

timid

tts

1 O

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thrix

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1 Th

orah

rs

cran

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1 1

Atha

uas

nite

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s G

alath

ea

boliv

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Nere

is co

stae

1

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dia

blut

elli

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nata

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phitr

ite

john

ston

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nula

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sa

Harm

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e sp

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chon

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mby

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roph

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acut

um

1 Am

phith

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ram

olld

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sidice

ni

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xam

ine

spin

ivest

ris

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s br

asilie

usis

Tr

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ra

sp.

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ce

sici

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to

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um

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ctica

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data

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alus

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ulttc

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sidice

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llarls

1 1 2

3 1 2

2 2 1 1 1

1 1 1 1 1

1

1

2 1

1 2

1 1

1

1 1 1 1 1 1

1 1 1 1 1

91

10

96

30.48

30

.48

100

11

79

7.70

38.18

73

8

68

5.71

43.89

82

9

50

7.49

51.38

82

9

44

4.52

55.90

82

9

41

10.50

66

.40

64

73

55

46

55

27

46

46

36 9 18

36

18

36 9

27

55

46

36

18

46

18

27

46

27

18 9 9 18

7 8 6 5 6 3 5 5 4 1 2 4 2 4 1 3 6 5 4 2 5 2 3 5 3 2 1 2

32

2.91

69.31

23

2.4

2 71

.73

21

1.78

73.51

16

0.9

7 74

.48

16

1.56

76.04

13

0.7

5 76

.79

10

1.13

77.92

9

0.86

78.78

9

0.43

79.21

9

2.15

81.36

9

0.27

81.63

8

0.48

82.11

7

0.65

82.76

6

0.43

83.19

6

1.24

84.43

6

0.38

84.81

5

0.48

85.29

4

0.59

85.88

4

0.32

86.20

4

0.32

86.52

3

0.43

86.95

3

0.38

87.33

3

0.32

87.65

2 0.6

4 88

.29

2 0.1

6 88

.45

2 0.3

2 88

.77

2 0.1

6 88

.93

1 0.2

7 89

.20

1 0.1

1 89

.31

TABLE 4. Fauna1 list of associated species and their characterisation according to the fauna1 and biological indices

A Characteristic species: none

B Preferential species constant: Colomastix pusilla Grube

Alpheus dentipes Guerin Lxucothoe spinicarpa (Abildgaard)

Catapaguroides timidus (Roux i Ophiothrisfragilis (Abildgaard) Thoralur cranchii Leach

C Accompanying species constant: Athanas nitescens (Leach)

Galathea bolivari 2. Alvarez Nereis costae Grube Nereis zonata Malmgren

common: Pisidia blutelli (Risso) Amphitrite johnstoni Malmgren Emarginula papillosa (Risso) Harmothoe spimfera (Ehlers) Dasychone bombyx (Dalyell) Amphithoe ranrondi Audouin Lysidice ninetta Audouin & M.E. Dcxamine spiniventris Costa Pilumnus spinifer M. Edwards Triphora sp.

Eunice siciliensir Grube

Potamilla torelli Malmgren Bittium reticulatum (da Costa) Lumbrinereis funchalensis (Kinberg) Serpula vermicularis Linnaeus Leptochelia savig+ (Kroyer) Muricopsis cristatus (Brocchi) Hiatella arctica (Linnaeus) Piltrmnus hirtellus (Linnaeus) Lysmata seticaudata Risso Lysidicc collaris Grube

rare: Corophium acutum Chevreux Erichthonius brasiliensis (Dana)

Knipouitschia caucasica (Kawrajky) Eualus occultus (Lebour)

D Accessory species constant: Aspidosiphon muelleri Diesing

common: Trypanosyllis zebra (Grube) Maera znaequipes (Costa) Tylodinaperversa Gmelin Platynereis dumeriiii (Audouin & M.E.)

Phascolosoma granulatum Leuckart Cla?xulus crusiatus (Linnaeus) Lepidasthenia elegans (Grube) Pagurus anachoretus Risso Spirobranchuspolytrema (Philippi) Syllis hyalina (Grube) Amphitrite variubilis (Risso) Columbella rustica (Linnaeus) Pista cristata Miiller Mantellum inf?atum (Chemnirz Janira maculosa Leach Dorvillea rubrovittata (Grube)

Elasmopus pocillimanus (Bare) Turbona sp.

rare: Microdeutopus stationis Della Valle Elasmopus rapax Costa Gammaropsis maculata (Johnston) Calcinus ornatus (Roux) Diodoragibberula (Lamarck) Processa edulis edulis (Risso) Lembos websteri Bate Lysianassa ceratina (Walker) Syllis prolifera (Krohn) Cymodoce pilosa M. Edwards Cymodoce truncata (Montagu) Dasybranchusgajolae Eisig Nicolea venustula (Montagu) Rissoa sp. Trophonopsis sp.

Xanthogranulicarpus Forest Acanthochitona fascicularis (Linnaeus) Barbatia barbara (Linnaeus) Calliostoma sp. Calliostoma zyzyphinum (Linnaeus) Chnuvetia sp. Chiton olivaceus Spengler Chlamys multiscriaca (Poli) Clibanarius erythropus (Latreille) Columbella sp.

Dromia personata (Linnaeus) Eunice sp. Galeomma turtoni (Sowerby) Gibbula sp. Golfingia vulgaris (Blainville) Harmothoe areolata (Grube) Herbstia condyliata (Fabricius) Hyale dolifusi Chevreux Hydroides pseudouncinata Zibrowius Irus irus (Linnaeus) Musculus costulatus (Risso) Nematorzereis unicornis (Grube) Panoploea minuta (Sars) Pisidia longimana (Risso) Podocerus variegatus Leach Pomatoceros triqueter (Linnaeus) Serpula concharum Langerhans Striarca lactea (Linnaeus) Syllis gracilis Grube Syllis krohnii (Ehlers) Syllis variegata (Grube) Terebella iapidaria Linnaeus Thracia sp. Tritaetagibbosa (Bate) Weinkaufia sp.

Macrofauna associated with a sponge 273

q POLYCHAETA

3 TANAIDACEA

q - ISOPODA

AMPHIPODA

DECAPODA

GASTROPODA

S~VALVIA

OTHERS

Figure 4. Pie diagram showing the importance of the different taxa in the sponge samples: (a) numerical composition of the associated fauna, (b) biomass (wet weight) of the associated fauna.

[D=(S- l)/log,N, where S is the total number of species and N the number of individuals] is sensitive to the number of species rather than to individuals, the Shannon- Wiener index (H= -Cpiloggi, where pi is the ratio of number of individuals of species i to the total number of individuals in the sample) depends not only on the number of species but also on the evenness of distribution of the individuals between species and it is independent of sample size (Dajoz, 1975). The diversity indices calculated for each sample by using the above equations have been related to the degree of exposure and to the vegetation cover in each sampling locality (Figures 6 and 7, respectively). In the first case the stations were arranged in order of increasing exposure. Assessment of the relative exposure (Figure 6) though arbitrary, was based on topographical details of the locality in relation to the prevailing winds. In the second case (Figure 7) the stations were arranged in order of increasing total algal cover which was independent of the prevailing exposure. From these results, despite the existing variations from station to station, a trend can be detected which shows that the diversity of the fauna inhabiting the sponge decreases with increased exposure. On the other hand diversity increases with increasing algal cover.

274 H. E. Vouhiadou-Koukoura et al.

Polyc haet a 100%

100 % 20 40 60 80 100 %

Amphipoda Deca poda Figure 5. Triangular diagram showing percentage contribution of the 3 main taxonomic groups in all sponge samples. Density values (indicated by solid squares) and biomass (shown by solid circles) bear the number of the corresponding station.

A

I

21 ~ 2.4 1 13 14 5 6 3 4 17 7 21 8 1 13 14 5 6 3 4 17 7 2, 8

eXPOSY,e s+rr,on.

Figure 6. Changes in the fauna1 diversity in sponge samples with increasing exposure (stations arranged in an exposure gradient where exposure has been assessed empirically). Diversity is expressed as (A) the Margalef richness index and (B) the Shannon-Wiener function.

Discussion

No correlation was found between the size of sponge samples (expressed by volume) and the total number of species or the number of individuals of the sponge associates. This could be due to the important variability of the space available and its utilization by the fauna. Nevertheless, we could accept as valid Frith’s view (1976) that larger branched or

Macrofauna associated with a sponge 275

/’ \, /

-. /’

A

/

‘--.

.’

/

4.4.

4.2.

./

4.0.

.3.8.

3.6.

1.4.

3.2.

3.0.

*a.

7.6 .‘\

/ _-. / .H’

.-’ 0 !

\, .-’

2 2.4 8 4 17 I 21 6 3 5 1 14 13 8 4 17 7 21 6 3 5 1 14 13

tota, COYel 0, vegeta,,on Sca+lonl

Figure 7. Changes in the faunal diversity in sponge samples using same diversity indices as in Figure 6 in relation to the importance of vegetation. Stations arranged in a gradient of increasing total cover of vegetation.

fistulose sponges (as in the case with Verongia aerophoba) attract more associates than smaller ones.

Pansini (1970) could find no statistical relationship between the volume of a number of sponge species (Ircinia fasciculata, Spongia officinalis, Petrosiaficiformis) and the number of their inquilines; nor did Sube (1970) find such a relationship in the species of sponge which he studied. On the other hand Pearse (1932) found that small sponges such as Spheciospongia vesparia contained a relatively larger number of species than larger sponges. Nevertheless, Westinga and Hoetjes (1981) who investigated a smaller number of sponges of the same species as Pearse concluded that the number of infaunal taxa increases logarithmically with the sponge volume; the total number of animals present, as well as their biomass were directly proportional to sponge volume, which suggested that all available living space is occupied. Labate and D’Addabbo Gallo (1974) also found a direct relationship between the volume of Stelleta grubii and Petrosia Fciformis and the density of their inquilines. The animals associated with massive sponges could be con- sidered as constituting an organismic assemblage (Peres, 1982). In the case of V. aerophoba however, because of the stable composition of the fauna1 association as expressed by the biological indices and their affinity values, this assemblage can be considered as a community.

Westinga & Hoetjes (1981) investigating the fauna1 community inhabiting the species S. vesparia found high affinity values always in excess of ~38.5~“. Affinity values in V. aerophoba were lower (Figure 2), probably as a result of the inclusion of the entire associ- ated fauna rather than taking into account the intra-sponge fauna only as in the case of S. vesparia. McCloskey (1970) working on the invertebrate community associated with the coral Oculina arbuscula, considered values of 36.0-64.8O,, to compare satisfactorily with affinity values reported from other community studies. However his values are lower than the affinity values calculated for Verongia aerophoba in this study. No specific macro- organisms have so far been reported to be associated with V. aerophoba, but meiofaunal and microfaunal organisms remain to be investigated in this regard.

A limited number of specific organisms has been reported (Bacescu, 1968; Bergquist, 1978; Lauckner, 1980) from a small number of sponge species only. There are few overall studies focussing on the highly specific organisms of sponge species. In the preferential species category shown in Table 3 are included species which by preference inhabit

certain sponge species although they have also been found in other types of environment or substratum. The amphipod C. pusilla which gave the highest biological index and the highest mean dominance was found not only in the canals but also on the sponge surface. Ledoyer (1968) has recorded this species around Marseilles from areas rich in sponges. So far this species has been recorded as inhabiting the sponge species Stematumenia foetida, S. strobilina, Spheciospongia vesparia, Spongia oficinalis (Pearse, 1932); Suberites domuncula (Bacescu & Mayer, 1960); Rhizaxinella pyrifera (Sube, 1970); Agelas ovoides,

Verongia aerophoba (Koukouras et al., 1979); Halichondria panicea (Peattie & Hoare, 1981).

The decapod Alpheus dentipes with the second highest biological index value is a species living in crevices as well as in detrital material (Ledoyer, 1968, 1969) or in Posidonia meadows (Peres & Picard, 1964). It could be concluded that the sponge environment fulfils the conditions necessitated by the sciaphilic behaviour of this species which like other members of the family Alpheidae is a well-known inhabitant of sponges (Arndt, 1933; Bacescu, 1971; Riitzler, 1975). A. dentipes has been reported from the Adriatic Sea inhabiting other sponge species (Arndt, 1933), particularly Geodia cydonium (Heller, 1863); it is also found in the northern Aegean, associated with Petrosiaficiformis, Spongia

officinalis, Verongia aerophoba and Geodia cydonium (Kourkouras et al., 1979). Leucothoe spinicarpa an amphipod species, a suspected parasite of sponges (Arndt, 1933;

Connes, 1967) having been reported from Speciospongia versparia (Pearse, 1932; Westinga & Hoetjes, 1981), Stematumenia strobilina, S. variabilis (Pearse, 1932); Mycale lingua (Arndt, 1933); Spirastrella inconstans (Fishelson, 1966); Tethya lyncurium (Connes, 1967); Spongia oficinalis (Pearse, 1932; Koukouras et al., 1979); Zrcinia fasciculata and I. muscat-urn (Koukouras et al., 1979). It is a nocturnally swimming species (Ledoyer, 1969) which is also reported from ascidians (Koukouras & Siamidou-Efremidou, 1978-1979). The occurrence of the decapods Catapaguroides timidus and Thoralus cranchii has pre- viously been reported from Verongia aerophoba and Petrosiaficiformis (Koukouras et al., 1979). Finally in the same category, the ophiuroid Ophiothrix fragilis has been widely reported from several sponge species (Vidal, 1967; Sube, 1970; Frith, 1976; Zavodnik, 1976). The six preferential species discussed above displayed a high constancy which is also obvious from their high cumulative dominance (66.4”,,).

Of the 29 accompanying species, the following twelve Athanas nitescens, Nereis costae, Amphitrite johnstoni, Harmothoe spinifera, Lysidice ninetta, Eunice siciliensis, Bittium reticulatum, Hiatella arctica, Pilumnus hirtellus, Lysidice collaris, Corophium acutum and Eualus occultus are well known associates of many different sponge species (Santucci, 1922; Fishelson, 1966; Vidal, 1967; Sube, 1970; Dauer, 1973; Riitzler, 1975; Frith, 1976; Kourkouras et al., 1979; Lauckner, 1980; Peattie & Hoare, 1981).

Of the 69 accessory species only 16 [i.e. Tylodina perversa, Phascolosoma gramdatum, Lepidasthenia elegans, Amphitrite variabilis, Janira maculosa, Platynereis dumerilii, Pagurus anachoretus, Columbella rustica, Lembos websteri, Syllis hyalina, S. prolifera, S. gracilis, S. variegata, Acanthochitona fascicularis, Striarca lactea, Tritaeta gibbosa] have been reported in the literature as inhabiting sponges (Santucci, 1922; Fage, 1928; Arndt, 1933; Bacescu & Mayer, 1960; Vidal, 1967; Sube, 1970; Dauer, 1973; Sara & Vacelet, 1973; Frith, 1976; Peattie & Hoare, 1981). Thus the remaining 34 species out of 104 mentioned in this paper (Table 3), are reported for the first time as associated with sponges.

Of the organisms inhabiting sponges the most numerous are usually polychaetes and crustaceans, which dominate such faunas (Pearse, 1932; Bacescu, 1971; Frith, 1976;

Macrofauna associated with a sponge 277

Koukouras et al., 1979). In this study the Crustacea were the dominant taxon (30,4O,,), particularly the small amphipod Colomastix pusilla. Such amphipod dominance has been noted by Frith (1976) in the sponges Halichondria panicea, Hymeniacidon perleve and Mycale mascilenta (dominance 59,46 and 7 1 0 0, respectively). The numerous crustaceans and especially the larger episponge decapods were the main contributors to the biomass figures. The small diameter canals of V. aerophoba do not allow the establishment of large bodied endosponge decapod species as occurs in other types of sponges (Pearse, 1932; Koukouras et al., 1979). Present observations confirm Riitzler’s (1975) remarks that ‘fewer but larger organisms dominate in hosts with large canals, whereas more but smaller endobionts find niches in sponges with small canals’.

The fauna1 diversity in the sponge samples at each station indicated that diversity is influenced by environmental factors such as exposure and the total vegetation cover. Many authors have inferred the influence of the environmental factors on the diversity of the fauna found in the sponges, but have not specified the factor in question. Thus Santucci (1922) found a larger number of endosponge species in the species Geodia inhabiting bottoms rich in detritus, than in those collected from rocky substrata. Pearse (1932) found high densities of organisms per cm3 in small individuals of Spheciospongicl

from deep water and concluded that the density of these organisms was dependent on locality and habitat (Pearse, 1950; McCloskey, 1970; Frith, 1976). Despite local differ- ences in the fauna1 diversity, the association of macrobenthic organisms with Verongiu uerophoba showed a high degree of constancy. However to acquire a better knowledge of the mechanisms determining the type and composition of the association of macrofaunal species with the different sponge species from different habitats, further detailed studies are necessary. Furthermore, studies on the interaction between the host and its inhabi- tants as well as relationships between the sponge inhabitants should be contemplated. Contradictory findings in the existing literature concerning the relationship between sponge volume and the density and diversity of inhabiting macrobenthic fauna emphasize the lack of reliable information, and suggest a need for further detailed investigation.

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