Reproductive Biology of Elasmobranchs

Reproductive Biology of Elasmobranchs

Chip Baumberger & Jeff GuertinChip Baumberger & Jeff Guertin10/16/0710/16/07

Chip Baumberger & Jeff GuertinChip Baumberger & Jeff Guertin10/16/0710/16/07

IntroductionIntroduction

Great diversityGreat diversity Brood sizes, ovarian cycles, gestation periods, Brood sizes, ovarian cycles, gestation periods,

mating systems, etcmating systems, etc Oviparity is common in the bony fishes (large Oviparity is common in the bony fishes (large

number of eggs and sperm released into number of eggs and sperm released into water for fertilization)water for fertilization)

All elasmos have internal fertilization (less All elasmos have internal fertilization (less energy expenditure)energy expenditure) Improve efficiency of fertilization, avoid wastageImprove efficiency of fertilization, avoid wastage

Great diversityGreat diversity Brood sizes, ovarian cycles, gestation periods, Brood sizes, ovarian cycles, gestation periods,

mating systems, etcmating systems, etc Oviparity is common in the bony fishes (large Oviparity is common in the bony fishes (large

number of eggs and sperm released into number of eggs and sperm released into water for fertilization)water for fertilization)

All elasmos have internal fertilization (less All elasmos have internal fertilization (less energy expenditure)energy expenditure) Improve efficiency of fertilization, avoid wastageImprove efficiency of fertilization, avoid wastage

Reproductive BiologyReproductive Biology Primarily studied from commercial fishery Primarily studied from commercial fishery landingslandings Data from captive Elasmobranchs limited to Data from captive Elasmobranchs limited to smaller speciessmaller species

Primarily studied from commercial fishery Primarily studied from commercial fishery landingslandings Data from captive Elasmobranchs limited to Data from captive Elasmobranchs limited to smaller speciessmaller species

Data collected typically includes:• Age/size at onset of sexual maturity

• Size and mass relationships between males and females

• Estimates of reproductive cycle length

• Sex ratio of male pups to female pups

• Size, development time of embryos (if possible)

• Reproductive system anatomy (when we’re lucky)

Internal FertilizationInternal Fertilization

All elasmobranchs have internal All elasmobranchs have internal fertilizationfertilization Improves likelihood and efficiency of Improves likelihood and efficiency of

fertilizationfertilizationTwo main groupsTwo main groups

Oviparous (egg-laying)Oviparous (egg-laying) Viviparous (live-bearing)Viviparous (live-bearing)

All elasmobranchs have internal All elasmobranchs have internal fertilizationfertilization Improves likelihood and efficiency of Improves likelihood and efficiency of

fertilizationfertilizationTwo main groupsTwo main groups

Oviparous (egg-laying)Oviparous (egg-laying) Viviparous (live-bearing)Viviparous (live-bearing)

Oviparous FormsOviparous Forms

Lay eggs on substrate or attach to bottom Lay eggs on substrate or attach to bottom structuresstructures

Nourished solely by yolk sacNourished solely by yolk sac Small slit in egg case for ventilation & Small slit in egg case for ventilation &

oxygenationoxygenation Primarily small, benthic, and bathyalPrimarily small, benthic, and bathyal Found only in three families and the skates Found only in three families and the skates

(primitive/ancestral condition)(primitive/ancestral condition)

Lay eggs on substrate or attach to bottom Lay eggs on substrate or attach to bottom structuresstructures

Nourished solely by yolk sacNourished solely by yolk sac Small slit in egg case for ventilation & Small slit in egg case for ventilation &

oxygenationoxygenation Primarily small, benthic, and bathyalPrimarily small, benthic, and bathyal Found only in three families and the skates Found only in three families and the skates

(primitive/ancestral condition)(primitive/ancestral condition)

Oviparous FormsOviparous Forms Found only in Heterondontidae, Scyliorhinidae, Found only in Heterondontidae, Scyliorhinidae,

Orectolobidae and RajiformesOrectolobidae and Rajiformes Mainly bottom dwellers, many shallow water and small Mainly bottom dwellers, many shallow water and small

speciesspecies Commonly observed in aquarium specimensCommonly observed in aquarium specimens For instance (in captivity):For instance (in captivity):

Found only in Heterondontidae, Scyliorhinidae, Found only in Heterondontidae, Scyliorhinidae, Orectolobidae and RajiformesOrectolobidae and Rajiformes

Mainly bottom dwellers, many shallow water and small Mainly bottom dwellers, many shallow water and small speciesspecies

Commonly observed in aquarium specimensCommonly observed in aquarium specimens For instance (in captivity):For instance (in captivity):

The chain dogfish, S. retifer:

• Sexually mature at 500-520 mm (M-F)•Sperm can be stored over 800 days•2 eggs laid every 15 days• Eggs released at 18 mm length• Hatch at 106 mm, ~256 days

Oviparous FormsOviparous Forms

Cat shark eggs on coral

Cat shark egg case

Cat shark open egg case close-up

OviparityOviparity Females store sperm, fertilization occurs in shell glandFemales store sperm, fertilization occurs in shell gland Secrete egg case in shell glandSecrete egg case in shell gland Paired eggs or multiple eggs, depending on speciesPaired eggs or multiple eggs, depending on species Eggs in tough cases, attached to substrate, vegetationEggs in tough cases, attached to substrate, vegetation Slit in egg case for water/O2 circulationSlit in egg case for water/O2 circulation External yolk sac for gestation, becomes internal in late External yolk sac for gestation, becomes internal in late

stagesstages

Females store sperm, fertilization occurs in shell glandFemales store sperm, fertilization occurs in shell gland Secrete egg case in shell glandSecrete egg case in shell gland Paired eggs or multiple eggs, depending on speciesPaired eggs or multiple eggs, depending on species Eggs in tough cases, attached to substrate, vegetationEggs in tough cases, attached to substrate, vegetation Slit in egg case for water/O2 circulationSlit in egg case for water/O2 circulation External yolk sac for gestation, becomes internal in late External yolk sac for gestation, becomes internal in late

stagesstages

David Doubilet

Swell shark, Cephaloscyllium ventriosum: retained oviparitySwell shark, Cephaloscyllium ventriosum: retained oviparity

Egg cases split open at 3 stages of development:1.Immediately after egg-laying, 2. 3-4 months, yolk begins to be used, 3. 6-7 months, yolk absorbed internally, 4. Immediately post-hatch

1

3

2

4

ViviparityViviparity

Retain embryos in the uterus during Retain embryos in the uterus during entire period of developmententire period of development

Can be divided into placental and Can be divided into placental and aplacental aplacental

Retain embryos in the uterus during Retain embryos in the uterus during entire period of developmententire period of development

Can be divided into placental and Can be divided into placental and aplacental aplacental

Aplacental ViviparityAplacental Viviparity Also called ovoviviparousAlso called ovoviviparous No placental connectionNo placental connection Three typesThree types

Depend soley on yolk reservesDepend soley on yolk reserves OophagousOophagous Nourished through placental analoguesNourished through placental analogues

Also called ovoviviparousAlso called ovoviviparous No placental connectionNo placental connection Three typesThree types

Depend soley on yolk reservesDepend soley on yolk reserves OophagousOophagous Nourished through placental analoguesNourished through placental analogues

Black dogfish embryos Porbeagle embryo (oophagous)

Aplacental Viviparity - Yolk Dependency

Aplacental Viviparity - Yolk Dependency

Embryos depend solely on yolkEmbryos depend solely on yolkEmbryos still in the uterus (protection)Embryos still in the uterus (protection)Relatively small at birthRelatively small at birth

Embryos depend solely on yolkEmbryos depend solely on yolkEmbryos still in the uterus (protection)Embryos still in the uterus (protection)Relatively small at birthRelatively small at birth

Aplacental Viviparity - OophagyAplacental Viviparity - Oophagy

Ovary is huge, many small eggsOvary is huge, many small eggsUses yolk at first, then ingests other Uses yolk at first, then ingests other

eggseggs Fertilized and unfertilizedFertilized and unfertilized

Intrauterine cannibalismIntrauterine cannibalismLarge size at birthLarge size at birth

Ovary is huge, many small eggsOvary is huge, many small eggsUses yolk at first, then ingests other Uses yolk at first, then ingests other

eggseggs Fertilized and unfertilizedFertilized and unfertilized

Intrauterine cannibalismIntrauterine cannibalismLarge size at birthLarge size at birth

Placental AnaloguesPlacental AnaloguesMore efficient than just yolk-sacMore efficient than just yolk-sacTrophonemata structure grows from uterine Trophonemata structure grows from uterine

lining - lining - for nutrient supply, once embryo has absorbed all yolkfor nutrient supply, once embryo has absorbed all yolk

Trophonemata envelop anterior of embryoTrophonemata envelop anterior of embryo enter gills/mouth, provide O2, waste removal and milkenter gills/mouth, provide O2, waste removal and milk

Uterine milk (histotroph) Uterine milk (histotroph) secreted by uterine epithelium, consists of lipids, proteinssecreted by uterine epithelium, consists of lipids, proteins

Found mainly in BatoidsFound mainly in Batoids Rhinoptera bonasus, Dasyatis sabina, Urolophus lobatusRhinoptera bonasus, Dasyatis sabina, Urolophus lobatus

More efficient than just yolk-sacMore efficient than just yolk-sacTrophonemata structure grows from uterine Trophonemata structure grows from uterine

lining - lining - for nutrient supply, once embryo has absorbed all yolkfor nutrient supply, once embryo has absorbed all yolk

Trophonemata envelop anterior of embryoTrophonemata envelop anterior of embryo enter gills/mouth, provide O2, waste removal and milkenter gills/mouth, provide O2, waste removal and milk

Uterine milk (histotroph) Uterine milk (histotroph) secreted by uterine epithelium, consists of lipids, proteinssecreted by uterine epithelium, consists of lipids, proteins

Found mainly in BatoidsFound mainly in Batoids Rhinoptera bonasus, Dasyatis sabina, Urolophus lobatusRhinoptera bonasus, Dasyatis sabina, Urolophus lobatus

Placental ViviparityPlacental Viviparity Most advanced formMost advanced form Yolk-sac attach to uterine wallYolk-sac attach to uterine wall Provides high growth potentialProvides high growth potential Found in about 30% of sharks Found in about 30% of sharks Order Carchariniformes,Order Carchariniformes,

Triakidae, Hemigalidae, Triakidae, Hemigalidae, Carcharhinidae, SphyrnidaeCarcharhinidae, Sphyrnidae

Most advanced formMost advanced form Yolk-sac attach to uterine wallYolk-sac attach to uterine wall Provides high growth potentialProvides high growth potential Found in about 30% of sharks Found in about 30% of sharks Order Carchariniformes,Order Carchariniformes,

Triakidae, Hemigalidae, Triakidae, Hemigalidae, Carcharhinidae, SphyrnidaeCarcharhinidae, Sphyrnidae

Placental ViviparityPlacental ViviparityStage 1: Preimplantation

• Uterine wall unmodified• Embryo utilizing yolk sac • Vascularization present in mucosa

Stage 2: Early implantation• Occurs at 70-85 mm in

Rhizoprionodon terraenovae• Egg envelope, ee, loosely attached Uterine wall has become modified with villi, V

ys- yolk sac, V – uterine villi, Lp – Lamina propriaLA - lymphoid aggregates, Ve – vascular elements,

Stage 3: Later Gestation• Yolk sac and Villi vascularly connected, exchange is two way• Embryonic wastes taken up, unlimited maternal nutrients flow into embryo

Male Reproductive SystemMale Reproductive System

Consists of Consists of testes, genital ducts, testes, genital ducts, urogenital papilla, siphon sacs, urogenital papilla, siphon sacs, claspersclaspers

Testes are paired, anterior end of Testes are paired, anterior end of coelomcoelom Vary in size during the yearVary in size during the year Three main morphologies Three main morphologies

Radial, Diametric, CompoundRadial, Diametric, Compound

Consists of Consists of testes, genital ducts, testes, genital ducts, urogenital papilla, siphon sacs, urogenital papilla, siphon sacs, claspersclaspers

Testes are paired, anterior end of Testes are paired, anterior end of coelomcoelom Vary in size during the yearVary in size during the year Three main morphologies Three main morphologies

Radial, Diametric, CompoundRadial, Diametric, Compound

Male Reproductive SystemMale Reproductive System

Male Reproductive SystemMale Reproductive System

Spermatogenesis occurs in testes in the Spermatogenesis occurs in testes in the ampullaeampullae

Spermatocyst is made up of many Spermatocyst is made up of many spermatoblasts, composed of Sertoli spermatoblasts, composed of Sertoli cells and their germ cellscells and their germ cells

Spermatocyst bursts, Sertoli cells Spermatocyst bursts, Sertoli cells fragment, spermatozoa released and fragment, spermatozoa released and conveyed through epididymis and into conveyed through epididymis and into the ductus deferensthe ductus deferens

Spermatogenesis occurs in testes in the Spermatogenesis occurs in testes in the ampullaeampullae

Spermatocyst is made up of many Spermatocyst is made up of many spermatoblasts, composed of Sertoli spermatoblasts, composed of Sertoli cells and their germ cellscells and their germ cells

Spermatocyst bursts, Sertoli cells Spermatocyst bursts, Sertoli cells fragment, spermatozoa released and fragment, spermatozoa released and conveyed through epididymis and into conveyed through epididymis and into the ductus deferensthe ductus deferens

Male Reproductive SystemMale Reproductive System

Male Reproductive SystemMale Reproductive System

Male Reproductive SystemMale Reproductive System

Morphological differences in both the Morphological differences in both the epididymis and claspers between epididymis and claspers between mature and immature malesmature and immature males

Most species only insert one clasperMost species only insert one clasper Sharp hook/spurSharp hook/spur

Rotate clasper to form a connection Rotate clasper to form a connection between clasper apopyle and urogenital between clasper apopyle and urogenital papillapapilla

Morphological differences in both the Morphological differences in both the epididymis and claspers between epididymis and claspers between mature and immature malesmature and immature males

Most species only insert one clasperMost species only insert one clasper Sharp hook/spurSharp hook/spur

Rotate clasper to form a connection Rotate clasper to form a connection between clasper apopyle and urogenital between clasper apopyle and urogenital papillapapilla

Male Reproductive SystemMale Reproductive System

Male Reproductive SystemMale Reproductive System

Sperm are packed in rounded or tubular Sperm are packed in rounded or tubular matricesmatrices Spermatophores - sperm encapsulated in a Spermatophores - sperm encapsulated in a

matrix (protection, etc)matrix (protection, etc) Spermozeugma - sperm embedded but Spermozeugma - sperm embedded but

unencapsulatedunencapsulatedLeydig glandLeydig glandMarshall’s glandMarshall’s gland

Sperm are packed in rounded or tubular Sperm are packed in rounded or tubular matricesmatrices Spermatophores - sperm encapsulated in a Spermatophores - sperm encapsulated in a

matrix (protection, etc)matrix (protection, etc) Spermozeugma - sperm embedded but Spermozeugma - sperm embedded but

unencapsulatedunencapsulatedLeydig glandLeydig glandMarshall’s glandMarshall’s gland

Female Reproductive SystemFemale Reproductive System

Ovaries at anterior end of systemOvaries at anterior end of systemOviducts run the length of bodyOviducts run the length of bodyShell gland within oviductsShell gland within oviducts

secrete egg membranes/shells and stores secrete egg membranes/shells and stores spermsperm

Uterus at posterior end of oviducts, Uterus at posterior end of oviducts, houses developing embyroshouses developing embyros Develop villi for gas/waste/nutrient Develop villi for gas/waste/nutrient

exchangeexchange

Ovaries at anterior end of systemOvaries at anterior end of systemOviducts run the length of bodyOviducts run the length of bodyShell gland within oviductsShell gland within oviducts

secrete egg membranes/shells and stores secrete egg membranes/shells and stores spermsperm

Uterus at posterior end of oviducts, Uterus at posterior end of oviducts, houses developing embyroshouses developing embyros Develop villi for gas/waste/nutrient Develop villi for gas/waste/nutrient

exchangeexchange

Female Reproductive SystemFemale Reproductive System

Female AnatomyFemale Anatomy

Female Reproductive AnatomyDogfish sharkFemale Reproductive AnatomyDogfish shark

• Visible under left lobe of liver• Yolk-sac viviparous, 3-4 embryos/uterus

– create a “candle” containing embyros

• Ova and Shell glands visible• Large developing Ova

OvaOva

External oocytes found on epigonal External oocytes found on epigonal organ in gymnovarium type ovary, large organ in gymnovarium type ovary, large ovaova

Internal ova (Lamnid sharks) release Internal ova (Lamnid sharks) release oocytes through ostium into oviducts, oocytes through ostium into oviducts, small ovasmall ova

External oocytes found on epigonal External oocytes found on epigonal organ in gymnovarium type ovary, large organ in gymnovarium type ovary, large ovaova

Internal ova (Lamnid sharks) release Internal ova (Lamnid sharks) release oocytes through ostium into oviducts, oocytes through ostium into oviducts, small ovasmall ova

Elasmobranch Sperm StorageElasmobranch Sperm StorageElasmobranch Sperm StorageElasmobranch Sperm StorageSperm stored in shell Sperm stored in shell

glandsglandsThree typesThree types

Non-storage: Non-storage: Alopias Alopias vulpinus, Lamna nasusvulpinus, Lamna nasus

Short Term: Short Term: Prionace Prionace glaucaglauca

Long Term: Long Term: Carcharinus Carcharinus obscurus, Sphyrna lewiniobscurus, Sphyrna lewini

Sperm stored in shell Sperm stored in shell glandsglands

Three typesThree types Non-storage: Non-storage: Alopias Alopias

vulpinus, Lamna nasusvulpinus, Lamna nasus Short Term: Short Term: Prionace Prionace

glaucaglauca Long Term: Long Term: Carcharinus Carcharinus

obscurus, Sphyrna lewiniobscurus, Sphyrna lewini

Non-storage sperm Non-storage sperm Packed in lumen or shallow tubesPacked in lumen or shallow tubesFor immediate use in oviductFor immediate use in oviduct

Packed in lumen or shallow tubesPacked in lumen or shallow tubesFor immediate use in oviductFor immediate use in oviduct

Long Term StorageLong Term Storage

Densely packed Densely packed spermsperm

Deep in glandsDeep in glandsNot highly visible in Not highly visible in

stainsstainsFound in nomadic Found in nomadic

sharkssharksStored for 10-15 Stored for 10-15

monthsmonths

Densely packed Densely packed spermsperm

Deep in glandsDeep in glandsNot highly visible in Not highly visible in

stainsstainsFound in nomadic Found in nomadic

sharkssharksStored for 10-15 Stored for 10-15

monthsmonths

Reproductive CyclesReproductive Cycles

Poorly understoodPoorly understoodConsist of ovarian cycle and gestation Consist of ovarian cycle and gestation

periodperiod May run consecutively or concurrentlyMay run consecutively or concurrently

Poorly understoodPoorly understoodConsist of ovarian cycle and gestation Consist of ovarian cycle and gestation

periodperiod May run consecutively or concurrentlyMay run consecutively or concurrently

Mating and Reproductive BehaviorMating and Reproductive BehaviorBehavioral and biological changesBehavioral and biological changes

Biting of females pectoral fins, peduncleBiting of females pectoral fins, peduncle Aggregations of mature adults Aggregations of mature adults Changes in tooth morphology with the onset Changes in tooth morphology with the onset

of mating seasonof mating seasonLarge variations in reproductive season, Large variations in reproductive season,

gestation period, frequency of matinggestation period, frequency of mating gestation periods range 3 months to gestation periods range 3 months to

over 3 yearsover 3 years

Behavioral and biological changesBehavioral and biological changes Biting of females pectoral fins, peduncleBiting of females pectoral fins, peduncle Aggregations of mature adults Aggregations of mature adults Changes in tooth morphology with the onset Changes in tooth morphology with the onset

of mating seasonof mating seasonLarge variations in reproductive season, Large variations in reproductive season,

gestation period, frequency of matinggestation period, frequency of mating gestation periods range 3 months to gestation periods range 3 months to

over 3 yearsover 3 years

Courtship BehaviorsCourtship BehaviorsPre-coupling behaviors documented in Pre-coupling behaviors documented in

Ginglymostoma cirratum Ginglymostoma cirratum included:included:Type 1: Type 1: occurred w/stationary female, shallow depth occurred w/stationary female, shallow depth

Short duration, females either avoided or accepted Short duration, females either avoided or accepted coupling behaviorcoupling behavior

Type 2: Type 2: Occurred w/swimming females, Following Occurred w/swimming females, Following behavior, multiple males, Longer duration from 1 to 90 behavior, multiple males, Longer duration from 1 to 90 minutesminutes

Type 3Type 3: Pectoral fin grasped by male, initiates : Pectoral fin grasped by male, initiates coupling behaviorcoupling behavior

Pre-coupling behaviors documented in Pre-coupling behaviors documented in Ginglymostoma cirratum Ginglymostoma cirratum included:included:

Type 1: Type 1: occurred w/stationary female, shallow depth occurred w/stationary female, shallow depth Short duration, females either avoided or accepted Short duration, females either avoided or accepted coupling behaviorcoupling behavior

Type 2: Type 2: Occurred w/swimming females, Following Occurred w/swimming females, Following behavior, multiple males, Longer duration from 1 to 90 behavior, multiple males, Longer duration from 1 to 90 minutesminutes

Type 3Type 3: Pectoral fin grasped by male, initiates : Pectoral fin grasped by male, initiates coupling behaviorcoupling behavior

Courtship BehaviorCourtship Behavior

Jeffrey C. Carrier

Lemon Sharks:Schooling, following behavior

Samuel Gruber

Nurse Sharks:Pectoral Grasp

Manta Rays:The waltz

Mantaray.com

Mating BehaviorsMating Behaviors

Once competition and courtship are overOnce competition and courtship are overMany methods of mating Many methods of mating

Smaller sharks- wrap around female with tail, Smaller sharks- wrap around female with tail, bringing clasper ventrally bringing clasper ventrally

Larger, less flexible sharks – put ventral Larger, less flexible sharks – put ventral surfaces together, clasper is flexed toward surfaces together, clasper is flexed toward cloacacloaca

Batoids – belly to belly, on the sea floor in Batoids – belly to belly, on the sea floor in benthic species, in water column for pelagic benthic species, in water column for pelagic raysrays

Once competition and courtship are overOnce competition and courtship are overMany methods of mating Many methods of mating

Smaller sharks- wrap around female with tail, Smaller sharks- wrap around female with tail, bringing clasper ventrally bringing clasper ventrally

Larger, less flexible sharks – put ventral Larger, less flexible sharks – put ventral surfaces together, clasper is flexed toward surfaces together, clasper is flexed toward cloacacloaca

Batoids – belly to belly, on the sea floor in Batoids – belly to belly, on the sea floor in benthic species, in water column for pelagic benthic species, in water column for pelagic raysrays

Mating Behavior on filmMating Behavior on film

Manta Mating http://www.youtube.com/watch?v=W_rQAmPQBV8

ConclusionConclusion

General trend from oviparity to viviparityGeneral trend from oviparity to viviparity Small number of youngSmall number of young

Reproductive adaptations now threaten Reproductive adaptations now threaten survivalsurvival Delayed maturity, long reproductive cycles, Delayed maturity, long reproductive cycles,

small broodssmall broods

General trend from oviparity to viviparityGeneral trend from oviparity to viviparity Small number of youngSmall number of young

Reproductive adaptations now threaten Reproductive adaptations now threaten survivalsurvival Delayed maturity, long reproductive cycles, Delayed maturity, long reproductive cycles,

small broodssmall broods

References:References:Cavaliere, A. 1955. Embrione di Trygon violacea. Boll. Pesca e Idrobiol. 9:197-200.Cavaliere, A. 1955. Embrione di Trygon violacea. Boll. Pesca e Idrobiol. 9:197-200.

Chen, W.K. and K.M. Liu. 2006. Reproductive biology of whitespotted bamboo shark Chen, W.K. and K.M. Liu. 2006. Reproductive biology of whitespotted bamboo shark Chiloscyllium plagiosum in northern waters off Taiwan. Fisheries Science 72: 1215–1224.Chiloscyllium plagiosum in northern waters off Taiwan. Fisheries Science 72: 1215–1224.

Pratt, H.L. Jr. 1993. The storage of spermatozoa in the oviducal glands of western North Atlantic Pratt, H.L. Jr. 1993. The storage of spermatozoa in the oviducal glands of western North Atlantic sharks. Environmental Biology of Fishes 38: 139-149sharks. Environmental Biology of Fishes 38: 139-149

Hamlett, W. C., A.M. Eulitt, R.L. Jarrell and M.A. Kelly. 1993. Uterogestation and placentation in Hamlett, W. C., A.M. Eulitt, R.L. Jarrell and M.A. Kelly. 1993. Uterogestation and placentation in elasmobranchs. J Exp Zoo. 266, No. 5, pp. 347-367.elasmobranchs. J Exp Zoo. 266, No. 5, pp. 347-367.

J. C. Carrier, H. L. Pratt, Jr. and L. K. Martin. 1994. Group Reproductive Behaviors in Free-Living J. C. Carrier, H. L. Pratt, Jr. and L. K. Martin. 1994. Group Reproductive Behaviors in Free-Living Nurse Sharks, Ginglymostoma Cirratum. Copeia, No. 3, pp. 646-656.Nurse Sharks, Ginglymostoma Cirratum. Copeia, No. 3, pp. 646-656.

M.P. Francis and J.D. Stevens. 2000. Reproduction, embryonic development, and growth of the M.P. Francis and J.D. Stevens. 2000. Reproduction, embryonic development, and growth of the porbeagle shark, porbeagle shark, Lamna nasus, Lamna nasus, in the southwest Pacific Ocean. Fish. Bull. 98, pp. 41–63.in the southwest Pacific Ocean. Fish. Bull. 98, pp. 41–63.

S.J. Joungand H.H. Hsu. 2005. Reproduction and Embryonic Development of the Shortfin Mako, S.J. Joungand H.H. Hsu. 2005. Reproduction and Embryonic Development of the Shortfin Mako, Isurus oxyrinchus Isurus oxyrinchus Rafinesque, 1810, in the Northwestern Pacific. Zoological Studies 44, no. 4, Rafinesque, 1810, in the Northwestern Pacific. Zoological Studies 44, no. 4, pp. 487-496.pp. 487-496.

Cavaliere, A. 1955. Embrione di Trygon violacea. Boll. Pesca e Idrobiol. 9:197-200.Cavaliere, A. 1955. Embrione di Trygon violacea. Boll. Pesca e Idrobiol. 9:197-200.

Chen, W.K. and K.M. Liu. 2006. Reproductive biology of whitespotted bamboo shark Chen, W.K. and K.M. Liu. 2006. Reproductive biology of whitespotted bamboo shark Chiloscyllium plagiosum in northern waters off Taiwan. Fisheries Science 72: 1215–1224.Chiloscyllium plagiosum in northern waters off Taiwan. Fisheries Science 72: 1215–1224.

Pratt, H.L. Jr. 1993. The storage of spermatozoa in the oviducal glands of western North Atlantic Pratt, H.L. Jr. 1993. The storage of spermatozoa in the oviducal glands of western North Atlantic sharks. Environmental Biology of Fishes 38: 139-149sharks. Environmental Biology of Fishes 38: 139-149

Hamlett, W. C., A.M. Eulitt, R.L. Jarrell and M.A. Kelly. 1993. Uterogestation and placentation in Hamlett, W. C., A.M. Eulitt, R.L. Jarrell and M.A. Kelly. 1993. Uterogestation and placentation in elasmobranchs. J Exp Zoo. 266, No. 5, pp. 347-367.elasmobranchs. J Exp Zoo. 266, No. 5, pp. 347-367.

J. C. Carrier, H. L. Pratt, Jr. and L. K. Martin. 1994. Group Reproductive Behaviors in Free-Living J. C. Carrier, H. L. Pratt, Jr. and L. K. Martin. 1994. Group Reproductive Behaviors in Free-Living Nurse Sharks, Ginglymostoma Cirratum. Copeia, No. 3, pp. 646-656.Nurse Sharks, Ginglymostoma Cirratum. Copeia, No. 3, pp. 646-656.

M.P. Francis and J.D. Stevens. 2000. Reproduction, embryonic development, and growth of the M.P. Francis and J.D. Stevens. 2000. Reproduction, embryonic development, and growth of the porbeagle shark, porbeagle shark, Lamna nasus, Lamna nasus, in the southwest Pacific Ocean. Fish. Bull. 98, pp. 41–63.in the southwest Pacific Ocean. Fish. Bull. 98, pp. 41–63.

S.J. Joungand H.H. Hsu. 2005. Reproduction and Embryonic Development of the Shortfin Mako, S.J. Joungand H.H. Hsu. 2005. Reproduction and Embryonic Development of the Shortfin Mako, Isurus oxyrinchus Isurus oxyrinchus Rafinesque, 1810, in the Northwestern Pacific. Zoological Studies 44, no. 4, Rafinesque, 1810, in the Northwestern Pacific. Zoological Studies 44, no. 4, pp. 487-496.pp. 487-496.