Fish and reptile reproduction Flashcards
Where are the gonads located in snakes?
Near gall bladder
Where are the gonads in most reptiles?
Near cranial pole of kidney
What determines onset of sexual maturity in reptiles?
Size (and so is linked with diet)
Describe the male reproductive anatomy in reptiles
- Intra-abdominal testes (right cranial to left)
- No accessory sex glands
- Phallus fibrocollagenous elastic erectile tissue
- Single or 2 hemipenes
What species of reptiles have a single penis?
Chelonians
What species of reptiles have 2 hemipenes?
- Lizards
- Snakes
Describe squamate hemipenes
- Paired, kept in tail base by retractor penis muscle
- In copulation evert hemipenis on one side
- Erection is vascular
- Sherp keratinised spines or flounces on surface
Describe the sexual segments
- In distal convoluted tubules of kidney
- Only actively present in breeding season
- Cuboidal to columnar cell change
- Large eosinophilic granules secreted into lumen
- Function unknown, amy be to separate urine and semen for copulation or form copulatory plug
Describe female reptile anatomy
- Ovaries paired in most
- Snake: elongated ovaries (some missing left oviduct)
- No true uterus
- Oviducts into cloaca: genital papillae
What is the function of the oviducts in reptiles?
Secrete albumin to produce the shell
What are the elements of the oviducts in reptiles?
- Not all elements in all species
- Infundibulum
- Uterine tube
- Isthmus
- Uterus/shell gland
- Vagina
What is a vitellogenic follicle in reptiles?
One that is close to ovulation
Describe intersexuality in reptiles
- Can be either true males/females or intersex (hermaphrodites)
- Females with hemipenes
- +/- ovotestes
- e.g. pit viper, all pregnant animals are intersex
Describe parthenogenesis in reptiles
- 30 species of lizards (incl. komodo, gecko, whiptail)
- No mating
- Chormosomes in unfertilised egg replicate in egg
- Embryo develops
- Females still display courting and pseudocopulation
- Some species use sexual and asexual reproduction
Describe male reproductive anatomy in fish
- Paired intra-abdominal testes
- Testicular duct (not salmonids)
What is the function of the testicular duct in fish?
Carries sperm outside body
How are sperm released by salmonids?
- Released into body cavity
- Then released by pores
What are the 2 types of female reproductive anatomy found in fish?
- Gymnovarian
- Cystovarian
Describe gymnovarian
Oocytes in coelom to oviduct funnel remants rather than via tube
Describe cystovarian
Ovarian ducts (not oviducts) grow posteriorly to form new ducts, oviducts regress and not present in adult form
How do the ovarian ducts of cystovarians form?
Peritoneal folds wrapped around each ovary
List the stages of reproduction in reptiles
- Oocyte development
- Vitellogenesis
- Oocyte maturation
- Ovulation
- Fertilisation
- Oviposition/parturition
Describe oocyte development in reptiles
- Majority of reprocdution
- Pre-vitellogqenic follicle developmentq
Describe vitellogenesis in reptile reproduction
- Yolk production
- Yolk proteins made in liver, deposited in developing oocyte in ovary
Describe fertilisation in reptiles
- Cranial oviduct
- Sperm viable at body temperature
- Sperm from multiple males can be stored hence can have multiple matings
- Higher fertility when bred in active cycle
How long can sperm be stored in reptiles?
Up to 6 years, so fertilisation can occur years after contact with male
Define oviparous
Egg laying
Define viviparous
Live bearing, can be lecithotrophy or matrotrophy
Define lecithotrophy
Egg in tract until hatching (nutrients mostly from yolk, hatch at time of parturition)
Define matrotrophy
Live bearing, chorioallantoic placenta (nutrients from mother)
What are the disadvantages of viviparity?
- Foetus takes up space limiting GI tract function
- Greater drain on maternal resources
- One clutch/year vs oviparous >1
What are the advantages of viviparity?
- Common in cold climates as keeps embryos warm during incubation
- higher chance of offspring survival
How long is gestation in viviparous species approximately?
1.5-6 months
Why is gestation hard to determine in reptiles?
- Sperm storage, unsure of when fertilisation takes place
- Mating event not good way of determining fertilisation
How long is incubation in oviparous species?
1-2 months typically, can be up to 270 days or more
What is the role of FSH and LH in chelonians?
- Similar to mammals
- FSH: ovarian growth and follicular development
- LH: surge stimulating ovulation
What are the reproductive hormones present in squamates?
- Only FSH-like compound (no LH)
- Oestrogen
- Progesterone
What is the role of oestrogen in reptiles?
- Yolk development
- Seasonal breeders high in early season (vitellogenesis)
Describe the role of progesterone in reptiles
- Ovulation tiggered by progesterone surge in chelonians
- Made by CL in those that have it
- Inhibits oviduct contraction (preventing embryo expulsion)
- In all seasonal breeders high after ovulation
- High during gestation in viviparous species
What reptilian species have a CL?
- All viviparous
- Not all chelonians make progesterone
List the stages of reproduction in fish
- Oocyte development
- Vitellogenesis
- Oocyte maturation
- Spawning
- Recovery
Describe oocyte development in fish
- Gonadotrophin independent
- Body size dependent (affected by nutrition)
Describe vitellogenesis in fish
Yolk production, is longest phase
Describe oocyte maturation in fish
Requires prostaglandins
Descrbe spawning in fish
- Release eggs and sperm
- Optimum environment for this is species dependent
- Mating behaviour
Describe post-spawing recovery in fish
- Body condition restored
- New oocyte development
Describe oviparity in fish
- Most common (97% of fish)
- Most use external fertilisation
Describe viviparity in fish
- Fewer young produced
- Internal fertilisation
- Lectitrophy or matrotrophy
Describe lecithotrophy in fish
- Nutrition from yolk sac
- Fertilised eggs stay in body of parent (majority)
- Does not have to be female parent e.g. seahorses
Describe matrotrophy in fish
- Placenta like structure (very rare)
- Oophagy and intrauterine cannibalism common
Describe reproductive endocrinology in fish in general
- No hypophyseal portal system
- GnRH to pituitary via direct innervation
- Pituitary releases GTH-I and GTH-II
What are the actions of GTH-I in female fish?
- GTH-I: stimulates ovary to release gonadohormones
- Positive feedback effect on pit stimulating release of GTH-II
What are the actions fo oestrogen and progesterone in female fish?
- Oestrogen: vitellogenesis
- Progesterone: maintaining offspring in live bearers
Explain how GTH-I carries out its action
- Oogenesis
- Stimulates release of gonadohormones
- Binds to theca and granulosa cells in follicles
- Testosterone production (theca) to E2 (granulosa)
- E2 to liver to stimulate vitellogenin production
Describe the actions fo GTH-II in the female fish
- Oocyte maturation/ovulatioin
- Progestins from granulosa cells
Describe the impact of season in reptile reproductioin
- Temperature cahnge is stimulus for seasonality
- Temperate spp.: spring after cooling period
- Tropical boidae: cooler period breeding or year round
- If rainfal is seasonal then rainfall is trigger
Describe the environmental stimuli in reptile reproduction
- Female primed by exposure to sexually mature male before mating (triggers egg prod)
- Males exposed to females stimulates gonadal development and spermatogenesis
- Humidity and barometric pressure
- Photoperiod
List the environmental factors affecting fish reproduction
- Photoperiod
- Temperature
- Presence/absence of opposite sex
- Currents, tides, stages of moon
- Spawning area
For the following chromosomal arrangements possible in reptiles, give the sex
a. ZZ
b. ZW
c. XX/XY
d. ZZ/ZW
e. ZWW
f. ZZZZ
g. ZZWW
a. male
b. female
c. male heteromorphic
d. female heteromorphic
e. female
f. male
g. female
Explain how temperature affects sex determination
- Affects enzyme activity
- Appropriate tem for females, produce more aromatase, T converted to E2
- Appropriate temp for males, produce more 5-alpha reductase (T converted to DHT)
Describe sexual dimorphism in chelonians
- Shell dimorphism
- male concave plastron for mating
- Tail dimorphism - male longer tail in some species
- Vent more distal in males
List sexing methods in squamates
- Manual eversion of hemipenes
- Hydrostatic eversion
- Cloacal probing
- Endocrinology
- Ultrasonography
- Endoscopy
Describe the manual eversion of hemipenes method of sexing squamates
- Not recommended
- Roll thumb up base of tail towards cloaca
- Pop out hemipene
- Can cause injury
Describe hydrostatic eversion of hemipenes in squamates
- Inject saline just below hemipene
- Increases pressure causing eversion
- Not recommended as can cause injury
Describe ultrasonography in sexing of squamates
- Particularly if female with eggs
- Requires mature female to definitively say is female
Describe cloacal probing for sexing of squamates
- Instrument into inverted hemipene
- Short distance = females
- Long distance = male
- Need to be experienced
- Seminal plugs in males can give misleading results
Describe blood endocrinology for sexing of squamates
- Breeding season has higher hormone production
- Look for sex hormones
Describe endocopy for sexing of squamates
- Surgical
- Anaesthetic risks
- Potential for surgical complications
What are the different reproductive models possible in fish?
- Separate male and female
- Hermaphodites
- Parthenogenesis
Describe fish sex determination
- Genetic, present in 10% of fish
- Male XY, female ZW
- Some temperature depenedence
List the types of reproductive cycles in reptiles
- Continuous
- Associated
- Dissociated
Describe continuous breeding in reptiles
- Tropical zone
- Throughout year
- minimal photoperiod or temp fluctuation in place of origin, hence no advantage to being seasonal
Describe associated reproductive cycles in reptiles
- Subtropical or temperate zone
- Male and female: gonadal/hormonal events coincide
- Gonadal activity at time of mating
- Long active season
- Emergence from hibernation is trigger
Describe dissociated reproductive cycles in reptiles
- Some temperate zone
- female and male reproductive events not linked
- Gonadal activity does not coincide with mating
- Short active season
- Mate before gonadogenesis
- Sperm used for fertilisation are from previous active season, produced in summer and stored in male over witner and used in next season
- Female can also carry sperm until ovulation takes place
List the different cycles of reproduction in fish
- Can be 4 weeks to many years
- Some continous spring and summer
- Or once/year to many times a year
- Or once in lifetime (pacific salmon)
