Reproduction of fish and reptiles

Question 1

Where do the testes lie?

Answer 1

The gonads lie near the cranial pole of the kidney in many species but in Snakes the gonads caudal to gall bladder

Question 2

Does puberty depend on age or size?

Answer 2

Onset sexual maturity varies and depends on size not age

The diet plays an important role and you can push puberty with the diet

Question 3

In squamates which testis lies cranially?

Answer 3

Right cranial to Left in many squamates

Question 4

Do reptiles have accessory sex glands?

Answer 4

No

Question 5

Which reptiles have a penis and which have hemipenes?

Answer 5

Penis: Chelonians

Hemi-penes: Lizards, snakes

Question 6

Where do the hemipenes lie?

Answer 6

Hemipenes are paired and kept in the tail base by the retractor penis muscle. During copulation the hemipenes is everted and becomes erect (vascular erection).
They may also have sharp keratinised spines or flounces

Question 7

What is the sexual segment?

Answer 7

The sexual segment in the Distal convoluted tubules of the kidney which are only present in the breeding season. The cells that are there go from cuboidal to columnar and increase in size 2-4x. Large eosinophillic granules secreted into lumen

Question 8

What is the function of the sexual segment?

Answer 8

Separate urine/semen copulation

Copulatory plug

Question 9

Do females have two ovaries?

Answer 9

Some missing left oviduct

Question 10

Do reptile have a uterus?

Answer 10

No

Question 11

Where do the oviducts empty?

Answer 11

Oviducts empty into cloaca on the genital papillae

Question 12

What do the oviducts consist of?

Answer 12

The oviducts consist of the: infundibulum, uterine tube, isthmus, uterus/shell gland and vagina but not all parts are present in all species.

Question 13

Can reptiles be hermaphrodites?

Answer 13

Reptiles can also present hermaphroditism (intersex) where the females have a hemipene with or without ovitestes, for example the pit viper where intersexes are more common than true females and all pregnant animals are intersexes.

Question 14

What is Parthenogenesis?

Answer 14

Is a type of asexual reproduction in which the offspring develops from unfertilized eggs
Occurs in around 30 spp of lizards

Question 15

Where does fertilisation occur?

Answer 15

Occurs in the cranial oviduct and like birds the sperm is viable at body temperature so can be stored for up to 6 years
Females can store sperm from multiple males and multiple matings

Question 16

What does oviparous mean?

Answer 16

Oviparous – egg-laying (all chelonians, most squamates)

Question 17

Define viviparous, what are the two subtypes?

Answer 17

Viviparous – live-bearing (20% squamates)
1. Lecithotrophy
Egg in tract until hatching (nutrients mostly from yolk)
Hatch at time of parturition
2. Matrotrophy
Livebearing
Chorioallantoic placenta (nutrients from mother)

Question 18

What are the pros and cons of viviparous young bearing in reptiles?

Answer 18

With viviparous bearing the foetus takes up space in the mother which limits GI function so little feeding can take place in the latter stages and only really allows one clutch per year. However in colder climates it will keep embros warm during incubation.

Question 19

How long do eggs gestate before hatching?

Answer 19

1-2 months

Question 20

What gonadotrophins do chelonians have?

Answer 20

FSH & LH in chelonians – similar role to mammals
FSH: ovarian growth, follicular development
LH surge: ovulation – many chelonians

Question 21

What gonadotrophins do squamates have?

Answer 21

1 gonadotropin - FSH-like compound

No LH equivalent

Question 22

What is the purpose of oestrogen and progesterone?

Answer 22

Oestrogen is involved in yolk development like it is in birds and in seasonal breeders it is high in the early season for vitellogenesis.

Progesterone in chelonians surges before ovulation like birds. Progesterone Inhibits oviduct contraction, prevents expulsion embryo. In seasonal breeders: high after ovulation, during gestation in viviparous spp.

Question 23

What is the stimulus in seasonal breeders?

Answer 23

The stimulus is temperature change:
Temperate spp: Spring after cooling period (hibernation/brumation)
Tropical boidae: Cooler period breeding (don’t hibernate), or year round
If rainfall seasonal, rainfall is trigger

Question 24

Birds need priming before mating, do reptiles need this?

Answer 24

Female primed for Egg production by exposure to sexually mature male before mating
If no priming will make shell-less or very thin shelled eggs
Males exposed to females stimulates gonadal development

Question 25

Name the three types of reproductive cycle

Answer 25

Continuous (Tropical Zone)

Associated (Subtropical or Temperate Zone)
Male and Female: gonadal/hormonal events coincide. Gonadal activity at time of mating, long season.

Dissociated (Some Temperate Zone)
Female and male repro events not linked
Males make sperm in summer, store over winter and copulate in the spring and the female will store the sperm until they ovulate
Short active season

Question 26

In lizards high incubation temperature is …………….. determining.

Answer 26

Male

Question 27

In chelonians high incubation temperature is …………….. determining.

Answer 27

Female

Question 28

How is temperature dependant sex determination believed to work?

Answer 28

Appropriate temp for females, produce more aromatase (T to E2)
Appropriate temp males, more 5α-reductase (T to DHT)

Question 29

How are reptiles sexed?

Answer 29

Cloacal probing
Ultrasonography - Particularly if female and has eggs
Endoscopy (surgical sexing)

Question 30

Where do the testes lie in fish and how do they exit?

Answer 30

Paired intra-abdominal testes (most)
Testicular duct (not salmonids where sperm are produced into the body cavity and exit at the caudal part of the coelum)

Question 31

Name the two types of female fish oviducts

Answer 31

Gymnovarian: oocytes into coelom via oviduct funnel like remnants (salmon)
Cystovarian: ovarian ducts (not oviducts)

Question 32

Do gonadotrophins effect fish oocyte development?

Answer 32

No

Question 33

Gestation of fish can be from days to months, what affects it?

Answer 33

Water temp.

Question 34

Very few fish are viviparous, name the two types of live bearer

Answer 34

1. Lecithotrophy: Nutrition from yolk sac
   Fertilized eggs stay in body of parent (majority); doesn’t have to be female parent
2. Matrotrophy: Placenta-like structure (very rare)
   Oophagy- embryos feed on eggs produced by the ovary
   Can have Intrauterine cannibalism

Question 35

How does the fish hypothalamus send GnRH to the pituitary?

Answer 35

No hypophysial portal system so GnRH produced by the hypothalamus by direct innervation

Question 36

Fish do not have LH and FSH, instead they have……

Answer 36

1. GtH-I (FSH-like)
   Causes vitellogenesis, early gonadal development, release GtH-II
   Binds theca/granulosa of follicles, T–> E2(stimulates production of vitellogenin, the egg yolk precursor protein)
2. GtH-II (LH-like)
   final oocyte maturation, ovulation
   progestins from granulosa cells

Question 37

In fish what do oestrogen and progesterone do?

Answer 37

Oestrogen goes to the liver to stimulate vitellogenesis

Progesterone - retain offspring in repro tract (viviparous spp)