Reproduction in reptiles, fish and small mammals

what determines sexual maturity in reptiles?

• size of the animal

• diet

what type of breeding do reptiles express

• seasonal - for when nutrients and temperature best suit having young offspring

where are the testes in squamates

• cranial to kidneys

where are the testes in chelonia

• dorsomedial coelomic cavity

which testes is more cranial in reptiles?

• right

are there accessory sex glands in male reptiles?

• no

what are the 2 types of reptilian phallus

• hemi-penes

  • penis

what species have hemi-penes?

• lizards

• snakes

how do animals reproduce with hemi-penes and penis?

• evert them to expose the inner, highly sensitive endothelium

what additional feature do some reptile phalluses have?

• keratinised spines

What does this show?

• the everted hemi-pene of a squamate

  • note they only have one

what is the sexual segment?

• distal convoluted kidney tubules which develop during the breeding season to release large eosinophilic granules into the lumen

what is the function of the sexual segment

• separate urine to semen

• copulatory plug

What is this demonstrating

• the sexual segment of the snake - the kidney appears to be abnormal, but this is normal during the breeding period

if we perform surgery on a snake and observe kidenys, as in the large image, should we be concerned

• not if it’s breeding season - expected change

• if it’s not breeding season, should consider potential pathologies

describe the ovaries of reptiles

• paired in most species

• R>L

what are the 5 parts of the oviduct in female reptiles

• ostrium

• aglandular segment

• magnum

• shell gland

• vagina

what does the oviduce empty into?

• cloaca

What is labelled here?

• OV = ovary

• KI = kidney - within the pelvic bones

• AD = adrenals

are these mature or prematre ovaries

• premature - very small with poorly distinguishable eggs

what are the 2 types of follicles we can observe in reptiles

• pre-vitellogenic follicles

• vitellogenic follicles

what are the 5 stages of female reptile reproduction

1. oocyte development

2. vitellogenesis

3. oocyte maturation

4. ovulation

5. oviposition/parturition

what develops in the first stage of female reptile development

• pre-vitellogenic follicle development

what takes place in vitellogenesis?

• yolk production

how does ovulation in reptiles and fish compare to species e.g. birds

• multiple eggs are released at the same time, not one at a time

what is involved in asexual reproduction in reptiles?

• no mating

• chromosome replication in the egg → embryo develops

what behaviour may a female display during asexual reproduction

• courting

• pseudocopulation

where does fertilisation take place in reptiles

• cranial oviduct

why are reptiles able to give birth without having come across a male

• able to store sperm in the body for months - years

• can mate with multiple males

what are oviparous reptiles

• egg-laying

what reptile speices are oviparous

• all chelonians

• most squamates

what are viviparous species

• live-bearing species

what is lecithotrophy

• the egg remains in the tract until hatching

• hatch at parturition

• in some squamate species

what is matrotrophy

• live-bearing reptiles

• have a chorioallantoic placenta - RARE

how long should viviparous reptile species gestation be?

• 1.5-6month

why is it hard to determine when gestation starts in reptiles?

• they can store sperm

what is the typical incubation of oviparous species

• 1-2 months

what hormones do chelonians have - reproductive ones

• FSH

• LH

what role do FSH and LH play in chelonians?

• similar to that of mammals

what hormones do squamates have - reproduction

• 1 gonadotrophin = FSH-like compount

do squamates have LH?

• NO

what role does oestrogen play in reptiles?

• yolk development

what role does progesterone play in reptiles?

• ovulatory surge in chelonians

in which type of reptilian species is there high progesterone during gestation?

• viviparous

what are 5 breeding stimuli ini reptiles?

• temperature change

• humidity

• day length

• presence of a mate

• environment

What does this demonstrate?

• follicular stasis

what is a concern of follicular stasis

• discomfort

• peritonitis risk if they burst/degrade → highly inflammatory

• pressure on other organs → reduced eating

what is the sex determinatino of snakes

• female = ZW

• male = ZZ

is there only one type of sex determination in lizards?

• no, highly variable!!!!!!!

what determines sex in reptiles (2)

• incubation temp

• choice of nest site determines sex ratio

in lizards what sex do the following conditions cause:

• high temp

• low temp

1. male

2. female

in chelonians what sex do the following conditions cause:

• high temp

  • low temp

1. female

2. male

in some chelonians and lizards what sex do the following conditions cause:

• extreme low + high temp

• intermediate temp

• female

• male

how can we often tell the sex of lizards?

• sexual dimorphism - large horns in males

what are 2 sexual dimorphisms of chelonians

• shell

• tail

what are 3 methods to sex squamates

• manual hemi-pene eversion

• hydrostatic hemi-pene eversion

• cloacal probing

Which of these methods for sex determination are NOT recommended:

• manual hemi-pene eversion

• hydrostatic hemi-pene eversion

• cloacal probing

1 + 2

what are 3 clinical sex determination methods in reptiles other than sexual dimorphism and cloacal probing

1. endocrinology

2. ultrasonography - females + eggs

3. endoscopy

what is the conclusion of fish reproduction

• highly variable

describe male fish reproductive anatomy

• paired intra-abdominal testes

• ductus deferens → UB → common urinary duct → genital pore

what is a gymnovarian fish

• oocytes → coelom → oviduct remnants

what is a cystovarian fish

• ovarian ducts (not oviducts)

what type of fish tend to be cystovarian

• many bony fish species

what are the 5 stages of fish female reproduction

1. oocyte development

2. vitellogenesis

3. oocyte maturation

4. spawning

5. recovery

what is oocyte development independent of

• gonadotrophin

what is the longest phase of fish reproduction in females?

• yolk production

what takes place in spawning?

• eggs and sperm are released - requires optimum environment

what modifies gestation in fish

• water temp

for oviparous fish species, where does fertilisation take place

• externally

for viviparous species, where does fertilisation take place

• internally

is the pregnant fish always the female?

• no can be male e.g. seahorse - lecithotrophy

describe fish breeding cycles

• highly variable

what are the hormones produced by the pituitay gland in fish

• GTH-I

• GTH-II

what is GTH-1 in fish, what does it cause and what feedback mechanism does it use?

• FSH like

• causes vitellogenesis and gonadal development

• positive feedback

what is GTH-II, what does it cause?

• LH-like

  • oocyte maturation and ovulation

are fish always one sex?

• no, simultaneously both biologically female and male in some species and can switch

what determines fish sex?

• genetics

• temperature

what are 5 environmental effects on fish reproduction

1. photoperiod

2. temperature

3. presence of opposite sex

4. currents, tides

5. proximity to spawning area

Describe the female rabbit reproductive anatomy

• no uterine body

• two uterine horns

• mesometrium fat storage

• vagina is long

why is it clinically relevant to note that female rabbits have a mesometrium fat storage

• this makes spaying difficult, especially as rabbit gets older

why is it important to note that the rabbit vagina is long surgically?

• need to ensure we don’t ligate it to avoid causing damage to the ureters and urinary bladder

describe the rabbit male reproductive anatomy

• scrotal sacs

• open inguinal canal

• penis is caudal to testicles

• no os penis

at what age do rabbit testicles descend

• 12 weeks old

why is it relevant that male rabbits have open inguinal canals

• the testicles are able to move in and out = voluntarily cryptorchid

what is important to note aobut the scrotal sac in rabbits

• it’s incredibly thin - easily damaged, especially by other males

what is sexual maturity dependent on in rabbits?

• breed

what is the typical age of sexual maturity in rabbits

• 4-6months

how does puberty and sexual maturity in rabbits correlate?

• puberty often comes before sexual maturity

at what age do we expect the first puberty to take place?

• 3-5months old

how does sexual maturity in males compare to females?

• females have sexual maturity before males but reach puberty earlier/around the same time

what kind of ovulators are rabbits

• induced

what is the interval between oestrus cycles in female rabbits?

• 4-6 days

how long does ovulation take place after copulation in rabbits?

• 10 hours

what is a unique feature of rabbit oestrus cycle after parturition

• post-partum oestrus

what is the gestation period of a rabbit

• 30-32 days

what are signs of pregnancy in rabbits? (5)

1. excessive digging

2. scenting

3. pulling hair

4. changes in temperament

5. nest building

what are signs of pseudopregnancy in rabbits

• infertile mating

• doe on doe mating

• stress

• pulling hair

how long does a pseudopregnancy last in a female rabbit

• 16-18days

describe the shape of male rabbit genitalia

• wide distance between anus and penis

• circular shape and rounded tip of penis

describe the presentation of female rabbit genitalia

• short distance b/w anus and vagina

• vagina has a noted groove and pointed shape