Reproduction in Reptiles and Fish------ Reptiles Flashcards
Where are the gonads situated?
Near the cranial pole of the kidney in many species (caudal to gall bladder in snakes)
What type of phallas is present?
Fibrocallagenous and muscular, elastic erectile tissue, chelonians – penis, lizards & snakes – hemipenes
What is the function of the sexual segment found in some squamates?
Separates urine from semen copulation, provides a copulatory plug
What is significant about the female anatomy?
No true uterus
What are the five stages of reproduction?
Oocyte development (pre-vitellogenic follicle development), vitellogenesis (yolk production), oocyte maturation, ovulation, oviposition/parturition
What are intersex reptiles?
Hermaphrodites – females with hemipenes
What is parthenogenesis?
When no matting occurs, chromosomes replicate in egg and embryo develops
Where does fertilisation take place?
Cranial oviduct (NB sperm can be stored for up to 6 years)
What is the difference between oviparous & ovoviviparous/viviparous?
Oviparous – lay eggs, all chelonians and most squamates
Ovoviviparous – egg in tract until hatching
Viviparous – live bearing, chorioallantoic placenta
What hormones are involved in the squamate reproductive cycle?
1 gonadotrophin, FSH-like compound, no LH equivalent
What roles do oestrogen and progesterone play?
Oestrogen – yolk development
Progesterone – ovulatory surge in chelonians, made by CL, prevents expulsion of the embryo
What environmental factors effect reproduction?
Primed by exposure to sexually mature male before mating, males exposed to females, humidity, barometric pressure & photoperiod
What are the sex chromosomes of reptiles?
Male – ZZ, female - ZW
What determines the sex when breeding?
Temperature
Most lizards – high = male, low = female
Chelonians – high = female, low = male
Few chelonians & lizards – high & low = female, intermediate = male
What enzymes are believed to be involved in this process?
Appropriate temperature for females produces more aromatase (T ->E2), appropriate temperature for males produces more 5α-reductase (T -> DHT)
