Chelonian Reproduction - Anatomy & Physiology

Male

Anatomy of the Male Chelonian

^{© L.Wilkie 2008}

Testes

• Long, yellow and oval in shape.
• Attached to the cranioventral pole of the kidneys.
• Ductus deferens runs alongside ureters to the cloaca.

Phallus

• Ventral proctodeum is modified and thickened into a single phallus.
• Two pairs of fibrous tissue separated by a central trough.
• Cannot be inverted (unlike lizards and snakes).
• Highly vascular.
• When inserted into the female cloaca it becomes engorged.
• Semen is conveyed through the central sulcus.
• A retractor muscle returns the phallus back into the cloaca.

Female

Ovary

• Paired ovaries lie symmetrically, cranial to the kidneys.
• Irregular, sac-like.
• Different sized ova that become prominent with mature follicles.

Sperm Storage in the Female Tract

• Females in some species can retain sperm in their uterus.
• Can successfully fertilize two or more clutches, often several years after copulation.

The Egg

All chelonians are oviparous.

Temperate Species

• Lay eggs with soft, flexible, leathery shells.
• Can absorb and loose moisture.
• Develop more rapidly.
  • Incubation ~2 months.

Tropical Species and Land Tortoises

• Lay eggs with a hard, brittle shell.
• Prevents eater loss.
• Develop less rapidly.
  • Incubation ~8-9 months.

• Egg hatching depends on climate conditions such as spring warmth and seasonal rains.

Copulation

• Courtship and mating is very vocal.
  • Crying, grunting and barking
• Male mounts from the rear.
• Internal fertilization