Snake and Lizard Reproduction - Anatomy & Physiology

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Lizards (Squamata)

Male

Testes

• Located cranial to the kidneys.
• Attached to the dorsal wall by a mesochorium.
• In some species, the kidney has a posterior sexual segment that becomes swollen during the breeding season and contributes to seminal fluid.
• Right testis lies cranial to the left.
  • Intimately connected to the vena cava by short blood vessels.
• Left testis lies close to the adrenal gland.
  • Has its own testicular blood vessels.

Phallus

• Paired hemipenes
• Stored in the base of the tail.
  • Visualised externally by bulges at the ventral proximal tail.
• Only one hemipene is used during copulation.
  • Erected by vascular engorgement and muscular action.
  • Everted to protrude through the cloaca.
• Sperm passes from the ductus deferens into the male urodeum.
• Sperm is then carried in a groove down the hemipene to be deposited in the female cloaca.

Female

Ovary

• Paired
• Consists of a cluster of oocytes lined by a thin mesovarium.
• Right ovary is close to the vena cava.
  • Attached to vena cava by tiny blood vessels.
• Left ovary lies close to the left adrenal gland.
  • Has its own ovarian blood supply.

Oviduct

• Paired
• Pleated
• Wide infundibulum

Oviparity

This is the usual state for lizards, including all Geckos and Iguanas.

• Eggs are retained within the mother until birth.
• Normal clutch size is 3-5.
• Eggs covered by a leathery shell
• Can appear shrunken when laid.

Viviparity

About 1/5 of lizards are viviparous including the common European Lizard.

• Foetus retained within the oviduct.
• Primative placental type of circulation.

Breeding Season

Temperate Species

• Gonads reach maximum size on emergence from hibernation.
• Gonads are smallest during the summer months.

Tropical Species

• Breeding season coincides with the start of the wet season.
  • Moisture for egg incubation.
  • Abundant food supply for hatchlings.

Snakes (Squamata Serpentes/Ophidia)

Sexual Maturity

• Smaller species can reach sexual maturity in 1 year.
• Larger, more long-lived species may not be sexually mature until 5 years of age.

Male

Anatomy of the Male Snake

^{©RVC 2008}

Testes

• Intra-abdominal
• Situated between the pancreas and the kidneys.

Phallus

• Two hemipenes
  • Paired, sac-like extensions of the cloaca.
• Lie within the ventral tail base.
• Each hemipene has a retractor muscle that extends from the tail vertebrae to the tip and sides of the hemipene.
• Large glands lie above the hemipenes.
• Hemipene retractor muscle and anal glands are all surrounded by a larger propulsor muscle.
• When the hemipene is engorged with blood, the propulsor muscle contracts.
  • Everts the hemipene.
• After engorgement has subsided, the retractor muscle contracts.
  • Inverts the hemipene.

Female

Female snakes can be oviparous, or viviparous.

Ovary

• Paired
• Located asymmetrically near the pancreas.
• Right oovary usually larger and more cranial.
• Left ovary may be reduced or undeveloped.

Sperm Storage

• Some female snakes can store sperm in a cavity lined by mucosa glands near the top of the oviduct.
  • Stored here until conditions are right.
• Can be stored for months or even years.
  • Thus snakes may suddenly appear fertile in abscence of a male.

Maternal Behaviour

The Indian Python is the only reptile to exibit maternal behaviour. This can be achieved owing to her large body size.

• Generate a 7ºC increase in heat by spasmodic contractions of muscles as they coil around the eggs.
• Coil tightly around the egg mass to prevent heat loss from the eggs.
• Unlike mammalian shivering, the muscle contractions are coordinated.
• Metabolic rate of the mother increases 20-fold.

Breeding Season

Temperate and Subtropical Species

• Breeding season is in Spring.

Tropical Species

• Breed at the start of the wet season.
  • Ideal climate for egg incubation.

Copulation

• Male initates courtship by moving his body over the female and rubbing his tail against her.
• If female is receptive, she dilates her cloaca and raises her tail.
• Copulation lasts 2-20 hours.
• During copulation one hemipene is evaginated and inserted into the female cloaca.
• Hemipene has spines and ridges that enable it to remain in the cloaca for a long period of time.
• Hemipene is withdrawn at the end of copulation by contraction of the retractor muscle.
• During multiple mating, the male can use the left and right hemipene alternately.