Expert from "Reptiles and How they Reporduce," By Dorothy Hinshaw Patent

Reptiles and How they Reproduce

By Dorothy Hinshaw Patent

Zekris HIGHLY recommends this book for further reading, it contains information about, not only the reproduction of many types of reptiles, but their life styles and biology as well.

this text has been edited to include only information relevant to S'kra (IE Lizards), if you question it's validity, go get the book! ::grins::

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4. Infants form Adults

Internal fertilization is required to allow the tiny, fragile sperm from the male to reach the egg in the female. We’ve seen that this required close physical contact between normally solitary animals. It also requires some physical structure allowing the male to transfer sperm into the female’s body. Mating must be carefully timed so that the eggs are ready to be fertilized, or else the female must be able to store the sperms until the birthing season.

How the Reproductive Systems Work

The males sex organs, called the testes, consist of long twisting little tubes whose inner walls are lined with cells called spermatogonia. These small, rounded cells undergo a complicated series of divisions which eventually produce sperms by the millions during the mating season. Sperms are very specialized cells with a head, containing the important genetic information from the male parent, and a tail, which thrashes back and forth, moving the sperms forward.

Each male reptiles has two testes. As the sperms are produced, they fill the centers of the little tubes. These tubes join and lead to a larger coiled tube where the sperms are stored until mating. From here, a duct leads to the cloaca of the male. The cloaca is a special chamber leading to the outside.

The eggs develop in the pared ovaries of the female. When the egg is fully developed, it breaks through the outer wall of the ovary and is released into the body cavity. The egg is then picked up by the wide upper opening of the oviduct, which, as it’s name implies, is an egg-carrier. The upper opening, called the funnel, actually envelops most of the ovary, so the eggs are picked up by it right away and moved by it’s muscular walls and it’s strongly beating, little hair-like cilia down into the oviduct.

Fertilization and Egg-packaging

The eggs are fertilized in the upper part of the oviduct. Somehow the struggling sperms must be able to swim up to the eggs while the muscles and cilia of the oviduct are pushing the other way, forcing the eggs down. This problem is solved in turtles and probably in other reptiles, too, by having a narrow band of cilia along one side of each oviduct which beat toward the funnel instead of away from it. The sperms can ride along this upwardly beating path of cilia.

When a sperm cell meets an egg cell, fertilization takes place. Only one sperm cell is able to enter the egg: after that happens, a protective membrane keeps other sperms out. The genetic information form the male parent then combines with that from the female parent present in the egg. With this union, new individual is begun, with it’s unique set of characteristics.

Mating and Sperm Storage

How do the sperms get from the male into the oviduct of the female? Most reptiles males have some sort of special structure to accomplish this.

Male lizards and snakes have a structure for transferring sperm called a “hemipenis.” Actually, each male has two of them. They are located under the skin at the base of the tail. Each hemipenis is a hollow tube which is expanded and turned inside out, like the finger of a glove, at mating time. It has a groove along the surface which guides the sperms. Only one hemipenis is used at a time, depending on which side of the female the male happens to be on.

Reproductive Cycles

Most reptiles breed during a limited part of the year. Birth or egg-hatching generally occurs when food is abundant. In areas with a cold winter and warm summer, reptiles, like other animals, tend to produce young in the spring and summer. While the ovaries and testes are actively producing sperms and eggs during this period, these organs are

inactive during other seasons. What causes these variations in sperm and egg production? Reproduction of the lizard

Anolis carolinensis, the American chameleon, has had deep study in the laboratory. This lizard is a favorite reptiles of scientific studies. It is small and easy to care for. Chameleons adjust well to laboratory life and carry on their normal behavior there, including courtship and mating.

Since temperature and light affect the reproductive cycles of birds, scientists decided to see if they are important in reptiles, too. After many experiments, it became clear that both light and temperature do indeed affect chameleon reproduction. In the late summer and early fall, the number of daylight hours decreases. This causes the testes of male chameleons to stop producing sperms. In the winter, while the lizards are dormant, the testes gradually grow. The increasing temperatures of early spring stimulate their further grown, resulting in male lizards which are ready to set up territories and mate.

Male chameleons emerge form winter dormancy before the females. They are quite aggressive at first as they set u their breeding territories. Males challenge one another with an impressive display. A displaying male turns sideways to an intruder and flattens his body, making his profile appear larger then it is. He bobs up and down and spreads our a bright red flap of skin under his throat called the dewlap. The other male may run off or he may refuse to back down, returning the challenge display. Then the two lizards circle around one another, alternating their displays, until one loses his nerve and flees.

Occasionally, if two very determined males are sparring, they may threaten with open jaws or even wrestle by clamping onto each other’s jaws and going into a push-pull match.

Just about the time the males have worked things out and settled down, the female lizards venture out. The longer day length and increased spring temperatures stimulate the ovaries. One egg begins to increase in size as it accumulates yolk. From then on thorough the breeding season one egg is produced every 10 to 14 days. During this time, males court the females and mate with them, and females lay one egg every two weeks or so.

The males uses the same challenge display with any lizard entering his territory, male or female. While another male either flees or returns the display, a receptive female merely remains where she is and nods her head. This is a cue for the male, who now approaches her with a courtship display. t first it resembles a challenge display without the flattened body. But as the male gets closer and closer to the female, his bobbing become faster and shallower.

In laboratory experiments, scientists have learned that light and temperature are not the only things which affect the female--the behavior of the male has an equally important effect. If females are left with aggressive males, most of them do not develop mature eggs. If they are cages with courting males, however, they do produce eggs with are ready for fertilization.

What features of male courtship stimulate egg production? To answer this question, scientists focused their attention to the dewlap. They put some females with normal males with red dewlaps and other s with males whose dewlaps had been dyed blue. A third group of males could not extend their dewlaps at all because the cartilage which spreads it out was removed. Despite this operation the behavior of these third-group males as normal in every other way.

These experiments gave clear results: females reacted to males with blue dewlaps just as if they were normal. The ovaries of the females were stimulated by them, and the females responded to their courtship. But males without a dewlap didn’t interest the females at all. They ignored the courtship of such males, and the ovaries of females caged with them did not produce yolked eggs.

Experiments like this teach us important lessons about how the life cycles of animals are coordinated. Things that happen in the environment help prepare the body for the right activity at the right time. But certain behavior among the animals themselves are also necessary to coordinate their body functions and their activities. It would be a waste of her body resources if a female lizard produced eggs when no courting males were on hand to fertilize them. But requiring both the proper environmental conditions and the presence of a male eager to mate, the reproductive readiness of the female comes at the appropriate time and is not wasted.

Printed in the United States of America

Library of Congress Cataloging in Publication Data

Patent, Dorothy Hinshaw.

Reptiles and how they reproduce.

SUMMARY: Discusses the characteristics and habits of members of the reptiles

family with particular attention to their mating and reproductive behavior.

I. Reptiles--Reproduction--Juvenile literature.

[I. Reptiles] I.Kalmenoff, Matthew. II. Title.

QL669.2.Ps7 598.I’04’56 773817

ISBN 0-8234-0310-6