Authored by Ron Tremper Leopard Gecko

BREEDING LEOPARD GECKOS

Follicle Grading

Every week, we get asked,

“How do I know when to put my geckos together?” And indeed, that question is very important and one that we want to teach you the answer to.

To understand how to determine the best time for introduction, you first need to have a basic knowledge of the reproductive biology of females. A female’s reproductive organs, which produce ova, are called ovaries. Inside the ovaries, when a female gecko reaches reproductive size, early stage ova (oocytes) inside ovarian follicles (specialized spaces in ovaries that house oocytes and form yolk), under the influence of hormones, begin the process of becoming mature eggs. The ovarian follicle will accumulate and provide yolk to the ova, a process called vitellogenesis. When mature and yolked, the ova (2) will then be released from the ovaries and captured by the oviducts; this is called ovulation. The tube-like oviducts complete the formation of an egg and lead it towards the cloaca. Soon after they enter the oviducts the ova can be fertilized.

In reptiles, receptivity of females and copulation commonly occurs prior to ovulation, and sperm is stored in an area of the oviducts near where the ova first enter and get fertilized. After fertilization, the ova then pass through an area of the oviduct that coats them with albumen. Further along, layers of egg membranes are applied and the egg then passes through the shell gland, a specialized area of the oviduct that will deposit a calcium matrix, forming the shell. Because the abdominal wall of leopard geckos is semi-translucent, different stages of egg formation can be observed. “Follicle grading” is a technique of manually bringing developing follicles/ova into view through the belly wall. Although it requires some experience to master, this procedure is well worth the effort to learn.

Study the photos below and notice how to grasp the female properly and how much to bend her back gently over your index finger. This makes her abdominal area flatten out and if any follicles are present they will appear between her organs near the surface of the semi translucent belly wall. The objects you are looking for do not appear side-by-side, but are offset from each other. When looking down on the geckos’ belly, with the head in the vertical position, one follicle will always appear on the upper left of the mid-abdominal region and the other will appear offset on the lower right, just above the bright white fat bodies, which are often mistaken for eggs, in the middle of the body.

This is the belly view of a female that is not showing any egg development. The lighter areas just above the hind legs are fat bodies.

Gently bending a female over your index finger brings the ripening follicles/ova into view. This female is ready to be placed with a male.

Follicles that are less than ½” in diameter have a yellowish orange appearance because of their yolks. Mature ova released and fertilized in the oviduct are ½”to 5/8” inch in diameter. Within 24 hours of fertilization the fertilized ova, will pass through an area near the end of the oviduct called the shell gland, which will coat it with a calcium carbonate matrix, forming a bright white shell.

By now some of you are probably wondering “So what’s the use of follicle grading?”. An important study (Rhen et al.2000) showed that before egg yolk formation, when no follicles are visible through the abdominal wall, female leopard geckos are unreceptive to males. A small percentage (20%) become receptive during the early stage of yolk formation (early vitellogenesis) when the follicles are less than 9 mm in diameter. But the great majority of females (80%) are only receptive to males during the late stage of yolk formation (late vitellogenesis) when the follicles are about a ½ inch (12-14 mm) in diameter. Females again become unreceptive after ovulation. Thus, monitoring the status of follicles will allow you to determine the best time to introduce a female to a male. Interestingly, females are most receptive when their testosterone levels are highest. (Rhen et al. 2000)

Reproductive Terminology

Oogenesis: Formation of female gametes (=ova)

Ovaries (sing. Ovary): Paired female reproductive organs housing follicles and their oocytes

Ovarian Follicle: A cavity in the ovary containing a developing oocyte surrounded by its encasing cells.

Oocyte: A developing egg cell in an ovarian follicle prior to ovulation.

Vitellogenesis: Formation of the yolk of the egg, which is deposited by mature follicles and accumulated by an oocyte (secondary)

Ovum (plural ova): Sometimes used a substitute for oocyte but here used to signify a mature yolked oocyte released from the ovary.

Ovulation: Release of ovum from ovary

Oviducts: Paired reproductive tracts that transport ova from ovary to cloaca

Cloaca: A sac enclosed cavity receiving the products of the digestive, urinary, and reproductive systems.

Vent: Opening of the cloaca leading to the outside.

Part 1 Leopard Gecko Breeding 101 | The Beginning. Breeding Part 3 will be presented in the next edition of Trempers Corner.

Respect,

Ron Tremper