SEXUAL CYCLES AND MATURITY OF THE TURTLE, CHRYSEMYS PICTA

¹ Department of Biology, Southwest Minnesota State College, Marshall, Minnesota 56258

1. A mature male Chrysemys picta can be distinguished from a female by its long forefoot claws, thickened base of the tail, and short post-anal tail length.

2. Males become sexually mature when they reach a plastron length of 80 to 90 mm. They usually mature in their fourth year, but probably do not mate until the spring of the fifth year.

3. All sexually mature females contain follicles with diameters greater than 15 mm. All females containing oviducal eggs found mating or nesting were over 110 mm in plastron length and at least five years old.

4. Sexual maturity is apparently a factor of size rather than age.

5. Spermatogenesis begins in March with the most active period of sperm production occurring in July and August. The cycle is completed in September when the sperm start to pass into the epididymis where they are stored during the winter.

6. The ovarian cycle in southeastern Pennsylvania begins in July and August after ovulation and nesting, and is completed by the end of October. No change occurs during the winter. This differs slightly from the cycle of more northern females.

7. The ovarian activity alternates, and extrauterine migration of ova is known to occur.