Chapter 45 Diseases of the Reproductive System
Diseases of the reproductive system in the snake include dystocias, oviduct and cloacal prolapse, and penile prolapse. Some species of snakes such as pythons, king snakes, milk snakes, rat snakes, and corn snakes are oviparous (lay eggs), and others, including boas, vipers, and garter snakes are viviparous (live bearing). The testes of the male snake are found internally in the dorsomedial portion of the coelomic cavity.
Snakes do not have an epididymis. The hemipenes are located in pouches lateral on each side of the cloaca. The location of the ovaries is similar to that of the testes. The oviducts have both an albumin and a shell-secreting function, and there is no true uterus. The oviducts empty into the cloaca.
The onset of sexual maturity in snakes is affected by size, care, and diet more so than age. Snakes fed well and forced to grow rapidly can reach sexual maturity faster than snakes fed poor diets with slower growth rates. When raised under optimum conditions, many snakes will mature between 2 and 3 years of age.
The majority of reptiles have a distinct breeding season, usually triggered by environmental stimuli such as light, temperature, rainfall, and the amount of food present. Many will begin breeding in the spring as temperatures warm; however, tropical snakes (the boas and pythons) tend to breed during the cooler periods of the season. The female must be in good health with energy reserves to breed; if not, breeding may not occur. A great deal of maternal energy is used for egg production or live births. Snakes that bear live young usually produce one clutch per year, whereas egg-laying snakes may produce a clutch several times. Female snakes may suspend feeding while giving birth and lose weight. Snakes provide no maternal care for their offspring except in choosing the site in which to deposit them. Neonates usually need no assistance in hatching and are ready to live on their own immediately after birth.
Methods used to determine the sex of a snake include probing the pouches that contain the hemipenes (the deeper pouches are found in the male), by everting the hemipenes, or by observing the spurs found just lateral to the vent (larger in male snakes). Ultrasound or endoscopy can be used to determine the presence of ovaries in the female snake.
Dystocia is the most common reproductive problem seen in captive snakes. Dystocias may be divided into two groups: obstructive and nonobstructive. Obstructive dystocias result from an inability to pass one or more eggs or fetuses through the oviduct and cloaca. This may result from extra-large or malpositioned eggs or fetuses, from maternal abnormalities, or as a result of other masses obstructing the path. Nonobstructive causes may result from poor physical condition of the female snake, poor husbandry, improper nesting site, malnutrition, improper temperatures, and other environmental conditions.
Prolapse occurs with prolonged straining to pass eggs or fetuses, but it may also be caused by excessive straining for any reason (Fig. 45-1). With a shell gland/oviduct prolapse, the shell gland/oviduct will have a lumen but no feces will be present (as opposed to a prolapse of the colon with feces), and longitudinal striations appear on the surface of the shell duct that are not present on the colon.
(From Mader DR: Reptile medicine and surgery, ed 2, St. Louis, 2006, Saunders, by permission.)