Evolutionary morphology of the caecilian urogenital system. I. The gonads and the fat bodies.

Abstract

AbstractThe comparative morphology of the gonads and fat bodies of members of 17 genera and 46 species of caecilians (Amphibia: Gymnophiona) is described and analyzed. Comparison is made with the morphology of salamanders and frogs in order to elucidate evolutionary trends and relationships within the order Gymnophiona and within the class Amphibia. The structure of the testis lobes and transverse and longitudinal ducts is described based on gross dissection and histological investigation. The pattern of spermatogenesis and interstitial tissue changes are described and compared with those of other amphibians. A trend toward fusion of testis lobes is analyzed. The characteristics of the seasonal reproductive cycle of male Gymnopis m. proxima are described, and evidence for cyclic reproductive activity in other forms is presented. The morphology of the ovaries and ova is described. Size of ovary and size and number of ova is dependent on the state of maturation of the ova. Some evidence for seasonal ovum production and breeding is presented. Fat body morphology is found to be correlated with size, nutrition, and gonad condition, as in other amphibians.