Seasonal variation in spermatogenic and androgenic activities in a caecilian testis (Ichthyophis tricolor)

Abstract

Caecilians are an order of amphibians with distribution confined to several of the tropical countries. They are subterranean animals and practice a form of internal fertilization. Several species are viviparous. Published reports on seasonal variation in male reproduction in caecilians are limited to a very few species. A study was undertaken to examine the seasonal variation of testicular activity with respect to spermatogenesis and steroidogenesis in a caecilian, Ichthyophis tricolor, fairly abundant in the Western Ghats of Kerala, India, using light and transmission electron microscopy, terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) staining and biochemical determination of 3-hydroxy-Δ⁵-steroid dehydrogenase (Δ⁵-3β-HSDH) activity. Three phases in spermatogenic activity, active spermatogenesis (July–November), early regression (December–March) and spermatogenic quiescence (April–June) are identified. Apoptosis seems to be the mechanism of germ cell death during the regression phase. Leydig cells are interstitial and not peritubular. Activity of testicular Δ⁵-3β-HSDH follows the same pattern as spermatogenic activity, although histometric data on the interstitial tissue reveal higher areas during the regression and quiescent phases. Our findings will be useful in evolving strategies for conservation of caecilians with special reference to Kerala, India.