A study of the epideictic behaviour patterns of male Xiphophorus helleri Heckel was made, and the social rank of individual fish in 12 groups of three was assessed over a ten-day period. Straight-line hierarchies were established in most groups. An anatomical study was made to locate the adrenocortical tissue, and the adrenocortical activity of each fish was assessed by measuring mean nuclear diameter of 25 adrenocortical cells. Although results were somewhat variable, the highest-ranking fish in 7 out of 12 groups showed the least adrenocortical activity. The remaining two fish showed no significant difference from each other in adrenocortical activity, though their rank was in most cases clearly distinguishable on behavioural grounds.
Several oxidative cnzymes in the testis of the teiid lizard Cnemidoph-OTUS tigris were studied histochemically. The cells of the circumtesticular sheath (Leydig cell tunic) are functionally equivalent to Leydig cells of the interstitium on the basis of similar histochemical reactions for the five enzyme systems studied. Both groups of cells were positive for 3P-hydroxysteroid dehydrogenase, l7g-hydroxysteroid dehydrogenase, NADH diaphorase, NADPH diaphorase, and glucose-&phosphate dehydrogenase. These results support the hypothesis that the circumtesticular sheath has endocrine function as indicated bv its vascularity and its ability to catalyze histochemical reactions involving steroid biosynthesis.
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