The process o f spermatogenesis in Rana esculenta (living in the surroundings of Naples) resurges gradually i n the spring months, proceeds actively through the summer and declines gradually in the winter months reaching an almost total "quiescence" for a short length of time. The repeating from year to year with a distinct regularity of spermatogenetic cycle suggests that environmental cues play a role in timing its various phases. Both temperature and photoperiod appear to be potential modifiers of spermatogenetic activity in this species. It is, however, probable that photoperiod acts only in a permissive way to facilitate the temperature response which seems to be the more direct modifier of the testicular activity.The proliferation of primary spermatogonia seems to be favoured by only low temperatures. The formation of secondary spermatogonia, and primary and secondary spermatocytes occurs when there occurs a gradual increase in the ambient temperature, day length and gonadotropin secretion. This period is characterized by very low plasma level of testosterone, that, through the reduced negative feedback to the hypothalamus, favours an increased secretion of FSHlike gonadotropin. Spennatid formation is entirely androgen-dependent as confirmed by the use of a specific antiandrogen, cyproterone acetate. In fact spermatid formation naturally occurs in a period when plasma level of testosterone is increasing and pituitary gonadotrops are declining in their secretory activity. In this period the ambient temperature and the photoperiod gradually decline.The importance of lateral eyes and the pineal gland in the mediation of influence of photic cues has been shown. It seems that without either the eyes or the pineal gland both light and temperature are completely ineffective in stimulating the early spermatogenesis, which shows the permissive role of light on temperature influence upon spermatogenesis.Hypophysectomy impairs spermatogenesis, which can be restored by a replacement therapy with homoplastic pituitary extract. Testosterone alone does not restore spermatogenesis except enhancing spermatid formation. Pituitary extract stimulates mitotic activity of spermatogonia and formation of primary and secondary spermatocytes. Testosterone is not involved because the stimulatory effects of pituitary extract are only marginally blocked by the antiandrogen. In fact spermatogonial multiplication is partially inhibited, while spermatid formation is totally blocked, indicating that ICSH-like gonadotropin acts upon the formation of spermatids through the stimulation of testosterone production.Thus i t has been found that there exists a complex interaction between the environmental factors and the "endogenous hormonal trigger" that subsequently steps into the regulation of spermatogenesis.A wealth of information on the reproduc-for reviews). Rana esculenta has a potentive patterns in amphibians has shown tially continuous type of spermatogenesis that species inhabiting cold zones have a (Galgano, '35 151

No abstract

No abstract

No abstract

Maize gluten (a byproduct from the starch industry) was used at four different levels (5, 10, 15 and 20% w/w) replacing the fish meal, a component of supplementary diet, under a semiintensive culture system. The impact of different diets on the physico-chemical parameters of water, growth and flesh quality of catla, Catla catla; rohu, Labeo rohita; and mrigal, Cirrhina mrigala was studied. Growth in terms of body weight gain was highest when fed a diet having 5% maize gluten (replacing fish meal at 25% level) for all the fish species. However, incorporation of maize gluten at higher levels led to decline in growth, since maize gluten is deficient in essential amino acids like methionine, lysine and threonine, etc. The flesh quality in terms of total protein, total lipid, total sugar, moisture and total ash was also determined at the termination of the experiment to see whether there was any significant variation with the incorporation of maize gluten or not.