Early maturing phase: Ovaries become slightly larger, thicker, opaque and are light yellowish in colour.Histologically, the ovary shows ovigerous lamellae, having nests of oogonia, and immature oocytes in the stage I and II are visible under a microscope. The ovaries occupy only a small part of the body cavity and ova are not visible to the naked eye. Resting phase (immature): The ovaries are small, thin, thread like, translucent, pale or dirty white in colour with inconspicuous vascularisation.
On the basis of shape, size, colour of the ovary and other histomorphological features, at least six maturity stages can be recognized. The entire period during which the gonads attain full maturity and spawning takes place in the population is called the breeding season of the species.Īfter spawning, gonadal recrudescence may occur in the same breeding season (multiple breeding) twice or thrice depending on the availability of certain crucial environmental factors like temperature and photoperiod ie increased daylength. Fish spawns during a specified periods of the year which coincides with the several environmental factors that are available during the said period only. The expulsion of gametes from the body into the surrounding water is called "spawning" resulting in fertilisation. Most of the fishes exhibit seasonal cycle in the production of gametes.
This is called maturation of the gonads, writes Professor Nihar Ranjan Chattopadhyay, West Bengal University of Animal and Fishery Sciences.
0 kommentar(er)
