Conservation of wild silkworm genetic resources through cryopreservation: Standardization of sperm processing

Abstract

Conservation of the invaluable sericigenous genetic resources is of prime importance with respect to their utilization and improvement for wider exploitation. Conservation of wild silkworms and its applicability in hybridization have limitations due to incompatibility, less amenability, change of behaviour under ex situ conditions, non-synchronization of moth eclosion and difficulties in mating between variables. In view of this, the newer technologies such as cryopreservation and artificial insemination are offering better strategies for preservation of biologically active samples like semen at sub-zero temperature (-196º C) conditions for longer duration. In this context, under standardization of sperms preservation from wild silkworms, two methods of semen collection were scrutinized for obtaining active and viable sperm for cryopreservation and further artificial insemination. Semen collection from the seminal vesicle of freshly emerged male moth and the other from the bursa copulatrix (BC) and spermatheca of the female moth after mating. The sperms in the semen collected from seminal vesicle are in the form of bundles known as eupyrene sperm bundles and apyrene sperms. The morphology and behaviour of these sperm bundles were recorded through microscopic examination. To study the density and motility behaviour of the sperms, sperm bundles were treated with proteolytic enzyme (~2-3µg/ml) to digest the membrane and release the sperms. The density and motility behaviour of sperms in the semen recovered from the BC and spermatheca of female moth after mating were higher compared to those released after digestion of sperm bundles from seminal vesicle of the male moth.