Histochemical characteristics of spermatophore layers of Scylla serrata (Forskal) (Decapoda: Portunidae)

The spermatophores of S. serrata are protected by an outer thick chitinous layer and an inner thin non-chitinous one. Both layers are rich in acid mucopolysaccharides containing sulphated (outer layer) and carboxylic groups (inner layer). The proteins of the two layers show much tryptophan, but lack tyrosyl, sulfhydryl and disulphide groups. No phenols or phenol oxidases could be detected histochemically in either layer, suggesting the absence of phenolic tanning in the spermatophore. The physical properties, as revealed from treatment with acids and alkali, indicate the resistant nature of the outer layer; the inner layer easily shrinks or disrupts under such treatment. The outer layer, though resistant, is readily permeable to low molecular weight dye substances employed in permeability experiments. The mechanism of sperm release is recorded and discussed. It is suggested that, in S. serrata, the dehiscence of spermatophore may be caused by imbibing of low molecular weight substances by the sperm mass substances of the spermatophore while the latter is inside the spermatheca.