Comparative spermatology of two morphologically similar species of <i>Solen</i> (Mollusca: Bivalvia)

Abstract

The fine structure of the spermatozoa and spermatogenesis in Solen cylindraceus and S. capensis were studied by electron microscopy. The morphology of the sperm of both species is similar. Both are of the primitive type with a head about 1.5 f'm long), mid-piece of five mitochondria, and tail. The head comprises a barrel-shaped electron-opaque nucleus (about 1,1 f'm x 1,2 f'm) which is capped by a small conical acrosome. The morphology of the acrosome of Solen is typical of heterodont bivalves, however, each species has an acrosome of differing dimensions which can thus be used to separate these two closely related bivalves. During spermatogenesis the pattern of nuclear chrornatin condensation is granular. The acrosome is formed by a single Golgi body. and the five large mitochondria of the mid-piece are probably formed by fusion of several small mitochondria. Die struktuur van die spermatozoa en spermatogenese in Solen cylindraceus en Solen capensis is met die electronmikroskoop bestudeer. Die morfologie van die sperma van albei spesies is soortgelyk. Albei is primitief met 'n kop (omtrent 1,5 f'm lank), middelstuk van vyf mitokondria en stert. Die kop bestaan uit 'n vaatvormige, elektrondigte kern (omtrent 1,1 f'm x 1,2 f'm) wat bedek is deur 'n klein keelvormige akrosoom. Die morfologie van die akrosoom van Solen is tipies van 'heterodont' tweekleppiges, nietemin het elke spesie 'n akrosoom van verskillende dimensies wat dus gebruik kan word om die twee naverwante tweekleppiges te sket. Gedurende spermatogenese is die patroon van die kernkromatinkondensasie korrelrig. Die akrosoom word gevorm deur 'n enkele Golgiliggaampie, en die vyf groot mitokondria van die middelstuk word waarskynlik gevorm deur die sames melting van etlike klein mitokondria.

S.-Afr.Tydskr.Dierk. 1987,22(4)