Introduction
Generally, spermatogenesis of teleost varies depending on species and inhabited environments. The burbot Lota lota is the only freshwater member of the cod family, Gadidae, living in cold waters (Scott and Crossman, 1973; McPhail, 1997). Almost no report is available on gonad development and ultrastructure of spermatogenesis in burbot. Therefore, aim of the current study was to investigate testis structure and ultrastructure of germ cells during spermatogenesis using transmission electron microscopy.
Materials and methods
The testes were cut into small fragments and fixed for 2 h in 3% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) and stored at 4° C. Thereafter, the material was post-fixed for 1-2 h in 1% osmium tetroxide in the same buffer, dehydrated in a graded ethanol series and subsequently transferred to ascending concentrations of acetone. Ultrathin sections were cut with ultramicrotome, stained with uranyl acetate and counterstained with lead citrate for later examination using a JEOL Ltd. transmission electron microscope.
Results
The testis of the burbot was tubular and the germ cells were arranged in cysts or clusters within the seminiferous lobules. The differentiation of spermiogenesis stage (spermatids) in this species was characterized by flagellum development, nuclear rotation, nuclear fossa formation, and excess cytoplasm elimination. Spermatozoon ultrastructure revealed that it is anacrosomal teleostean type with round head consisting oval heterogeneously electron dense nucleus. The distal centriole and proximal centriole constituting the centriolar complex were oriented incompletely perpendicular to each other.