A description of spermatozoan ultrastructure and some anatomical characters in Branchiobdella kozarovi Subchev, 1978 (Annelida: Clitellata), and review of the spermatozoan morphology within the genus

Abstract

The use of spermatozoan ultrastructural morphology to produce a meaningful phylogeny requires a critical number of descriptions from representative species in a taxon. Branchiobdella spermatozoan morphology is considered to be aberrant within the Clitellata. The description of the spermatozoon of B. kozarovi has extended the information on interspecific variation in this genus. The spermatozoa of this species have an acrosome (16 μm long), nucleus (4.5 μm long), midpiece (1.5 μm long), and tail (158 μm long), with a total length of about 180 μm. The acrosome is a thick helix with about 15 gyres, contains an acrosome tube and acrosome vesicle which has branches penetrating into the central subacrosomal space. The acrosomal “button” is located on the anterior surface, with the “cork” and secondary tube at the posterior. The rod-shaped nucleus has a concavity in both the anterior and posterior surfaces. The midpiece has seven, parallel mitochondria twisted about the central axis. The centriolar remnant with an indistinct ninefold symmetry in cross section is located posterior to the mitochondria. The prominent central sheath extends from the mitochondria to the end of the flagellum, which has no end piece. The axoneme has glycogen granules located along its length, and an helical marginal fiber. A review of descriptions of spermatozoa of Branchiobdella shows some inconsistencies. The observations of two anterior nephridial pores and an eversible penis completes the anatomical characters of B. kozarovi used in current branchiobdellidan taxonomy.