CRASSATELLIDAE, Ferussac, 1822

Healy, John M., Mikkelsen, Paula M. & Bieler, Rüdiger, 2008, Sperm ultrastructure in Hemidonax pictus (Hemidonacidae, Bivalvia, Mollusca): comparison with other heterodonts, especially Cardiidae, Donacidae and Crassatelloidea, Zoological Journal of the Linnean Society 153 (2), pp. 325-347 : 337

( CRASSATELLIDAE , CARDITIDAE , ASTARTIDAE )

Sperm ultrastructure has been examined in three species of Crassatellidae , one species of Carditidae and one species of Astartidae ( Healy, 1995a, b, 1996a; present study: Fig. 7). The crassatelloidean spermatozoon differs profoundly from those of Hemidonax in almost all features: (1) the acrosomal vesicle is long and attenuate and the subacrosomal material is developed as a thick axial rod ( Hemidonax : acrosomal vesicle short and squat; subacrosomal material diffuse and granular); (2) the nucleus is narrow and rod-shaped ( Hemidonax : nucleus short and wide); (3) the proximal centriole transforms into an electrondense rod connecting the distal centriole (and axoneme) to the nuclear base ( Hemidonax : proximal centriole unmodified); and (4) the midpiece consists of eight (occasionally seven or nine) wedge-shaped mitochondria, tightly packed around the centriolar complex ( Hemidonax : midpiece exhibits four round, unmodified mitochondria). The idea of a crassatelloidean affinity for Hemidonax (e.g. Hedley, 1906, 1909, 1923) or for that matter a link between the Carditidae and Hemidonax + Cardiidae (e.g. Schneider & Carter, 2001) can safely be rejected purely on spermatological grounds.