The spermatozoon of Lumbrineris (Scholetoma) impatients (Claparède, 1868) (Polychaeta, Lumbrineridae)

The sperm morphology of the polychaete Lumbrineris (Scoletoma) impatiens (Claparede, 1868) (Polychaeta, Lumbrineridae) of a sub-tidal population from the Gulf of Naples was studied both by transmission electron microscopy (TEM) and high-resolution scanning electron microscopy (HRSEM). In particular, the ultrastructural characteristics of mature male cells, the shape and structure of the acrosome, the nucleus and the flagellum were investigated by TEM. HRSEM images show the sperm external morphology and allow to classify the male gamete as an ect-aquasperm, by having a short head, four to five rounded mitochondria and a long tail, and generally associated with free-spawning. The structure of the spermatozoon of L. impatiens strictly recalls that of the male cell of the Lumbrineris sp. collected in New South Wales, Australia, the only one of the genus so far examined. On the other hand, by comparing these findings with those obtained on the external morphology of male gametes of the Lumbrineris sp. from Grappler Inlet, Vancouver Island, it emerges once again that significant variations are present. This confirms the extraordinary variability of polychaetes' reproductive characters even at genus level.