Spermatozoal ultrastructure in four genera of Homolidae (crustacea, decapoda): Exemplified byHomologenus sp.,Latreillopsis sp.,Homolomannia sibogae andParomolosis boasi

Abstract

The spermatozoa ofHomologenus sp.,Latreillopsis sp.,Homolomannia sibogae andParomolopsis boasi confirm characteristics of a distinctive homolid spermatozoon previously established forHomola sp.,Paromola sp. andParomola petterdi. Homolid features are (1) moderate anteroposterior depression of the acrosome (ratio of length: width 0.4–0.6) as in lyreidine raninids (0.5), depression being greater in dromiids and dynomenids (both 0.3); (2) the capitate form of the perforatorium, shared with dromiids, dynomenids and lyreidine raninids; (3)the autapomorphic spiked-wheel form of the anterior expansion of the perforatorium; (4) horizontal zonation of the acrosome is possibly a unique synapomorphy of homolids with dromiids and dynomenids, and therefore an autapomorphy of the dromioid-homolid assemblage. In dromiids the posterior zone is proportionately the larger, while in homolids the anterior zone is the larger. The anterior zone is complexly subdivided in dynomenids; (5) the autapomorphic presence of numerous radial arranged extension of the acrosomal operculum into the perforatorium; (6) presence of nuclear arms, a symplesiomorphy of all investigated crabs, but small or questionably sometimes absent in Dromiidae; (7) absence of microtubules from the nuclear arms, as in dromiids, raninids, higher heterotremes and thoracotremes; (8) transient presence of a posterior median process of the nucleus. The process is not seen in dromiids but occurs in anomurans and lower heterotremes; (9) apical perforation of the operculum, also seen, apparently symplesiomorphically, in dromiids, raninids, and lower heterotreme families; (10) absence of an acrosome ray zone, probably homoplasic with absence in raninids; (11) location of most of the cytoplasm, including tortuous membranes and degenerating mitochondria, below the acrosome, also seen inLyreidus; (12) presence, in at least some species, of centrioles, unknown in dromiids and raninids and variable in occurrence in heterotremes.