Ultrastructure of the spermatozoa of Aristaeopsis edwardsiana and Aristeus varidens (Crustacea, Dendrobranchiata, Aristeidae)

The acrosome-less spermatozoon of Aristaeopsis edwardsiana (Crustacea, Aristeidae), which consists of a central non-membrane bound nuclear region surrounded by a thin peripheral cytoplasm, much resembles that of the previously studied aristeid Aristaeomorpha foliacea. The marked spermatozoal similarities between these two species appear to indicate a close phylogenetic proximity. A considerably different spermatozoal pattern is observed in aristeids from the genus Aristeus (A. varidens and A. antennatus), whose spermatozoa possess an anterior spherical acrosome, lacking a spike, and partially embedded in (instead of capping) the main sperm body. The two distinct sperm types found in the Aristeidae differ significantly from the spiked sperm typically found in most penaeoids (Penaeidae, Solenoceridae and Sicyoniidae), thus suggesting a phylogenetic separation of the Aristeidae from the remaining Penaeoidea.