Ultrastructural analysis of the spermatozoa of three antarctic fish species

Male gametes of two icefishes, Chionodraco hamatus and Champsocephalus gunnari, family Channichthyidae were studied (with transmission and scanning electron microscopy), and a preliminary study was undertaken with scanning electron microscopy on Notothenia coriiceps, family Nototheniidae. Both families belong to the suborder Notorthenioidei, the perciform fish group endemic to Antarctic waters. At scanning electron microscopy level, all the three species show a rather similar morphology, common to most perciform species. At transmission electron microscopy, C. hamatus shows some differences: two nuclear fossae, and abundant membranous ornamentations of the head. While most Perciformes show anacrosomal spermatozoa, the portions of membrane of C. hamatus spermatozoa resemble acrosomoid vesicles, indicating a possible role in fertilization. In both C. gunnari and C. hamatus, the head membranes are bound, with different distribution, by PSA (Pisum sativum agglutinin), that generally presents affinity sites in acrosome membranes of mammalian spermatozoa.