Reinvestigation of spermatic flagella structure: the teleostean Cyprinodontidae

The study of 7 genera and 15 species of teleostean fishes belonging to the family Cyprinodontidae shows a similar morphology of mobile spermatozoa and a wide diversity of structure of the spermatic flagellum. The flagellar membrane has one, two, or three lateral expansions depending on the species. Peripheral doublets of axonema show only the external arm, except for two species that completely lack them. Intratubular differentiations (ITD) are present in A or B tubules of peripheral doublets as in central tubules of some species, whereas others are totally devoid of them. The ITD can affect all doublets or preferentially doublets 1, 5, and 6. These variations may be due to neutral mutations.