Ultrastructural study of spermiogenesis and the spermatozoon of Cavisoma magnum (Southwell, 1927) (Acanthocephala, Palaeacanthocephala, Cavisomidae), from Siganus lineatus (Pisces, Teleostei, Siganidae) (Valenciennes, 1835) in New Caledonia

► Description of ultrastructure of spermiogenesis and spermatozoon of a cavisomatid. ► Elaboration of a flagellum of 9 + 2 pattern during spermiogenesis. ► Specificity of the distribution, size and form of protein granules in the mature spermatozoon. ► Posterior extremity appears like a lamina.