ULTRASTRUCTURE OF SPERMIOGENESIS AND SPERMATOZOA IN EUZETREMA-KNOEPFFLERI (PLATYHELMINTHES, MONOGENEA)

Euzetrema knoepffleri is a monogenean parasite in the relict urodele a mphibian Euproctus montanus in the island of Corsica, Spermiogenesis w as studied by electron microscopy. The spermatid has a zone of differe ntiation containing two parallel centrioles, on elongating nucleus and mitochondrion, and no peripheral microtubule. The spermatozoon is for med by a lengthening of the zone of differentiation. The mature sperma tozoon contains two axonemes of the platyhelminth 9+''1'' pattern, a m itochondrion, a nucleus, and no peripheral microtubule. The spermatozo on corresponds to type 2 in the classification of Justine, Lambert & M attei (1985). This type 2 is characteristic of certain monopisthocotyl ean Monogenea. In the absence of supplementary apomorphies, it is not possible to specify the phylogenetic position of Euzetrema in the Mono pisthocotylea from spermatozoal ultrastructure.