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

Euzetrema knoepffleri is a monogenean parasite in the relict urodele amphibian Euproctus montanus in the island of Corsica, Spermiogenesis was studied by electron microscopy. The spermatid has a zone of differentiation containing two parallel centrioles, on elongating nucleus and mitochondrion, and no peripheral microtubule. The spermatozoon is formed by a lengthening of the zone of differentiation. The mature spermatozoon contains two axonemes of the platyhelminth 9+''1'' pattern, a mitochondrion, a nucleus, and no peripheral microtubule. The spermatozoon corresponds to type 2 in the classification of Justine, Lambert & Mattei (1985). This type 2 is characteristic of certain monopisthocotylean Monogenea. In the absence of supplementary apomorphies, it is not possible to specify the phylogenetic position of Euzetrema in the Monopisthocotylea from spermatozoal ultrastructure.