PHYLOGENY OF THE MONOGENEA BASED UPON A P ARSIMONY ANALYSIS OF CHARACTERS OF SPERMIOGENESIS AND SPERMATOZOON ULTRASTRUCTURE INCLUDING RECENT RESULTS

Characters of spermiogenesis and spermatozoa were used for a parsimony analysis of the Monogenea using the software PAUP. Data include a mat rix previously published (JUSTINE, 1991, Int. J. Parasitol. 21: 821-83 8) and data recently published. A matrix including 27 taxa is proposed , but since some of these taxa are redundant or ill-defined (the sperm atozoon is known but spermiogenesis was not described), the parsimony analysis was performed on only 15 taxa. The data set includes the Dige nea considered as an outgroup and the Polyopisthocotylea considered as a single taxon. The strict consensus tree computed after this analysi s has a length of 32 steps and a consistency index of 0,750. The Polyo pisthocotylea and the Monopisthocotylea are each defined on the basis of synapomorphies for the spermatozoon, but there is no sperm synapomo rphy for the entire Monogenea. A group which contains the Loimoidae an d Monocotylidae appears as a sister group for all other Monopisthocoty leans. A polytomy exists in the other Monopisthocotyleans ; phylogenet ic relationships between the Acanthocotylidae, Capsalidae and Gyrocoty lidae are not resolved. The Monoaxonematidea (monopisthocotylean monog eneans with uniflagellate spermatozoa) appear monophyletic. Within thi s group, Calceostoma, Cleithrarticus and Pseudodactylogyrus appear to constitute a monophyletic group.