Preliminary Phylogenetic Analysis of Subfamilies of the Proteocephalidea (Eucestoda)

Cladistic analysis based on comparative morphology was used to examine the subfamily-level relationships within the cestode order Proteocephalidea. A single most parsimonious tree (70 steps, CI = 0.571; RC = 0.295; HI = 0.471) is consistent with monophyly for the Proteocephalidea and showed a relatively high consistency at the family level with the diagnosis of two major subclades. Unambiguous support for a Proteocephalidae subclade, including the Corallobothriinae, Proteocephalinae, Gangesiinae and Sandonellinae, and a Monticelliidae subclade, including the Marsypocephalinae, Zygobothriinae, Monticelliinae, Rudolphiellinae, Ephedrocephalinae and Othinoscolecinae was evident. Two subfamilies, the Acanthotaeniinae (historically in the Proteocephalidae) and Nupeliinae (historically in the Monticelliidae), were however, basal to all other subfamilies, indicating that neither family as currently conceived is monophyletic. Trees one or two steps longer, however, would be consistent with monophyly for the Proteocephalidae and Monticelliidae (excluding Acanthotaeniinae) or would result in the monophyly for both families, including all respective subfamilies congruent with current concepts for systematics of the order. Zoogeographical analysis demonstrated a strong Gondwanan association; proteocephalideans originated in Africa, with subsequent development linking Africa and South America. Colonisation of the Northern Hemisphere by proteocephalid subfamilies, the Proteocephalinae, Corallobothriinae and Gangesiinae, was secondary. Analysis of parasite-host relationships indicated that the basal hosts for the Proteocephalidea are equivocal; siluriform teleosts were, however, the basal hosts for the Nupeliinae + the Monticelliidae and Proteocephalidae subclades and an extensive co-evolutionary history with this host group is postulated. Independent colonisation events of reptilians by species of the Proteocephalinae and Acanthotaeniinae, non-siluriform teleosts associated with the Sandonellinae and some Proteocephalinae, and amphibians by some Proteocephalinae, are recognised. Some points which should be considered for further development of the systematics of the group are proposed, with special emphasis given to thorough morphological descriptions and investigations of life-cycles