A monograph of the order Lecanicephalidea (Platyhelminthes: Cestoda)

Date of Completion

January 2001

Keywords

Biology, Molecular|Biology, Zoology

Degree

Ph.D.

Abstract

This represents the first monographic and phylogenetic treatment of the order Lecanicephalidea. The main objective was to treat the Lecanicephalidea at the generic level, while providing information on taxonomic history, host associations, geographic distribution, morphology, and phylogenetic relationships of the group. As part of a character analysis, identification of homologous components of apical structures in lecanicephalideans was attempted. Museums around the world were visited to locate type material. The taxonomic status of 42 genera that had been associated with the Lecanicephalidea was evaluated. As a result, 16 genera were considered to belong to other cestode orders, two were considered genera inquirenda et incertae sedis, one was determined to be a nomen nudum, two were considered to be junior synonyms of other lecanicephalidean genera, eight were considered to be lecanicephalidean genera inquirenda, and 12 were recognized to be valid members in the order. Treatment of the valid genera, in each case, included comments on the type species and on at least one additional species. As a result, 22 lecanicephalidean species were treated, seven of which were described as new. If material was available, a complete characterization of the microthrix pattern of a species, as observed with scanning electron microscopy, was presented. Six new combinations are created for lecanicephalidean species. The character analysis resulted in 64 morphological characters that were included in a series of phylogenetic analyses performed to investigate relationships among lecanicephalidean genera. These analyses included 18 lecanicephalidean species, representing the 12 valid genera, and two tetraphyllidean and proteocephalidean species each, used as outgroups. Effects of different amounts of missing data, coding strategies for inapplicable characters and the effect of outgroup selection on tree topology were investigated. None of the trees resulting from these analyses were well supported. In general, these trees suggested a monophyletic Lecanicephalidea relative to the outgroups, a basal position for lecanicephalideans lacking an apical structure, and a clade containing species possessing an apical structure, with a trend towards an increase in apical organ size within this clade. Host associations and geographic distribution of the Leanicephalidea were expanded. Underestimated generic diversity and morphological disparity was demonstrated. ^

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