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Copepod-chondrichthyan coevolution : a cladistic consideration Deets, Gregory B.


A revision of the species of Eudactylina (Eudactylinidae : Siphonostomatoida) and Kroyeria (Kroyeriidae : Siphonostomatoida) was conducted, based on type and other specimens of parasitic copepods from museums and personal collections. A description of the external morphology of each genus is included. Taxonomic, phyloge netic, and functional significance of the morphology of the general habitus, first and second antennae, oral and thoracic appendages are discussed. The taxonomic account of the above genera recognized all nominal species in the literature. Illustrations and phylogenetic analyses, however, were necessarily restricted to only the material examined in an attempt to standardize the abstractions and interpretations associated with character observation. Detailed redescriptions are given of E. acuta, E. aspera, E. chilensis, E. corrugata, E. indivisa, E. insolens, E. Iongispina, E. myliobatidos, E. oliveri, E papillosa, E. peruensis, E. pollex, E. pusilla, E. similis, E. spinifera, E. squamosa, E tuberifera, E. turgipes, and new descriptions (all in press) are given of, E. aphiloxenous, E. dactylocerca, E. diabolophila, E. epakto Iampte’ E. hornbosteli, E. nykterimyzon, E. pristiophori, E. urolo phi, and E. vaquetillae followed by the detailed reclescriptions of K. carchariaeglauci, K. caseyi, K. dispat K. elongata, K. gemursa, K. lineata, K. longicauda, K. papillipes, K. spatulata, K. sphyr nae, K. triakos and new descriptions (all in press) of K. branchioecetes, Kcresseyi, K. decepta, K. procerobscena, and K. rhophemophaga. In an attempt to unravel evolutionary relationships of their elasmobranch hosts and themselves a phylogenetic analysis of each genus is presented. In the heuristic analysis of Eudactyilna, 75 morphological characters resulted in a single tree with a consisitency index of 0.77 and a retention index of 0.88, indicating a high degree of character congruence. An exact search of nine species of Eudactylina with 55 charac ters resulted in a single tree with a consistency index of 0.88 and a retention index of 0.88. The Eudactylina-derived host cladograms posit monophyly of the shark-like squaloids , squatinids, pristiophorids, and batoids. This suggests that shark-like squaloids, angelsharks, and sawsharks are more closely related to rays than to other galeomorph sharks, whereas the pristiophorids represent the sister taxon to batoids. The eudactylinid dade found on the rhinopterids and mobulids appears to represent a colonization event followed by tight cospeciation. Eudactylina-derived carcharhinid relationships approximate conventional or currently accepted hypotheses. Eudactylina derived phyogenetic relationships of a subset of species from Squatina and Myliobatis indicate speciation patterns consistent with major vicariant events associated with the breakup of Pangaea during the Jurassic period approximately 160 MY. The phylogenetic analysis of Kroyeria, using 44 morphological characters result ed in a single tree with a consistency index of 0.75 and a retention index of 0.75. The Kroyeria-derived and Kroyeria-Kroeyerina-derived host cladograms posit an unconven tional placement for Galeocerdo. Galeocerdo diverges at the bottom of the tree before the Triakidae. A sphyrnid dade follows, functioning as the sister taxon to remaining members of the Carcharhinidae. The genus Carcharhinus appears paraphyletic with Negaprion and Prionace imbedded within this dade, corroborating similarly held views by other systematists. Congruent host and parasite cladogram topologies from both holocephalan and elasmobranch hosts suggest the existence of well-established and specific host-para site associations as early as the late Devonian, approximately 400 MY.

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