Orders out of chaos – molecular phylogenetics reveals the complexity of shark and stingray tapeworm relationships

Abstract

Novel molecular data are presented to resolve the long-standing issue of the non-monophyly of the elasmobranch-hosted tapeworm order Tetraphyllidea relative to the other acetabulate eucestode orders. Bayesian Inference analyses of various combinations of full ssrDNA, and full or partial lsrDNA (D1-D3), sequence data, which included 134 species representing 97 genera across the 15 eucestode orders, were conducted. New ssrDNA data were generated for 82 species, partial lsrDNA data for 53 species, and full lsrDNA data for 29 species. The monophyly of each of the elasmobranch-hosted orders Cathetocephalidea, Litobothriidea, Lecanicephalidea, and Rhinebothriidea was confirmed, as was the non-monophyly of the Tetraphyllidea. Two relatively stable groups of tetraphyllidean taxa emerged and are hereby designated as new orders. The Onchoproteocephalidea n. ord. is established to recognize the integrated nature of one undescribed and ten described genera of hook-bearing tetraphyllideans, previously of the family Onchobothriidae, with the members of the order Proteocephalidea. The Phyllobothriidea n. ord. is established for a subset of 12 non-hooked genera characterized by scoleces bearing four bothridia each with an anterior accessory sucker; most parasitise sharks and have been assigned to the Phyllobothriidae at one time or another. Tentative ordinal placements are suggested for 8 additional genera; placements for the remaining tetraphyllidean genera have not yet emerged. We propose these 17 genera remain in the "Tetraphyllidea". Among these, particularly labile across analyses were Anthobothrium, Megalonchos, Carpobothrium, Calliobothrium, and Caulobothrium. The unique association of Chimaerocestus with holocephalans, rather than with elasmobranchs, appears to represent a host-switching event. Both of the non-elasmobranch hosted clades of acetabulate cestodes (i.e., Proteocephalidea and Cyclophyllidea and their kin) appear to have had their origins with elasmobranch cestodes. Across analyses, the sister group to the clade of "terrestrial" cestode orders was found to be an elasmobranch-hosted genus; as was the sister to the Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts freshwater fish and tetrapod-hosted Proteocephalidea. Whilst further data are required to resolve outstanding nomenclatural and phylogenetic issues, the present analyses contribute significantly to an understanding of the evolutionary radiation of the entire Cestoda. Clearly, elasmobranch tapeworms comprise the backbone of cestode phylogeny.

A new genus of rhinebothriidean cestodes from batoid elasmobranchs, with the description of five new species and two new combinations

“…Host specificity in S. ashleyae, S. campbelli, S. jeanfortiae, S. hyphantoseptum and S. amuletum was much more strict and also much more in line with that seen in other non-trypanorhynch orders of elasmobranch-hosted cestodes (see Caira and Jensen 2014), for each was found to parasitise only a single host species. Host specificity in S. cadenati is also slightly more relaxed in that is has been reported from two species, Zanobatus schoenleinii and Rh- inobatos rhinobatos, both in Senegal.…”

A new genus and species of proteocephalidean tapeworm (Cestoda), first parasite found in the driftwood catfish Tocantinsia piresi (Siluriformes: Auchenipteridae) from Brazil

“…Based on a molecular phylogenetic study of tetraphyllidean-like cestodes of elasmobranchs, Caira et al (2014) proposed a new order, Onchoproteocephalidea, to accommodate several taxa from elasmobranchs previously placed in the tetraphyllidean family Onchobothriidae Braun, 1900 and the entire order Proteocephalidea Mola, 1928. However, this new order was not sufficiently circumscribed and no morphological synapomorphies were provided in its brief diagnosis.…”

Conflict between morphology and molecular data: a case of the genus Caryophyllaeus (Cestoda: Caryophyllidea), monozoic tapeworms of cyprinid fishes

“…Monozoic fish cestodes of the order Caryophyllidea Carus, 1863 seem to represent the most basal group of 'true' tapeworms (Eucestoda) (Olson et al 2001, Waeschenbach et al 2012, Caira et al 2014). Subtle differences in shape and size of the scolex and the anteriormost extent of vitelline follicles and testes play the central role in species identification of some groups of caryophylideans (Dubinina 1987, Oros et al 2010.…”