Review of South African genera of the family hexabothriidae price, 1942, parasites of chondrichthyan fishes
Vaughan, David Brendan
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The oligonchoinean monogenean family Hexabothriidae Price, 1942 currently consists of approximately 60 valid species, representing 15 genera. Hexabothriids are gill parasites of chondrichthyan fishes (sharks, rays and chimaeras). Some hexabothriid species have been reported as problematic in public aquaria, directly responsible for host pathology and subsequent host mortalities. However, without information on specific hexabothriid species and their host associations, accurate captive management of hexabothriids in public aquaria is hindered. Hexabothriid taxonomy is in a state of confusion. The historic taxonomic restoration of the priority of Hexabothrium sees the beginning of the taxonomic uncertainty of the hexabothriids, and is continued into the present literature particularly among lower-level taxa in Hexabothriidae. In addition, there is currently no consensus for a single accepted morphometric protocol for the discrimination of hexabothriid taxa, which leads to unnecessary ambiguity of character variable nomenclature, measurement and interpretation. A call for stability in the nomenclature and morphometric discrimination of species is therefore proposed. A novel morphometric protocol is tested for the sclerotised haptoral armature, supported by the proteolytic digestion of structures for optimal representation. Character variables, subjected to univariate and multivariate analyses were systematically accepted or rejected based on their potential to discriminating species of Callorhynchocotyle Suriano and Incorvaia, 1986. The hexabothriid genera Callorhynchocotyle and Branchotenthes, represented by South African taxa, are reviewed, using these variables. Four Callorhynchocotyle species and 2 Branchotenthes species are redescribed with the inclusion of some new voucher specimens.