This study presents the first comprehensive phylogenetic analysis of the interrelationships of the morphologically diverse elasmobranch-hosted tapeworm order Lecanicephalidea, based on molecular sequence data. With almost half of current generic diversity having been erected or resurrected within the last decade, an apparent conflict between scolex morphology and proglottid anatomy has hampered the assignment of many of these genera to families. Maximum likelihood and Bayesian analyses of two nuclear markers (D1-D3 of lsrDNA and complete ssrDNA) and two mitochondrial markers (partial rrnL and partial cox1) for 61 lecanicephalidean species representing 22 of the 25 valid genera were conducted; new sequence data were generated for 43 species and 11 genera, including three undescribed genera. The monophyly of the order was confirmed in all but the analyses based on cox1 data alone. Sesquipedalapex placed among species of Anteropora and was thus synonymized with the latter genus. Based on analyses of the concatenated dataset, eight major groups emerged which are herein formally recognised at the familial level. Existing family names (i.e., Lecanicephalidae, Polypocephalidae, Tetragonocephalidae, and Cephalobothriidae) are maintained for four of the eight clades, and new families are proposed for the remaining four groups (Aberrapecidae n. fam., Eniochobothriidae n. fam., Paraberrapecidae n. fam., and Zanobatocestidae n. fam.). The four new families and the Tetragonocephalidae are monogeneric, while the Cephalobothriidae, Lecanicephalidae and Polypocephalidae comprise seven, eight and four genera, respectively. As a result of their unusual morphologies, the three genera not included here (i.e., Corrugatocephalum, Healyum and Quadcuspibothrium) are considered incertae sedis within the order until their familial affinities can be examined in more detail. All eight families are newly circumscribed based on morphological features and a key to the families is provided. Aspects of morphological evolution and host associations are discussed in a phylogenetic context for each family and for the order as a whole. Lecanicephalidean genera lacking apical structures were confirmed as the earliest diverging lineages. Proglottid anatomy was determined to be much more conserved and indicative of phylogenetic affinities than scolex morphology. Collectively, the Lecanicephalidea parasitize three of the four orders of Batoidea-their almost exclusive absence from skates (Order Rajiformes) appears to be real; only a few records from sharks exist. At the family level, the breadth of host associations is correlated with taxonomic diversity of the family. The degree to which factors such as intermediate host use or host specificity at any stage in the life-cycle shape these patterns is currently unknown.
Hexacanalis Perrenoud, 1931 was erected for H. abruptus (Southwell, 1911) Perrenoud, 1931 based on the presence of six excretory vessels, a unique feature among the Lecanicephalidea. The genus has since been considered a junior synonym of Cephalobothrium Shipley & Hornell, 1906 or Lecanicephalum Linton, 1890, or as a genus inquirendum. Based on examination of the syntype series of H. abruptus, this species is redescribed and a lectotype designated. Examination of cestodes from the zonetail butterfly ray Gymnura zonura (Bleeker) from off Indonesian Borneo resulted in the discovery of a second species. Hexacanalis folifer n. sp. is unique among lecanicephalideans in its possession of an ovary that is U-shaped in cross-section and craspedote proglottids with prominent posterior dorso-ventral processes in the form of large lappets. The presence of six excretory vessels, confirmed in both species, supports the validity of Hexacanalis. An additional species, H. pteroplateae (Zaidi & Khan, 1976) n. comb., also from a butterfly ray, G. micrura (Bloch & Schneider) [as Pteroplatea micrura (Bloch & Schneider)], is transferred to this genus from Cephalobothrium Shipley & Hornell, 1906. A revised diagnosis of Hexacanalis is presented. Seven species of this genus remain species inquirendae. Hexacanalis appears to parasitise species of the Gymnuridae van Hasselt; however, specific identifications of the hosts are in need of re-evaluation. A summary of the cestode parasites of the Gymnuridae is presented.
This is the published version of the article, made available with the permission of the publisher. The original published version can be found at the link below. Janine N. Caira, Ph.D.Order of Authors Secondary Information:Abstract: Floriparicapitus n. gen. (Cestoda: Lecanicephalidea), with F. euzeti n. gen. n. sp. as its type, is erected to house 3 new tapeworm species and 2 known species that are transferred to the new genus, all parasitizing sawfishes and guitarfishes (order Rhinopristiformes) in Indo-Pacific waters. The new genus differs from the 20 valid lecanicephalidean genera in its possession of a large scolex bearing a laterally expanded apical organ in the form of a rugose sheet in combination with a cirrus conspicuously armed with spinitriches and 3 pairs of excretory vessels. It most closely resembles Lecanicephalum, but differs conspicuously in its possession of 3, rather than 1, pair of excretory vessels. Two new species are described from sawfishes: Floriparicapitus euzeti n. sp., from Pristis clavata and Floriparicapitus juliani n. sp. from Pristis microdon, both from Australia. Floriparicapitus plicatilis n. sp. is described from the guitarfish Glaucostegus typus in Australia and the guitarfish Glaucostegus thouin in Malaysian Borneo. Two species formerly assigned to Cephalobothrium are transferred to the new genus; Floriparicapitus variabilis (Southwell, 1911) n. comb. from the sawfish Anoxypristis cuspidata in Sri Lanka and Floriparicapitus rhinobatidis (Subhapradha, 1955) n. comb. from the guitarfish Glaucostegus granulatus in India. The species from guitarfish differ conspicuously from those parasitizing sawfish in their possession of only 4 (F. plicatilis n. sp.) or 5 (F. rhinobatidis n. comb.) testes per proglottid, versus 9 or more in the 3 sawfish-parasitizing species. The latter 3 species differ from one another in scolex width, acetabular size, number of proglottids, and cirrus sac size. As it stands, the new genus appears to be restricted to a subclade of the Rhinopristiformes consisting of the sawfishes and species of Glaucostegus.
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