The Rhoptrobothriidae are one of the more enigmatic families of cestodes of elasmobranchs. Opinions on the taxonomic status of the family’s three original genera (i.e., Myzophyllobothrium, Rhoptrobothrium, and Myzocephalus) have varied over the 115 years since they were erected. Some authors have considered all three valid, others have considered Rhoptrobothrium to be a synonym of Myzopyllobothrium or a genus inquirendum, yet others have considered Myzocephalus to be a synonym of the phyllobothriid genus Thysanocephalum. All three genera were established for specimens collected from eagle rays off Sri Lanka. The erection of Mixophyllobothrium for two specimens from a cowtail stingray off India three decades ago added additional confusion to the situation, with some authors considering it valid and others a synonym of Myzocephalus. These disagreements stem largely from differences in interpretation of the complex morphology of the scolex of members of these genera. Furthermore, with the exception of Rhoptrobothrium comprising four species, each genus is monotypic. All but Rhoptrobothrium has not been considered in detail for nearly a century, largely because of a lack of available material. The taxonomic status of these genera is assessed here based on light and scanning electron microscopy, and molecular data generated from new material collected from eagle rays off Indonesian and Malaysian Borneo, Japan, Sri Lanka, and Viet Nam. Morphological work indicates that the genera differ largely only in the degree of folding of the four remi that extend from the cephalic peduncle. A molecular phylogeny based on sequence data for the D1–D3 region of the 28S rRNA gene, which include new data for eight specimens of four species, indicates that Myzophyllobothrium, Myzocephalus, and Rhoptrobothrium are not mutually monophyletic. The latter two genera and Mixophyllobothrium are considered synonyms of Myzophyllobothrium and five species are transferred to that genus. Myzophyllobothrium okamuri n. comb. is considered a species inquirendum. Myzophyllobothrium nagasawai n. sp. is described from Aetobatus narutobiei off Japan. Myzophyllobothrium narinari n. comb. is re-described based on newly collected cestodes from the type host and locality (i.e., Aetobatus ocellatus off Sri Lanka). Despite consisting of only a single genus, the family status of the group is retained in recognition of the unusual configuration of the scolex, which bears four biloculate bothridia and four remi extending from the cephalic peduncle. The ordinal placement of the family remains uncertain, but affinities with the Phyllobothriidea, rather than “Tetraphyllidea” are considered.
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Phylogenetic analysis and diversity of peculiar new lecanicephalidean tapeworms (Eniochobothriidae) from cownose rays across the globe
The three members of the lecanicephalidean tapeworm family Eniochobothriidae are unusual among tapeworms in that they lack a vagina and possess a series of expanded proglottids forming a trough at the anterior end of their body. They exclusively parasitise cownose rays of the genus Rhinoptera (Myliobatiformes: Rhinopteridae). New collections from six of the nine known species of cownose rays from the waters off Australia, Mexico, Mozambique, Senegal, Taiwan and the United States (off Mississippi, Louisiana and South Carolina) yielded eight new species and a new genus of eniochobothriids. Here we erect Amiculucestus, gen. nov. and describe six of the eight new species – four in the new genus and two in Eniochobothrium – expanding the number of genera in the family to two and the number of described species in the family to nine. Morphological work was based on light and scanning electron microscopy. The tree resulting from a maximum likelihood analysis of sequence data for the D1–D3 region of the 28S rDNA gene for 11 species of eniochobothriids supports the reciprocal monophyly of both genera. The mode of attachment to the mucosal surface of the spiral intestine of the host was investigated using histological sections of worms in situ. These cestodes appear to use the anterior trough-like portion of their body, which consists of an unusual series of barren proglottids, rather than their scolex, to attach to the mucosal surface. Based on our new collections, we estimate that the total number of eniochobothriids across the globe does not exceed 27 species. ZooBank LSID: urn:lsid:zoobank.org:pub:0740EC72‐AC3F‐43AA‐BD41‐B9820BA9D0CE
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- NSF-PAR ID:
- 10448718
- Editor(s):
- Worsaae, Katrine
- Date Published:
- Journal Name:
- Invertebrate Systematics
- Volume:
- 36
- Issue:
- 10
- ISSN:
- 1445-5226
- Page Range / eLocation ID:
- 879 to 909
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The genus
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1071/IS22018
