Morphological and molecular description of Rhadinorhynchus laterospinosus Amin, Heckmann & Ha, 2011 (Acanthocephala, Rhadinorhynchidae) from marine fish off the Pacific coast of Vietnam

Abstract

Rhadinorhynchus laterospinosus Amin, Heckmann & Ha, 2011 (Rhadinorhynchidae) was described from a single female collected from a trigger fish, Balistes sp. (Balistidae) from the northern Pacific coast of Vietnam in Halong Bay, Gulf of Tonkin. More recent collections of fishes in 2016 and 2017 revealed wider host and geographical distributions. We report this Acanthocephala from nine species of fish representing six families (including the original record from Balistes sp.) along the whole Pacific coast of Vietnam. The fish species are Alectis ciliaris (Carangidae), Auxis rochei (Scombridae), Auxis thazard (Scombridae), Leiognathus equulus (Leiognathidae), Lutjanus bitaeniatus (Lutjanidae), Megalaspis cordyla (Carangidae), Nuchequula flavaxilla (Leiognathidae), and Tylosurus sp. (Belonidae). We provide a complete description of males and females of R. laterospinosus, discuss its hook metal microanalysis using EDAX, and its micropores. Specimens of this species characteristically have lateral trunk spines bridging the anterior ring of spines with posterior field of ventral spines and a proboscis with 15–19 longitudinal alternating rows of 21–26 hooks each varying with host species. We demonstrate the effect of host species on the distribution and size of the trunk, proboscis, proboscis hooks, trunk spines, and reproductive structures. The molecular profile of this acanthocephalan, based on 18S rDNA and cox1 genes, groups with other Rhadinorhynchus species and further seems to confirm the paraphyly of the genus, which is discussed.

Molecular characterisation of acanthocephalans from Australian marine teleosts: proposal of a new family, synonymy of another and transfer of taxa between orders

“…Preliminary analyses indicated taxonomic changes to the Rhadinorhynchidae Lühe, 1912 may be required, therefore additional phylogenetic analyses were performed for available sequences of this and related lineages alone using only 18S rDNA sequences, including taxa for which 28S rDNA sequences were not available. Both Amin et al (2019) and Lisitsyna et al (2019) commented on some sequences available on GenBank which have been incorrectly assigned to the genus Rhadinorhynchus; we have followed these authors regarding currently accepted sequences of rhadinorhynchids. Rotifers were used for outgroup taxa for the Acanthocephalawide analyses and a single species each of the Archiacanthocephala and Eoacanthocephala were used as outgroup taxa for the rhadinorhynchid sub-analyses.…”

The molecular profile of Paratrajectura longcementglandatus Amin, Heckmann et Ali, 2018 (Acanthocephala: Transvenidae) from percid fishes in the marine waters of Iran and Iraq

“…In the present study, the higher level of variation in cox1 gene compared to the 18S rDNA gene provides better resolution of the relationships within closely related taxa. While Amin et al (2019a) presented relationships in their analysis of Rhadinorhynchus based on cox1 sequences, it was not clearer than 18S rDNA due to the lack of sufficient sequences of this gene in GenBank. One of the most commonly used molecular markers for classification of acanthocephalans is the small subunit from RNA ribosomal gene or 18S rRNA.…”

Helminth infections in fish in Vietnam: A systematic review

“…The following families were recorded in marine fish: Arhythmacanthidae, Cavisomatidae, Echinorhynchidae, and Neoechinorhynchidae, Rhadinorhynchidae and Transvenidae ( Amin et al, 2018a , b , 2019c ). In the South , only acanthocephalans of the following families were reported in marine fish: Cavisomatidae, Neoechinorhynchidae, Quadrigyridae and Rhadinorhynchidae ( Amin et al, 2014 , 2019a , b , e ).…”