The Pseudoplagioporinae, a new subfamily in the Opecoelidae Ozaki, 1925 (Trematoda) for a small clade parasitizing mainly lethrinid fishes, with three new species

Abstract

The Pseudoplagioporinae n. subf. (Opecoelidae) is proposed for species of Pseudoplagioporus Yamaguti, 1938, Fairfaxia Cribb, 1989, and Shimazuia Cribb, 2005, a small group of relatively distinctive, Indo‐West Pacific taxa reliably known almost entirely from emperor fishes (Perciformes: Lethrinidae). These taxa were previously recognized in the Plagioporinae Manter, 1947, but that subfamily has recently been restricted to a clade of Holarctic, freshwater taxa, whereas analyses of new genetic data find the pseudoplagioporines to form a distinct clade among a larger assemblage of marine taxa. New material was sourced from fishes collected mainly in Queensland waters, Australia, but with some specimens from off Western Australia, the Northern Territory, and Japan. Orthodena tropica Durio & Manter, 1968 is transferred to Pseudoplagioporus as P. tropicus (Durio & Manter, 1968) n. comb., and Orthodena Durio & Manter, 1968 thus becomes a synonym of that genus. Three new species of Pseudoplagioporus are proposed. One, P. mediocris n. sp., like other species of Pseudoplagioporus, occurs in several species of Lethrinus. The other two new species, P. labiatus n. sp. and P. roseovulatus n. sp., apparently do not infect species of Lethrinus and were instead found only in the Bigeye emperor Monotaxis grandoculis (Forsskål) and the Redfin emperor M. heterodon (Bleeker), respectively. New host‐locality combinations and the first genetic data, for the ribosomal ITS2 DNA region, and the 28S rRNA, 18S rRNA, and cox1 mtDNA genes, are reported for Pseudoplagioporus lethrini Yamaguti, 1938, P. interruptus Durio & Manter, 1968, P. tropicus, Fairfaxia lethrini Cribb, 1989, Fairfaxia cribbi Hassanine & Gibson, 2005, and Shimazuia lethrini (Yamaguti, 1938) Cribb, 2005.

A Phylogenetic Re-Evaluation of the Stenakrine Opecoelids (Trematoda, Digenea: Opecoeloidea) with Some Taxonomic Novelties

“…To assess the phylogenetic affinities of nominal stenakrine taxa, maximum likelihood and Bayesian inference analyses were performed against a concatenated 18S + 28S alignment including the novel data as well as other relevant sequences from GenBank. Sequences for general alignment of the main subfamilies/clades, including the Opecoelidae, other xiphidiate families belonging to the Gorgoderoidea, Haploporoidea, Troglotrematoidea, Microphalloidea, Plagiorchioidea and Brachycladioidea, as well as non-xiphidiate taxa including from the Monorchiata, Lepocreadiata, Opisthorchiata, Apocreadiata, Gymnophallata, and Hemiurata were downloaded from GenBank database [3,8,9,11,18,20,22,27,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] with custom R script [45] based on the "ape" package [46]. To concatenate sequences of 18S and 28S rRNA genes "catfasta2phyml.pl" script [47] was used with "-f" parameter.…”

“…For example, the absence of the canalicular seminal receptacle is also typical for opecoelines, and Shimazuia Cribb, 2005 (Pseudoplagioporinae) is defined for relatively short fields of vitelline follicles [7]. However, all together they do not occur in any subtaxon of the Opecoelidae (compare with [3,4,7,9,11]). The Stenakridae stat.…”

“…The family has a complex taxonomic structure. According to the modern concept, which is based on phylogenetic and morphological data, 11 subfamilies and several early-branching clades are distinguished within the Opecoelidae [3][4][5][6]. Nomenclatural formalization at the subfamily level for these early branching clades is clearly required.…”

“…It is a relatively small group, comprising eight genera: Biospeedotrema Bray, Waeschenbach, Dyal, Littlewood and Morand, 2014, Caudotestis Issaitschikov, 1928, Hexagrammia Baeva, 1965, Holsworthotrema Martin, Huston, Cutmore, and Cribb, 2019, Neonotoporus Srivastava, 1942, Pseudopecoelina Yamaguti, 1942, Scorpidotrema Aken'Ova and Cribb, 2003, andStenakron Stafford, 1904 [7-9]. Originally, the Stenakrinae was erected as a subfamily in the Fellodistomidae Nicoll, 1909 [10], but subsequently began to be regarded as a subfamily of the Opecoelidae [3,4,[7][8][9]11,12]. Notably, members of the Stenakrinae originally placed outside of this subfamily were considered as fellodistomid, opecoelid, or allocreadiid concepts [13][14][15][16][17].…”

Retroporomonorchis pansho n. g., n. sp., an unusual monorchiid trematode exploiting an atypical host

“…Cryptogonimids in lutjanids and pseudoplagioporine opecoelids in lethrinids are two groups which have been relatively thoroughly surveyed, yet Miller & Cribb (2013) found Siphomutabilus bitesticulatus Cribb, 2013 andS. raritas Miller &Cribb, 2013 in only 1 of 21 Pterocaesio marri (Schultz) and 1 of 18 Caesio cuning (Bloch) respectively, and Martin et al (2020a) found Pseudoplagioporus lethrini Yamaguti, 1938 in only 1 of 51 Lethrinus miniatus (Forster) and 1 of 60 Lethrinus nebulosus (Forsskål). The nature of sampling is such that rarity is ultimately only demonstratable at local scales, and it remains possible that R. pansho is more common elsewhere, and/or in habitats, fishes or at depths beyond those we have surveyed.…”