A world of taxonomic pain: cryptic species, inexplicable host-specificity, and host-induced morphological variation among species of Bivesicula Yamaguti, 1934 (Trematoda: Bivesiculidae) from Indo-Pacific Holocentridae, Muraenidae and Serranidae

Abstract

The taxonomy of species of Bivesicula Yamaguti, 1934 is analysed for samples from holocentrid, muraenid and serranid fishes from Japan, Ningaloo Reef (Western Australia), the Great Barrier Reef (Queensland), New Caledonia and French Polynesia. Analysis of three genetic markers (cox1 mtDNA, ITS2 and 28S rDNA) identifies three strongly supported clades of species and suggests that Bivesicula as presently recognized is not monophyletic. On the basis of combined morphological, molecular and biological data, 10 species are distinguished of which five are proposed as new. Bivesicula Clade 1 comprises seven species of which three are effectively morphologically cryptic relative to each other; all seven infect serranids and four also infect holocentrids. Bivesicula Clade 2 comprises three species of which two are effectively morphologically cryptic relative to each other; all three infect serranids and one also infects a muraenid. Bivesicula Clade 3 comprises two known species from apogonids and a pomacentrid, and forms a clade with species of Paucivitellosus Coil, Reid & Kuntz, 1965 to the exclusion of other Bivesicula species. Taxonomy in this genus is made challenging by the combination of low resolving power of ribosomal markers, the existence of regional cox1 mtDNA populations, exceptional and unpredictable host-specificity and geographical distribution, and significant host-induced morphological variation.

Integrated characterisation of nine species of the Schistorchiinae (Trematoda: Apocreadiidae) from Indo-Pacific fishes: two new species, a new genus, and a resurrected but ‘cryptic’ genus

“…Specimens for molecular analysis were processed according to the protocols used by Cribb et al ( 2022 ). Three genetic markers were sequenced, the second internal transcribed spacer region (ITS2 rDNA), the large (28S) ribosomal subunit RNA coding region and the cytochrome c oxidase subunit 1 ( cox 1 mtDNA) mitochondrial region.…”

Molecular species delimitation of marine trematodes over wide geographical ranges: Schikhobalotrema spp. (Digenea: Haplosplanchnidae) in needlefishes (Belonidae) from the Pacific Ocean and Gulf of Mexico

“…(2022), Cribb et al . (2022) and Cutmore et al . (2021), the hypothesis we present herein for Schikhobalotrema is based heavily on the interpretation of the cox 1 data; although partially supportive of the cox 1 relationships, ribosomal data are proving to be less informative to delineate species in trematodes that have conserved morphology, but still a proper marker to separate species (see Pérez-Ponce de León and Hernández-Mena, 2019).…”

“…(2022) demonstrated that Helicometroides longicollis Yamaguti, 1934 (Monorchiidae) is distributed between Japan and Australia, and Cribb et al . (2022) showed that Bivesicula claviformis Yamaguti, 1934 is found, at least, in Japan and of both the Indian and Pacific coasts of Australia. It must be noted, however, that for each of these widespread species, all these above studies demonstrated that at least some of their congeners were highly restricted with equally convincing data.…”

Evidence for two morphologically cryptic species of Hysterolecitha Linton, 1910 (Trematoda: Lecithasteridae) infecting overlapping host ranges in Moreton Bay, Australia

“…However, the genetic differences among some closely related, non-cryptic species has been reported to be much lower. For example, studies on morphologically distinguishable species of bivesiculids (Trieu et al, 2015 ; Cribb et al, 2022 ) and lepocreadiids (Bray et al, 2018 ; Bray et al, 2022 ) from GBR fishes have reported differences at one to two base positions in the ITS2 region and up to 52 base positions in the cox 1 region. We conclude that use of a ‘yardstick’ approach to the interpretation of the significance of levels of molecular distinction is problematic.…”