Abstract
Three species of Opisthomonorcheides Parukhin, 1966 are reported for the first time from Indonesian waters: O. pampi (Wang, 1982) Liu, Peng, Gao, Fu, Wu, Lu, Gao & Xiao, 2010 and O. ovacutus (Mamaev, 1970) Machida, 2011 from Parastromateus niger (Bloch), and O. decapteri Parukhin, 1966 from Atule mate (Cuvier). Both O. pampi and O. ovacutus can now be considered widespread in the Indo-Pacific region, with earlier records of these species being from Fujian Province, China and Penang, Malaysia, respectively. We redescribe O. decapteri from one of its original hosts, Atule mate, off New Caledonia, and report this species from Jakarta Bay, Indonesia, extending its range throughout the Indian Ocean into the south-western Pacific. All three species possess a genital atrium that is long, sometimes very long, and a genital pore that is located in the forebody. This validates the interpretation that the original description was erroneous in reporting the genital pore in the hindbody, well posterior to the ventral sucker. These observations verify the synonymy of Retractomonorchis Madhavi, 1977 with Opisthomonorcheides. A major discrepancy between the species of Opisthomonorcheides is that some are described with the uterus entering the terminal organ laterally and some with it entering terminally; this feature needs further analysis. Based on the length of the genital atrium and the posterior extent of the vitellarium, the 27 species of Opisthomonorcheides considered valid can be divided into four groups. Among the 53 host records analysed, the families Carangidae (53% of records), Stromateidae (17%) and Serranidae (5.7%) are the most common; the reports are overwhelmingly from members of the Perciformes (91%), with further records in the Clupeiformes (5.7%), Gadiformes (1.9%) and Pleuronectiformes (1.9%). Two fish genera (Parastromateus Bleeker and Pampus Bonaparte) dominate the recorded hosts, with the black pomfret Parastromateus niger harbouring six species, the silver pomfret Pampus argenteus (Euphrasen) harbouring six, and the Chinese silver pomfret P. chinensis (Euphrasen) two. A host-parasite checklist is presented. We discuss the host-specificity of members of the genus, questioning some records such as that of O. decapteri in a deep-sea macrourid. We also comment on the morphological similarity, but phylogenetic distance, between the various Pomfret species, advancing the possibility that a series of host misidentifications has occurred. Sequences of the ITS2 rDNA gene generated for O. pampi and O. ovacutus are briefly discussed and molecular data are lodged in the GenBank database.
Highlights
Fish parasitological studies in Indonesian waters demonstrate the difficulty of an enormous biodiversity confronted by a meagre research effort and a lack of competent investigations
Several new parasite species have been described in recent years (e.g. Palm, 2004; Bray & Palm, 2009; Yong et al, 2016), the fauna remains largely unknown (Cribb et al, 2016); it can be expected that many more species await description and many other known species from the Indo-Pacific region occur off Indonesia
This genus was erected by Parukhin (1966) for a species reported from Decapterus sp. and Atule mate (Cuvier) in the Gulf of Tonkin, described with a genital pore in the hindbody well posterior to the ventral sucker
Summary
Fish parasitological studies in Indonesian waters demonstrate the difficulty of an enormous biodiversity confronted by a meagre research effort and a lack of competent investigations. We report three species of Opisthomonorcheides Parukhin, 1966, a genus not yet recorded off Indonesia, from two carangid species. Madhavi (1977) later described a new genus, Retractomonorchis Madhavi, 1977 (for R. delicatus Madhavi, 1977), from Pampus chinensis (Euphrasen) and P. argenteus (Euphrasen) off the Waltair Coast, India. She described the genus with a genital pore in the posterior. Machida (2011) described worms identified as belonging to the type-species of Opisthomonorcheides, O. decapteri Parukhin, 1966, from Rastrelliger kanagurta (Cuvier) off Palawan, the Philippines, with a long genital atrium and the genital pore in the posterior forebody. & Xiao, 2010, O. ovacutus (Mamaev, 1970) Machida, 2011 and O. decapteri are described for the first time from Indonesian waters
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