Molecular and morphological identification of helminthes found in Japanese smelt, Hypomesus transpacificus nipponensis, with notes on new host records of Eustrongylides ignotus and Raphidascaris gigi

Abstract

As an adult, Eustrongylides ignotus, recognized as a zoonotic parasite, is a parasitic nematode found in the gastrointestinal tract of fish-eating birds. As larvae, they are found in the connective tissue or body cavities of freshwater fish. In Japan, E. ignotus and E. tubifex have been found in three avian species, but their distribution in intermediate and paratenic hosts remains unclear. For this study, 16 commercial raw Japanese smelts, Hypomesus transpacificus nipponensis, were used for parasitological examination. A pinkish red worm collected from the abdominal wall of one smelt (6.3%) was identified as E. ignotus based on the high sequence similarity (99.9%) of the partial 18S ribosomal RNA gene and the morphology of its cephalic and caudal ends. Furthermore, a Raphidascaris-like nematode was found in the intestines of five smelts examined (31.3%) and was identified as R. gigi in view of the absence of lateral cuticular alae. Eustrongylides ignotus and R. gigi have been reported in various freshwater fish, but not in smelts. Therefore, this finding of E. ignotus and R. gigi in H. transpacificus nipponensis represents a new host record.

Rhabdochona angusticaudata sp. n. (Nematoda: Rhabdochonidae) from the Japanese eel Anguilla japonica, and new records of some other nematodes from inland fishes in Japan

“…(both Gobiidae) and Channa argus (Channidae) (Yamaguti 1941, Shimazu et al 2000. Currently, based on molecular and morphological studies, a pinkish worm from the abdominal wall of the Japanese smelt Hypomesus nipponensis McAllister (reported as H. transpacificus nipponensis) (Osmeridae) caught in Lake Biwa, Shiga Prefecture, Honshu, was identified as a larva of Eustrongylides ignotus Jägerskiöld, 1909 (see Abe 2011). In this study, one specimen of Eustrongylides sp.…”

Parasites of zoonotic interest in selected edible freshwater fish imported to Australia

“…Eight specimens (sample numbers 378–5; 380–1; 447–1; 477–1; 477–2; 478–1; 479–1 and 481–1) belonging to Eustrongylides had the 18S ribosomal RNA gene sequence of 774 bp long and showed 100% similarity with GenBank sequences assigned for E. ignotus (accession number AB558484 ) identified from Japanese smelts ( Hypomesus transpacificus nipponensis ) in Lake Biwa, Japan ( Abe, 2011 ). Due to the poor quality of the chromatogram, no sequences were obtained for specimen 481–2.…”

First detection of Eustrongylides excisus (Nematoda: Dioctophymatidae) in big-scale sand smelt (Atherina boyeri) from the lake Massaciuccoli (Northwest Tuscany, Italy): implications for public health and seafood quality

“…Interestingly, these molecular outcomes seem to concord with the geographical distribution across Europe and Asia reported by Measures (1988b) for this species E. excisus. However, further molecular studies are needed to elucidate the geographical distribution, as well as the epidemiology and the taxonomical classification (Abe, 2011).…”