Descriptions of acanthocephalans, Cathayacanthus spinitruncatus (Rhadinorhynchidae) male and Pararhadinorhynchus magnus n. sp. (Diplosentidae), from marine fish of Vietnam, with notes on Heterosentis holospinus (Arhythmacanthidae).

Nguyen Van Ha,Omar M Amin,Ha Duy Ngo,Richard A Heckmann

doi:10.1051/parasite/2018032

Abstract

Males of Cathayacanthus spinitruncatus Amin, Heckmann & Ha, 2014 (Rhadinorhynchinae Lühe, 1912) are described for the first time from Leiognathus equulus in Hai Phong and Nha Trang and from pony fish Nuchequula flavaxilla in Quang Ninh in the Pacific waters of Vietnam. The male allotype status is designated. Males of C. spinitruncatus are smaller and have fewer and smaller proboscis hooks and trunk spines than females. The male reproductive structures are in the posterior fifth of the trunk and with 6 club-shaped cement glands gradually merging into 6 independent cement gland ducts. The proboscis receptacle is more than half as long as the trunk and with a cephalic ganglion at its anterior end. In females, the receptacle is only about one fifth the length of the trunk. Specimens described as Cathayacanthus bagarii Moravec & Sey, 1989 were shown to have been wrongly assigned to Cathayacanthus. Pararhadinorhynchus magnus n. sp. (Diplosentidae) is described from Scatophagus argus off Hai Phong in the Gulf of Tonkin. It is the third species of the genus and is readily distinguished from the Australian species by having a considerably larger trunk and male reproductive structures, and more proboscis hooks. X-ray microanalysis (EDAX) of intact and gallium-cut hooks of P. magnus showed high calcium and phosphate mainly in the central core. Specimens of Heterosentis holospinus Amin, Heckmann & Ha, 2011 (Arhythmacanthidae) are also reported from L. equulus off Quang Binh, new host and locality records.

Highlights

Most of the recent taxonomic work on the Acanthocephala from Vietnam has been reported by the Amin-Heckmann-Ha team since 2000; see Amin & Ha [2, 3] and Amin et al [4,5,6,7, 9,10,11,12,13]
We describe males of Cathayacanthus spinitruncatus Amin, Heckmann & Ha, 2014 (Rhadinorhynchidae) previously known from females only [13], a new species of the genus Pararhadinorhynchus Johnston & Edmonds, 1947 (Diplosentidae), and record Heterosentis holospinus Amin, Heckmann & Ha, 2011 in a new host and locality
For a better understanding of the chemical elements of hooks and their relationship to hook structure, intact and gallium-cut hooks of P. magnus were scanned with X-ray (EDAX) and analyzed for percent chemical elements in various parts of the hooks

Summary

Introduction

Most of the recent taxonomic work on the Acanthocephala from Vietnam has been reported by the Amin-Heckmann-Ha team since 2000; see Amin & Ha [2, 3] and Amin et al [4,5,6,7, 9,10,11,12,13]. Twenty species of acanthocephalans in 5 families were collected more recently from fishes in the Pacific and amphibians in central Vietnam, in 2016 and 2017. For a better understanding of the chemical elements of hooks and their relationship to hook structure, intact and gallium-cut hooks of P. magnus were scanned with X-ray (EDAX) and analyzed for percent chemical elements in various parts of the hooks. This procedure has become a standard in our laboratory studies of the Acanthocephala [8, 19, 20]

Methods

Results

Conclusion