Echinocephalus inserratus sp. n. (Nematoda: Gnathostomatidae) from the stingray Pastinachus ater (Dasyatidae) and new records of congeneric and some other nematode larvae from teleost fishes off New Caledonia.

Jean-Lou Justine,František Moravec

doi:10.14411/fp.2021.014

Abstract

Based on light and electron microscopical studies, a new nematode parasite, Echinocephalus inserratus sp. n. (Spirurida: Gnathostomatidae), is described from the spiral valve of the broad cowtail stingray Pastinachus ater (Macleay) (Dasyatidae, Myliobatiformes) from off New Caledonia. The new species is morphologically and biometrically most similar to Echinocephalus overstreeti Deardorff et Ko, 1983, differing from it mainly in the absence of serrations on the posterior parts of pseudolabia and on interlabia, and in having a longer gubernaculum (150-299 µm long). Morphologically unidentifiable, mostly encapsulated larvae of Echinocephalus spp. were recorded from the following six species of teleost fishes collected in New Caledonian waters, serving as paratenic hosts: Perciformes: Acanthopagrus berda (Forsskål) (Sparidae) and Nemipterus furcosus (Valenciennes) (Nemipteridae); Tetraodontiformes: Abalistes stellatus (Anonymous), Pseudobalistes fuscus (Bloch et Schneider) (both Balistidae), Lagocephalus sceleratus (Gmelin) (Tetraodontidae) and Aluterus monoceros (Linnaeus) (Monacanthidae). Co-parasitising larvae of Ascarophis sp. and Hysterothylacium sp. were also collected from P. fuscus. All these findings represent new host and geographical records. A key to valid species of Echinocephalus Molin, 1858 is provided.

Highlights

As mentioned by Moravec and Justine (2006), the taxonomy of nematodes of the gnathostomatid genus Echinocephalus Molin, 1858 remains rather confused, mainly because of the inadequate descriptions of many species, often based on larval forms collected from teleost fishes or some marine invertebrates, which probably serve only as paratenic or second intermediate hosts for these parasites (Ivashkin and Khromova 1976, Anderson 2000)
The recent examination of nematodes collected from the stingray Pastinachus ater (Macleay) (Dasyatidae) and some teleosts of the perciform and tetraodontiform families Balistidae, Monacanthidae, Nemipteridae, Sparidae and Tetraodontidae off New Caledonia during 2005–2009, revealed the presence of adult nematodes representing a new species of Echinocephalus in the ray and congeneric larvae (Echinocephalus spp.) in teleosts
Whereas Ancyracanthus includes one species parasitic in Neotropical characids and another one parasitising chelonians, and Mooleptus is represented by a single species from sharks, many nominal species of Echinocephalus were described from elasmobranchs and teleosts (Moravec 2007, Gibbons 2010, Özdikmen 2010)

Summary

Introduction

As mentioned by Moravec and Justine (2006), the taxonomy of nematodes of the gnathostomatid genus Echinocephalus Molin, 1858 remains rather confused, mainly because of the inadequate descriptions of many species, often based on larval forms collected from teleost fishes or some marine invertebrates, which probably serve only as paratenic or second intermediate hosts for these parasites (Ivashkin and Khromova 1976, Anderson 2000). The revision of the respective literature shows that only elasmobranchs, mainly rays and less often sharks, are the definitive hosts (as defined by Odening 1976) of Echinocephalus spp. Other nematodes from elasmobranchs (sharks) off News Caledonia were reported by Moravec and Justine (2020). This study adds new records of fish parasites off New Caledonia, already abundantly documented (Justine 2010, Justine et al 2010a,b, 2012a)

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