A New Species of Waginella (Crustacea: Thecostraca: Ascothoracida) Parasitic on a Stalked Crinoid From Tasman Sea, With Notes on Morphology of Related Genera

Gregory A Kolbasov,Alexandra S Savchenko,Benny K K Chan,William A Newman

doi:10.3389/fmars.2021.616001

Abstract

A new ectoparasitic ascothoracidan species has been discovered off northern Tasman Sea at a depth of 520 m. Single female, described herein as Waginella ebonita Kolbasov and Newman sp. nov. in the family Synagogidae Gruvel, 1905, was collected on the column of crinoid Metacrinus sp. This is the first study of a new form of Waginella to be based on the extensive use of both light and scanning electron microscopy to document the fine-scale external morphology. We studied the external morphology of other two species of Waginella, W. cf. axotremata and W. sandersi utilizing SEM and compared fine structures of all congeners. The genus Waginella represents a monophyletic taxon including at least 4 species having similar and unique morphology even on the ultrastructural level. Two species, W. cf. axotremata and W. cf. metacrinicola may represent at least two complexes of species. The morphology of an attachment apparatus in all species of Waginella suggests that they remain attached to the host for a considerable period of time. The lattice organs of Waginella have a unique structure distinguishing from all Thecostraca. Waginella ebonita sp. nov. is the second species of this genus known to harbor hyperparasitic cryptoniscid isopods representing parasitic castrators.

Highlights

The Ascothoracida are relatively little known, exclusively parasitic crustaceans that range from ecto- to endoparasites found on cnidarians (Alcyonacea, Antipatharia, Scleractinia, and Zoantharia) and echinoderms (Asteroidea, Crinoidea, Echinoidea, and Ophiuroidea) when compared to other crustacean parasitic taxa including parasitic copepods and isopods (Figure 1)
We have shown that genus Waginella represents a monophyletic taxon including at least 4 species having similar and unique morphology even on the ultrastructural level albeit the Atlantic morphotype is distinct form that of the Indo-Pacific
The lattice organs of Waginella have a unique structure distinguishing from all Thecostraca. It appears that only the morphology of lattice organs in homologous stages can currently be used in the phylogenetic reconstructions of Thecostraca

Summary

Introduction

The Ascothoracida are relatively little known, exclusively parasitic crustaceans that range from ecto- to endoparasites found on cnidarians (Alcyonacea, Antipatharia, Scleractinia, and Zoantharia) and echinoderms (Asteroidea, Crinoidea, Echinoidea, and Ophiuroidea) when compared to other crustacean parasitic taxa including parasitic copepods and isopods (Figure 1). Deep-Water Parasitic Ascothoracida parasites of non-crinoid echinoderms The monophyly of these two orders is yet to be tested by molecular methods (Chan et al, 2021). The family Synagogidae represents the basal group of ascothoracidans, the most generalized of which belong to the genera Synagoga Norman, 1888, Sessilogoga Grygier, 1990b, and Waginella Grygier, 1983a. Adults of these genera retain some degree of vagility throughout their lives and are characterized by a bivalve carapace enclosing the whole body, the head with a pair of W-shaped, six-segmented prehensile antennules and an oral cone enclosing piercing mouthparts. Sessilogoga includes two species representing the vagile endoparasites of antipatharians (Grygier, 1990a; Kolbasov et al, 2020)

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