Do circum-Antarctic species exist in peracarid Amphipoda? A case study in the genus Epimeria Costa, 1851 (Crustacea, Peracarida, Epimeriidae)

Anne Loerz,Elizabeth Maas,Charles Oliver Coleman,Katrin Linse

doi:10.3897/zookeys.18.103

Abstract

The amphipod genus Epimeria is species rich in the Southern Ocean and at present eight of its 19 species are reported with circum-Antarctic distributions. For the first time, specimens of epimeriid species from the Antarctic Peninsula, the Weddell Sea and the Ross Sea were analysed using partial COI genes sequences and morphological characters. In total 37 specimens of 14 species of Epimeria and two species of Epimeriella were analysed and the resulting molecular topology checked by critically reviewing taxonomic characters. The genus Epimeriella, genetically grouping within Epimeria is synonymised with the genus Epimeria. Sequences distances between populations of the nominal species Epimeria robusta from the Weddell and Ross Sea led to detailed morphological investigations, resulting in the description of Epimeria robustoides sp. n. from the Weddell Sea. Epimeria robusta Barnard, 1930 from the Ross Sea is redescribed. Sequences of a damaged Epimeria specimen of a species new to science from the lower continental shelf of the eastern Weddell Sea were included. Based on the current study, the hypothesis of circum-Antarctic species’ distributions in brooding amphipods proved to be unlikely.

Highlights

In the Southern Ocean’s benthic ecosystem, crustaceans are by far the most specious taxon
We studied more than 30 E. robusta specimens from the Ross Sea and all agree with the type description: having a keel pleonite only well developed on segment 3, the posterior margin of pleonite 1 is drawn into a tooth and short teeth occur only on pleonite 3 and urosomite 1
Since our data either show intraspecific variation of less than 2.5%, and an interspecific variation of at least 8.4%, we suggest that Epimeria walkeri is in the process of speciation

Summary

Introduction

In the Southern Ocean’s benthic ecosystem, crustaceans are by far the most specious taxon. Twenty-five species of Epimeriidae are known from Antarctic waters, that is 19 Epimeria Costa, 1851, four Epimeriella Walker, 1906, one Metepimeria Schellenberg, 1931a and one Uschakoviella Gurjanova, 1955b. Based on their distribution records from the Weddell and Ross Sea shelves, eight species of Epimeriidae Epimeria robusta Barnard, 1930 was originally described from the Ross Sea but because of insufficient descriptions and images Coleman (1994) redescribed E. robusta based on specimens from the Weddell Sea. Five of the epimeriid species (Epimeria extensa, E. heldi, E. reoproi, E. vaderi and E. truncata) are known from locations only on the Antarctic Peninsula. Epimeria rimicarinata Watling and Holman, 1980 and the recently described E. schiaparelli Lörz, Maas, Linse and Fenwick, 2007 are found exclusively in the Ross Sea

Methods

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Discussion

Conclusion