First record of Ericthonius megalopus (Sars, 1879) from bathyal Sagami Bay, central Japan, including synonymization of Ericthonius tolli Brüggen, 1909 with Ericthonius megalopus (Crustacea: Amphipoda: Ischyroceridae)

Abstract

A couple of ischyrocerid amphipods included in the genus Ericthonius were collected from bathyal Sagami Bay (1456 m), central Japan. Morphological characters of the specimens closely resemble those of Ericthonius megalopus (Sars, 1879) and Ericthonius tolli Brüggen, 1909. Examining males and females of E. megalopus and E. tolli deposited in the Natural History Museum of Denmark, the specimens of both the species were quite similar to the Japanese specimens, although the shapes of appendages vary with growth and locality; therefore, E. tolli is synonymized with E. megalopus and all the specimens are identified as E. megalopus. Ericthonius megalopus is distributed in the northern sea areas of the world at a wide range of depths, and the present occurrence from Japan is the southernmost and deepest record of the species.

Keywords:

• Amphipoda
• Ischyroceridae
• Ericthonius
• Japan
• synonym

Acknowledgements

We express our sincere thanks to Drs Jørgen Olesen and Tom Schioette of the Natural History Museum of Denmark for the loan and the permission for dissection of precious specimens. We would like to thank Dr Vjacheslav S. Labay of the Sakhalin Research Institute of Fisheries and Oceanography, and Dr Shigeyuki Yamato of the Seto Marine Biological Laboratory, Kyoto University for sending literature. We are grateful to the operation team of the ROV Hyper-Dolphin and the captain and crew of the R/V Natsushima for the sample collection. We thank also anonymous reviewers for their critical reading of the manuscript.