Commensal Leucothoidae (Crustacea, Amphipoda) of the Ryukyu Archipelago, Japan. Part I: ascidian-dwellers

Kristine White,James Reimer

doi:10.3897/zookeys.163.2003

Abstract

Commensal leucothoid amphipods have been collected from the branchial chambers of their ascidian hosts throughout the Ryukyu Archipelago, Japan. Seven new species are described in two genera with valuable location data and host records. An identification key to ascidian-dwelling Leucothoidae of the Ryukyu Archipelago is provided.

Highlights

The Leucothoidae are a family of marine gammaridean amphipods that can be found inhabiting sessile invertebrate hosts worldwide
L. elegans, and L. trulla each have a small accessory flagellum on antenna 1. This character is unusual in leucothoid species and apparently much more common in Pacific species than in Caribbean species. It is interesting because these three species have limited distributions in the Ryukyu Archipelago
It is possible that these patterns in amphipod distributions are partly attributable to the ephemeral nature of their ascidian hosts

Summary

Introduction

The Leucothoidae are a family of marine gammaridean amphipods that can be found inhabiting sessile invertebrate hosts worldwide. The leucothoid clade inhabits tropical to polar waters and exhibits minimal to moderate sexual dimorphism This clade contains the genera Leucothoe Leach, 1814 and Paraleucothoe Stebbing, 1899. All currently described Japanese leucothoids are reported from mainland Japan, with no species documented from the Ryukyu Archipelago. Of these seven species, only L. nagatai has been reported with its host. There are currently recognized biogeographic boundaries within the Ryukyu Archipelago; the Hachisuka, Watase, and Miyake lines (Fig. 1) These boundaries apply to terrestrial organisms such as insects, mammals, reptiles, amphibians, and birds due to the past connection of the island chain to the Eurasian continent by land bridges (Kizaki and Oshiro 1977; 1980; Ota et al 2004).

Methods

Discussion