Parasitic Crustaceans and Marine Invasions: Two Case Studies from Kuroshio Region (extended abstract of the 7th Kuroshio Symposium)

Parasitic crustaceans are ubiquitous in marine environment. They have negative effects on host individuals and populations, and even on the ecosystem where the host species plays a great role. In this short review, we show two case studies of marine invasions related with parasitic crustaceans from Kuroshio Region. One is the native pinnotherid crab parasitizing introduced mussels and the other is the bopyrid isopod introduced from Asia to US Pacific Coast. The green mussel Perna viridis, native to the tropical Indo-Pacific region, has recently been introduced worldwide. Although the native mussel populations in India suffer from parasitic effects of the pinnotherid crab Arcotheres placunae, mussels are relatively free from parasitic crabs in invaded regions (parasite escape). We investigated pea crab infections in P. viridis in Uranouchi Inlet, Kochi Prefecture, Japan. Results showed that the native generalist pea crab A. sinensis utilized the non-indigenous mussel P. viridis, though the prevalence is much lower. The introduced Asian parasitic bopyrid isopod, Orthione griffenis, was first discovered on the Pacific coast of North America ca. 25 years ago. High prevalence of Orthione infestations decreased many local populations of the host mud shrimp Upogebia pugettensis as well as the diverse symbiotic fauna in the host burrows. We investigated the distribution and host specificity of the bopyrid in western Japan. Results showed that O. griffenis was a rare species in Japan. Further ecological studies on parasitic crustaceans are needed in both native (source) and introduced (recipient) habitats.