Redescription of the branchial parasitic bopyrid isopod Gyge ovalis (Shiino, 1939) prevalent in the mud shrimp Upogebia major from Korean tidal flats

초록

Over 34,000 tons of manila clams (Ruditapes philippinarum), valued at over $66.3 million, were produced in Korean waters in 2010. Most of this production occurs in the West Coast although these clams are also produced in the South and East Seas of Korea. Recently, the production drastically declined by 90% from 2011 in some localities due to the sudden and unusual invasion of the clam habitat by the mud shrimp (Upogebia major). In the course of the population dynamics studies of this critical ecosystem engineer, we found these invaders significantly parasitized by the bopyrid isopods in some places of the Korean clam beds. Similar parasitism, a bopyrid isopod Orthione griffensis infected to its burrowing mud shrimp host Upogebia pugettensis has been reported in Willapa Bay from the west coast of the United States and intense infestations are associated with the apparent demise of many local populations of mud shrimp (Dumbauld et al. 2011; Chapman et al., 2012). Therefore, the branchial parasitic bopyrid isopods infected to the mud shrimp were investigated on the basis of the Upogebia specimens collected between February 2012 and August 2012 from Korean clam beds. The most prevalent species was Gyge ovalis (Shiino, 1939) and prevalence was seriously high especially in Jugyo tidal flat, infecting 30% in winter to 86% in summer of the mud shrimp. Here, we report the complete description of this species and discuss some of the previously undescribed morphological characters based on the recently collected materials form Korean tidal flats.