Annual catch landings of the Manila clam Ruditapes philippinarum have decreased in Japan since the early 1980s because of the decreased size of many Manila clam populations. It is hypothesized that Perkinsus olseni infection contributed to these decreases. However, the effect of Perkinsus infection on the survival and physiology of Manila clam is poorly understood. We examined the influence of Perkinsus infection on clearance rate, tolerance against high water temperature, and burrowing activity in a captive adult clam population. Infection intensity did not affect clearance rates, burrowing activity, or tolerance against high water temperature. In addition, we monitored infection intensity in wild, adult clams from a tidal flat lacated in western Seto Inland Sea over a one-year period. Infection levels were relatively stable in the wild population between June 2004 and May 2005, but we noted a significant decrease in the infection intensity at the end of the spawning period in November 2004. However, in the present study, clear evidence showing the negative impact of Perkinsus on clam physiology and survival was not obtained.
2010 The Japanese Society of Fish Pathology