Fisheries Science

, Volume 79, Issue 5, pp 779–786 | Cite as

Experimental challenges of juvenile and adult Manila clams with the protozoan Perkinsus olseni at different temperatures

Original Article Biology


Infection with Perkinsus species, primarily P. olseni, is thought to be a major cause of the decline of Manila clam populations in Japan since the 1980s. However, the pathogenicity of the infection has not been sufficiently evaluated to estimate the impact of infection on wild Manila clam populations. We experimentally challenged juvenile (3- to 6-mm shell length) and adult (18- to 22-mm shell length) Manila clams with P. olseni at 18, 23, 28, and 30 °C. Mortality was significantly higher in challenged groups than in control groups. The difference in mean mortality between the challenged and control groups (all life stages and temperatures) was only significant above a threshold of infection intensity ~106 cells/g soft wet tissue (SWT). As temperature increased, the onset of mortality occurred more rapidly. The increase in mortality occurred earlier in juveniles than adults at 28 °C and lower. Our results suggest that the pathogenicity of P. olseni is higher in juveniles than in adults and at higher water temperatures. Given the infection intensities (ca. 106 cells/g SWT) previously reported in wild Manila clams, the parasite likely has considerable impact on wild Manila clam populations, particularly juveniles during periods of high temperature.


Perkinsus olseni Manila clam Ruditapes phillipinarum Pathogenicity Temperature Host size 



This research was supported by JSPS KAKENHI (22380106). We thank the Fisheries Research Institute, Oita Prefectural Agriculture, Forestry and Fisheries Research Center, for providing us with uninfected hatchery-raised clams.


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Copyright information

© The Japanese Society of Fisheries Science 2013

Authors and Affiliations

  1. 1.Department of Aquatic Bioscience, Graduate School of AgricultureThe University of TokyoTokyoJapan

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