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Effect of temperature and salinity on virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus (Temminck et Schlegel)
Author(s) -
Zheng Dahai,
Mai Kangsen,
Liu Shuqing,
Cao Limin,
Liufu Zhiguo,
Xu Wei,
Tan Beiping,
Zhang Wenbing
Publication year - 2004
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.2004.01044.x
Subject(s) - edwardsiella tarda , paralichthys , olive flounder , biology , virulence , flounder , salinity , pathogen , incubation , microbiology and biotechnology , zoology , veterinary medicine , fish <actinopterygii> , fishery , ecology , biochemistry , medicine , gene
Experiments were designed to determine the effects of temperature and salinity on the virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus . In the temperature experiment, a two‐factor design was conducted to evaluate the effects of both pathogen incubation temperature and fish cultivation temperature on pathogen virulence. E. tarda was incubated at 15, 20, 25 and 30±1°C, and the fish (mean weight: 10 g) were reared at 15, 20 and 25±1°C respectively. The fish reared at different temperatures were infected with the E. tarda incubated at different temperatures. The results of a 4‐day LD 50 test showed that temperature significantly affected the virulence of E. tarda ( P <0.01) and the interaction between the two factors was also significant ( P <0.01). For fish reared at 15°C the virulence of E. tarda was the highest at 25°C of pathogen incubation, followed by 20, 15 and 30°C. When the fish rearing temperature was raised to 20 and 25°C, the virulence of E. tarda incubated at all temperatures increased. Isolation testing demonstrated results similar to those of LD 50 . The higher rearing temperature increased the proliferation rate of the pathogen in fish. In the salinity experiment, the incubation salinity of E. tarda was at 0, 10, 20 and 30 g L −1 , respectively, and the fish with mean weight of 50 g were cultured in natural seawater of 30 g L −1 . The results of one‐way anova in 4‐day LD 50 test showed that incubation salinity significantly affected virulence. Virulence was lower when the salinity of the incubation medium was at 0 and 30 g L −1 , higher at 10 and 20 g L −1 . The results of isolation test were in accordance with those of LD 50 . At 20 g L −1 E. tarda had a faster proliferation rate than that at 10 g L −1 .