Effect of temperature on the occurrence of Metschnikowia bicuspidata disease in Eriocheir sinensis

Eriocheir sinensis aquaculture has been significantly impeded by "milky disease," which is caused by Metschnikowia bicuspidata. This disease exhibits distinct seasonality and is closely associated with temperature fluctuations. The present study investigated the impact of temperature on the proliferation and pathogenicity of M. bicuspidata and the immune capacity of E. sinensis. We observed a significant temperature-dependent effect on the proliferation rate of M. bicuspidata in vitro and in vivo. Although low temperatures (4 degrees C) suppressed M. bicuspidata proliferation, different temperatures did not have a considerable influence on pathogenicity (P > 0.05). Cultivation at lower temperatures significantly reduced the proliferation rate of pathogens in infected E. sinensis and the time to death. Further, the bacteriostatic capacity of E. sinensis serum was significantly enhanced under high temperatures compared with that under low-temperature conditions (P < 0.01). Transcriptome analysis of hemocytes from E. sinensis at different breeding temperatures indicated that the host's metabolism and immunity were differentially affected at 4 degrees C compared to 32 degrees C, with pathways associated with growth and development primarily affected under low-temperature conditions and pathways related to energy supply predominantly influenced under high-temperature conditions. Notably, temperature also led to changes in the expression of genes closely linked to immunity and apoptosis, such as acid phosphatase, C-type lectin, glutathione peroxidase, caspase, and initiator caspase-8. The current findings have significant implications for understanding the effect of temperature on M. bicuspidata pathogenicity in E. sinensis and preventing milky disease infection during aquaculture.