Effects of low salinity stress on osmoregulation and gill transcriptome in different populations of mud crab Scylla paramamosain

Animals living in estuaries suffer from rapid and continuous salinity fluctuations, while the global warming and ex-treme precipitation aggravate this situation. Osmoregulation is important for estuarine animals adapt to salinity fluc-tuations. The present study investigated the effects of low salinity stress on osmoregulation and gill transcriptome in two populations of mud crab from Hangzhou Bay and Zhangzhou Bay of China, respectively. Crabs were transferred from salinity 25 ppt to 5 ppt for 96 h. Edematous swelling in gill filaments was caused by low salinity stress and was more serious in Zhangzhou Bay population. Gill Na+/K+-ATPase activity increased (p < 0.01) in both populations under the low salinity stress and was significantly higher (p < 0.01) in Hangzhou Bay population than in Zhangzhou Bay population. According to transcriptome analysis, there were 191 genes differentially expressed under the low sa-linity stress in gill tissue of both populations. Several ion transport and energy metabolism related pathways, as well as the arginine and proline metabolism pathway, were enriched by these genes. On the other hand, 272 genes were iden-tified to differentially express between two populations under the low salinity stress, but not under the control salinity. The enrichment analysis showed that these genes were mainly related to ion transport, energy metabolism, osmolytes metabolism and methyltransferase activity. In conclusion, the present study suggested that mud crab exploited a com-bination of extracellular anisosmotic regulation and intracellular isosmotic regulation for osmoregulation under the low salinity stress. Hangzhou Bay population showed a greater osmoregulatory capacity, which is probably due to the enhanced ion transport, energy supply, and osmolytes regulation. Meanwhile, epigenetic modification might also contribute to an inherent osmoregulation ability for Hangzhou Bay population to response to salinity fluctuation rapidly.

Automated summary

Two populations of mud crab from Hangzhou Bay and Zhangzhou Bay in China have different osmoregulatory capacities under low salinity stress, with the population from Hangzhou Bay showing stronger ion transport, energy supply, and osmolyte regulation. Additionally, epigenetic modification may contribute to the rapid response to salinity fluctuation in the Hangzhou Bay population.