Abstract
BackgroundMud crab, Scylla paramamosain, a euryhaline crustacean species, mainly inhabits the Indo-Western Pacific region. Wild mud crab spawn in high-salt condition and the salinity reduced with the growth of the hatching larvae. When the larvae grow up to megalopa, they migrate back to estuaries and coasts in virtue of the flood tide, settle and recruit adult habitats and metamorphose into the crablet stage. Adult crab can even survive in a wide salinity of 0–35 ppt. To investigate the mRNA profile after salinity stress, S. paramamosain megalopa were exposed to different salinity seawater (low, 14 ppt; control, 25 ppt; high, 39 ppt).ResultsFirstly, from the expression profiles of Na+/K+/2Cl- cotransporter, chloride channel protein 2, and ABC transporter, it turned out that the 24 h might be the most influenced duration in the short-term stress. We collected megalopa under different salinity for 24 h and then submitted to mRNA profiling. Totally, 57.87 Gb Clean Data were obtained. The comparative genomic analysis detected 342 differentially expressed genes (DEGs). The most significantly DEGs include gamma-butyrobetaine dioxygenase-like, facilitated trehalose transporter Tret1, sodium/potassium-transporting ATPase subunit alpha, rhodanese 1-like protein, etc. And the significantly enriched pathways were lysine degradation, choline metabolism in cancer, phospholipase D signaling pathway, Fc gamma R-mediated phagocytosis, and sphingolipid signaling pathway. The results indicate that in the short-term salinity stress, the megalopa might regulate some mechanism such as metabolism, immunity responses, osmoregulation to adapt to the alteration of the environment.ConclusionsThis study represents the first genome-wide transcriptome analysis of S. paramamosain megalopa for studying its stress adaption mechanisms under different salinity. The results reveal numbers of genes modified by salinity stress and some important pathways, which will provide valuable resources for discovering the molecular basis of salinity stress adaptation of S. paramamosain larvae and further boost the understanding of the potential molecular mechanisms of salinity stress adaptation for crustacean species.
Highlights
Mud crab, Scylla paramamosain, a euryhaline crustacean species, mainly inhabits the Indo-Western Pacific region
To preliminary explore the molecular level alterations of osmoregulation under different salinity and period of exposure time, the expressions of osmoregulation related genes Na+/K+/2Cl- cotransporter (NKCC), Chloride channel protein 2 (ClC2) and ABC transporters (ABCs), which were closely related to the osmotic changes, were detected under low and high salinity after 0 h, 12 h, 24 h, 48 h and 72 h (Fig. 1)
Genes showed no significant differences after 48 h and 72 h under salinity alterations, especially at 48 h the expressions were nearly the same in the three groups and a little deviation presented at 72 h between the three levels of salinity treatment
Summary
Scylla paramamosain, a euryhaline crustacean species, mainly inhabits the Indo-Western Pacific region. Wild mud crab spawn in high-salt condition and the salinity reduced with the growth of the hatching larvae. Scylla paramamosain is a euryhaline crab which can live in a wide range of salinities and mostly distribute in the Indo-Western Pacific region. It has become a fairly important economic mariculture species and popular seafood in the South-East Asian countries [50]. Mud crab spends most of its life in brackish, saltwater estuaries or mangrove forests, while mature females move to offshore for spawning and hatching larvae [40]. Megalopa constitute a dominant phase for successful larval rearing in mud crab aquaculture, since mass mortality often happens during this stage [12], which makes it an urgent issue to further promote the development of the mud crab aquaculture industry
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