Crustaceans are generally considered more sensitive to ocean warming due to their lack of certain efficient regulators. However, the alterations in the physiology and behavior of crustaceans in response to thermal stress differ vastly even among the infraspecific populations of heterogeneous landscapes. Consequently, understanding the impact of temperature fluctuation on crustacean infraspecific populations might be essential for maintaining a sustainable persistence of populations at existing locations. In the present study, we chose the Japanese mantis shrimp (Oratosquilla oratoria) as the representative crustacean population, and conducted transcriptome analyses in two divergent O. oratoria populations (the Zhoushan and Qingdao populations) under same thermal stress (20–28 °C) to identify the population-specific expression response to thermal stress. The results showed significant differences in gene expressions, GO terms and metabolic pathways between the two populations. We hypothesized that intraspecific mutations in the same or different genes might lead to thermal adaptive divergences. Temperature increases from 20–28 °C produced significant enrichment in GO terms and altered the metabolic pathways in the Zhoushan population despite the lack of differentially expressed unigenes. Therefore, several functional genes with large pleiotropic effects may underlie the response to thermal stress in the Zhoushan population. Furthermore, the most significantly enriched biological processes of the Qingdao population were associated with the state or activity of cells and its significant enriched pathways with genetic information processing as well as immune and environmental information processing. In contrast, the differentially regulated unigenes of the Zhoushan population were primarily involved in the regulatory cellular and transcription processes and the most significant pathways found were metabolic and digestive. Consequently, the regulatory mechanisms of the Zhoushan population are probably more efficient than those of the Qingdao population under the same thermal stress.

The intertidal salinity fluctuations provide pose a significant physical challenge for the crustaceans that live here. In the present study, Charybdis japonica was selected as the research species to explore the genetic regulatory mechanisms of intertidal crustaceans responding to salinity fluctuations. We cultured C. japonica s with three salinity gradients (the salinity of 15‰, 25‰, and 35‰) and 68.90 Gb clean transcriptome reads were obtained by RNA-seq. All clean reads were then de novo assembled to 41,058 unigene with a mean length of 1,179.39 bp and an N50 length of 2,033 bp. Furthermore, a total of 18,100 (24.74%) unigenes were successfully matched with the sequences from at least one database. We further analyzed the transcriptome structure of C. japonica and a total of 26,853 CDSs and 12,190 SSRs were predicted. The gene expression levels of C. japonica at 25‰ were used as control, and 204 and 5,392 DEGs were found at the salinity of 35‰ and 15‰, respectively. Based on the annotated information of DEGs, we speculated that C. japonicas were subjected to greater stress under the salinity of 35‰ and isotonic intracellular regulation was activated. Furthermore, neuronal activity, oxidation response, intracellular regulatory activity and osmotic regulation-related genes were speculated to be critical genes for C. japonica to cope with salinity fluctuations. The present results will provide fundamental information for revealing the salinity fluctuation-related genetic regulatory mechanisms of C. japonica and other intertidal crustaceans, and then help us predict how future salinity changes will affect the survival of crustaceans.

Sillago species lives in the demersal environments and face multiple stressors, such as localized oxygen depletion, sulfide accumulation, and high turbidity. In this study, we performed transcriptome analyses of seven Sillago species to provide insights into the phylogeny and positively selected genes of this species. After de novo assembly, 82,024, 58,102, 63,807, 85,990, 102,185, 69,748, and 102,903 unigenes were generated from S. japonica, S. aeolus, S. sp.1, S. sihama, S. sp.2, S. parvisquamis, and S. sinica, respectively. Furthermore, 140 shared orthologous exon markers were identified and then applied to reconstruct the phylogenetic relationships of the seven Sillago species. The reconstructed phylogenetic structure was significantly congruent with the prevailing morphological and molecular biological view of Sillago species relationships. In addition, a total of 44 genes were identified to be positively selected, and these genes were potential participants in the stress response, material (carbohydrate, amino acid and lipid) and energy metabolism, growth and differentiation, embryogenesis, visual sense, and other biological processes. We suspected that these genes possibly allowed Sillago species to increase their ecological adaptation to multiple environmental stressors.