The swimming crab (Portunus trituberculatus) is an economically important species in China, and its growth traits show obvious sexual dimorphism. Thus, it is important to study the mechanism of sex determination and differentiation in this species. Herein, we identified 2138 differentially expressed genes and 132 differentially expressed long non-coding RNAs (lncRNAs) using Oxford Nanopore Technology full-length transcriptome sequencing. We predicted 561 target genes of the differentially expressed lncRNAs according to their location and base pair complimentary principles. Furthermore, pathways related to sex determination, differentiation, and reproduction were enriched for lncRNAs according to gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses. This indicated that lncRNAs might play regulatory roles in these pathways. Our results could form the basis for future studies of sex determination and differentiation in P. trituberculatus.

According to a previous study, in insects, cyp307A1 plays a central role in ecdysteroid synthesis, which is a member of the cytochrome P450 family. However, the function of cyp307A1 in crustaceans remains unclear. In this study, we explored the function of Eccyp307a1 in Exopalaemon carinicauda through a series of experiments. The sequence of Eccyp307a1 encoded 529 amino acids, and the protein was found to possess typical P450 domains and heme-binding sites. The mRNA of Eccyp307a1 was expressed at a higher level during the early stages of ovary development, but was expressed less during the mature stage. Furthermore, employing eyestalk ablation and RNAi experiments, we determined that Eccyp307a1 could be regulated by neuroendocrine factors and is essential for the normal initiation of ovary development. These findings provided insights into the gene function of Eccyp307a1 in early ovary development in E. carinicauda, and our study further elucidates the molecular mechanisms of ovary development in crustaceans.

The cytochrome P450 (CYP450) superfamily plays important roles in a wide range of biological processes. The classification of CYP450 family members has been studied in some plants and animals; however, there are no reports on CYP450 family members in Exopalaemon carinicauda. Based on publicly available whole-genome data for E. carinicauda, we identified 58 CYP450 family members based on the genome-wide alignment and analyzed their domains, gene structures and chromosomal locations, as well as physicochemical properties of the encoded proteins. The results revealed that CYP450 family members, widely distributed across multiple chromosomes, exhibit diverse protein properties, gene structures, and conserved motifs. Phylogenetic analysis indicated that these members are primarily clustered into subfamilies 2, 3, and 4, and the mitochondrial clan, showing close genetic relationships with homologous genes from other crustaceans. In this study, we revealed the genetic structural characteristics of the CYP450 family in E. carinicauda. We identified candidate genes for future research on the molecular mechanisms of CYP450 in development and reproduction. These findings are expected to serve as a foundation for further studies in this field.