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.

To mitigate the challenges of excessive tilting angles and the risk of overturning during the submersion and ascent of the net cage, this study developed an automatic control and management system for submersible net cages. The system employs proportional–integral–derivative (PID) control technology, optimizing PID parameters through tilt signals and control algorithms to adjust actuators, thereby enabling automatic regulation of the net cage tilt angle. The accompanying management system integrates several functionalities, including submersion and elevation control, suspension control, water level monitoring, pressure data monitoring, current velocity measurement, water quality monitoring, GPS positioning, and underwater camera surveillance. Through a series of experiments, the most suitable buoyancy-to-gravity ratio for the net cage was determined to be 1.2. Experimental results identified optimal PID parameters for submersion (P = 100, I = 1000, D = 0) and ascent (P = 50, I = 800, D = 0), and suspension control was achieved using a compressed air pressure of 0.40 kPa. By integrating modular control systems and data modules into a unified framework, this study addresses key limitations in the automatic systems for deep-sea submersible net cages, achieving a tilting angle of less than 15° during submersion and less than 5° during ascent. The proposed automatic control system represents a critical technological advancement for the industrialization of deep-sea aquaculture and provides essential data and theoretical foundations for the future development and application of deep-sea submersible net cages.

Portunus trituberculatus is a commercially crucial marine aquaculture crab species in China, renowned for its high economic value. Spawning performance is one of the most important target traits in selective breeding programs for this species; however, the genetic architecture underlying this trait remains largely uncharacterized. In the present study, 160 artificially cultivated broodstock individuals were subjected to genomic analysis, with high-throughput liquid chip arrays employed for individual SNP genotyping. By combining these data with phenotypic records of spawning traits, the heritability of the target trait was estimated to be 0.065. A genome-wide association study (GWAS) using a mixed linear model detected nine SNP loci suggestively associated with spawning performance, with an average proportion of phenotypic variance explained (PVE) of 1.96%. One-way ANOVA of these suggestive loci revealed significant differences in phenotypic values among genotype groups, supporting the marker–trait associations; however, because this analysis used the same cohort as the GWAS, it should be considered exploratory rather than independent validation. These suggestive loci were distributed across 8 chromosomes including chromosome 24, 26, 30, 31, 32, 33, 36, and 48. The genetic effect analysis revealed that among the 9 suggestive loci, 8 exhibited additive genetic effects and the remaining 1 locus showed dominant effects. Based on the physical position information of these associated SNPs, 38 positional candidate genes were identified in adjacent genomic regions; 15 of these genes had clear annotation information, including three genes previously documented as reproduction-related: MOXD1, NFAT5, and DDX11. These results delineate the preliminary genetic basis of spawning traits in P. trituberculatus and provide important molecular markers and promising candidate genes for breeding improved varieties with high fecundity.