Chunlin Wang

The distribution of white spots on the shell is one of the remarkable characteristics of the appearance of Portunus trituberculatus, but there have been no reports on its characteristics and genetic analysis. In this study, seven parameters of white spots were extracted based on computer vision, including white spot number (WSN), white spot area (WSA), white spot regional area (WSRA), percentage of white spot area (PWSA), percentage of white spot regional area (PWSRA), white spot number of white spot regional area (WSNRA), and white spot number of carapace area (WSNCA). Using 22 full-sib families, we estimated genetic parameters of these white spot traits and their genetic correlations with growth carapace area (CA). Results demonstrated that these parameters exhibit continuous variation, but the performance of these white spot indicators was not consistent. Based on comprehensive principal component analysis (PCA), they could be categorized into three distinct groups within the full-sib families. The heritability estimated under the animal model ranged from 0.00 to 0.35 for white spot traits and was 0.18 for CA. Most white spot traits showed low to moderate heritability. The genetic correlations among WSN, WSA, WSRA, PWSA, and CA were significantly positive, indicating that selection for one of these traits would result in the improvement of others. This study presents the first estimation of characteristics and genetic parameters of white spot traits of P. trituberculatus, providing valuable information for understanding these traits and facilitating the optimization of breeding strategies for this species.

Surfactin is a lipopeptide biosurfactant with significant industrial potential, but high production costs have hindered its commercialization. In this study, we developed a sustainable and cost-effective bioprocess for surfactin biosynthesis using Bacillus subtilis 55033, utilizing kitchen waste as the primary fermentation substrate without any previous pretreatment—an advantage that simplifies the process and reduces costs compared to previous reports. To maximize productivity, the fermentation parameters were systematically optimized through single-factor and orthogonal experimental designs. The optimal conditions were as follows: a fermentation temperature of 31 °C, a duration of 48 h, a 5% v/v inoculum, a 7% w/v solid-to-liquid ratio, an initial pH of 7.5, and an agitation speed of 200 rpm. Under these conditions, the surfactin yield reached 371.67 mg/L, an increase of 100.5% from 185.4 mg/L prior to optimization. We performed a comparative analysis of the surfactin biosynthetic gene clusters between B. subtilis 55033 and the model strain B. subtilis 168. The produced surfactin exhibited potent antagonistic activity against aquatic pathogens, significantly inhibiting the growth of several species of Vibrio and the division and hatching of Cryptocaryon irritans Tomonts. These findings demonstrate that our platform not only provides a high-value valorization route for organic waste but also enables preliminary exploration of surfactin applications in aquaculture, in line with the principles of a circular bioeconomy.

To investigate the growth patterns and sexual differences in pond-cultured mud crabs (Scylla paramamosain), this study measured eight growth patterns in pond-cultured S. paramamosain aged 1 to 5 months, including internal carapace width (ICW), abdomen width (AW), body height (BH), carapace length (CL), propodus length (PL), merus length (ML), first periopod merus length (1PML), and body weight (BW), with measurements taken monthly. The growth patterns for females, males, and a mixed-sex group were fitted using the following three growth curve models: Logistic, Gompertz, and von Bertalanffy. The fitting results indicate that the optimal growth model for male S. paramamosain is the Logistic model, while the optimal growth model for female S. paramamosain is the von Bertalanffy model. The predicted growth inflection points and inflection weight for male S. paramamosain are 3.15 months and 155.00 g, respectively; for female S. paramamosain, the predicted growth inflection point and inflection weight are 4.25 months and 228.71 g, respectively; and for mixed-sex S. paramamosain, the growth inflection point and inflection weight are 3.22 months and 151.80 g, respectively. Males achieve a rapid growth period earlier (at 3–4 months of age) than females, with the weight of male crabs significantly greater than that of females at four months of age (p < 0.05). Males exhibit slow weight gain from the fourth to the fifth month, while females demonstrate a rapid weight gain rate during the same period. These results provided a theoretical basis and reference for the refined pond culture of S. paramamosain.

The swimming crab Portunus trituberculatus is a commercially important species in aquaculture, and its aggressiveness strongly influences productivity, making quantitative assessment a priority. However, such an assessment is hindered by behavioral complexity and a lack of high-throughput approaches. Here, we present a machine learning framework for quantifying aggressive behavior using DeepLabCut-SIMBA (Simple Behavioral Analysis). By converting video data into quantifiable durations of aggression-related events, we established a Time-weighted Aggression Index (TAI) that enables standardized, high-throughput assessment. The TAI showed strong concordance with conventional methods, confirming its validity. To demonstrate its applicability, we examined the correlation between TAI and serotonin levels, revealing distinct physiology-behavior associations. We then stratified crabs into three aggression categories based on TAI and conducted pairwise fighting trials. The frequency of aggressive interactions differed significantly across group combinations, indicating that TAI-based grouping effectively predicts behavioral outcomes. This framework offers a reliable, scalable tool for behavioral phenotyping and practical value for selective breeding programs.

The insulin-like androgenic gland (IAG) gene is considered a crucial factor in the process of sexual differentiation in decapod crustaceans. In this study, we characterized the structural features and ontogenetic expression profile of the IAG gene in the swimming crab P. trituberculatus (Pt-IAG). To further elucidate its biological roles, we performed long-term RNA interference (RNAi) to evaluate the physiological impacts of sustained Pt-IAG suppression. Results showed that the gene structure of Pt-IAG is conserved with the characteristic B-C-A polypeptide arrangement that is representative of decapod IAGs. Transcripts of Pt-IAG were detectable as early as the zygote stage, which may imply its potential role during early-stage development. Although no completesex reversal was observed, continuous knockdown of Pt-IAG resulted in a decrease in body weight and a delay in gonad development in both sexes, underscoring its pleiotropic role in coordinating growth and maturation. Furthermore, the silencing of Pt-IAG led to a significant downregulation of insulin-like growth factor-binding protein (Pt-IGFBP), and a decrease in insulin-receptor (Pt-IR) expression was observed in males. Notably, the Pt-IR gene was not detected in female ovaries. These findings suggest that IAG may modulate male development through an insulin-like signaling axis; however, the absence of ovarian Pt-IR expression implies the potential existence of alternative regulatory pathways in females. Collectively, this study identifies a dual regulatory role of IAG in both growth and reproduction, providing a specific theoretical basis for developing sex-control and growth-optimization strategies in crab aquaculture.