Environmental stressors such as nitrogen and phosphorus play a critical role in regulating the growth and physiological functions of Litopenaeus vannamei, a key species in aquaculture. This study investigates the effects of nitrogen and phosphorus stress on shrimp growth, oxidative stress, tissue damage, and molecular mechanisms. Exposure to increasing concentrations of nitrogen and phosphorus significantly reduced growth rates. Oxidative stress markers, including superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), and malondialdehyde (MDA), indicated heightened oxidative damage under both stress conditions, with nitrogen stress causing more severe responses than phosphorus stress. Histopathological analysis revealed substantial damage to the gills and hepatopancreas, organs essential for respiration and metabolism. Transcriptomic analysis identified differentially expressed genes (DEGs) enriched in apoptosis, lysosome, sphingolipid metabolism, and phagosome pathways, suggesting shared molecular responses to nitrogen and phosphorus stress. The results demonstrate that L. vannamei initiates oxidative and immune responses to cope with environmental stressors, but the adaptive capacity remains limited. These findings provide a foundation for understanding the stress tolerance mechanisms in shrimp and inform future strategies for breeding high-resistance strains in aquaculture.

The leopard coral grouper (Plectropomus leopardus) is a commercially significant tropical marine species. With the ongoing effects of global climate change, increasing attention has been focused on leopard coral grouper’s susceptibility to extreme cold weather. This study investigates the effects of acute cold exposure and temperature recovery on the liver of P. leopardus. Histological observations and enzyme activity assays revealed that temperature fluctuations caused significant disruptions to normal liver physiology, including lipid accumulation and alterations in antioxidant levels. Transcriptomic analysis of liver tissue identified 2744 differentially expressed genes (DEGs) across three experimental groups: 25 °C (control), 13 °C (cold exposure), and rewarming at 25 °C (R-25 °C). Functional enrichment analysis revealed that these DEGs were significantly associated with biological processes such as lipid metabolism and antioxidant defense, as well as pathways related to metabolism, fatty acid biosynthesis, and ferroptosis. Furthermore, dynamic regulation of lipid metabolism, immune responses, and oxidative stress pathways was observed in response to both cold stress and rewarming. Notably, several redox-related DEGs were identified, and their interactions with lipid metabolism were further explored. Additionally, representative DEGs associated with antioxidants and lipid metabolism, such as got1, gpx1a, gpt, and g6pcla.2, were validated by qRT-PCR and fluorescence in situ hybridization (FISH). Taken together, this study provides a systematic analysis of the effects of acute cold exposure and temperature recovery stress on the liver of the leopard coral grouper, laying the groundwork for further research on the temperature stress responses in teleost species.

Vasa (Ddx4, DEAD box polypeptide 4), an extremely specific marker of germ cells in vivo, is an ATP-dependent RNA helicase that plays an essential role in germ cell development and gametogenesis. However, the expression and function information about this gene in groupers remains lacking. Here, vasa homolog termed Plvasa was isolated and identified Plvasa as a putative germ cell marker in the leopard coral grouper, (Plectropomus leopardus). Results indicated that Plvasa contained 17 exons in the genomic sequence and 9 conserved motifs of the DEAD-box protein by sequence analysis. The sequence comparison, phylogenetic analyses and synteny analyses showed that Plvasa was homologous with other teleosts. Additionally, the expression of Plvasa was significantly higher in gonads than in other tissues in adult individuals (p < 0.05). Further, the distribution of Plvasa revealed that it was only expressed in the germ cells, such as spermatids, germline stem cells and oocytes at different stages, and could not be detected in the somatic cells of gonads. The current study verified that the Plvasa gene is a valuable molecular marker of germ cells in leopard coral grouper, which potentially plays an important role in investigating the genesis and development of teleost germ cells.

Sexually dimorphic traits such as growth and body size are often found in various crustaceans. Methyl farnesoate (MF), the main active form of sesquiterpenoid hormone in crustaceans, plays vital roles in the regulation of their molting and reproduction. However, understanding on the sex differences in their hormonal regulation is limited. Here, we carried out a comprehensive investigation on sexual dimorphic responses to MF in the hepatopancreas of the most dominant aquacultural crustacean—the white-leg shrimp (Litopenaeus vannamei). Through comparative transcriptomic analysis of the main MF target tissue (hepatopancreas) from both female and male L. vannamei, two sets of sex-specific and four sets of sex–dose-specific differentially expressed transcripts (DETs) were identified after different doses of MF injection. Functional analysis of DETs showed that the male-specific DETs were mainly related to sugar and lipid metabolism, of which multiple chitinases were significantly up-regulated. In contrast, the female-specific DETs were mainly related to miRNA processing and immune responses. Further co-expression network analysis revealed 8 sex-specific response modules and 55 key regulatory transcripts, of which several key transcripts of genes related to energy metabolism and immune responses were identified, such as arginine kinase, tropomyosin, elongation of very long chain fatty acids protein 6, thioredoxin reductase, cysteine dioxygenase, lysosomal acid lipase, estradiol 17-beta-dehydrogenase 8, and sodium/potassium-transporting ATPase subunit alpha. Altogether, our study demonstrates the sex differences in the hormonal regulatory networks of L. vannamei, providing new insights into the molecular basis of MF regulatory mechanisms and sex dimorphism in prawn aquaculture.

In Plectropomus leopardus, Vibrio disease and Hirudo parasitic disease are relatively common. Timely recognition of these diseases can improve the survival rate of Plectropomus leopardus and prevent their spread. However, early-stage diseases are difficult to distinguish due to their small size and subtle characteristics. Traditional manual recognition methods rely on personal experience and subjective judgment, leading to time-consuming and error-prone diagnoses. To address the challenges in detecting and classifying Plectropomus leopardus diseases, this paper proposes PLDNet (Plectropomus Leopardus Disease Detection Network), a real-time detection and recognition method that provides faster and more accurate diagnoses for fish farms. PLDNet incorporates two significant advancements: First, it employs FocalModulation, which enhances the model’s ability to identify key disease characteristics in images. Second, it introduces the MPDIoU (Minimum Point Distance-based Intersection over Union) for bounding box similarity comparison, optimizing the loss function and improving recognition accuracy. This paper also presents the PLDD (Plectropomus Leopardus Disease Dataset), a newly developed dataset that includes comprehensive images of healthy and diseased specimens. PLDD addresses the scarcity of data for this species and serves as a valuable resource for advancing research in marine fish health. Empirical validation of PLDNet was conducted using the PLDD dataset and benchmarked against leading models, including YOLOv8-n, YOLOv9-m, and YOLOv9-c. The results show that PLDNet achieves superior detection performance, with an average detection accuracy of 84.5%, a recall rate of 86.6%, an mAP@o.5 of 88.1%, and a real-time inference speed of 45 FPS. These metrics demonstrate that PLDNet significantly outperforms other models in both accuracy and efficiency, providing practical solutions for real-time fish disease management.

Accurate and non-invasive measurement of fish phenotypic characteristics in underwater environments is crucial for advancing aquaculture. Traditional manual methods require significant labor to anesthetize and capture fish, which not only raises ethical concerns but also risks causing injury to the animals. Alternative hardware-based approaches, such as acoustic technology and active structured light techniques, are often costly and may suffer from limited measurement accuracy. In contrast, image-based methods utilizing low-cost binocular cameras present a more affordable solution, although they face challenges such as light refraction between water and the waterproof enclosure, which can cause discrepancies between image coordinates and actual positions. To address these challenges, we have developed a fish keypoint detection dataset and trained both a fish object detection model and a keypoint detection model using the RTMDet and RTMPose architectures to identify keypoints on Plectropomus leopardus. Since the binocular camera must be housed in a waterproof enclosure, we correct for birefringence caused by the water and the enclosure by applying refraction corrections to the detected keypoint coordinates. This ensures that the keypoint coordinates obtained underwater are consistent with those in air, thereby improving the accuracy of subsequent stereo matching. Once the corrected keypoint coordinates are obtained, we apply the least squares method, in conjunction with binocular stereo imaging principles, to perform stereo matching and derive the actual 3D coordinates of the keypoints. We calculate the fish body length by measuring the 3D coordinates of the snout and tail. Our model achieved 98.6% accuracy in keypoints detection (AP@0.5:0.95). Underwater tests showed an average measurement error of approximately 3.2 mm (MRPE=3.50%) for fish in a tank, with real-time processing at 28 FPS on an NVIDIA GTX 1060 GPU. These results confirm that our method effectively detects keypoints on fish bodies and measures their length without physical contact or removal from the tank. By eliminating invasive procedures, our approach not only improves measurement efficiency but also aligns with ethical standards in aquaculture. Compared to existing techniques, our method offers enhanced accuracy (reducing MRPE by 53.8% compared to baseline methods) and practicality, making it a valuable tool for the aquaculture industry.