The hybrid of female white crucian carp (Carassius auratus cuvieri, WCC) × male red crucian carp (Carassius auratus red var. RCC) (WR), combines desirable characteristics of both parents, including tender meat, rapid growth rate, and strong resistance. To test the hypoxia tolerance of WR, an experiment of exposure to hypoxic conditions was conducted on WR, RCC, and WCC. The results showed that WR and RCC exhibited stronger hypoxia tolerance capacity compared to WCC. The strong resistance to hypoxia of WR and RCC was manifested by the absence of damage to the hepatopancreas after hypoxia, and the fish can adapt to the hypoxic environment by enhancing the hematopoietic function of hematopoietic tissue, remodeling gill morphology, and activating the antioxidant system. By contrast, after hypoxia, the number of red blood cells and the concentration of hemoglobin in the blood of WCC decreased, and the hepatopancreas was seriously damaged, indicating that the WCC is not as tolerant to low oxygen conditions as RCC and WR.

Fish phenotyping plays an important role in growth evaluation, selective breeding, and precision aquaculture. Conventional phenotypic measurement methods are labor-intensive, time-consuming, and susceptible to observer variability. To improve measurement efficiency and reproducibility, this study proposes an automated fish phenotyping framework based on Transformer-enhanced instance segmentation. Specifically, a Mask2Former decoder was integrated into the Mask R-CNN architecture to improve boundary delineation and segmentation quality. Based on segmentation outputs, phenotypic parameters, including body length, body height, and projected area, were automatically extracted using PCA-assisted orientation estimation and geometric measurement. In addition, a standardized anatomical landmark annotation framework consisting of 12 reference points was introduced to support reproducible phenotypic description and future extensible morphometric analysis. Body weight was further estimated using polynomial regression based on extracted morphological traits. Experiments were conducted using images from three crucian carp varieties under controlled imaging conditions. The proposed framework achieved 92.7% mAP and 89.4% Boundary IoU, improving segmentation performance over the baseline model. Automated measurement yielded average relative errors of 2.16% for body length and 3.85% for body height, while weight prediction achieved an R² of 0.9479 and a mean relative error of 7.31%. These results demonstrate that Transformer-enhanced segmentation can support accurate and efficient automated phenotyping under standardized conditions and provide a foundation for future deployment in more complex aquaculture environments.

During meiosis, ataxia telangiectasia mutated (ATM) kinase senses DNA double-strand breaks (DSBs) and regulates multiple downstream processes, including DSB repair and p53-mediated apoptosis. The allotriploid crucian carp (3nAT, 3n = 150), derived from distant hybridization between female diploid red crucian carp (2nRCC) and male allotetraploid hybrids (4nAT), is sterile and exhibits extensive germ cell apoptosis associated with abnormal meiosis. Here, we used the ATM kinase inhibitor KU55933, to investigate the sterility mechanism. Following intraperitoneal treatment with KU55933 (KU-3nAT), germ cell apoptosis was markedly reduced, and a small number of morphologically abnormal gametes were produced. Meiosis- and gamete maturation-related genes were upregulated, whereas pro-apoptotic genes were downregulated, indicating that meiotic arrest was partially attenuated. However, KU-3nAT sperm exhibited abnormal structures with rounded heads, retained cytoplasm, and absent or malformed flagella. Self-crossed and hybrid embryos with 2nRCC arrested at gastrulation, while a few KU-3nAT ♀ × 4nAT ♂ embryos hatched. These results suggest that ATM/p53-associated apoptosis contributes to germ cell loss at the proposed pachytene checkpoint in 3nAT, while ATM inhibition permits limited gamete production but does not restore normal gamete function or embryonic development.