EFFECTS OF GRADUAL WARMING ON GROWTH PERFORMANCE AND SYMBIOTIC MICROBIOTA OF JUVENILE CHINESE MITTEN CRABS (ERIOCHEIR SINENSIS)

The Chinese mitten crab (Eriocheir sinensis) is an important freshwater aquaculture species in China, and its larval stage critically determines seedling quality and aquaculture efficiency. Temperature is a key factor affecting the growth, development, and homeostasis of E. sinensis larvae. This study aimed to investigate the effects of different warming rates on larval growth, development, and symbiotic functional microbiota in E. sinensis. Three warming treatments were established with the same initial temperature of 14℃, which was gradually increased over 14 days to 19℃ in the low-temperature group (L), 23℃ in the moderate-temperature group (M), and 27℃ in the high-temperature group (H). The results showed that accelerated warming significantly increased larval total length and head length (P<0.05). Compared with the L group, the rostral and dorsal spines were significantly elongated in the M group (P<0.05), whereas degeneration of both spines was observed in the H group. The ACE index in the M group was significantly lower than that in the H group, while the Shannon index was significantly higher than that in the H group (P<0.05), with no significant difference compared with the L group. In addition, microbial β-diversity differed significantly among the three groups (P<0.05). At the phylum level, the relative abundance of Cyanobacteriota in the L group, Bacillota and Actinomycetota in the M group, and Bacteroidota in the H group was significantly higher than that in the other groups (P<0.05). At the genus level, the relative abundance of unclassified_o_Chloroplast in the L group; Demequina, Methylobacterium, and Acinetobacter in the M group; and Vibrio, Tritonibacter, Ruegeria, and Leucothrix in the H group was significantly higher than that in the other groups (P<0.05). The L, M, and H groups contained 73, 69, and 57 unique microbial taxa, respectively, and the H group showed the lowest microbial community stability. Furthermore, the nitrate reduction function of the microbiota in the M group was significantly lower than that in the other two groups (P=0.005), whereas aerobic anoxygenic phototrophy, animal parasites or symbionts, aromatic compound degradation, and fermentation were significantly enhanced in the M group. In conclusion, this study demonstrates that accelerated warming can promote larval development in E. sinensis and alter microbial community diversity. Gradually increasing the temperature from 14℃ to 23℃ within 14 days may be beneficial for the growth and development of E. sinensis larvae without causing adverse effects.