Background Molting is an important physiological process in the growth and development of arthropoda, which is mainly regulated by juvenile hormone and ecdysone. CYP302A1 is a key enzyme which plays a critical role in the synthesis of ecdysone in insects, but it has not been identified in cladocera. Results The CYP302Al gene of Daphnia sinensis was cloned and its function was analyzed in this paper. The CYP302Al gene of D. sinensis was 5926 bp in full-length, with an open reading frame (ORF) of 1596 bp that encoded 531 amino acids (aa), a molecular weight of 60.82 kDa and an isoelectric point of 9.29. The amino acid sequence analysis revealed that there were five characteristic conserved regions of cytochrome P450 family (namely helix-C, helix-K, helix-I, PERF and heme-binding). In dsRNA mediated experiment, the expression level of CYP302A1 gene decreased significantly (knock-down of 56.22%) in the 5% Escherichia coli concentration treatment. In addition, the expression levels of EcR and USP and HR3 genes in the downstream were also significantly decreased, whereas that of FTZ-f1 gene increased significantly. In the 5% E. coli treatment, the molting time at maturity of D. sinensis prolonged, and the development of embryos in the incubation capsule appeared abnormal or disintegrated. The whole-mount in situ hybridization showed that the CYP302A1 gene of D. sinensis had six expression sites before RNA interference (RNAi), which located in the first antennal ganglion, ovary, cecae, olfactory hair, thoracic limb and tail spine. However, the expression signal of the CYP302A1 gene of D. sinensis disappeared in the first antennal ganglion and obviously attenuated in the ovary after RNAi. Conclusion The CYP302A1 gene played an important role in the ecdysone synthesis pathway of D. sinensis, and the knock-down of the gene affected the molting and reproduction of D. sinensis.

Background Molting is an important physiological process in the growth and development of arthropoda, which is mainly regulated by juvenile hormone and ecdysone. CYP302A1 is a key enzyme which plays a critical role in the synthesis of ecdysone in insects, but it has not been identified in cladocera. Results The CYP302Al gene of D. sinensis was cloned and its function was analyzed in this paper. The CYP302Al gene of D. sinensis was 5926 bp in full-length, with an open reading frame (ORF) of 1596 bp that encoded 531 amino acids, a molecular weight of 60.82 kDa and an isoelectric point of 9.29. The amino acid sequence analysis revealed that there were five characteristic conserved regions of cytochrome P450 family (namely helix-C, helix-K, helix-I, PERF and heme-binding). In dsRNA mediated experiment, the expression level of CYP302A1 gene decreased significantly (knock-down of 56.22%) in the 5% Escherichia coli concentration treatment. In addition, the expression levels of EcR and USP and HR3 genes in the downstream decreased also significantly, whereas that of FTZ-f1 gene increased significantly. In the 5% E. coli concentration treatment, the molting time at first pregnancy of D. sinensis prolonged, and the development of embryos in the incubation capsule appeared abnormal or disintegrated. The whole-mount in situ hybridization showed that the CYP302A1 gene of D. sinensis had six expression sites before RNA interference (RNAi), which located in the first antennal ganglion, ovary, gastric coeca, olfactory hair, thoracic limb and tail spine. However, the expression signal of the CYP302A1 gene of D. sinensis disappeared in the first antennal ganglion and obviously attenuated in the ovary after RNAi. Conclusions In conclusion, the CYP302A1 gene played an important role in the ecdysone synthesis pathway of D. sinensis, and the knock-down of the gene affected the molting and reproduction of D. sinensis.

Usually, physo-chemical parameters can affect the growth and development of phytoplankton, and even influence spatial distribution of phytoplankton community structure. However, whether environmental heterogeneity causing by several physo-chemical factors together can affect spatial distribution of phytoplankton is still unclear. In this study, seasonal variation and spatial distribution of phytoplankton community structure and its relationships with environmental factors in Lake Chaohu were investigated from August 2020 to July 2021. A total of 190 species from 8 phyla were recorded and these species were divided into 30 functional groups, including 13 dominating functional groups. Average annual phytoplankton density and biomass were (5.46 ± 7.17)×107cells/L and 4.80 ± 4.61 mg/L, respectively. Both density and biomass of phytoplankton were higher in summer ((14.64 ± 20.34)×107cells/L, 10.61 ± 13.16 mg/L) and autumn ((6.79 ± 3.97)×107cells/L, 5.57 ± 2.40mg/L), with the M and H2 of dominant functional groups. The dominant functional groups were N, C, D, J, MP, H2 and M in spring, whereas C, N, T and Y dominated in winter. The distribution of phytoplankton community structure and dominant functional groups in Lake Chaohu had significantly spatial heterogeneity, which was consistent with environmental heterogeneity of the lake and could be divided into four locations. Phytoplankton density and biomass in Location I was higher than those in the other three locations. Moreover, M, C and H2 of dominant function groups appeared in the whole lake, and all 13 dominant functional groups occurred in Location II. Our results suggested that environmental heterogeneity was one of key reasons affecting spatial distribution of phytoplankton community structure and functional groups in Lake Chaohu.

The growth and development of phytoplankton are influenced by physico-chemical parameters, which can also affect the spatial distribution of phytoplankton community structure. However, it is unclear whether environmental heterogeneity caused by multiple physico-chemical factors can affect the spatial distribution of phytoplankton and its functional groups. In this study, we investigated the seasonal variation and spatial distribution of phytoplankton community structure and its relationships with environmental factors in Lake Chaohu from August 2020 to July 2021. We recorded a total of 190 species from 8 phyla, which were divided into 30 functional groups, including 13 dominating functional groups. The average annual phytoplankton density and biomass were (5.46 ± 7.17) × 107 cells/L and 4.80 ± 4.61 mg/L, respectively. The density and biomass of phytoplankton were higher in summer ((14.64 ± 20.34) × 107 cells/L, 10.61 ± 13.16 mg/L) and autumn ((6.79 ± 3.97) × 107 cells/L, 5.57 ± 2.40 mg/L), with the M and H2 of dominant functional groups. The dominant functional groups were N, C, D, J, MP, H2, and M in spring, whereas functional groups C, N, T, and Y dominated in winter. The distribution of phytoplankton community structure and dominant functional groups exhibited significant spatial heterogeneity in the lake, which was consistent with the environmental heterogeneity of the lake and could be classified into four locations. Location I had higher phytoplankton density and biomass than the other three locations. Additionally, dominant functional groups M, C, and H2 were present throughout the lake, and all 13 dominant functional groups were observed in Location II. Our findings suggest that environmental heterogeneity is a key factor influencing the spatial distribution of phytoplankton functional groups in Lake Chaohu.