Wei Zhang

Tiger barb (Puntigrus tetrazona) is an economically important ornamental cyprinid widely cultured in the global aquarium trade; however, comprehensive information on its early development and reproductive performance remains limited. This study characterized embryonic development, larval and juvenile ontogeny, and reproductive performance under controlled hatchery conditions. Fertilized eggs were continuously observed from fertilization to hatching using stereomicroscopy, while larval development was monitored from hatching to 30 days post-hatching (dph). Reproductive performance was evaluated across five consecutive spawning cycles by determining estimated mean egg production per stocked female, fertilization rate, hatching rate, and larval survival. At 26.5–27.5 °C, embryonic development progressed through cleavage, blastula, gastrula, neurula, and organogenesis, and hatching commenced at 25 h 10 min post-fertilization; approximately 50% of viable embryos had hatched by 27 h 17 min, and hatching was completed by approximately 35 h 28 min. Newly hatched larvae measured 3.88 ± 0.56 mm in total length, and complete yolk-sac absorption occurred at approximately 7 dph. Characteristic vertical body pigmentation appeared at 15 dph, whereas juvenile characteristics were evident by approximately 20 dph, while complete scale coverage and adult-like coloration were observed by 30 dph. Reproductive performance declined significantly with successive spawning events, with fecundity decreasing from 182.33 ± 1.57 to 64.33 ± 3.52 eggs female⁻¹ between the first and fifth spawnings, accompanied by reductions in fertilization, hatching, and larval survival rates. These findings provide a morphological developmental reference and practical hatchery benchmarks that can support broodstock management, larval rearing, and seed production of tiger barb in ornamental aquaculture.

Amur minnow (Rhynchocypris lagowskii), an economically important freshwater fish, inhabits tributaries of the Heilongjiang River to Yangtze River in China. Thus far, no genome data of this species have been reported. In this study, we constructed chromosome-level genome assembly for R. lagowskii by integration of MGI, PacBio HiFi and Hi-C sequencing technologies. The assembled genome was 1,041.22 Mb in size, with the scaffold N50 of 32.63 Mb, and 99.04% of the sequences (1,007.75 Mb) were anchored to 25 chromosomes. A total of 32,425 protein-coding genes were predicted in the final assembly, of which 91.09% were functionally annotated. The BUSCO score of genome assembly and protein annotation were 96.32% and 97.53%, respectively, indicating a high quality of genome assembly. The high-quality genome serves as a critical resource for in-depth investigations on comparative genomics, population genetics, molecular breeding, and functional exploration of this economically important fish.

Rhynchochypris lagowskii is a small freshwater economic fish species selected by the Ministry of Agriculture and Rural Affairs as one of the top 10 characteristic aquatic germplasm resources in 2022. To investigate the genetic diversity of the R. lagowskii populations in northern China and provide references for its conservation and genetic breeding, Genotyping by sequencing (GBS) was used to develop single nucleotide polymorphism (SNP) markers and analyze genetic characteristics of 109 individuals from four R. lagowskii populations in Ninghe, Jizhou, Juhe (Tianjin), and Taizihe (Liaoning). Through sequencing, a total of 3723530 SNP markers were obtained, and 133536 high-quality SNP loci were screened for genetic analysis after filtering. The expected heterozygosity (H_e) of the four populations was 0.0397—0.0884, the observed heterozygosity (H_o) was 0.0394—0.0818, the nucleotide diversity (P_i) was 0.0406—0.098, the polymorphic information content (PIC) value was 0.0327—0.0717, the genetic differentiation coefficient (F_ST) was 0.0039—0.8148, and the inbreeding coefficient (F_is) within population was 0.0567—0.5480. Genetic structure analysis showed that four populations clustered into three distinct groups, with individuals from the Ninghe and Jizhou populations in Tianjin clustered into one branch, and individuals from the Taizihe and Juhe populations in Liaoning and Tianjin clustered into one branch, respectively. Population specific SNP markers were identified for all four populations, serving as candidate molecular markers for species identification, population genetics, trait association analysis, and evolutionary studies. Population history dynamics research indicates that the four populations of R. lagowskii all underwent a process characterized by a sharp decline in effective population size (N_e) during the Quaternary glacial period.