In this study, we employed geometric morphometrics (GMs) to analyze the shell shape differences among two mass-selected strains of bay scallops (red shell strain (RS) and black shell strain (BS)) and a control group (CG). The results revealed distinct shell shape differences corresponding to shell coloration, with the black shell strain displaying a more elliptical shell compared to the red shell strain. Additionally, the umbonal angle of the red shell strain was smaller than that of the black shell strain, indicating that the black shell strain had a more favorable jet direction that could enhance swimming capabilities. To evaluate the model’s performance in practical applications, leave-one-out cross-validation was carried out on the two shell strains and one control group. The results demonstrated discrimination accuracy rates of 67.44%, 47.62%, and 68.18% for the BS strain, RS strain, and CG, respectively. Similarly, for the right valves, the discrimination accuracy rates were 62.79%, 50.00%, and 75.00% for the BS strain, RS strain, and CG, respectively.

The Ylistrum japonicum is a commercially valuable scallop known for its long-distance swimming abilities. Despite its economic importance, genetic and genomic research on this species is limited. This study presents the first complete mitochondrial genome of Y. japonicum. The mitochondrial genome is 19,475 bp long and encompasses 13 protein-coding genes, three ribosomal RNA genes, and 23 transfer RNA genes. Two distinct phylogenetic analyses were used to explore the phylogenetic position of the Y. japonicum within the family Pectinidae. Based on one mitochondrial phylogenetic analysis by selecting 15 Pectinidae species and additional outgroup taxa and one single gene phylogenetic analysis by 16S rRNA, two phylogenetic trees were constructed to provide clearer insights into the evolutionary placement of Y. japonicum within the family Pectinidae. Our analysis reveals that Ylistrum is a basal lineage to the Pectininae clade, distinct from its previously assigned tribe, Amusiini. This study offers critical insights into the genetic makeup and evolutionary history of Y. japonicum, enhancing our knowledge of this economically vital species.

Both genetic and environmental factors affect the morphology of oysters. Molecular identification is currently the primary means of species identification, but it is inconvenient and costly. In this study, we assessed the ability of geometric morphometric (GM) methods to identify two species of oysters (Crassostrea gigas and C. ariakensis). We used traditional morphometric and GM methods, including principal component analysis (PCA), thin-plate spline analysis (TPS), and canonical variable analysis (CVA), to identify specific features that distinguish the two species. We found that differences in shape can be visualized using GM methods. The Procrustes analysis revealed significant differences in shell morphology between C. gigas and C. ariakensis. The shells of C. ariakensis are more prominent at the widest point and are more scattered and have a greater variety of shapes. The shells of C. gigas are more oval in shape. PCA results indicated that PC1 explained 45.22%, PC2 explained 22.09%, and PC3 explained 10.98% of the variation between the two populations, which suggests that the main morphological differences are concentrated in these three principal components. Combining the TPS analysis function plots showed that the shell shape of C. ariakensis is mainly elongated and spindle-shaped, whereas the shell shape of C. gigas is more oval. The CVA results showed that the classification rate for the two populations reached 100% which means that C. ariakensis and C. gigas have distinct differences in shell morphology and can be completely separated based on morphological characteristics. Through these methods, a more comprehensive understanding of the morphological characteristics of different oyster populations can be obtained, providing a reference for oyster classification and identification.

The Ylistrum japonicum is a commercially valuable scallop known for its long-distance swimming abilities. Despite its economic importance, genetic and genomic research on this species is limited. This study presents the first complete mitochondrial genome of Y. japonicum. The mitochondrial genome is 19,475 bp long and encompasses 13 protein-coding genes, 3 ribosomal RNA genes, and 23 transfer RNA genes. By selecting 15 Pectinidae species and additional outgroup taxa, we have constructed phylogenetic trees to elucidate the evolutionary placement of Ylistrum within the family Pectinidae. Our analysis reveals that Ylistrum is a basal lineage to the Pectininae clade, distinct from its previously assigned tribe, Amusiini. This study offers critical insights into the genetic makeup and evolutionary history of Y. japonicum, enhancing our knowledge of this economically vital species.

Capulus danieli, a distinct member of Capulidae, exhibits a unique ecological behaviour by attaching and drilling onto the pecten, distinguishing itself from other gastropods. Herein, we present the first characterisation of the mitochondrial genome of Capulus danieli. The results showed that the genome spans 15600 base pairs, with an A + T content of 71.12% and a G + C content of 28.88%. Within this genetic makeup, we identified 13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes. Phylogenetic analysis revealed a close evolutionary relationship between Capulus danieli and members of the Ficoidea superfamily. The divergence time estimation suggested that Capulus danieli diverged approximately 52.29 million years ago. These findings significantly contribute to our understanding of the evolutionary history and genetic architecture of Capulus danieli, shedding light on its unique ecological adaptations to the marine environment.

Neptunea arthritica cumingii is an economically important large marine gastropod in northern China; however, overfishing has drastically reduced its commercial resource. Here, we investigated fecundity variations and gonadal gene expression profiles in female N. arthritica cumingii with three distinct shell colors: reddish-brown (HZ), yellowish-brown (HH), and white (BS). Significant fecundity variations were recorded across groups, with BS exhibiting remarkably higher fecundity than other groups. Transcriptomics revealed significant gene expression differences in gonads across groups (a total of 9 RNA-seq samples with 3 replicates for each group); 11,702, 14,731, and 15,706 differentially expressed genes (DEGs) were identified in HZ vs. BS, HH vs. BS, and HZ vs. HH groups, respectively. GO and KEGG enrichment analyses indicated that DEGs were involved in different biological processes. Notably, a DEG subset was significantly enriched for reproduction- and development-related pathways, including estrogen signaling, ovarian steroidogenesis, and oocyte meiosis. Candidate genes associated with fecundity were identified, including Vtg, Foxl2, 17β-HSDs, SOX9, and Dmrt1. Associated gene expression levels were significantly up-regulated in the BS group, suggesting these genes are potentially associated with female gonadal development and oogenesis processes. Furthermore, gene expression patterns were validated by qRT-PCR. The study provides a basis for future studies of fecundity-related traits in N. arthritica cumingii.