The Ovulidae family, closely related to Cypraeidae (cowries), comprises approximately 260–280 species predominantly inhabiting tropical and subtropical shallow marine environments. Traditional morphological classification within Ovulidae has been challenging due to significant variability influenced by their host organisms. In this study, we collected 15 Ovulidae species from China’s offshore waters, including the first regional record of Habuprionovolva aenigma (M. Azuma & C. N. Cate, 1971). We sequenced the mitochondrial genomes of 14 species and found that, except for H. aenigma, they exhibit typical metazoan mitochondrial structures. Phylogenetic analyses based on mitochondrial genome data were conducted to elucidate relationships among Ovulidae genera. Notably, we discovered that the subfamily Prionovolvinae exhibits a unique mitochondrial tRNA gene order. Our results suggest that mitochondrial gene rearrangements occurred after the divergence of the Prionovolvinae and Ovulinae subfamilies. Additionally, we found that Ovulidae species display significantly higher Ka/Ks ratios compared to Cypraeidae, indicating different selective pressures possibly linked to their unique feeding habits. Based on these findings, we propose reclassifying certain genera from the Simniinae subfamily to the Prionovolvinae subfamily. This research enhances the understanding of Ovulidae phylogeny and provides genomic resources for future studies.

This study identified 260 lanternfish larvae specimens belonging to 20 species from 12 genera, which were obtained from 544 samples of the Ninety East Ridge waters in the Indian Ocean using the COI DNA barcoding. Among the samples, the intra-specific genetic distances ranged from 0% to 2.99%, while inter-specific genetic distances ranged from 1.88% to 25.71%. With the exception of Notolychnus valdiviae, the maximum intra-specific genetic distances were lower than the minimum inter-specific genetic distances for all species. The haplotypes of nine species were analyzed, revealing significant differences in the number, structure, and spatial distribution patterns. Notably, Ceratoscopelus warmingii and Notolychnus valdiviae displayed a significant north-south divergence pattern. The results indicated that seamount topography may influence the gene flow and horizontal distribution patterns of some lanternfish species, as shown by the distribution patterns of different populations of some species.

In 2003, Kandelia obovata was identified as a new mangrove species differentiated from Kandelia candel. However, little is known about their chloroplast (cp) genome differences and their possible ecological significance. In this study, 25 whole cp genomes, with seven samples of K. candel from Malaysia, Thailand, and Bangladesh and 18 samples of K. obovata from China, were sequenced for comparison. The cp genomes of both species encoded 128 genes, namely 83 protein-coding genes, 37 tRNA genes, and eight rRNA genes, but the cp genome size of K. obovata was ~2 kb larger than that of K. candle due to the presence of more and longer repeat sequences. Of these, tandem repeats and simple sequence repeats exhibited great differences. Principal component analysis based on indels, and phylogenetic tree analyses constructed with homologous protein genes from the single-copy genes, as well as 38 homologous pair genes among 13 mangrove species, gave strong support to the separation of the two species within the Kandelia genus. Homologous genes ndhD and atpA showed intraspecific consistency and interspecific differences. Molecular dynamics simulations of their corresponding proteins, NAD(P)H dehydrogenase chain 4 (NDH-D) and ATP synthase subunit alpha (ATP-A), predicted them to be significantly different in the functions of photosynthetic electron transport and ATP generation in the two species. These results suggest that the energy requirement was a pivotal factor in their adaptation to differential environments geographically separated by the South China Sea. Our results also provide clues for future research on their physiological and molecular adaptation mechanisms to light and temperature.