Cerithidea sinensis is a common and important component of mangrove ecosystem. In this study, the mitochondrial genome of C. sinensis was determined for the first time using next-generation sequencing; the overall base components of mitogenome consisting of 15633 bp was 31.14% for A, 35.70% for T, 16.65% for G, 16.51% for C, and its GC content was 33.16%. The mitochondrial circular genome was composed of 13 protein-coding genes, 22 tranfer RNAs, and 2 ribosomal RNAs. Polygenetic analysis showed that the C. sinensis was more closed to Semisulcospira libertina than Turritella bacillum and Tylomelania sarasinorum. We may speculate that the C. sinensis is evolved from freshwater species.

The Sox family plays essential roles as transcription factors in vertebrates; however, little is known about the Sox family in Lutraria sieboldii. L. sieboldii are pleasant to eat with a short growth cycle and have become one of the best bottom-seeded enrichment species in Guang Xi. In this study, Sox2 (named LsSox2) and Sox9 (named LsSox9) from L. sieboldii were cloned, and their expression patterns were analyzed. The length of the LsSox2 gene coding sequence was 1011 bp, encoding 336 amino acids, and LsSox9 was 1449 bp, encoding 482 amino acids. LsSox2 had its highest expression levels in the ovary, which were 356 times those in testis, whereas LsSox9 presented higher expression in testis, which was 6 times more highly expressed than in the ovary. LsSox2 exhibited the highest expression during the morula stage, which was 20 times that of the D-shaped larvae or zygote. LsSox9 exhibited two expression peaks, one at the four-cell stage and the other at the trochophore stage, while the lowest expression was in the zygote. LsSox9 was 73 times more highly expressed in the four-cell stage than in the zygote stage. During gonadal development, LsSox2 presented the highest expression in the mature ovary, which was 756 times more highly expressed than in mature testis. LsSox9 presented higher expression in testis at the emission stage which was 6 times more highly expressed than in the ovary. These results indicate that LsSox2 and LsSox9 may play important roles in embryonic and gonadal development.

Sipunculus nudus, a marine species of substantial medicinal and commercial importance, requires genetic enhancement to boost its production yield. However, progress in genetic research and selective breeding has been constrained by two critical limitations: the scarcity of available molecular markers and the absence of systematic genetic diversity assessments across China’s Beibu Gulf. To address these challenges, our genome-wide investigation identified 168,771 InDel variations, from which we developed 25,558 primer pairs. Experimental validation showed 82 out of 85 synthesized primers (96.47%) successfully amplified target regions, with 81 demonstrating polymorphism. Sixteen high polymorphic markers were subsequently employed to analyze 153 samples collected along the Beibu Gulf coastline, revealing 142 distinct alleles. The number of alleles, effective number of alleles, observed heterozygosity, expected heterozygosity, Shannon’s index and polymorphic information content ranged from 4 to 15 (mean of 8.875), 2.110 to 6.009 (mean of 4.110), 0.009 to 0.768 (mean of 0.232), 0.526 to 0.834 (mean of 0.734), 0.919 to 2.085 (mean of 1.576), and 0.440 to 0.816 (mean of 0.692), respectively. Population structure analysis revealed four genetically distinct subpopulations within the Beibu Gulf population. This delineation of population substructure provides critical insights for optimizing selective breeding programs and formulating germplasm conservation strategies in S. nudus.