Mantle microstructure and transcriptome of the Chicoreus Torrefactus shed light on the crossed lamellar shell formation

Chicoreus torrefactus, which has a typical crossed lamellar structure, was utilized as an ideal species to investigate the structure and function of the mantle in shell formation. Field emission scanning electron microscopy was used to study the microstructure of the gastropod shell. Histological methods, histochemical methods and transcriptome sequencing were used to understand the roles of central mantle and mantle edge in crossed lamellar structure formation. In the central mantle and mantle edge, acidic-neutral mucopolysaccharides were observed. The Gene Ontology (GO) functional enrichment analyses of differentially expressed genes (DEGs) between the mantle edge and foot, as well as between the central mantle and foot, were mainly associated with chitin binding and calcium ion binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DEGs revealed that 15 pathways were significantly enriched in both the mantle edge and foot, as well as in the central mantle and foot, with 12 pathways being shared. In the domain annotation, comparisons were made between the five most abundant domains in the mantle edge and foot, central mantle and foot, three of which were shared. A total of 86 DEGs were detected between the mantle edge and central mantle. Our study could provide a preliminary basis for studying the formation mechanism of crossed lamellar shell structure.