Candidate genes for shell colour polymorphism in Cepaea nemoralis

Area of Science:

• Genomics
• Evolutionary Biology
• Molluscan Shell Formation

Background:

• The land snail *Cepaea nemoralis* exhibits significant shell color and banding polymorphism, making it a model for studying adaptation and genetics.
• Understanding the genetic basis of this polymorphism is crucial for evolutionary and ecological studies.

Purpose of the Study:

• To identify candidate genes responsible for the shell color and banding polymorphism in *Cepaea nemoralis* using transcriptomic approaches.
• To investigate the genetic regulation underlying shell coloration in this species.

Main Methods:

• RNA sequencing (RNAseq) was performed on foot and mantle tissues from two distinct *Cepaea nemoralis* phenotypes.
• A de novo transcriptome was assembled, followed by differential gene expression analysis and single nucleotide polymorphism (SNP) analysis.
• Candidate genes were identified by overlapping differentially expressed transcripts and those with phenotype-specific SNPs.

Main Results:

• A de novo transcriptome of 147,397 contigs was generated.
• 1,961 transcripts were upregulated in mantle tissue, and 2,592 transcripts showed phenotype-specific SNPs.
• 197 candidate transcripts were identified, with 38 annotated; four are linked to nacreous layer production, and eight metallothionein transcripts suggest a role in melanin inhibition.

Conclusions:

• This study provides a foundational set of candidate genes for the genetic regulation of *Cepaea nemoralis* shell color polymorphism.
• The findings offer insights into the molecular mechanisms controlling shell pigmentation and structural components.
• The identified genes serve as a starting point for further functional studies on snail shell evolution.