Complete mitochondrial genomes of two scaphopod molluscs

Area of Science:

• Marine Biology
• Genomics
• Molluscan Evolution

Background:

• Scaphopoda, or tusk shells, are a unique class of marine molluscs with distinct shell morphology.
• Mitochondrial genomes provide valuable markers for phylogenetic and evolutionary studies in invertebrates.
• Previous genomic studies in scaphopods have revealed variations in gene order and content.

Purpose of the Study:

• To determine and analyze the complete mitochondrial genomes of two scaphopod species: Antalis entalis (Dentaliida) and an unidentified Antarctic gadilid.
• To compare the genomic organization and gene arrangement between different scaphopod taxa.
• To conduct phylogenetic analyses to clarify the evolutionary relationships within Scaphopoda.

Main Methods:

• Whole-genome sequencing of mitochondrial DNA from Antalis entalis and an Antarctic gadilid.
• Bioinformatic analysis to annotate mitochondrial genes (protein-coding and rRNA) and assess genome structure.
• Phylogenetic reconstruction using concatenated sequences of 13 protein-coding and 2 rRNA genes.

Main Results:

• Complete mitochondrial genomes were obtained for A. entalis and the Antarctic gadilid, with minor gaps in the latter.
• The Antarctic gadilid mitochondrial genome organization is highly similar to Siphonodentalium, while A. entalis shows differences in gene transposition compared to Graptacme.
• Phylogenetic analyses strongly support the monophyly of Scaphopoda, Gadilida, and Dentaliida.

Conclusions:

• The study provides new genomic data for scaphopod molluscs, enhancing our understanding of their molecular evolution.
• Comparative genomic analysis highlights conserved and variable features in scaphopod mitochondrial genomes.
• The robust phylogenetic results confirm the current classification and evolutionary history of major scaphopod lineages.