53 / 2026-03-31 19:43:11

Complete mitochondrial genome characterization and phylogenomic analysis of the mangrove snail Ellobium aurimisdae

Mangrove snails,Ellobium aurismidae,Mitochondrial genome evolution

Background: Ellobium aurismidae is an ecologically dominant mangrove gastropod distributed widely across Asian coastal zones, yet remains genomically understudied compared to its congener Ellobium chinense. Mitochondrial genomes serve as powerful tools for resolving phylogenetic relationships and understanding genome evolution in Gastropoda, offering both conserved gene content and variable structural features that provide robust evolutionary signals. The absence of genomic resources for Ellobium aurismidae limits comparative mitogenomic analyses within Ellobiidae and hinders our understanding of evolutionary adaptations in mangrove-associated snails. In this study, we present the first complete mitochondrial genome of Ellobium aurismidae obtained through hybrid assembly of long- and short-read sequencing technologies, and conducted comprehensive comparative mitogenomic analyses with other Panpulmonata species.



Methods: A single adult Ellobium aurismidae specimen was collected from Guangdong Neilingding-Futian Mangrove National Nature Reserve. The genomic DNA was extracted and sequenced using hybrid assembly combining PacBio HiFi long-read and Illumina NovaSeq X Plus short-read sequencing. The draft mitochondrial genome was assembled with MitoHifi and polished using Pilon, followed by annotation with MITOS2 and Proksee. The comparative mitochondrial phylogenetic analysis was performed on 24 Panpulmonata species using maximum likelihood methods in MEGA v12.1. Codon usage bias, positive selection analysis (dN/dS ratios), and gene arrangement comparisons were conducted using bioinformatic tools PhyloSuite, MAFFT, MACSE, and HyPhy.



Results: The complete circular mitochondrial genome of Ellobium aurismidae was 13,958 bp in length and contained the typical 37 genes (13 protein‑coding, 22 tRNA, and 2 rRNA genes), with an overall GC content of 43.57%. The mitochondrial phylogenetic analysis revealed Ellobium aurismidae was closely related to Ellobium chinense within the order Ellobiida, positioning this lineage between marine Systellommatophora and terrestrial Stylommatophora. Gene arrangements among Ellobiida species are highly conserved compared to other panpulmonates. Codon usage analysis revealed weak codon bias in Ellobium aurismidae, primarily shaped by purifying selection. Positive selection analysis identified 155 sites under positive selection in the mitochondrial genome of Ellobium aurismidae across 13 protein-coding genes, with ND5 (21 sites) and ND4 (20 sites) showing the strongest adaptive signals, suggesting roles in energy metabolism adaptations.



Conclusion: These findings provide the first mitogenomic resource for Ellobium aurismidae, refine ellobiid phylogenetic relationships, and highlight candidate mitochondrial loci potentially involved in adaptation to intertidal and mangrove environments, thereby offering insights into the mitochondrial underpinnings of marine–terrestrial transitions and informing future comparative, functional, and conservation genomic investigations of mangrove gastropods.