Gene Rearrangement in the Mitochondrial Genomes of the Sand Crabs Albunea symmysta (Anomura:Hippoidea) with Insights into Phylogenetic Relationships in the Anomura (Crustacea: Decapoda).

The complete mitochondrial genome of Albunea symmysta (Anomura: Hippoidea: Albuneidae) was sequenced and annotated, yielding a circular genome of 15,640 bp comprising 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and a control region (CR). Substantial gene rearrangements were detected in A. symmysta, including five major rearranged gene clusters, suggesting the involvement of tandem duplication-random loss, reversal, and transposition events. Phylogenetic relationships were reconstructed using nucleotide sequences of 13 PCGs from 55 Anomura species, and both Bayesian Inference (BI) and Maximum Likelihood (ML) analyses supported the monophyly of Hippoidea. Within Hippoidea, A. symmysta formed a robust clade with Stemonopa insignis, and the superfamily was resolved as ((Albuneidae + Hippidae) + Blepharipodidae). Gene rearrangement patterns provided additional support for the evolutionary placement of Hippoidea. In contrast, Paguroidea was polyphyletic and comprised three distinct clades: (1) monophyletic Lithodidae and paraphyletic Paguridae; (2) monophyletic Coenobitidae and paraphyletic Diogenidae; and (3) basal Pylochelidae. These results offer new insights into the mitochondrial gene order evolution of Hippoidea and reinforce the potential of mitochondrial gene rearrangement as a phylogenetic marker in Anomura.