The COX1 mutation drives structural innovation despite silent tRNA variation in semiaquatic bugs

The semiaquatic bugs represent an aquatic clade within the Hemiptera. These insects inhabit a variety of microhabitats across both freshwater and marine environments. There is a notable lack of structural studies on mitochondrial genes within the Gerroidea. This study significantly expands the available data, presenting 16 newly sequenced mitochondrial genomes and a mitochondrial full-length transcriptome. These additions address existing data gap, particularly for the Microveliinae, Veliinae, and Eotrechinae. Our analysis of mitochondrial gene arrangement revealed that two tRNA have relocated to new positions within the Microveliinae. Selective pressure analysis revealed that approximately 64.11 % of codons are under negative selection, indicating high conservation in the protein-coding genes (PCGs). Our structural analysis suggests that the significantly longer average length of the COX1 gene in Ptilomerinae may correlate with the presence of additional strand structures. However, full-length transcriptome data demonstrate that additional strand structures are not transcribed in Potamometra zhengi. Observations of lineages that have undergone tRNA rearrangement or duplication indicate corresponding changes in the structural diversity. We propose that these unique mitochondrial traits in this specific lineage likely result from random genetic variation under purifying selection, rather than from selection-driven genetic adaptation.