The complete mitochondrial genome of the Antarctic springtail Cryptopygus antarcticus (Hexapoda: Collembola)

Background: Mitogenomics data, i.e. complete mitochondrial genome sequences, are popular molecular markers used forphylogenetic, phylogeographic and ecological studies in different animal lineages. Their comparative analysis has been used toshed light on the evolutionary history of given taxa and on the molecular processes that regulate the evolution of themitochondrial genome. A considerable literature is available in the fields of invertebrate biochemical and ecophysiologicaladaptation to extreme environmental conditions, exemplified by those of the Antarctic. Nevertheless, limited molecular dataare available from terrestrial Antarctic species, and this study represents the first attempt towards the description of amitochondrial genome from one of the most widespread and common collembolan species of Antarctica.Results: In this study we describe the mitochondrial genome of the Antarctic collembolan Cryptopygus antarcticus Willem, 1901.The genome contains the standard set of 37 genes usually present in animal mtDNAs and a large non-coding fragment putativelycorresponding to the region (A+T-rich) responsible for the control of replication and transcription. All genes are arranged inthe gene order typical of Pancrustacea. Three additional short non-coding regions are present at gene junctions. Two of theseare located in positions of abrupt shift of the coding polarity of genes oriented on opposite strands suggesting a role in theattenuation of the polycistronic mRNA transcription(s). In addition, remnants of an additional copy of trnL(uag) are presentbetween trnS(uga) and nad1. Nucleotide composition is biased towards a high A% and T% (A+T = 70.9%), as typically found inhexapod mtDNAs. There is also a significant strand asymmetry, with the J-strand being more abundant in A and C. Within theA+T-rich region, some short sequence fragments appear to be similar (in position and primary sequence) to those involved inthe origin of the N-strand replication of the Drosophila mtDNA.Conclusion: The mitochondrial genome of C. antarcticus shares several features with other pancrustacean genomes, althoughthe presence of unusual non-coding regions is also suggestive of molecular rearrangements that probably occurred before thedifferentiation of major collembolan families. Closer examination of gene boundaries also confirms previous observations on thepresence of unusual start and stop codons, and suggests a role for tRNA secondary structures as potential cleavage signalsinvolved in the maturation of the primary transcript. Sequences potentially involved in the regulation of replication/transcriptionare present both in the A+T-rich region and in other areas of the genome. Their position is similar to that observed in a limitednumber of insect species, suggesting unique replication/transcription mechanisms for basal and derived hexapod lineages. Thisinitial description and characterization of the mitochondrial genome of C. antarcticus will constitute the essential foundationprerequisite for investigations of the evolutionary history of one of the most speciose collembolan genera present in Antarcticaand other localities of the Southern Hemisphere