The Mitochondrial Genome of Arctica islandica; Phylogeny and Variation

Gernot Glöckner,Matthias Platzer,Doris Abele,David Caramelli,Christoph Held,Ivonne Heinze

doi:10.1371/journal.pone.0082857

Abstract

Arctica islandica is known as the longest-lived non-colonial metazoan species on earth and is therefore increasingly being investigated as a new model in aging research. As the mitochondrial genome is associated with the process of aging in many species and bivalves are known to possess a peculiar mechanism of mitochondrial genome inheritance including doubly uniparental inheritance (DUI), we aimed to assess the genomic variability of the A. islandica mitochondrial DNA (mtDNA). We sequenced the complete mitochondrial genomes of A. islandica specimens from three different sites in the Western Palaearctic (Iceland, North Sea, Baltic Sea). We found the A. islandica mtDNA to fall within the normal size range (18 kb) and exhibit similar coding capacity as other animal mtDNAs. The concatenated protein sequences of all currently known Veneroidea mtDNAs were used to robustly place A. islandica in a phylogenetic framework. Analysis of the observed single nucleotide polymorphism (SNP) patterns on further specimen revealed two prevailing haplotypes. Populations in the Baltic and the North Sea are very homogenous, whereas the Icelandic population, from which exceptionally old individuals have been collected, is the most diverse one. Homogeneity in Baltic and North Sea populations point to either stronger environmental constraints or more recent colonization of the habitat. Our analysis lays the foundation for further studies on A. islandica population structures, age research with this organism, and for phylogenetic studies. Accessions for the mitochondrial genome sequences: KC197241 Iceland; KF363951 Baltic Sea; KF363952 North Sea; KF465708 to KF465758 individual amplified regions from different speciemen

Highlights

The Iceland clam Arctica islandica (Linnaeus 1767, common name „ocean quahog”) is the longest-lived non-colonial metazoan with a recorded maximum lifespan potential (MLSP) of more than 507 years reported for the subpolar population from the North Icelandic shelf [1]
First investigations of the transcriptome of this longevity champion indicate that specimens from low salinity environments (Baltic Sea) transcribe a number of stress genes upon exposure to anoxia, whereas individuals from Iceland and the North Sea largely shut down gene transcription under anoxia and, instead, enter a state of metabolic rate reduction in which only cellular maintenance is supported [8]
While the salinity in the North sea (33-34‰) is like that of the Icelandic shelf (34‰), the salinity at the Baltic sea sampling site is much lower with only 25 ‰ but fluctuations are high, depending on episodic inflow of more saline water via the Kattegat

Summary

Introduction

The Iceland clam Arctica islandica (Linnaeus 1767, common name „ocean quahog”) is the longest-lived non-colonial metazoan with a recorded maximum lifespan potential (MLSP) of more than 507 years reported for the subpolar population from the North Icelandic shelf [1]. First investigations of the transcriptome of this longevity champion indicate that specimens from low salinity environments (Baltic Sea) transcribe a number of stress genes upon exposure to anoxia, whereas individuals from Iceland and the North Sea largely shut down gene transcription under anoxia and, instead, enter a state of metabolic rate reduction in which only cellular maintenance is supported [8] The mitochondria, their chemical composition, their energy conserving electron transport systems and their capacity to generate free radicals under different metabolic and stress conditions are being extensively studied and related to longevity of vertebrate and invertebrate species [9,10,11,12,13,14]

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