Dataset Information

Aquatic Adaptation and Depleted Diversity: A Deep Dive into the Genomes of the Sea Otter and Giant Otter.

ABSTRACT: Despite its recent invasion into the marine realm, the sea otter (Enhydra lutris) has evolved a suite of adaptations for life in cold coastal waters, including limb modifications and dense insulating fur. This uniquely dense coat led to the near-extinction of sea otters during the 18th-20th century fur trade and an extreme population bottleneck. We used the de novo genome of the southern sea otter (E. l. nereis) to reconstruct its evolutionary history, identify genes influencing aquatic adaptation, and detect signals of population bottlenecks. We compared the genome of the southern sea otter with the tropical freshwater-living giant otter (Pteronura brasiliensis) to assess common and divergent genomic trends between otter species, and with the closely related northern sea otter (E. l. kenyoni) to uncover population-level trends. We found signals of positive selection in genes related to aquatic adaptations, particularly limb development and polygenic selection on genes related to hair follicle development. We found extensive pseudogenization of olfactory receptor genes in both the sea otter and giant otter lineages, consistent with patterns of sensory gene loss in other aquatic mammals. At the population level, the southern sea otter and the northern sea otter showed extremely low genomic diversity, signals of recent inbreeding, and demographic histories marked by population declines. These declines may predate the fur trade and appear to have resulted in an increase in putatively deleterious variants that could impact the future recovery of the sea otter.

SUBMITTER: Beichman AC

PROVIDER: S-EPMC7967881 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Aquatic Adaptation and Depleted Diversity: A Deep Dive into the Genomes of the Sea Otter and Giant Otter.

Beichman Annabel C AC Koepfli Klaus-Peter KP Li Gang G Murphy William W Dobrynin Pasha P Kliver Sergei S Tinker Martin T MT Murray Michael J MJ Johnson Jeremy J Lindblad-Toh Kerstin K Karlsson Elinor K EK Lohmueller Kirk E KE Wayne Robert K RK

Molecular biology and evolution 20191201 12

Despite its recent invasion into the marine realm, the sea otter (Enhydra lutris) has evolved a suite of adaptations for life in cold coastal waters, including limb modifications and dense insulating fur. This uniquely dense coat led to the near-extinction of sea otters during the 18th-20th century fur trade and an extreme population bottleneck. We used the de novo genome of the southern sea otter (E. l. nereis) to reconstruct its evolutionary history, identify genes influencing aquatic adaptati ...[more]

PMID: 31212313

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Project description:BackgroundThe deep sea harbors the majority of the microbial biomass in the ocean and is a key site for organic matter (OM) remineralization and storage in the biosphere. Microbial metabolism in the deep ocean is greatly controlled by the generally depleted but periodically fluctuating supply of OM. Currently, little is known about metabolic potentials of dominant deep-sea microbes to cope with the variable OM inputs, especially for those living in the hadal trenches-the deepest part of the ocean.ResultsIn this study, we report the first extensive examination of the metabolic potentials of hadal sediment Chloroflexi, a dominant phylum in hadal trenches and the global deep ocean. In total, 62 metagenome-assembled-genomes (MAGs) were reconstructed from nine metagenomic datasets derived from sediments of the Mariana Trench. These MAGs represent six novel species, four novel genera, one novel family, and one novel order within the classes Anaerolineae and Dehalococcoidia. Fragment recruitment showed that these MAGs are globally distributed in deep-sea waters and surface sediments, and transcriptomic analysis indicated their in situ activities. Metabolic reconstruction showed that hadal Chloroflexi mainly had a heterotrophic lifestyle, with the potential to degrade a wide range of organic carbon, sulfur, and halogenated compounds. Our results revealed for the first time that hadal Chloroflexi harbor pathways for the complete hydrolytic or oxidative degradation of various recalcitrant OM, including aromatic compounds (e.g., benzoate), polyaromatic hydrocarbons (e.g., fluorene), polychlorobiphenyl (e.g., 4-chlorobiphenyl), and organochlorine compounds (e.g., chloroalkanes, chlorocyclohexane). Moreover, these organisms showed the potential to synthesize energy storage compounds (e.g., trehalose) and had regulatory modules to respond to changes in nutrient conditions. These metabolic traits suggest that Chloroflexi may follow a "feast-or-famine" metabolic strategy, i.e., preferentially consume labile OM and store the energy intracellularly under OM-rich conditions, and utilize the stored energy or degrade recalcitrant OM for survival under OM-limited condition.ConclusionThis study expands the current knowledge on metabolic strategies in deep-ocean Chlorolfexi and highlights their significance in deep-sea carbon, sulfur, and halogen cycles. The metabolic plasticity likely provides Chloroflexi with advantages for survival under variable and heterogenic OM inputs in the deep ocean. Video Abstract.

Dataset Information

Aquatic Adaptation and Depleted Diversity: A Deep Dive into the Genomes of the Sea Otter and Giant Otter.

Publications

Aquatic Adaptation and Depleted Diversity: A Deep Dive into the Genomes of the Sea Otter and Giant Otter.

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