Abstract

The Western Antarctic Peninsula (WAP) is among the areas of the planet showing some of the most significant increases in air and water temperature. It is projected that increasing temperature will modulate coastal ecosystems at species ecological performance and molecular composition. The main way that the organisms can cope with large thermal variation is by having a reversible phenotypic plasticity, which provides the organisms with a compensatory physiological response when facing challenging conditions. The giant Antarctic isopod Glyptonotus antarcticus is one of most common species in Antarctic waters. This species has a larval development inside of the maternal marsupium, where juveniles have a short period to acclimate to environmental conditions after birth. In this sense, we hypothesize that juveniles exposed to unusual temperature increases even for short periods, would not respond adequately showing a narrow phenotypic plasticity. We experimentally assessed if early juveniles of G. antarcticus have the molecular plasticity when exposed to increased temperature at 5°C during 1, 6, 12 and 24 h. Sequenced libraries were compared between control (0°C) and each experimental treatment to detect differentially expressed transcripts. The main molecular pathways affected by thermal stress were antioxidant, proteases, endopeptidases and ubiquination transcripts which were up-regulated and mitochondrial respiratory chain, cuticle, cytoskeleton and a molt transcript which were down-regulated. Regarding the HSP transcript, only 3 were up-regulated at least in two points of the stress kinetic, without classical Hsp70 and Hsp90 transcripts. This study shows that juveniles of G. antarcticus do not show molecular phenotypic plasticity to cope with acute short-term heat stress, even for one or few hours of exposure with an absence of an eco-physiological capacity to respond. This may have consequences at the ecological population level, showing a reduced individual ability to survive decreasing population recruitment.

Highlights

  • The Western Antarctic Peninsula (WAP) is among the areas of the planet showing most significant increases in air and water temperature (Stenni et al, 2017), with evidence indicating that the mean atmospheric temperatures increased by 3◦C (0.6◦C per decade) and sea surface temperatures by 1◦C (SST in the upper 100 m) between 1955 and 2004 (Moffat and Meredith, 2018)

  • The aim of this study is to determine if early juveniles of the giant isopod G. antarcticus have the molecular plasticity once they are exposed to an acute (1, 6, 12 and 24 h) 5◦C heat shock

  • The transcript expression level counting with normalized Transcripts Per Millions” (TPM) were compared between Control 1 h (1◦C 1 h) and 1◦C 24 h to assess the effects of sampling time during the experiment

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Summary

Introduction

The Western Antarctic Peninsula (WAP) is among the areas of the planet showing most significant increases in air and water temperature (Stenni et al, 2017), with evidence indicating that the mean atmospheric temperatures increased by 3◦C (0.6◦C per decade) and sea surface temperatures by 1◦C (SST in the upper 100 m) between 1955 and 2004 (Moffat and Meredith, 2018). The IPCC report for Polar regions has shown that in recent years (2005–2017), the Southern Ocean was responsible for an increased proportion of the global ocean heat increase (45–62%) (high confidence) (Meredith et al, 2019). These evidences confirm that this region includes a major center of considerable, recent warming in the shallows, and this is forecast to be sustained (Barnes et al, 2021). The Antarctic marine species are more sensitive to temperature variations than other marine groups from other regions (Peck, 2011, Peck et al, 2013). The projected that rising temperatures could be modulate communities of coastal ecosystems at species ecological performance and molecular composition (Ashton et al, 2017; Peck, 2018; Morley et al, 2020)

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