Warm Temperatures, Cool Sponges: The Effect of Increased Temperatures on the Antarctic Sponge Isodictya sp.

Although the cellular and molecular responses to exposure to relatively high temperatures (acute thermal stress or heat shock) have been studied previously, only sparse empirical evidence of how it affects cold-water species is available. As climate change becomes more pronounced in areas such as the Western Antarctic Peninsula, it has become crucial to understand the capacity of these species to respond to thermal stress. Here we use the Antarctic sponge Isodictya sp. to investigate how sessile organisms (particularly Porifera) can adjust to heat shock, by exposing this species to 3 and 5 °C, corresponding to predicted temperatures under the 2080 IPCC-SRES scenarios. Assembling a de novo reference transcriptome (90,188 contigs, >93.7% metazoan BUSCO cassette) we have discerned the molecular componentry employed by Isodictya to adjust to environmental insult. Our analyses suggest that TGF-β, ubiquitin and hedgehog cascades are involved, alongside other genes. However, the degree and type of response changed little from 3 to 5 °C, suggesting that even moderate rises in temperature could cause stress at the limits of this organism9s capacity. Given the importance of sponges to Antarctic ecosystems, our findings are vital for discerning the consequences of increases in Antarctic ocean temperature on these and other species.