Pre-adapted to the maritime Antarctic? - Rapid cold hardening of the midge, Eretmoptera murphyi

Everatt, M.J.; Worland, M.R.; Bale, J.S.; Convey, P. ORCID: https://orcid.org/0000-0001-8497-9903; Hayward, S.A.L.. 2012 Pre-adapted to the maritime Antarctic? - Rapid cold hardening of the midge, Eretmoptera murphyi. Journal of Insect Physiology, 58 (8). 1104-1111. 10.1016/j.jinsphys.2012.05.009

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Abstract/Summary

During the 1960s, the midge, Eretmoptera murphyi, was transferred from sub-Antarctic South Georgia (55oS 37oW) where it is endemic to a single location on maritime Antarctic Signy Island (60oS 45oW). Its distribution has since expanded considerably, suggesting that it is pre-adapted to the more severe conditions further south. To test one aspect of the level of its pre-adaptation, the rapid cold hardening (RCH) response in this species was investigated. When juvenile (L1–L2) and mature (L3–L4) larvae of E. murphyi were directly exposed to progressively lower temperatures for 8 h, they exhibited Discriminating Temperatures (DTemp, temperature at which there is 10–20% survival of exposed individuals) of −11.5 and −12.5 °C, respectively. The mean SCP was above −7.5 °C in both larval groups, confirming the finding of previous studies that this species is freeze-tolerant. Following gradual cooling (0.2 °C min−1), survival was significantly greater at the DTemp in both larval groups. The response was strong, lowering the lower lethal temperature (LLT) by up to 6.5 °C and maintaining survival above 80% for at least 22 h at the DTemp. RCH was also exhibited during the cooling phase of an ecologically relevant thermoperiodic cycle (+4 °C to −3 °C). Mechanistically, the response did not affect freezing, with no alteration in the supercooling point (SCP) found following gradual cooling, and was not induced while the organism was in a frozen state. These results are discussed in light of E. murphyi’s pre-adaptation to conditions on Signy Island and its potential to colonize regions further south in the maritime Antarctic.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.jinsphys.2012.05.009
Programmes:	BAS Programmes > Polar Science for Planet Earth (2009 - ) > Ecosystems
ISSN:	0022-1910
Additional Keywords:	freeze-tolerance, alien species, climate warming, supercooling point, Belgica antarctica, Chironomidae
Date made live:	02 Apr 2012 08:40 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/17494

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