کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5922028 | 1165344 | 2012 | 8 صفحه PDF | دانلود رایگان |
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 â11.5 and â12.5 °C, respectively. The mean SCP was above â7.5 °C in both larval groups, confirming the finding of previous studies that this species is freeze-tolerant. Following gradual cooling (0.2 °C minâ1), 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 â3 °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.
Highlights⸠The midge, Eretmoptera murphyi, was accidentally introduced to maritime Antarctic Signy Island (60oS 45oW). ⸠The rapid cold hardening (RCH) response of the midge larvae was investigated in the context of the maritime Antarctic environment. ⸠A strong RCH response was demonstrated in both juvenile (L1-L2) and mature (L3-L4) larvae. ⸠E. murphyi has the potential to spread to considerably higher southern latitudes.
Journal: Journal of Insect Physiology - Volume 58, Issue 8, August 2012, Pages 1104-1111