16As small bodied poikilothermic ectotherms, invertebrates, more so than any other animal 17 group, are susceptible to extremes of temperature and low water availability. In few places is 18 this more apparent than in the Arctic and Antarctic, where low temperatures predominate and 19 water is unusable during winter and unavailable for parts of summer. Polar terrestrial 20invertebrates express a suite of physiological, biochemical and genomic features in response to 21 these stressors. However, the situation is not as simple as responding to each stressor in 22 isolation, as they are often faced in combination. We consider how polar terrestrial 23 invertebrates manage this scenario in light of their physiology and ecology. Climate change is 24 also leading to warmer summers in parts of the polar regions, concomitantly increasing the 25 potential for drought. The interaction between high temperature and low water availability, and 26 the invertebrates' response to them, are therefore also explored. 27 28
During the 1960s, the midge, Eretmoptera murphyi, was transferred from sub-Antarctic South Georgia (55°S 37°W) where it is endemic to a single location on maritime Antarctic Signy Island (60°S 45°W). 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 8h, 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°Cmin(-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 22h 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.
In the Maritime Antarctic and High Arctic, soil microhabitat temperatures throughout the year typically range between -10 and +5 °C. However, on occasion, they can exceed 20 °C, and these instances are likely to increase and intensify as a result of climate warming. Remaining active under both cool and warm conditions is therefore important for polar terrestrial invertebrates if they are to forage, reproduce and maximise their fitness. In the current study, lower and upper thermal activity thresholds were investigated in the polar Collembola, Megaphorura arctica and Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus. Specifically, the effect of acclimation on these traits was explored. Sub-zero activity was exhibited in all three species, at temperatures as low as -4.6 °C in A. antarcticus. At high temperatures, all three species had capacity for activity above 30 °C and were most active at 25 °C. This indicates a comparable spread of temperatures across which activity can occur to that seen in temperate and tropical species, but with the activity window shifted towards lower temperatures. In all three species following one month acclimation at -2 °C, chill coma (=the temperature at which movement and activity cease) and the critical thermal minimum (=low temperature at which coordination is no longer shown) occurred at lower temperatures than for individuals maintained at +4 °C (except for the CTmin of M. arctica). Individuals acclimated at +9 °C conversely showed little change in their chill coma or CTmin. A similar trend was demonstrated for the heat coma and critical thermal maximum (CTmax) of all species. Following one month at -2 °C, the heat coma and CTmax were reduced as compared with +4 °C reared individuals, whereas the heat coma and CTmax of individuals acclimated at +9 °C showed little adjustment. The data obtained suggest these invertebrates are able to take maximum advantage of the short growing season and have some capacity, in spite of limited plasticity at high temperatures, to cope with climate change.
13Polar amplification of global warming has led to an average 2 o C rise in air temperatures in parts of the 14 polar regions in the last 50 years. Poikilothermic ectotherms that are found in these regions, such as 15Collembola and mites, may therefore be put under pressure by changing environmental conditions. 16However, it has also been suggested that the thermal sensitivity of invertebrates declines with higher 17 latitudes and, therefore, that polar ectotherms may not be at risk. In the current study, the heat 18 tolerance and physiological plasticity to heat stress of two well-studied
Harmonized regulation of invertebrate biological control agents (IBCAs) is a major challenge for the 51 countries of the European and Mediterranean Plant Protection Organization (EPPO). Although some of these member countries in the EPPO region have well‐defined regulations and follow a common approach, others do not. The North American Plant Protection Organization (NAPPO) has achieved a common approach in North America through the development of Regional Standards for Phytosanitary Measures specific to IBCAs that outline the information required for submission of a request to release an agent. NAPPO has also developed a process to ensure that submissions are reviewed by experts and regulatory officials in all three member countries. It is proposed that EPPO takes advantage of the experience of NAPPO in developing a harmonized approach for regulating IBCAs.
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