Thermal tolerance and expression of Hsp70 in larvae of Diamesa spp.

Air temperature and precipitation patterns are likely to change under a scenario of global climate warming, with consequent effects on water temperature and hydrology of running waters, especially of those fed by glaciers. Invertebrates living in these habitats (mainly Chironomidae Diamesinae) are extremely specialised and have developed unique survival strategies to face environmental constraints. The ability to survive heat-shocks was investigated in cold stenothermal species, threatened of extinction by global warming. IV instar larvae of Diamesa cinerella gr. were collected seasonally (from March 2005 to March 2006) in the Noce river (Trentino, NE Italy) at two altitudes (1300 and 2600 m a.s.l.). Larvae were acclimated in a thermostatic chamber for 24 h at 4°C and then exposed for 1 h to heat-shocks from 26 to 35°C. Survival was recorded 1 h after the shock and thermal tolerance was evaluated as LT50. D. cinerella gr. resulted thermotolerant (LT50 varied from 30.1 to 32.9°C). Hsp70 were detected and quantified both in heat-shocked and un-shocked larvae of D. cinerella gr and in un-shocked larvae of other Diamesa species by means of SDS-Page and immunoblotting. An increase of Hsp70 expression was detected in shocked larvae of D. cinerella gr. collected in summer. Constitutive stress proteins were found in all species maintained at 4°C. This could explain the high resistance to brief heat-shocks found in D. cinerella gr