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The Journal of Experimental Biology 205, 2115-2124 (2002)
© 2002 The Company of Biologists Limited

Extreme resistance to desiccation and microclimate-related differences in cold-hardiness of gall wasps (Hymenoptera: Cynipidae) overwintering on roses in southern Canada

Jason B. Williams1,*, Joseph D. Shorthouse2 and Richard E. Lee, Jr1

1 Department of Zoology, Miami University, Oxford, OH 45056, USA
2 Department of Biology, Laurentian University, Sudbury, Ontario, Canada P3E 2C6

* e-mail: willia37{at}muohio.edu

Accepted 2 May 2002

Four species of cynipid wasp of the genus Diplolepis that induce galls on roses (Rosa species) in southern Canada and two species of inquiline cynipid associated with these galls were studied for their cold-hardiness and resistance to water loss and for possible links between these adaptations. Mid-winter-acclimated supranivean D. spinosa and Periclistus pirata had lower supercooling points (-38 to -40°C) and higher hemolymph osmolalities (1760-1849 mosmol kg-1) than subnivean D. polita, D. gracilis, D. radicum and Periclistus sp. (-31 to -32°C and 977-1464 mosmol kg-1, respectively). During a simulated transition from summer/fall to mid-winter conditions, the glycerol concentration of D. spinosa more than tripled, reaching a final value of 0.98 moll-1, while its supercooling point decreased by 13°C from the initial value of -27.4°C; however, glycerol concentration and supercooling point did not change for the subnivean species. The permeability of the cuticle of all species was extremely low (0.33-1.00 µg h-1 cm-2 mmHg-1 at 5°C and 0 % relative humidity; 1 mmHg=0.133 kPa), even compared with that of desert species; however, there was no difference in cuticular permeability between supranivean and subnivean prepupae. Transition temperatures ranged between 32.3 and 34.6°C; below 30°C, temperature had little effect on rates of water loss for all species (Q10=1.13-1.87).

Key words: desiccation, cold-hardiness, water loss, permeability, overwintering, gall wasp, Diplolepis sp., Periclistus sp., hibernaculum






© The Company of Biologists Ltd 2002