TY - JOUR
T1 - Cold tolerance of the Australian spur-throated locust, Austracris guttulosa
AU - Woodman, James D.
PY - 2012/3
Y1 - 2012/3
N2 - The cold tolerance of overwintering adult Spur-throated locusts, Austracris guttulosa, was examined using measures of supercooling point relative to gender, environmental acclimation and feeding state as well as mortality for a range of sub-zero temperature exposure treatments. Freezing was lethal and supercooling points ranged from -6 to -12.8°C, but were statistically independent of fresh mass, body water content, acclimation, and/or gut content in fed and starved individuals. A significant interaction effect of gender and feeding status showed that the larger bodied females had decreased supercooling capacity with increased food material in the digestive tract. Post-freezing dissections revealed differences in the amount of freshly consumed and retained food material in the digestive tract between fed and starved individuals of each gender, which could explain this effect based on inoculation of ice crystallisation by food particles. Above supercooling temperatures, neither gender nor the rate of cooling had a significant effect on mortality. When cooled from 25°C at 0.1 or 0.5°Cmin -1 to a range of experimental minimum temperatures held for 3h, survival was ≥74% to -7°C, but declined sharply to ≤37% when cooled to -8°C or lower. Although the laboratory experiments reported here suggest that A. guttulosa is not freeze tolerant and unable to rapidly cold harden, exposure to typical cold and frosty nights that very rarely reach below -8°C as a night minimum in the field would be unlikely to cause mortality in the vast majority of overwintering aggregations.
AB - The cold tolerance of overwintering adult Spur-throated locusts, Austracris guttulosa, was examined using measures of supercooling point relative to gender, environmental acclimation and feeding state as well as mortality for a range of sub-zero temperature exposure treatments. Freezing was lethal and supercooling points ranged from -6 to -12.8°C, but were statistically independent of fresh mass, body water content, acclimation, and/or gut content in fed and starved individuals. A significant interaction effect of gender and feeding status showed that the larger bodied females had decreased supercooling capacity with increased food material in the digestive tract. Post-freezing dissections revealed differences in the amount of freshly consumed and retained food material in the digestive tract between fed and starved individuals of each gender, which could explain this effect based on inoculation of ice crystallisation by food particles. Above supercooling temperatures, neither gender nor the rate of cooling had a significant effect on mortality. When cooled from 25°C at 0.1 or 0.5°Cmin -1 to a range of experimental minimum temperatures held for 3h, survival was ≥74% to -7°C, but declined sharply to ≤37% when cooled to -8°C or lower. Although the laboratory experiments reported here suggest that A. guttulosa is not freeze tolerant and unable to rapidly cold harden, exposure to typical cold and frosty nights that very rarely reach below -8°C as a night minimum in the field would be unlikely to cause mortality in the vast majority of overwintering aggregations.
KW - Acclimation
KW - Cold hardiness
KW - Feeding
KW - Freezing
KW - Insect
KW - Low temperature
KW - Pre-freeze mortality
KW - Total body water content
UR - http://www.scopus.com/inward/record.url?scp=84857793530&partnerID=8YFLogxK
U2 - 10.1016/j.jinsphys.2011.12.015
DO - 10.1016/j.jinsphys.2011.12.015
M3 - Article
SN - 0022-1910
VL - 58
SP - 384
EP - 390
JO - Journal of Insect Physiology
JF - Journal of Insect Physiology
IS - 3
ER -