THE EFFECT OF ACCLIMATION UPON THE SURVIVAL OF PTINUS TECTUS AND TENEBRIO MOLITOR WHEN EXPOSED TO LOW TEMPERATURES

Abstract

Ptinus tectus and Tenebrio molitor adults were acclimated for 24 hours to 15°, 25° and 35°. Evidence of acclimation was given by measurement of the chill coma point, heart beat and respiration rates. The respective chill coma points for insects acclimated to 15°, 25° and 35° were 2.9°, 3.7° and 4.7° for P. tectus, and 5.4°, 6.9° and 8.3° for T. molitor. The rates of heart beat and oxygen intake showed that P. tectus could acclimate from 25° to 15° but not to 35°, whilst T. molitor could acclimate from 25° to 35° but not to 15°. Acclimation also affected the undercooling point and fat content, but not the water content. The acclimated insects were exposed to a range of low temperatures for varying periods of time and allowed to recover at 15°, 25° or 35°. The dosage mortality data produced were subjected to probit analyses. In both species mortality varied with the time and temperature of exposure. In P. tectus there was a zone of resistance to freezing extending from 0° (L.D.50 = 1820h) to —9° (L.D.50 = 49—76h) and acclimation affected the terminal region (—9° to —12°) of this zone by altering the undercooling point. Resistance to freezing was minimal in T. molitor and was unaffected by acclimation. The time taken to recover in both species varied with the recovery temperature and the quantity and intensity of cold, but was unaffected by acclimation. Résumé EFFET DE L'ACCLIMATATION PRÉALABLE À DIVERSES TEMPÉRATURES SUR LA SURVIE AU FROID DE PTINUS TECTUS ET DE TENEBRIO MOLITOR Ptinus tectus et Tenebrio molitor furent maintenus pendant 24 h à des températures de 15°, 25° et 35°, puis testés quant à leur résistance au froid, par la détermination de la température provoquant le coma et par les variations de leur rythme cardiaque ou de leur consommation d'oxygène. Dans les deux espèces on observe que le coma se manifeste pour une température d'autant moins basse que la température d'acclimatation était plus élevée. Les adultes de ces mêmes insectes ont été exposés à des températures sub‐létales inférieures à 0°, pendant des durées variables, puis ramenés à des températures de 15°, 25° et 35°. La mortalité est alors estimée et comparée entre des lots préalablement acclimatés à des températures de 15°, 25° et 35°. Chez les deux espèces étudiées la mortalité augmente avec la durée d'action de la température sub‐létale (facteur quantité) et avec la baisse de température subie (facteur intensité). La température d'acclimatation préalable n'affecte pas, chez Tenebrio molitor la D.L. 50, alors que chez Ptinus tectus il se révèle qu'une acclimatation à la plus basse température, diminue la mortalité après action de températures sub‐létales comprises entre —9° et —12°. On a également comparé le taux de mortalité pour des températures égales ou supérieures à 0° (6° − 15° − 25° − 29° − 35°) chez des insectes acclimatés à 25° et ramenés à cette température après action du froid. La mortalité minimum s'observe alors pour une température de restauration de 15°. Les températures de surfusion, la teneur en eau et en lipides furent p...

Thermal Acclimation in Several Species of Stored-Grain Beetles.

“…Further work is needed to determine whether changes in fresh weight have any biological significance in terms of acclimation strategies. Nuttall (1970) noted differences in the fresh weight, water content, dry weight and fat content of cold-and warm-acclimated P, tectus and T. molitor but concluded that long-term survival at sub-zero temperatures was not affected by such differences.…”

“…Cold acclimation lowered the chill coma temperatures of adult Ptinus tectus (Boield. ), three species of Sitophilus, Tenebrio molitor L. and Tribolium confusum Jacq, du Val (Mutchmor and Richards 1961;Nuttall 1970;Evans 1979) but in its effect upon their oxygen consumption proved to be variable. Thus, the oxygen consumption of P. tectus was increased by exposure to cold, that of T. molitor was not affected and that of the Sitophilus species and T .…”

“…It has been manifested as changes in survival at sub-zero or close-to-zero temperatures (Edwards 1958;Mathlein 1961;Nowosielski-Slepowron et al 1968;SBmme 1968;Nuttall 1970;David et al 1977;Evans 1980), chill coma temperature (Mutchmor and Richards 1961 ;Nuttall 1970;Anderson and Mutchmor 197 1;Evans 1977Evans , 1979Evans , 1980, locomotor activity and dispersal (Deal 1941;Gunn and Hopf 1942;Barlow and Kerr 1969;Ernst and Mutchmor 1969;Evans 1977), respiration rate (Howe and Oxley 1952;Edwards 1958;SQmme 1968;Nuttall 1970;Anderson and Mutchmor 1971;Evans 1977Evans , 1979Evans , 1980, susceptibility to fumigants (Sun 1947), heart beat (Nuttall 1970), and enzyme kinetics and other biochemical characteristics (Mutchmor and Richards 196 1 ;Anderson and Mutchmor 1971;Nuttall 1970). Recent general reviews on acclimation are listed by Evans (1980).…”

“…Thus, the oxygen consumption of P. tectus was increased by exposure to cold, that of T. molitor was not affected and that of the Sitophilus species and T . confusum was lowered (Edwards 1958;SBmme 1968;Nuttall 1970;Evans 1979). This last effect, termed inverse acclimation, was considered by Evans (1977) to be an adaptive, energysaving strategy.…”

Physiological adaptations of coccinellidae to supranivean and subnivean hibernacula

“…1973. 1975: HAZEL and PROSSER, 1974 (LUHMANN and DREES, 1952;MARZUSCH, 1952;DEHNEL and SEGAL, 19.56;BUFFINGTON, 1969;and NUTTALL, 1970). For an insect exposed to fluctuating temperatures this reduction may result in significant metabolic savings during dormancy when it is not possible to replenish energy reserves.…”