@article {13987, title = {Sperm storage and viability within females of Euscepes postfasciatus: effect of irradiation on sperm abundance and viability within female}, journal = {Journal of Insect Physiology}, volume = {55}, number = {9}, year = {2009}, month = {September}, pages = {813-817}, abstract = {Irradiation has been widely used in suppression or eradication programs that use the sterile insect technique (SIT) or in studying sperm competition. Although it is well known that irradiation has negative impacts on reproductive (sperm) cells, previous studies have assumed that sperm from irradiated males behave identically to normal sperm in the female reproductive tract after mating. In this study, we used the West Indian sweetpotato weevil Euscepes postfasciatus to investigate the effect of irradiation on the abundance and viability of sperm in female spermatheca for 14 days after copulation. The abundance of sperm in females did not change throughout the experimental period, and sperm viability gradually decreased regardless of irradiation. In this weevil, irradiated sperm appear to behave identically to normal sperm in females for 14 days following irradiation/copulation. Therefore, the effect of irradiation on sperm viability within the female spermatheca is considered to be insignificant}, keywords = {Euscepes postfasciatus}, isbn = {0022-1910}, author = {Kumano, Norikuni and Haraguchi, Dai and Kohama, Tsuguo} } @article {13915, title = {Physiological and biochemical analysis of overwintering and cold tolerance in two Central European populations of the spruce bark beetle, Ips typographus}, journal = {Journal of Insect Physiology}, volume = {57}, number = {8}, year = {2011}, month = {August}, pages = {1136-1146}, abstract = {Overwintering success is one of the key aspects affecting the development and outbreaks of the spruce bark beetle, Ips typographus (L.) populations. This paper brings detailed analysis of cold tolerance, and its influence on overwintering success, in two Central European populations of I. typographus during two cold seasons. Evidence for a supercooling strategy in overwintering adults is provided. The lower lethal temperature corresponds well to the supercooling point that ranges between -20 and -22 [degree]C during winter months. The supercooled state is stabilized by the absence of internal ice nucleators and by seasonal accumulation of a mixture of sugars and polyols up to the sum concentration of 900 mM. The cryoprotective function of accumulated metabolites is probably based on increasing the osmolality and viscosity of supercooled body fluids and decreasing the relative proportion of water molecules available for lethal formation of ice nuclei. No activity of thermal hysteresis factors (stabilizers of supercooled state) was detected in hemolymph. Lethal times for 50\% mortality (Lts50) in the supercooled state at -5, -10 or -15 [degree]C are weeks (autumn, spring) or even months (winter), suggesting relatively little mortality caused by chill injury. Lts50 at -15 [degree]C are significantly shorter in moist (6.9 days) than in dry (>42 days) microenvironment because there is higher probability of external ice nucleation and occurrence of lethal freezing in the moist situation.}, keywords = {Ips typographus}, isbn = {0022-1910}, author = {Kostal, V. and Dolezal, P. and Rozsypal, J. and Moravcova, M. and Zahradnickova, H. and Simek, P.} } @article {13916, title = {Multiple component system of sugars and polyols in the overwintering spruce bark beetle, Ips typographus}, journal = {Journal of Insect Physiology}, volume = {53}, number = {6}, year = {2007}, month = {June}, pages = {580-586}, abstract = {Overwintering adults of the spruce bark beetle, Ips typographus (L.) showed an unusually complex sugar/polyol cryoprotectant system. The major components of the multiple system were: glucose (177.6 mmol L-1, March); trehalose (175.0 mmol L-1, December); sorbitol (147.9 mmol L-1, January); mannitol (81.2 mmol L-1, March); and erythritol (40.7 mmol L-1, March) (in the parentheses, the maximum concentrations are shown and the month when they were reached). Other minor components were glycerol, fructose, threitol, myo-inositol, arabinitol and ribitol. Distinct seasonal patterns of accumulation/depletion in various components were found. Glycerol, trehalose and glucose started to accumulate first, during early autumn, when the air temperatures fluctuated between 20 and 0 [degree]C, and diapause beetles continued in feeding. Glycerol was depleted, glucose remained stable and trehalose continued in accumulation during late autumn when the temperatures oscillated around 0 [degree]C. During early winter severe frosts reaching -20 [degree]C came, the beetles terminated their diapause and trehalose was partially depleted, while mannitol, sorbitol, fructose, threitol and erythritol started to accumulate. Cold weather continued also during late winter when the beetles remained quiescent. During this period, trehalose was re-accumulated, threitol and erythritol continued to increase, mannitol remained stable and sorbitol, fructose decreased. All cryoprotectans were finally cleared in the beetles which were spontaneously leaving bark during early spring. The seasonal maximum of total concentration of all cryoprotectants (578.2 mOsmol L-1) was reached in March. Such a concentration results in colligative depression of melting point of body fluids down by 1.08 [degree]C only. It suggests that the potential cryoprotective effect of accumulated sugars and polyols was related rather to their non-colligative functions}, keywords = {Ips typographus}, isbn = {0022-1910}, author = {Kostal, V. and Zahradnickova, H. and Simek, P. and Zeleny, J.} } @article {12359, title = {Thermal response and reversibility of prolonged larval diapause in the chestnut weevil, Curculio sikkimensis}, journal = {Journal of Insect Physiology}, volume = {56}, number = {6}, year = {2010}, month = {Jun}, pages = {616-621}, abstract = {Curculio sikkimensis undergoes prolonged larval diapause that is terminated by chilling and warming cycles. To examine the effects of warming temperatures and their duration on diapause termination, we exposed diapause larvae that had not been reactivated after chilling at 5[degree]C to 20 or 25[degree]C and chilled them again before incubation at 20[degree]C. With increasing warming duration at 20[degree]C, diapause termination after chilling increased and shorter chilling durations became effective. In contrast, few or no larvae warmed at 25[degree]C terminated diapause after chilling, irrespective of the warming duration. To investigate the effect of warming temperature on diapause intensity, larvae with diapause weakened by initial incubation at 20[degree]C after the first chilling were subsequently incubated at 15, 20, or 25[degree]C, then chilled at 5[degree]C before incubation at 20[degree]C. Diapause termination increased significantly after the larvae were treated at 15 or 20[degree]C but decreased significantly after they were treated at 25[degree]C. The intensification of prolonged diapause at 25[degree]C was reversed when the larvae were transferred to 20[degree]C. Diapause intensity in C. sikkimensis therefore decreases at 20[degree]C, increases at 25[degree]C, and can be reversed by alternately exposing diapause larvae to 20[degree]C and 25 [degree]C. In C. sikkimensis, prolonged diapause does not always proceed in one direction, and its intensity fluctuates in response to ambient temperature conditions. (C) 2009 Elsevier Ltd. All rights reserved.}, keywords = {Curculio sikkimensis}, isbn = {0022-1910}, author = {Higaki, Morio and Ihara, Fumio and Toyama, Masatoshi and Mishiro, Koji} } @article {11879, title = {Prepupal diapause and instar IV developmental rates of the spruce beetle, Dendroctonus rufipennis (Coleoptera: Curculionidae, Scolytinae)}, journal = {Journal of Insect Physiology}, volume = {57}, number = {10}, year = {2011}, month = {Oct}, pages = {1347-1357}, abstract = {The spruce beetle, Dendroctonus rufipennis (Kirby), is an important mortality agent of native spruces throughout North America. The life-cycle duration of this species varies from 1 to 3 years depending temperature. The univoltine cycle (one generation per year) is thought to maximize outbreak risk and accelerate host mortality in established outbreaks. Prepupal diapause is associated with the semivoltine cycle (one generation per 2 years) and we investigated thermal conditions that result in diapause induction. Preliminary experiments used respirometry in an attempt to distinguish the diapause state of experimental insects but the technique was apparently confounded by low respiration before and during pupation, regardless of diapause status. Therefore, diapause induction was deduced using developmental delays. The observed developmental response was not a "switch", with developmental delay either present or absent, but instead varied continuously. We found that temperatures <15 [degree]C from instar Ill through mid-instar IV were associated with developmental delays beyond that expected from cool temperatures. Moreover, the duration of exposure to cool temperatures was important in determining the degree of developmental delay. Small, if any, delays were observed if the cumulative exposure to <15 [degree]C was <20 d whereas >40 d cumulative exposure was associated with distinct developmental suppression. Intermediate exposure to cool temperatures resulted in minor developmental delays. We used our results to parameterize a maximum likelihood estimation model of temperature-dependent instar IV developmental rates, including the effect of diapause. This model can be included as part of a spruce beetle phenology model for predicting population dynamics. Published by Elsevier Ltd.}, keywords = {Dendroctonus rufipennis}, isbn = {0022-1910}, author = {Hansen, E. Matthew and Bentz, Barbara J. and Powell, James A. and Gray, David R. and Vandygriff, James C.} } @article {9197, title = {Overwintering strategy of two weevils infesting three gorse species: When cold hardiness meets plant-insect interactions}, journal = {Journal of Insect Physiology}, volume = {56}, number = {2}, year = {2010}, month = {February}, pages = {170-177}, abstract = {The cold hardiness of two closely related weevil species, Exapion ulicis and E. lemovicinum was studied in relation to their life cycles. These two seed-eating weevils reproduce on Ulex plant species with different fruiting phenologies. E. ulicis lays eggs in spring and overwinters as an adult while E. lemovicinum lays eggs in autumn and overwinters as a larva. Adult weevils were collected in natural populations of Brittany (Western France) and characterized with morphological and molecular tools before experiments. We showed that both weevil species exhibited low supercooling points (SCPs) with mean seasonal values below -17 [degree]C. Fresh mass, moisture content and sex were not correlated to supercooling ability. Weevils died upon freezing and the lower lethal temperatures (LLT) were within the range of SCP, indicating that both species are freezing intolerant. Comparison between species for SCP, LLT and survival to exposure at -8 [degree]C in winter showed a higher cold resistance for E. ulicis than for E. lemovicinum. In addition, the seasonal evolution of cold hardiness differed depending on the species. These features suggest that response to cold of weevils is linked to their life cycles, and thus to the life history of their host plants.}, keywords = {Exapion ulicis}, isbn = {0022-1910}, author = {Barat, Myriam and Vernon, Philippe and Tarayre, Michele and Atlan, Anne} } @article {9018, title = {Specificity and redundancy in the olfactory system of the bark beetle Ips typographus: single-cell responses to ecologically relevant odors}, journal = {Journal of Insect Physiology}, volume = {55}, number = {6}, year = {2009}, month = {June}, pages = {556-567}, abstract = {We screened 150 olfactory sensilla in single-sensillum recordings to unravel the mechanisms underlying host selection in the spruce bark beetle, Ips typographus (Coleoptera: Curculionidae: Scolytinae). Odor stimuli comprised of pheromone (various bark beetle spp.). host, and non-host compounds elicited strong and selective responses from 106 olfactory receptor neurons (ORNs), 45 of which were tuned to pheromone compounds, 37 to host compounds, and 24 to non-host volatiles (NHV). In addition, 26 ORNs responded only weakly to any odor stimulus. Strongly responding ORNs were classified into 17 classes. Seven classes responded primarily to the Ips pheromone compounds: cis-verbenol, ipsenol, ipsdienol (two classes), 2-methyl-3-buten-2-ol, amitinol, or verbenone, respectively. Six classes responded to the host compounds: [alpha]-pinene, myrcene, p-cymene, myrcene and p-cymene, 1,8-cineole, or [DELTA]3-carene, respectively. Four classes responded to NHV: 3-octanol, 1-octen-3-ol, trans-conophthorin, or indiscriminately to the repellent green leaf volatiles (GLVs) 1-hexanol, Z3-hexen-1-ol and E2-hexen-1-ol, respectively. Indiscriminate responses from GLV neurons might explain a behavioral redundancy among these GLVs. This is the first description of individual bark beetle ORNs dedicated to NHV perception. These comprise almost 25\% of the strongly responding neurons, demonstrating that a large proportion of the olfactory system is devoted to signals from plants that the insect avoids. [copyright] 2009 Elsevier Ltd. All rights reserved.}, isbn = {0022-1910}, author = {Andersson, Martin N. and Larsson, Mattias C. and Schlyter, Fredrik} } @article {8961, title = {The effects of acclimation and rates of temperature change on critical thermal limits in Tenebrio molitor (Tenebrionidae) and Cyrtobagous salviniae (Curculionidae)}, journal = {Journal of Insect Physiology}, volume = {58}, number = {5}, year = {2012}, month = {May}, pages = {669-678}, abstract = {Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing thermal environments on such survival. However, investigations of these limits may be affected by the circumstances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temperature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. salviniae. In T. molitor, faster rates of change reduced both CTmax (c. 2 [degree]C) and CTmin (c. 3 [degree]C), while in C. salviniae faster rates of change increased both CTmax (c. 6 [degree]C) and CTmin (c. 4 [degree]C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 [degree]C (from 25 [degree]C) and was complete within 24 h. The time course of acclimation of CTmax in C. salviniae was 2 days when exposed to 36 [degree]C (from c. 26 [degree]C), while that of CTmin was less than 3 days when exposed to 18 [degree]C. In T. molitor, the time course of reacclimation to 25 [degree]C after treatments at 15 [degree]C and 35 [degree]C at 75\% RH was longer than the time course of acclimation, and varied from 3-6 days for CTmax and 6 days for CTmin. In C salviniae, little change in CTmax and CTmin in (<0.5 [degree]C) took place in all treatments suggesting that reacclimation may only occur after the 7 day period used in this study. These results indicate that both T. molitor and C salviniae may be restricted in their ability to respond to transient temperature changes at short-time scales, and instead may have to rely on behavioral adjustments to avoid deleterious effects at high temperatures. (C) 2012 Elsevier Ltd. All rights reserved.}, isbn = {0022-1910}, author = {Allen, Jessica L. and Clusella-Trullas, Susana and Chown, Steven L.} } @article {2184, title = {Development of teratocytes associated with Microctonus aethiopoides Loan (Hymenoptera: Braconidae) in natural and novel host species.}, journal = {Journal of Insect Physiology}, volume = {47}, year = {2001}, note = {ORIG-Title-Journal-Volume-Combination: Development of teratocytes associated with Microctonus aethiopoides Loan (Hymenoptera: Braconidae) in natural and novel host species. Journal of Insect Physiology 47}, pages = {257-262}, author = {Barratt, B. I. P. and Sutherland, M.} }