Effects of Starvation and Thermal Stress on the Thermal Tolerance of Silkworm, Bombyx mori: Existence of Trade-offs and Cross-Tolerances

Abstract

Organisms, in nature, are often subjected to multiple stressors, both biotic and abiotic. Temperature and starvation are among the main stressors experienced by organisms in their developmental cycle and the responses to these stressors may share signaling pathways, which affects the way these responses are manifested. Temperature is a major factor governing the performance of ectothermic organisms in ecosystems worldwide and, therefore, the thermal tolerance is a central issue in the thermobiology of these organisms. Here, we investigated the effects of starvation as well as mild heat and cold shocks on the thermal tolerance of the larvae of silkworm, Bombyx mori (Linnaeus). Starvation acted as a meaningful or positive stressor as it improved cold tolerance, measured as chill coma recovery time (CCRT), but, at the same time, it acted as a negative stressor and impaired the heat tolerance, measured as heat knockdown time (HKT). In the case of heat tolerance, starvation negated the positive effects of both mild cold as well as mild heat shocks and thus indicated the existence of trade-off between these stressors. Both mild heat and cold shocks improved the thermal tolerance, but the effects were more prominent when the indices were measured in response to a stressor of same type, i.e., a mild cold shock improved the cold tolerance more than the heat tolerance and vice versa. This improvement in thermal tolerance by both mild heat as well as cold shocks indicated the possibility of cross-tolerance between these stressors.

Accumulation and trafficking of zinc oxide nanoparticles in an invertebrate model, Bombyx mori, with insights on their effects on immuno-competent cells

“…Thus, uptake and trafficking of NPs and their impact on immune-competent cells (and therefore innate immune system) can be determined following the exposure which closely mimics the manner various organisms are exposed in the natural environment. Fourth instar larvae (at 48 h after ecdysis) were selected, as the insects at this stage can be easily observed, handled, manipulated, enough test sample can be obtained and damage to the larvae is reduced/minimal 44 .…”

Environmental degradation amplifies species’ responses to temperature variation in a trophic interaction

“…At the highest level of resource degradation, severe resource limitation during juvenile development might have drastically reduced activity in adult parasitoids, promoting longer life span independently of temperature variation. Furthermore, starvation can impair heat tolerance (Mir & Qamar, ). Parasitoids that develop in unlimited resources may be able to counteract the energetic costs associated with exposure to suboptimal temperatures and heat tolerance, thus buffering the effects of temperature variation on foraging activity and adult life span (Colinet et al, ).…”

Oxidative stress delays development and alters gene function in the agricultural pest moth, Helicoverpa armigera

“…In the former study, the intriguing hypothesis of hormesis was raised to explain the fact that a compound that has an inhibitory or toxic effect at high doses can actually be beneficial at low doses (sensu Mattson, 2008). In fact, there is substantial research regarding hormesis due to the impacts of environmental stress on aging and longevity in invertebrate species (Le Bourg, 2009;Hunt et al, 2011;Scharf et al, 2017;Gilad et al, 2018;Mir & Qamar, 2018), including Helicoverpa Celorio-Mancera et al, 2011;Gulzar & Wright, 2015). In our case chronic oxidative stress extended the larval period in H. armigera, which is the developmental stage that causes the most damage to crops.…”