Journal of insect physiology最新文献

In Drosophila, the 20-hydroxyecdysone (20E) hormone regulates numerous essential biological processes. Here, we studied the contribution of 20E to the activity of immune signaling pathways and antimicrobial activity using the model Drosophila S2 cells. We found that while 20E alone has no essential effect on this system, pretreating S2 cells with 20E followed by incubation with Escherichia coli or Micrococcus luteus stimulates the induction of a limited number of antimicrobial peptide (AMP) genes, such as Diptericin (Dpt) and Drosomycin (Drs). Contrary to this, cells pretreatment with 20E simulates the activity of numerous Bacillus subtilis-induced AMP genes. Interestingly, it also significantly promotes the expression of components of both the Toll (Dif, Dorsal, etc.) and the IMD pathways (Relish, IMD, etc.) in the presence of Bacillus subtilis. Unexpectedly, simultaneous treatment of S2 cells by 20E and all three bacteria shows another pattern of activity and leads to a suppression of Drosocin (Dro) induction, in particular. Our study reveals that the contribution of 20E to immune genes activity varies for different genes and depends on the mode of 20E interplay with the pathogen and the nature of the pathogen itself.

Climate-induced shifts in flowering phenology can disrupt pollinator-floral resource synchrony, especially in desert ecosystems where rainfall dictates both. However, baseline metrics to gauge pollinator health in the wild amidst rapid climate change are lacking. Our laboratory-based study establishes a baseline for pollinator physiological state by exploring how osmotic conditions influence survivorship in a desert hawkmoth pollinator, Manduca sexta. We sampled hemolymph osmolality from over 1000 lab-grown moths at 20 %, 50 %, and 80 % ambient humidity levels. Starved moths maintained healthy osmolality of 350–400 mmol/kg for 1–3 days after eclosion regardless of ambient humidity, but it sharply rose to 550 mmol/kg after 4–5 days in low and moderate humidity, and after 5 days in high humidity. Starved moths in low humidity conditions perished within 5 days, while those in high humidity survived twice as long. Moths fed synthetic Datura wrightii nectar, synthetic Agave palmeri nectar, or water, maintained osmolality within a healthy range of 350–400mmol/kg. The same was true for moths fed authentic floral nectars from Datura and Agave plants, although moths consumed more synthetic than authentic nectars, possibly due to non-sugar constituents. Simulating a 4-day mismatch between pollinator emergence and nectar availability, a single nectar meal osmotically rescued moths under dry ambient conditions. Our findings highlight hemolymph osmolality as a rapid and accurate biomarker distinguishing dehydrated from hydrated states in insect pollinators.

In the cold, chill susceptible insects lose the ability to regulate ionic and osmotic gradients. This leads to hemolymph hyperkalemia that drives a debilitating loss of cell membrane polarization, triggering cell death pathways and causing organismal injury. Biotic and abiotic factors can modulate insect cold tolerance by impacting the ability to mitigate or prevent this cascade of events. In the present study, we test the combined and isolated effects of dietary manipulations and thermal acclimation on cold tolerance in fruit flies. Specifically, we acclimated adult Drosophila melanogaster to 15 or 25 °C and fed them either a K⁺-loaded diet or a control diet. We then tested the ability of these flies to recover from and survive a cold exposure, as well as their capacity to protect transmembrane K⁺ gradients, and intracellular Na⁺ concentration. As predicted, cold-exposed flies experienced hemolymph hyperkalemia and cold-acclimated flies had improved cold tolerance due to an improved maintenance of the hemolymph K⁺ concentration at low temperature. Feeding on a high-K⁺ diet improved cold tolerance additively, but paradoxically reduced the ability to maintain extracellular K⁺ concentrations. Cold-acclimation and K⁺-feeding additively increased the intracellular K⁺ concentration, aiding in maintenance of the transmembrane K⁺ gradient during cold exposure despite cold-induced hemolymph hyperkalemia. There was no effect of acclimation or diet on intracellular Na⁺ concentration. These findings suggest intracellular K⁺ loading and reduced muscle membrane K⁺ sensitivity as mechanisms through which cold-acclimated and K⁺-fed flies are able to tolerate hemolymph hyperkalemia.