Alteration of the eclosion rhythm and eclosion behavior in the flesh fly, Sarcophaga crassipalpis, by low and high temperature stress

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The transcriptional responses of insects to long-term, ecologically relevant temperature stress are poorly understood. Long-term exposure to low temperatures, commonly referred to as chilling, can lead to physiological effects collectively known as chill injury. Periodically increasing temperatures during long-term chilling has been shown to increase survival in many insects. However, the transcripts responsible for this increase in survival have never been characterized. Here, we present the first transcriptome-level analysis of increased longevity under fluctuating temperatures during chilling. Overwintering post-diapause quiescent alfalfa leafcutting bees (Megachile rotundata) were exposed to a constant temperature of 6°C, or 6°C with a daily fluctuation to 20°C. RNA was collected at two different time points, before and after mortality rates began to diverge between temperature treatments. Expression analysis identified differentially regulated transcripts between pairwise comparisons of both treatments and time points. Transcripts functioning in ion homeostasis, metabolic pathways and oxidative stress response were up-regulated in individuals exposed to periodic temperature fluctuations during chilling. The differential expression of these transcripts provides support for the hypotheses that fluctuating temperatures protect against chill injury by reducing oxidative stress and returning ion concentrations and metabolic function to more favorable levels. Additionally, exposure to fluctuating temperatures leads to increased expression of transcripts functioning in the immune response and neurogenesis, providing evidence for additional mechanisms associated with increased survival during chilling in M. rotundata.

Section: Ion and Metabolic Imbalance Resulting From Membrane Phase Trmentioning

confidence: 99%

Section: Neurological Benefits Of Fluctuating Temperaturesmentioning

confidence: 99%

Transcriptional responses to fluctuating thermal regimes underpinning differences in survival in the solitary bee Megachile rotundata

Torson

Yocum

Rinehart

et al. 2015

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“…Eclosion patterns within the long-day L:D cycle were also noted. Emergence was monitored at 25°C by placing pupae within an eclosion counting device (Yocum et al, 1994) set to record eclosion events every 2·h. RH conditions during this period were 59.5±1.4% RH (mean ± S.E.M.…”

Section: Survival and Emergence Timementioning

confidence: 99%

Desiccation and rehydration elicit distinct heat shock protein transcript responses in flesh fly pupae

Hayward

Rinehart

Denlinger

2004

Self Cite

106

delayed adult eclosion noted in samples desiccated for more than 3·days at <5% relative humidity/25°C. In diapausing pupae, hsp23 and hsp70 transcripts are already highly expressed and are not further upregulated by desiccation stress. Both of the constitutive Hsps investigated, Hsp90 and Hsc70, were unresponsive to desiccation in both nondiapausing and diapausing pupae. However, both Hsp90 and Hsc70 were upregulated upon rehydration in nondiapausing and diapausing pupae. These results indicate distinct roles for the different Hsps during desiccation stress and rehydration/stress recovery. The response to desiccation recovery (rehydration) is similar to the Hsp response to cold recovery identified in S. crassipalpis: Hsp90 and Hsc70 are upregulated in both cases.

“…The loss of nervous membrane excitability was attributed to the preceding decrease of resting potential due to the effect of low temperature on transport mechanisms involved in ion balance (Heitler et al, 1977;Kivivouri et al, 1990;Cossins et al, 1995). Thus, the neuronal damage is one of the likely causes of injury inflicted by chilling (Yocum et al, 1994). Pullin and Bale (1988) and Pullin et al (1990) studied pre-freeze mortality in the nettle aphid Microlophium carnosum.…”

mentioning

confidence: 99%

On the nature of pre-freeze mortality in insects: water balance, ion homeostasis and energy charge in the adults ofPyrrhocoris apterus

Košťál

Vambera

Bastl

2004

235

118

SUMMARYThree acclimation groups [i.e. non-diapause (LD), diapause (SD) and diapause, cold-acclimated (SDA)] of the adult bugs Pyrrhocoris apterus differed markedly in their levels of chill tolerance. Survival time at a sub-zero, but non-freezing, temperature of –5°C (Lt50)extended from 7.6 days, through 35.6 days, to >60 days in the LD, SD and SDA insects, respectively. The time necessary for recovery after chill-coma increased linearly with the increasing time of exposure to –5°C, and the steepness of the slope of linear regression decreased in the order LD>SD>SDA. The capacity to prevent/counteract leakage of Na+ down the electrochemical gradient (from haemolymph to tissues) during the exposure to –5°C increased in the order LD<SD<SDA. As a result, the rates of counteractive outward movement of K+, and of the EK dissipation, decreased in the same order. The least chill-tolerant insects (LD) showed the highest rate of body-water loss. Most of the water was lost from the haemolymph compartment. The ability to regulate a certain fraction of ion pools into the hindgut fluid was the highest in the SDA group, medium in the SD group and missing in the LD group. The adenylate energy charge in the fat body cells was constant in all three groups. The total pools of ATP, ADP and AMP, however, decreased in the SD and SDA groups but remained constant in the LD group. The inability of insects to maintain ion gradients at sub-zero temperature is discussed as an important cause of pre-freeze mortality.