Summer diapause induced by high temperatures in the oriental tobacco budworm: ecological adaptation to hot summers

Abstract

Summer diapause in Helicoverpa assulta (Hübner), which prolongs the pupal stage, particularly in males, is induced by high temperatures. In the laboratory, 3rd-, 4th-, 6th-instar and prepupal larvae were exposed to high temperatures – 33 and 35 °C with a photoperiod of LD16:8 – until pupation to induce summer diapause. The results showed that the incidence of summer diapause was influenced by temperature, stage exposed, and sex. The higher the temperature, the more often summer diapause was attained. Sixth-instar and prepupal larvae were the sensitive stages for summer diapause induction. H. assulta summer-diapausing pupae needed diapause development to resume development when temperatures became favorable. Furthermore, both body mass and energy storage capacity (lipid and glycogen) were significantly affected by diapause rather than sex, and were significantly higher in summer-diapausing pupae than in non-diapausing pupae. In addition, the body mass loss and respiration rate showed that the rate of metabolism in the summer-diapausing pupae was consistently lower than in non-diapausing pupae, which were significantly affected by diapause and pupal age. We conclude that summer diapause in H. assulta is a true diapause, and H. assulta has evolved mechanisms to accumulate energy storage and to lower its metabolism to adapt to hot summers.

Emergent Protective Organogenesis in Date Palms: A Morpho-Devo-Dynamic Adaptive Strategy during Early Development

“…Changes in environmental conditions can modulate this process, thereby providing an adaptive developmental plasticity to overcome environmental challenges. In animals, diapause causes a temporary arrest in development to allow the embryo to survive harsh conditions and to ensure that postnatal development can be completed when environmental conditions become more favorable (Apfeld and Kenyon, 1998;Fielenbach and Antebi, 2008;Fenelon et al, 2014;Liu et al, 2016). In plants, this process is called dormancy during which a fully developed embryo rests inside the seed.…”

Fatty acid synthase 2 contributes to diapause preparation in a beetle by regulating lipid accumulation and stress tolerance genes expression

“…Energy reserves accumulated during the diapause preparation stage are therefore critical to surviving diapause, and consequently can influence the decision to enter or terminate diapause, as well as post-diapause survival and fitness7. Lipids accumulated as fat reserves in the fat body provide a significant energy reserve for insects undergoing diapause678. Therefore, understanding the molecular mechanisms involved in lipid accumulation during diapause preparation is essential to understanding the metabolic processes that regulate diapause in insects7.…”

Developmental plasticity in metabolism but not in energy reserve accumulation in a seasonally polyphenic butterfly

“…In addition, many diapause-generation individuals pupate early in the summer and therefore also experience a long pre-winter warm period in pupal diapause. This may be particularly stressful as higher temperatures should lead to increased fat reserve depletion in ectotherms (Han and Bauce, 1998; Irwin and Lee, 2003; Bosch et al, 2010; Williams et al, 2014; see also Liu et al, 2016). Although there was no inter-pathway difference in the accumulation of energy reserves, final-instar P. napi larvae accumulate lots of lipids in their bodies during this instar, as indicated by the hyperallometric increase in total lipid mass in the body (Fig.…”

“…These physiological differences culminate in the life stage that is capable of entering diapause, because surviving a long adverse period in the dormant state of diapause necessitates a very different physiology compared to direct development into reproductive adult (e.g. Han and Bauce, 1998; Hahn and Denlinger, 2007, 2011; Liu et al, 2007, 2016; Rozsypal et al, 2013; Lehmann et al, 2016, 2018).…”

“…Besides metabolic rate, the diapause and direct development pathways are expected to show also other pre-diapause physiological differences. Overwinter survival necessitates energy reserves that can fuel metabolism through the whole dormant period during which feeding is either not possible at all or insufficient to fully fuel metabolism (Tauber et al, 1986; Danks, 1987; Hahn and Denlinger, 2007, 2011; Lehmann et al, 2016, 2018; see Liu et al, 2016 for energy reserves for summer diapause). These energy reserves must be accumulated before the beginning of diapause, which may result in differences between pathways in the allocation of resources to building reserves (Tauber et al, 1986; Danks, 1987; Hahn and Denlinger, 2007, 2011; Liu et al, 2007).…”