Termination of pupal diapause in the pine processionary moth Thaumetopoea pityocampa

Abstract

Diapause development is a complex process involving several eco‐physiological phases. Understanding these phases, especially diapause termination, is vital for interpreting the life history of many insect species and for developing suitable predictive models of population dynamics. The pine processionary moth is a major defoliator of pine and a vertebrate health hazard in the Mediterranean region. This species can display either univoltine or semivoltine development, with a pupal diapause extending from a few months to several years, respectively. Although the ecological and applied importance of diapause is acknowledged, its physiological regulation in either case remains obscure. In the present study, we characterize pre‐termination, termination and post‐termination phases of pupae developing as univoltine or remaining in prolonged diapause. Changes in metabolic activity are monitored continuously using thermocouples, comprising a novel method based on direct calorimetry, and periodically by use of O2 respirometry. The two methods clearly detect diapause termination in both types of pupae before any visible morphological or behavioural changes can be observed. Univoltine individuals are characterized by an increase in metabolic activity from pre‐termination through to termination and post‐termination, ultimately resulting in emergence. Remarkably, a synchronous termination is observed in individuals that enter prolonged diapause instead of emerging; however, in these pupae, the increased metabolic activity is only transient. The present study represents a starting point toward understanding the eco‐physiology of diapause development processes in the pupae of the pine processionary moth.

Warming Causes Atypical Phenology in a Univoltine Moth With Differentially Sensitive Larval Stages

“…In contrast, phenological change can cause maladaptation when delayed or advanced life stages are exposed to detrimental conditions there are not typically tolerant to. Partial resynchronization of PPM diapause termination among individuals showing different pupation timings was observed (Salman et al, 2019b), which suggests that adults emerging from early individuals may not experience more unfavorable conditions than adults emerging from more median larvae. The absence of larval diapause, however, makes such resynchronization mechanisms impossible during prepupal stages.…”

“…Pupal diapause was not integrated to our model because of the complexity of both obligatory diapause and nonobligatory prolonged diapause mechanisms, which remain poorly understood in this species. Recent work showed, however, that the obligatory phase of diapause that immediately follows pupation procession may vary in duration in a given population depending on procession timing, thereby contributing to resynchronizing emergences and matings (Salman et al, 2019b). A better understanding of how pupal diapause is modulated would be necessary before associated parameters can be integrated in the model to simulate the entire life cycle from the egg to the adult, and loop several generations in silico without reinitialization from observational flight data.…”

Development and diapause induction of the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) at different photoperiods

“…For instance, the sterile insect technique (SIT) and augmentative natural enemy control have been neither practical nor possible due to diapause responses that prevent or interfere with continuous mass rearing 64 . There are many examples in this regard, including the European cherry fruit fly 65 , the Apple maggot fly 66 , the Chinese citrus fruitfly 67 , the Russian melon fly 68 , and processionary moths 69 . Bloemi et al 64 noted that diapause induction, originally developed for individually reared codling moth, can be applied to the mass-rearing system used by the Sterile Insect Release (SIR) eradication program.…”

Trade-offs in dormancy phenology in endotherms and ectotherms

“…In keystone species, such as pollinating, parasitoid insects or zooplankton, variations in dormancy phenology may alter the ecosystem services that these species provide and thus modify entire ecosystems (Doi et al, 2008;Edwards and Richardson, 2004;Hegland et al, 2009;Ji et al, 2010;Kudo and Ida, 2013;Tougeron et al, 2020;Vadadi Fülöp and Hufnagel, 2014). From a more anthropocentric point of view, changes in dormancy phenology may have consequences for the transmission of diseases (Huestis and Lehmann, 2014;Streicker et al, 2012) or human-wildlife conflicts (Johnson et al, 2018;Salman, 2018;Skendžić et al, 2021).…”