Termination of pupal diapause in the pine processionary moth Thaumetopoea pityocampa

Md Habibur R Salman,Mathieu Laparie,Andrea Pitacco,Folco Giomi,Philipp Lehmann,Andrea Battisti

doi:10.1111/phen.12277

Md Habibur R Salman, Mathieu Laparie + Show 4 more

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https://doi.org/10.1111/phen.12277

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Abstract

AbstractDiapause 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.

Highlights

Diapause comprises a generic resistance form found in many arthropods in response to indirect cues predicting adverse conditions (Danks, 1987; Hodek, 2002)
By adopting a novel approach for measuring pupal metabolic activity continuously via thermocouple-based direct calorimetry, the present study identifies the termination phase of diapause in both univoltine and prolonged diapause individuals, as confirmed by oxygen consumption
The discovery of a distinct termination phase concurs with the study by Démolin (1990), who refers to this as the ‘key period’ based on a destructive method of dissecting prolonged diapause individuals, as well as the finding of the corpus luteum or yellow body in the ovaries, as a likely remnant of the attempt to resume development (Biliotti et al, 1964)

Summary

Introduction

Diapause comprises a generic resistance form found in many arthropods in response to indirect cues predicting adverse conditions (Danks, 1987; Hodek, 2002). This dynamic process temporarily pauses morphogenesis and decreases metabolic activity (Tauber et al, 1986; Danks, 1987). The intensity of diapause decreases with time, whereas sensitivity to diapause terminating conditions increases. Abiotic factors such as temperature, humidity or presence of liquid water may regulate this phase. Diapause termination may be spontaneous or, more commonly, may require specific environmental conditions (Tauber & Tauber, 1976; Koštàl, 2006)

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