Within-generation variation of critical thermal limits in adult Mediterranean and Natal fruit flies Ceratitis capitata and Ceratitis rosa: thermal history affects short-term responses to temperature

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Publication Details

Author list: Nyamukondiwa C, Terblanche JS

Publisher: Wiley

Place: MALDEN

Publication year: 2010

Journal: Physiological Entomology (0307-6962)

Journal acronym: PHYSIOL ENTOMOL

Volume number: 35

Issue number: 3

Start page: 255

End page: 264

Number of pages: 10

ISSN: 0307-6962

eISSN: 1365-3032

Languages: English-Great Britain (EN-GB)

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Abstract

Insect thermal tolerance shows a range of responses to thermal history depending on the duration and severity of exposure. However, few studies have investigated these effects under relatively modest temperature variation or the interactions between short- and longer-term exposures. In the present study, using a full-factorial design, 1 week-long acclimation responses of critical thermal minimum (CT(min)) and critical thermal maximum (CT(max)) to temperatures of 20, 25 and 30 degrees C are investigated, as well as their interactions with short-term (2 h) sub-lethal temperature exposures to these same conditions (20, 25 and 30 degrees C), in two fruit fly species Ceratitis capitata (Wiedemann) and Ceratitis rosa Karsch from South Africa. Flies generally improve heat tolerance with high temperature acclimation and resist low temperatures better after acclimation to cooler conditions. However, in several cases, significant interaction effects are evident for CT(max) and CT(min) between short- and long-term temperature treatments. Furthermore, to better comprehend the flies' responses to natural microclimate conditions, the effects of variation in heating and cooling rates on CT(max) and CT(min) are explored. Slower heating rates result in higher CT(max), whereas slower cooling rates elicit lower CT(min), although more variation is detected in CT(min) than in CT(max) (approximately 1.2 versus 0.5 degrees C). Critical thermal limits estimated under conditions that most closely approximate natural diurnal temperature fluctuations (rate: 0.06 degrees C min-1) indicate a CT(max) of approximately 42 degrees C and a CT(min) of approximately 6 degrees C for these species in the wild, although some variation between these species has been found previously in CT(max). In conclusion, the results suggest critical thermal limits of adult fruit flies are moderated by temperature variation at both short and long time scales and may comprise both reversible and irreversible components.

Keywords

Acclimation, Phenotypic plasticity, rapid cold hardening, rapid heat hardening, sterile insect release

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