Fitness Costs of Rapid Cold-Hardening In ceratitis Capitata

Abstract

Rapid cold-hardening (RCH) is a unique form of phenotypic plasticity which confers survival advantages at low temperature. The fitness costs of RCH are generally poorly elucidated and are important to understanding the evolution of plastic physiology. This study examined whether RCH responses, induced by ecologically relevant diel temperature fluctuations, carry metabolic, survival, or fecundity costs. We predicted that potential costs in RCH would be manifested as differences in metabolic rate, fecundity, or survival in flies which have hardened versus those which have not, or flies that have experienced more RCH events would show greater costs than those which have experienced fewer events. One group of flies cooled to 10 • C for 2 h for 11 consecutive days experienced daily RCH (Hardened), whereas the other group exposed to 15 • C for the same 2-h period each day formed a Control group. Hardened flies had higher survival at -5 • C for 2 h than control flies (69 ± 9% vs. 44 ± 19%, P = 0.04). Hardened flies showed no metabolic or fecundity costs, but had reduced average survival (P = 0.0403). Thus, a major cost to repeated low temperature exposures in Ceratitis capitata is through direct mortality caused by chilling injury, although this appears not to be a direct cost of RCH. K E Y W O R D S :Drosophila, fecundity, metabolic rate, rapid cold-hardening, survival.

Constraints, independence, and evolution of thermal plasticity: Probing genetic architecture of long- and short-term thermal acclimation

“…After 3 d of egglaying, parents were removed for density control of experimental flies. Offspring were sorted by sex and were allowed to age for 5-7 d (11,18). Three replicates of 10-20 flies were moved to empty vials to avoid the influence of the food on the freezing temperature of flies.…”

“…Much work has focused on the physiological mechanisms and the ecological implications of both DACC and RCH, particularly to cold (14)(15)(16)(17)(18)(19). Despite its ecological importance, the physiological and genetic mechanisms underlying RCH have been challenging to unravel using physiological, transcriptomic, or metabolomic techniques, particularly because the physiological responses are both fast and transient (20)(21)(22)(23)(24)(25).…”

Analysis of survival, gene expression and behavior following chill-coma in the medfly Ceratitis capitata: Effects of population heterogeneity and age

“…It is important to understand the factors that determine its distribution and abundance and, in this regard, the ability of C. capitata to adjust to temperature variations has been recently investigated, showing a broad thermal tolerance (Nyamukondiwa and Terblanche, 2009;Nyamukondiwa et al, 2010;Weldon et al, 2011;Basson et al, 2012). Basson et al (2012) demonstrated that cold exposure reduced C. capitata survival, which suggests the possibility of a chill-dependent injury, although flies showed no metabolic or fecundity costs. Therefore, it would be interesting to investigate the effects that cold exposure produce in the physiological state of C. capitata individual flies within a population, and how this affects their survival and distribution.…”

Effects of Thermal Regimes, Starvation and Age on Heat Tolerance of the Parthenium Beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae) following Dynamic and Static Protocols

“…For example, short-term ‘hardening’, involving a pre-exposure to sublethal high (heat shock) or low (cold shock) temperatures, have been shown to improve survival under subsequent more extreme temperatures [9–11]. Similar plastic responses can also be induced by longer pre-exposure times prior to exposure in extreme temperatures, referred to as acclimation [12–15].…”