Stress and asymmetry during arrested development of the Australian sheep blowfly

Abstract

The dieldrin and diazinon resistance systems of the Australian sheep blow£y (Lucilia cuprina) have been used previously to relate stress, departures from bilateral symmetry, developmental stability and relative ¢tness. These systems are now used to consider stress and asymmetry in a developmental context. Larval to adult development is shown to be signi¢cantly impaired after arrested development at 8 8C, however the asymmetry score of adults of a given genotype is similar after arrested or continuous development. Selection against dieldrin-resistant and unmodi¢ed diazinon-resistant genotypes occurs during arrested development because greater proportions of these genotypes pupate at 8 8C than do susceptible or modi¢ed diazinon-resistant genotypes. Pre-pupae of all genotypes complete development equally successfully when transferred from 8 8C to 27 8C. Adults fail to emerge when pupae formed at 8 8C undergo this temperature transition. Temperature-shift experiments show the asymmetry score is determined between pre-pupal and pupal stages of the life cycle. This stage occurs at 27 8C in arrested and continuously developing cultures providing an explanation for the independence of stress, selective mortality during developmental arrest and asymmetry score. The results emphasize the need for genetic, environmental and developmental data before an asymmetry phenotype can be directly related to developmental stability and relative ¢tness.

Developmental stability in yellow dung flies (Scathophaga stercoraria): fluctuating asymmetry, heterozygosity and environmental stress

“…(2000) suggest that searching for universal FA rules is wasteful of research time and money. We are not so pessimistic and, like McKenzie (1997), suggest that further study is required before the importance of departures from symmetry can be fully evaluated in ecological and evolutionary contexts (e.g. Brakefield & Breuker, 1996).…”

“…Developmental stability refers to processes that define an individual’s ability to withstand environmental and genetic perturbations to produce the phenotype ( Waddington, 1942; Clarke, 1998). It is therefore a fundamental developmental characteristic, and the better individuals can maintain developmental stability, the fitter they should be ( Fowler & Whitlock, 1994; McKenzie, 1997). However, the genetic basis for developmental stability is unclear ( Markow, 1995; Clarke, 1998; Vøllestad et al ., 1999 ), but two major hypotheses are that stability relates to either genome‐wide heterozygosity or genomic coadaptation ( Markow, 1995; Clarke, 1998).…”

The Genetics and Evolution of Fluctuating Asymmetry

“…In fact, environmental stresses in genetically variable populations may result in selection of certain genes that ameliorate the immediate stress but that themselves perturb developmental processes and result in increased asymmetry. An outstanding example of this effect is seen in populations of the Australian blowfly, Lucilia cuprina, that have developed resistance to exposure to various insecticides such as dieldrin, diazinon, or malathion but that also show increased levels of FA in bristle numbers compared to susceptible (nonexposed) populations (McKenzie 1997(McKenzie , 2003.…”

The evolution of new enzyme function: lessons from xenobiotic metabolizing bacteria versus insecticide‐resistant insects

“…The Gly to Asp mutation greatly reduces the native carboxylesterase activity and, in L . cuprina at least, this impairs development, producing asymmetric bristle and wing vein patterns and measurable loss of fitness (McKenzie 1994, 1997; Batterham et al. 1996; Newcomb et al.…”

“…It is interesting to note that the activity of the Wheelock and Scott (1992), Zhang and Scott (1996), Feyereisen (2005), Li et al (2007) and Muller et al (2008) Evolution of new enzyme function Russell et al wild-type LcaE7 enzyme for OPs with either of the most common alkoxy group substituents is not zero, so again the start point for the evolution of the 'new' function has been an enzyme that already has low promiscuous activity for that function. The Gly to Asp mutation greatly reduces the native carboxylesterase activity and, in L. cuprina at least, this impairs development, producing asymmetric bristle and wing vein patterns and measurable loss of fitness (McKenzie 1994(McKenzie , 1997Batterham et al 1996;Newcomb et al 1997a,b). The Trp to Leu mutation in LcaE7 reduces the stability of the enzyme in vitro (C. J. Jackson, J-W. Liu and J. G. Oakeshott, unpublished data), although its effects on fitness, if any, are unknown.…”