Biology subjects

Zajitschek, S. R. K.

Publications and source records attributed to Zajitschek, S. R. K..

4 recordsLinked to original sources

bioRxiv2022

Dietary restriction fails to extend life in stressful environments

Moderate dietary restriction often prolongs life in laboratory animals, and this response has been interpreted as an adaptive strategy that promotes survival during famine. However, dietary restriction can also increase frailty, and it therefore remains unclear whether restricted diets prolong life under stressful conditions like those experienced by wild animals. We manipulated adult dietary protein of Drosophila melanogaster across a gradient of ambient temperature. We found that protein restriction increased longevity of both sexes at benign ambient temperatures (25-27{degrees}C), but failed to extend or even reduced longevity of flies maintained in cold (21-23{degrees}C) or hot (29{degrees}C) conditions. Protein restriction also generally reduced reproductive performance, and did not consistently enhance performance of F1, F2 or F3 descendants. Our results challenge the long-held idea that extended longevity of diet-restricted laboratory animals represents an adaptive survival strategy in natural populations, and suggest instead that this response is an artefact of benign laboratory conditions.

evolutionary biology↗

bioRxiv2022

Sex differences in allometry for phenotypic traits indicate that females are not scaled males

Sex differences in the lifetime risk and expression of disease are well-known. Preclinical research targeted at improving treatment, increasing health span, and reducing the financial burden of health care, has mostly been conducted on male animals and cells. The extent to which sex differences in phenotypic traits are explained by sex differences in body weight remains unclear. We quantify sex differences in the allometric relationship between trait value and body weight for 375 phenotypic traits in male and female mice, recorded in >2.1 million measurements from the International Mouse Phenotyping Consortium. We find sex differences in allometric parameters (slope, intercept, residual SD) are common (76% traits). Body weight differences do not explain all sex differences in trait values but scaling by weight may be useful for some traits. Our results support a trait-specific patterning of sex differences in phenotypic traits, promoting case-specific approaches to drug dosage scaled by body weight.

evolutionary biology↗

bioRxiv2020

Sex and Power: sexual dimorphism in trait variability and its eco-evolutionary and statistical implications

Biomedical and clinical sciences are experiencing a renewed interest in the fact that males and females differ in many anatomic, physiological, and behavioral traits. Sex differences in trait variability, however, are yet to receive similar recognition. In medical science, mammalian females are assumed to have higher trait variability due to estrous cycles (the estrus-mediated variability hypothesis); historically in biomedical research, females have been excluded for this reason. Contrastingly, evolutionary theory and associated data support the greater male variability hypothesis. Here, we test these competing hypotheses in 218 traits measured in >26,900 mice, using meta-analysis methods. Neither hypothesis could universally explain patterns in trait variability. Sex-bias in variability was trait-dependent. While greater male variability was found in morphological traits, females were much more variable in immunological traits. Sex-specific variability has eco-evolutionary ramifications including sex-dependent responses to climate change, as well as statistical implications including power analysis considering sex difference in variance.

evolutionary biology↗

bioRxiv2019

Costs and benefits of giant sperm and sperm storage organs in Drosophila melanogaster

In the Drosophila lineage, both sperm and the primary female sperm storage organ, the seminal receptacle (SR), may reach extraordinary lengths. In D. melanogaster, long SRs bias fertilization toward long sperm during the displacement stage of sperm competition. This sperm-SR interaction, together with a genetic correlation between the traits, suggests that the coevolution of exaggerated sperm and SR lengths may be driven by Fisherian runaway selection. To further understand the costs and benefits of long sperm and SR genotypes in both sexes, we measured male and female fitness in inbred lines of D. melanogaster derived from four populations previously selected for long sperm, short sperm, long SRs, or short SRs. We specifically asked: do long SRs impose costs or benefits on the females that bear them? Do genotypes that generate long sperm in males impose a fitness cost on females sharing those genotypes? Is long sperm an honest indicator of male viability and associated with increased fitness? And finally, are the benefits of long sperm restricted to competitive fertilization success, or do long-sperm males also have increased mating success and fecundity in single matings? We found that both sexes have increased longevity in long sperm and long SR genotypes, with fewer reproduction-related benefits and evidence for trade-offs in males, compared to females. Our results suggest that sperm length and SR length are both indicators of increased viability.

evolutionary biology↗