Evolution under juvenile malnutrition impacts adult metabolism and fitness

Juveniles are often first to suffer from nutrient shortage, and juvenile undernutrition is likely an important force of natural selection shaping animal physiology, with consequences potentially extending into adulthood. We combined RNAseq, targeted metabolomics and genomics to study the consequences of experimental evolution under juvenile undernutrition for metabolism of reproductively active adult females of Drosophila melanogaster. Compared to six Control populations maintained on standard diet, six Selected populations evolved for over 230 generations on a nutrient-poor larval diet showed major changes in adult gene expression and metabolite abundance. In particular, Selected flies were relatively deficient in essential amino acids and purine nucleotides, but showed overabundance of several non-essential amino-acids involved in purine synthesis and overexpression of multiple enzymes catalyzing this pathway. Selected flies also accumulated medium-chain acylcarnitines suggestive of congestion in beta-oxidation, possibly linked to deficiency of electron transporters. Some aspects of the metabolic profile of Selected flies resembled that of flies subject to starvation. Furthermore, differences between Selected and Control populations in adult gene expression were in general positively correlated with differences in larval expression, consistent with pleiotropy in gene regulation between the life stages. Finally, Selected flies were less fit in terms of fecundity than Controls even when both were raised under the conditions under which the Selected populations evolved. These results suggest that evolutionary adaptation to juvenile undernutrition has large pleiotropic consequences for adult metabolism, and that they are costly rather than adaptive for adult fitness.

Glue genes are subjected to diverse selective forces during Drosophila development

Molecular evolutionary studies usually focus on genes with clear roles in adult fitness or on developmental genes expressed at multiple time points during the life of the organism. Here, we examine the evolutionary dynamics of Drosophila glue genes, a set of eight genes tasked with a singular primary function during a specific developmental stage: the production of glue that allows animal pupa to attach to a substrate for several days during metamorphosis. Using phenotypic assays and integrating data from transcriptomics, PacBio genomes, and genetic variation from global populations, we explore the selective forces acting on the glue genes within the cosmopolitan D. melanogaster species and its five closely related species, D. simulans, D. sechellia, D. mauritiana, D. yakuba, and D. teissieri. We observe a three-fold difference in glue adhesion between the least and the most adhesive D. melanogaster strain, indicating a strong genetic component to phenotypic variation. These eight glue genes are among the most highly expressed genes in salivary glands yet they display no notable codon bias. New copies of Sgs3 and Sgs7 are found in D. yakuba and D. teissieri with the Sgs3 coding sequence evolving rapidly after duplication in the D. yakuba branch. Multiple sites along the various glue genes appear to be constrained. Our population genetics analysis in D. melanogaster suggests signs of local adaptive evolution for Sgs5 and Sgs5bis and traces of selective sweeps for Sgs1, Sgs3, Sgs7 and Sgs8. Our work shows that stage-specific genes can be subjected to various dynamic evolutionary forces.

The post 16 gap: how do young people conceptualise PE? An exploration of the barriers to participation in physical education, physical activity and sport in senior school pupils

Previous studies have identified several key barriers to Physical Education, Physical activity and Sport (PEPAS). However, there is a paucity of qualitative evidence investigating why young people do and do not participate in PA and the relationship between their levels of participation at different stages of life. This study builds on a previous study and aims to investigate the barriers to PEPAS in adolescents at transition stage. The extant literature highlights that instilling regular PA throughout life strongly relies on developing physical literacy through participation in high quality physical education. Despite the understanding of the importance of high quality physical education, there is an over emphasis on the short term outcomes of physical education (PE) sessions which have been noted to overemphasise immediate physical activity rather than focus on educational outcomes important to physical literacy. Anecdotally, the recent Covid 19 Global pandemic and subsequent lockdown has resulted in a digitalisation of PE in schools and a subsequent reliance of PA programmes based on adult fitness classes, which may not necessarily be categorised as PE in its true sense. Twenty-four respondents aged 16–19 were divided into five focus groups. Data were analysed verbatim using NVivo following the guidelines by Braun and Clark (2006) on thematic analysis. The findings indicated that most respondents equated PE with team sports. Findings suggest that Physical Educators need to acknowledge how past and present experience of PE impacts young people’s future motivation to continue PA beyond school. Delivery of traditional PE lessons, prioritising sporting ability, can act as a participation barrier to pupils who consider themselves “non-sporty”. Accordingly, a shift towards inclusive pedagogical models with an emphasis on a holistic approach, may best promote the physical literacy necessary for the competence and confidence to continue movement in a lifelong capacity.

Mosquito-bacteria interactions during larval development trigger metabolic changes with carry-over effects on adult fitness

In animals with distinct life stages such as holometabolous insects, adult phenotypic variation is often shaped by the environment of immature stages, including their interactions with microbes colonizing larval habitats. Such carry-over effects were previously observed for several adult traits of the mosquito Aedes aegypti after larval exposure to different bacteria, but the mechanistic underpinnings are unknown. Here, we investigated the molecular changes triggered by gnotobiotic larval exposure to different bacteria in Ae. aegypti. We initially screened a panel of 16 bacterial isolates from natural mosquito breeding sites to determine their ability to influence adult life-history traits. We subsequently focused on four bacterial isolates (belonging to Flavobacterium, Lysobacter, Paenibacillus, and Enterobacteriaceae) with significant carry-over effects on adult survival and found that they were associated with distinct transcriptomic profiles throughout mosquito development. Moreover, we detected carry-over effects at the level of gene expression for the Flavobacterium and Paenibacillus isolates. The most prominent transcriptomic changes in gnotobiotic larvae reflected a profound remodeling of lipid metabolism, which translated into phenotypic differences in lipid storage and starvation resistance at the adult stage. Together, our findings indicate that larval exposure to environmental bacteria trigger substantial physiological changes that impact adult fitness, uncovering a mechanism underlying carry-over effects of mosquito-bacteria interactions during larval development.

Development of an Alternative Low-Cost Larval Diet for Mass Rearing of Aedes aegypti Mosquitoes In Sri Lanka

Background Aedes aegypti is a major vector of arboviruses that may be controlled on an area-wide basis using novel approaches such as Sterile Insect Technique (SIT) and Incompatible Insect Technique (IIT). Larval diet is a major factor in mass-rearing of Aedes mosquitoes for SIT and IIT programs. Therefore, current study aimed to evaluate the effects of two novel diets developed from dry fish powder on growth and development of immature stages and adult fitness-related characteristics of Ae. aegypti in Sri Lanka. Method: Three batches of 250 Ae. aegypti first instar larvae were exposed to three different larval diets as, standard dry fish powder (D1), dry fish powder meal and brewer’s yeast (D2) and International Atomic Energy Agency (IAEA) reccomanded diet (D3), separately. Morphometric and developmental parameters of 4th instar larvae, pupae and adult mosquitoes reared under different dietary treatments were measured. General Linear Model (GLM) was used for statistical analysis. Results Significant diet-based variations were observed in the head length, head width, thoracic length, thoracic width, abdominal length, abdominal width and total length (F2, 87>4.811; P < 0.05) of Ae. aegypti larvae. The highest pupation success and the larval size were observed from the larvae fed with D2 diet, while the lowest was reported from D1. All adult morphometric parameters of adult male and female Ae. aegypti mosquitoes also denoted significant dietary variations, reporting the best sized adults from D2 diet (F2, 87>3.54; P < 0.05). Further, significantly higher fecundity and male longevity were also shown by the adult Ae. aegypti (F2, 6>7.897; P < 0.01) reared under diet D2. Conclusion Based on all the growth and developmental parameters, D2 diet reported the best quality adult mosquitoes similar to the IAEA recomanded diet, while being more inexpensive. Therefore, larval diet D2 could be recomaded as the ideal diet for for mass-rearing of Ae. aegypti for IIT and SIT-based vector control in Sri Lanka.

Cooperative foraging during larval stage affects fitness in Drosophila

SummaryCooperative behavior can confer advantages to animals. This is especially true for cooperative foraging which provides fitness benefits through more efficient acquisition and consumption of food. While examples of group foraging have been widely described, the principles governing formation of such aggregations and rules that determine group membership remain poorly understood. Here we take advantage of an experimental model system featuring cooperative foraging behavior in Drosophila. Under crowded conditions, fly larvae form coordinated digging groups (clusters), where individuals are linked together by sensory cues and group membership requires prior experience. However, fitness benefits of Drosophila larval clustering remain unknown. We demonstrate that animals raised in crowded conditions on food partially processed by other larvae experience a developmental delay presumably due to the decreased nutritional value of the substrate. Intriguingly, same conditions promote formation of cooperative foraging clusters which further extends larval stage compared to non-clustering animals. Remarkably, this developmental retardation also results in a relative increase in wing size, serving an indicator of adult fitness. Thus, we find that the clustering-induced developmental delay is accompanied by fitness benefits. Therefore, cooperative foraging, while delaying development, may have evolved to give Drosophila larvae benefits when presented with competition for limited food resources.