Drosophila melanogaster larvae make nutritional choices that minimize developmental time.

Organisms from slime moulds to humans carefully regulate their macronutrient intake to optimize a wide range of life history characters including survival, stress resistance, and reproductive success. However, life history characters often differ in their response to nutrition, forcing organisms to make foraging decisions while balancing the trade-offs between these effects. To date, we have a limited understanding of how the nutritional environment shapes the relationship between life history characters and foraging decisions. To gain insight into the problem, we used a geometric framework for nutrition to assess how the protein and carbohydrate content of the larval diet affected key life history traits in the fruit fly, Drosophila melanogaster. In no-choice assays, survival from egg to pupae, female and male body size, and ovariole number - a proxy for female fecundity - were maximized at the highest protein to carbohydrate (P:C) ratio (1.5:1). In contrast, development time was minimized at intermediate P:C ratios, around 1:2. Next, we subjected larvae to two-choice tests to determine how they regulated their protein and carbohydrate intake in relation to these life history traits. Our results show that larvae targeted their consumption to P:C ratios that minimized development time. Finally, we examined whether adult females also chose to lay their eggs in the P:C ratios that minimized developmental time. Using a three-choice assay, we found that adult females preferentially laid their eggs in food P:C ratios that were suboptimal for all larval life history traits. Our results demonstrate that D. melanogaster larvae make foraging decisions that trade-off developmental time with body size, ovariole number, and survival. In addition, adult females make oviposition decisions that do not appear to benefit the larvae. We propose that these decisions may reflect the living nature of the larval nutritional environment in rotting fruit. These studies illustrate the interaction between the nutritional environment, life history traits, and foraging choices in D. melanogaster, and lend insight into the ecology of their foraging decisions.

Rodrigues MA ，Martins NE ，Balancé LF ，Broom LN ，Dias AJ ，Fernandes AS ，Rodrigues F ，Sucena É ，Mirth CK ... -  《-》

Drosophila females trade off good nutrition with high-quality oviposition sites when choosing foods.

Animals, from insects to humans, select foods to regulate their acquisition of key nutrients in amounts and balances that maximise fitness. In species in which the nutrition of juveniles depends on parents, adults must make challenging foraging decisions that simultaneously address their own nutrient needs as well as those of their progeny. Here, we examined how the fruit fly Drosophila melanogaster, a species in which individuals eat and lay eggs in decaying fruits, integrate feeding decisions (individual nutrition) and oviposition decisions (offspring nutrition) when foraging. Using cafeteria assays with artificial diets varying in concentrations and ratios of protein to carbohydrates, we show that D. melanogaster females exhibit complex foraging patterns, alternating between laying eggs on high carbohydrate foods and feeding on foods with different nutrient contents depending on their own nutritional state. Although larvae showed faster development on high protein foods, both survival and learning performance were higher on balanced foods. We suggest that the apparent mismatch between the oviposition preference of females for high carbohydrate foods and the high performances of larvae on balanced foods reflects a natural situation where high carbohydrate ripened fruits gradually enrich in proteinaceous yeast as they start rotting, thereby yielding optimal nutrition for the developing larvae. Our findings that animals with rudimentary parental care uncouple feeding and egg-laying decisions in order to balance their own diet and provide a nutritionally optimal environment to their progeny reveal unsuspected levels of complexity in the nutritional ecology of parent-offspring interactions.

Lihoreau M ，Poissonnier LA ，Isabel G ，Dussutour A ... -  《-》

Comparing the impacts of macronutrients on life-history traits in larval and adult Drosophila melanogaster: the use of nutritional geometry and chemically defined diets.

Protein and carbohydrate are the two major macronutrients that exert profound influences over fitness in many organisms, including Drosophila melanogaster. Our understanding of how these macronutrients shape the components of fitness in D. melanogaster has been greatly enhanced by the use of nutritional geometry, but most nutritional geometric analyses on this species have been conducted using semi-synthetic diets that are not chemically well defined. Here, we combined the use of nutritional geometry and chemically defined diets to compare the patterns of larval and adult life-history traits expressed across 34 diets systematically varying in protein:carbohydrate (P:C) ratio and in protein plus carbohydrate (P+C) concentration. The shape of the response surfaces constructed for all larval and adult traits differed significantly from one another, with the nutritional optima being identified at P:C 1:4 for lifespan (P+C 120 g l-1), 1:2 for egg-to-adult viability (120 g l-1), 1:1 for female body mass at adult eclosion (240 g l-1) and lifetime fecundity (360 g l-1), 2:1 for larval developmental rate (60 g l-1) and 8:1 for egg production rate (120 g l-1). Such divergence in nutritional optima among life-history traits indicates that D. melanogaster confined to a single diet cannot maximize the expression of these traits simultaneously and thus may face a life-history trade-off. Our data provide the most comprehensive and nutritionally explicit analysis of the impacts of macronutrients on life-history traits in D. melanogaster and support the emerging notion that the fundamental trade-offs among life-history traits are mediated by macronutrients.

Jang T ，Lee KP 《-》

Differences in larval nutritional requirements and female oviposition preference reflect the order of fruit colonization of Zaprionus indianus and Drosophila simulans.

Species coexist using the same nutritional resource by partitioning it either in space or time, but few studies explore how species-specific nutritional requirements allow partitioning. Zaprionus indianus and Drosophila simulans co-exist in figs by invading the fruit at different stages; Z. indianus colonizes ripe figs, whereas D. simulans oviposits in decaying fruit. Larvae feed on yeast growing on the fruit, which serves as their primary protein source. Because yeast populations increase as fruit decays, we find that ripe fruit has lower protein content than rotting fruit. Therefore, we hypothesized that Z. indianus and D. simulans larvae differ in their dietary requirements for protein. We used nutritional geometry to assess the effects of protein and carbohydrate concentration in the larval diet on life history characters in both species. Survival, development time, and ovariole number respond differently to the composition of the larval diet, with Z. indianus generally performing better across a wider range of protein concentrations. Correspondingly, we found that Z. indianus females preferred to lay eggs on low protein foods, while D. simulans females chose higher protein foods for oviposition when competing with Z. indianus. We propose the different nutritional requirements and oviposition preference of these two species allows them to temporally partition their habitat.

Matavelli C ，Carvalho MJ ，Martins NE ，Mirth CK ... -  《-》

Fruit flies may face a nutrient-dependent life-history trade-off between secondary sexual trait quality, survival and developmental rate.

Optimal life-history strategies are those that best allocate finite environmental resources to competing traits. We used the geometric framework for nutrition to evaluate life-history strategies followed by Drosophila melanogaster by measuring the condition-dependent performance of life-history traits, including the morphology of male secondary sexual characters, sex combs. We found that depending on their rearing environment flies faced different forms of trait trade-offs and accordingly followed different life-history strategies. High-energy, high-carbohydrate, low-protein diets supported development of the largest and most symmetrical sex combs, however, consistent with handicap models of sexual selection these foods were associated with reduced fly survival and developmental rate. Expressing the highest quality sex combs may have required secondary sexual trait quality to be traded-off with developmental rate, and our results indicated that flies unable to slow development died. As larval nutritional environments are predominantly determined by female oviposition substrate choice, we tested where mated female flies laid the most eggs. Mothers chose high-energy, high-protein foods associated with rapid larval development. Mothers avoided high-carbohydrate foods associated with maximal sex comb expression, showing they may avoid producing fewer 'sexy' sons in favour of producing offspring that develop rapidly.

Gray LJ ，Simpson SJ ，Polak M 《-》