Effects of adult nutrition on female reproduction in a fruit-feeding butterfly: the role of fruit decay and dietary lipids

It was generally believed that butterflies and other holometabolous insects rely primarily on reserves accumulated during the larval stage for reproduction. Recent studies, however, highlight the often fundamental importance of adult nutrition to realize the full reproductive potential. While the importance of carbohydrates is fairly well understood, the role of most other adult-derived substances is only partially resolved. We here focus on the effects of dietary lipids (cholesterol, polyunsaturated fatty acids) and fruit decay (dietary yeast, ethanol) on female reproduction in the tropical, fruit-feeding butterfly Bicyclus anynana (Nymphalidae). We found that banana-fed control females outperformed all other groups fed on sucrose-based diets. Lipids, yeast or ethanol added to a sugar solution did not yield a similarly high reproductive output compared to fruit-fed females. Groups fed fresh or decaying banana showed no differences in reproductive performance. As we could not identify a single pivotal substance, we conclude that resource congruence (the use of nutrient types in a specified ratio) rather than any specific nutrient component is of key importance for maximum reproductive output. Further, dietary quality may affect egg hatching success in spite of no obvious effects on egg size and number. Thus, any implications about potential fitness effects of different diets need to consider egg (and hatchling) viability in addition to fecundity.     

Effects of larval starvation and adult diet-derived amino acids on reproduction in a fruit-feeding butterfly

Availability of adequate nutrition is among the most important factors affecting growth, development, and reproduction in animals. In holometabolous insects, diets and nutritional needs change between life stages, with larval storage, and adult feeding and reproduction being linked to one another. In several butterfly species, adult feeding is of fundamental importance to realize the full reproductive potential, primarily due to a prominent role of adult diet-derived carbohydrates. In contrast, the role of adult diet-derived amino acids is still under debate, despite the fact that butterflies were often found to preferentially feed on amino acid-rich substrates. Recently it was found that amino acids from adult income could compensate for adverse effects of larval food quality. In our study on the tropical butterfly Bicyclus anynana (Butler) (Lepidoptera: Nymphalidae), we used larval starvation to investigate corresponding effects on female reproductive output. Short periods of larval starvation prolonged development time and reduced larval survival, larval growth rate, pupal mass, and egg size. Regardless of the degree of larval starvation, access to amino acids in the adult diet increased egg size, whereas egg number remained largely unaffected. Thus, although there was some evidence for adult diet-derived amino acids being overall beneficial to reproduction, there was no indication that they can compensate for larval starvation.     

Host strain specific sex pheromone variation in Spodoptera frugiperda

Background

In the Lepidoptera it was historically believed that adult butterflies rely primarily on larval-derived nutrients for reproduction and somatic maintenance. However, recent studies highlight the complex interactions between storage reserves and adult income, and that the latter may contribute significantly to reproduction. Effects of adult diet were commonly assessed by determining the number and/or size of the eggs produced, whilst its consequences for egg composition and offspring viability were largely neglected (as is generally true for insects). We here specifically focus on these latter issues by using the fruit-feeding tropical butterfly Bicyclus anynana, which is highly dependent on adult-derived carbohydrates for reproduction.

Results

Adult diet of female B. anynana had pronounced effects on fecundity, egg composition and egg hatching success, with butterflies feeding on the complex nutrition of banana fruit performing best. Adding vitamins and minerals to a sucrose-based diet increased fecundity, but not offspring viability. All other groups (plain sucrose solution, sucrose solution enriched with lipids or yeast) had a substantially lower fecundity and egg hatching success compared to the banana group. Differences were particularly pronounced later in life, presumably indicating the depletion of essential nutrients in sucrose-fed females. Effects of adult diet on egg composition were not straightforward, indicating complex interactions among specific compounds. There was some evidence that total egg energy and water content were related to hatching success, while egg protein, lipid, glycogen and free carbohydrate content did not seem to limit successful development.

Conclusion

The patterns shown here exemplify the complexity of reproductive resource allocation in B. anynana, and the need to consider egg composition and offspring viability when trying to estimate the effects of adult nutrition on fitness in this butterfly and other insects.     

Introduced fire ants can exclude native ants from critical mutualist-provided resources

After over 30 years of research, it was recently shown that nectar amino acids increase female butterfly fecundity. However, little attention has been paid to the effect of nectar amino acids on male butterfly reproduction. Here, we show that larval food conditions (nitrogen-rich vs. nitrogen-poor host plants) and adult diet quality (nectar with or without amino acids) affected the amount of consumed nectar in Coenonympha pamphilus males. Furthermore, amino acids in the nectar diet of males increased progeny’s larval hatching mass, irrespective of paternal larval reserves. Our study takes the whole reproductive cycle of male butterflies into account, and also considers the role of females in passing male nutrients to offspring, as males’ realized reproduction was examined indirectly via nuptial gifts, by female performance. With this comprehensive approach, we demonstrate for the first time that nectar amino acids can improve male butterfly reproduction, supporting the old postulate that nectar amino acids generally enhance butterfly fitness.     

Larval starvation reduces responsiveness to feeding stimuli and does not affect feeding preferences in a butterfly

It is commonly assumed that holometabolic insects such as Lepidoptera rely primarily on larval storage reserves for reproduction. Recent studies though have documented a prominent role of adult-derived carbohydrates for butterfly reproduction. Moreover, a few studies have shown that adult butterflies may also benefit from adult-derived amino acids, at least when larval storage reserves are reduced. Given that in holometabolous insects larval deficiencies are carried over into the adult stage, reduced storage reserves have the potential to modulate adult feeding preferences and responses in order to allow for a successful compensation. We tested this hypothesis here in the fruit-feeding butterfly Bicyclus anynana using larval food stress to manipulate storage reserves. Alcohols (methanol, ethanol, butanol, propanol), sugars (maltose, glucose, fructose, sucrose), and acetic acid acted as feeding stimuli, while butterflies did not respond to other substances such as amino acids, yeast, salts, or vitamins. Contrary to expectations, stressed butterflies showed a weaker response than controls to several feeding stimuli. In preference tests, butterflies preferred sugar solutions containing proline, arginine, glutamic acid, acetic acid, or ethanol over plain sugar solutions, but discriminated against salts. However, there were no general differences among starved and control butterflies. We conclude that larval food-stress does not elicit compensatory feeding behavior such as a stronger preference for amino acids or other essential nutrients in B. anynana. Instead, the stress imposed by a period of starvation yielded negative effects.     

Stochasticity in reproductive opportunity and the evolution of egg limitation in insects

Is reproduction by adult female insects limited by the finite time available to locate hosts (time limitation) or by the finite supply of eggs (egg limitation)? An influential model predicted that stochasticity in reproductive opportunity favors elevated fecundity, rendering egg limitation sufficiently rare that its importance would be greatly diminished. Here, I use models to explore how stochasticity shapes fecundity, the likelihood of egg limitation, and the ecological importance of egg limitation. The models make three predictions. First, whereas spatially stochastic environments favor increased fecundity, temporally stochastic environments favor increases, decreases, or intermediate maxima in fecundity, depending on egg costs. Second, even when spatially or temporally stochastic environments favor life histories with less‐frequent egg limitation, stochasticity still increases the proportion of all eggs laid in the population that is laid by females destined to become egg limited. This counterintuitive result is explained by noting that stochasticity concentrates reproduction in the hands of a few females that are likely to become egg limited. Third, spatially or temporally stochastic environments amplify the constraints imposed by time and eggs on total reproduction by the population. I conclude that both egg and time constraints are fundamental in shaping insect reproductive behavior and population dynamics in stochastic environments.     

Grape variety affects female but also male reproductive success in wild European grapevine moths

Abstract.  1. For insect herbivores the quality of the larval host plant is a key determinant of their fitness. Only little attention, however, has been given to the effects of plants on mating success of males and its consequence for the reproductive output of their mates. In addition, almost all the studies that have investigated the influence of host plants on herbivore fitness components have been done in the laboratory, and less is known of these effects in natural conditions.
2. Using the phytophagous European grapevine moth ( Lobesia botrana Den. & Schiff., Lepidoptera: Tortricidae), we tested the influence of grape cultivars as larval food on the probability of acquiring a mate for both sexes, and on the reproductive output of females and males.
3. Results from this study stress the importance of larval host plants on the reproductive success of both sexes. Larval diet differentially affected mating success and reproductive output of male and female moths. Fecundity, egg size, and egg hatchability were significantly different when larvae were fed on particular grape cultivars.
4. A given cultivar that is of poor quality for females is generally also of poor quality for males. A cultivar, however, could be suitable for females but not for males and vice-versa. Apparently, the nutrients required for adult reproduction are not necessarily the same for males and females.
5. The important conclusion from this study is that evaluating the differential effect of host-plant species on traits associated with reproductive success of herbivores requires that the effects on both sexes be taken into account.     

Effects of food stress and density in different life stages on reproduction in a butterfly

Availability of adequate nutrition and (rearing) density are among the most important factors affecting growth, development and reproduction in animals. In holometabolous insects diets and energetic needs change between life stages, with storing of larval resources, adult feeding and reproduction being linked strategies. Nevertheless, studies investigating nutritional (and density) effects across metamorphic boundaries are largely lacking. We aim at disentangling the functional basis of reproductive patterns by independently manipulating larval and adult (1) density and (2) access to food, respectively, in the tropical butterfly, Bicyclus anynana. (1) A high larval rearing density had, contrary to common wisdom, very little impact on body size, but reduced larval development time through increased growth rates. The latter is thought to be an adaptation to high densities, driven by the risk of larval food resources becoming exhausted before reaching metamorphosis. Larval density and male company during oviposition (i.e. adult density) had no detectable effects on female reproduction. (2) Larval food stress prolonged larval development time and reduced larval growth rate, body size, fecundity and reproductive investment. Detrimental effects on female reproduction were mediated through a reduction in body size. Additional negative effects of adult food stress on fecundity were largely confined to females being fed as larvae ad libitum, while those being previously starved showed reduced performance regardless of adult income. Effects on egg size were inconsistent and, overall, marginal. Our results show that restricted food access in different developmental stages may set different limits to reproduction, either posed by shortage of larval‐derived storage reserves (i.e. nitrogenous compounds) or adult income (i.e. carbohydrates). Thus, one should be cautious when stating that one or the other type of nutrients is ultimately limiting to reproduction. Rather, our findings highlight the importance of resource congruence and of considering both, larval‐ and adult‐derived resources for reproduction.     

Macronutrient intake affects reproduction of a predatory insect

Prey quality has previously been shown to affect the growth and reproduction of predatory arthropods, however relatively little is known about the specific nutrients responsible for these effects. We tested if the macronutrient content (i.e. lipid and protein) of live prey affected mate attraction, reproductive behavior, egg production and nutrient reserves of adult female praying mantids, Pseudomantis albofimbriata. Females on a high‐protein diet produced more than twice as many eggs as females on a high‐lipid diet despite being fed the same overall biomass of prey. Furthermore, the lipid and protein composition of eggs and the female body was directly related to the diet that females were fed (i.e. high lipid content on the high‐lipid diet). Even more striking was the effect of diet treatment on the number of males attracted to females – only one male was attracted to females on the high‐lipid treatment and 56 males were attracted to females on the high‐protein treatment. Although it is not unexpected that females with more eggs would attract more males, the extreme nature of this difference is certainly surprising because previous studies have shown that females with only a couple of eggs can attract multiple males. Hence, our results suggest that female pheromone production may be affected by the quality/nutritional composition of eggs rather than simply the number of eggs. We found no significant difference in any of the other behaviours measured during mating trials, including the frequency of sexual cannibalism. The positive effects of prey protein content on mate attraction and egg production suggest that praying mantids might be expected to choose more protein‐biased prey in nature or, if prey choice is limited, to have higher reproductive output or population growth in communities dominated by protein‐rich prey.     

Single dietary amino acids control resting egg production and affect population growth of a key freshwater herbivore

The enormous success of the genus Daphnia in freshwater ecosystems is at least partially due to their cyclical parthenogenetic life cycle, in which asexual and sexual reproduction alternate periodically. This temporal change between reproductive strategies allows for (1) rapid population growth via subitaneously developing eggs when environmental conditions are appropriate and (2) the maintenance of genetic diversity via sexual reproduction and the production of resting eggs when environmental conditions deteriorate. We show here that dietary amino acids are involved in triggering the switch between reproductive modes in Daphnia pulex. Supplementation experiments demonstrate that specific dietary amino acids, in particular arginine and histidine, avert crowding-induced resting egg production, enhance subitaneous reproduction by increasing algal food quality and, as a combined effect of both processes, increase population growth rates. These findings suggest that the availability of single dietary amino acids potentially affects the seasonal dynamics and long-term persistence of Daphnia populations in the field, which may have consequences for the efficiency of carbon transfer and thus the trophic structure of freshwater food webs.     

Amino acid sources in the adult diet do not affect life span and fecundity in the fruit-feeding butterfly Bicyclus anynana

Abstract.  1. In tropical forests, the adults of many butterfly species feed on fruits rather than nectar from flowers and have long life spans. Rotting fruit and nectar differ from each other in many respects, including sources of amino acids and microbial life. If amino acids in the adult diet can be used for reproduction, this may have facilitated the evolution of extended life spans in this guild.
2. This issue was addressed by investigating effects of banana, yeast, and amino acids in the adult diet of the fruit-feeding butterfly Bicyclus anynana (Lepidoptera) on longevity and female reproductive output in two experiments.
3. Results showed that in the fruit-feeding butterfly B. anynana : (i) banana juice, but not sliced banana or added amino acids extend life span compared with a sugar solution of similar composition; (ii) compared with this sugar solution, other cohorts (banana juice-amino acid enriched) did not have significantly higher reproductive outputs; (iii) yeast does not represent a valuable source of nutrients; (iv) caloric restriction may cause decreased life span and rate of reproduction; and (v) increased rates of reproduction have a life span cost.     

Effects of a food supplementation experiment on reproductive investment and a post-mating sexually selected trait in magpies Pica pica

Food availability is an important factor affecting breeding success in birds. Food supplementation experiments in birds have in general focused on the effects on reproductive success in terms of female investment (laying date, clutch size, egg size), however, it is also known that the estimation of mate quality based on sexually selected signals influences female reproductive investment. In the particular case of magpies, females use nest size, a post-mating sexually selected signal, to assess male's likelihood to invest in reproduction, and accordingly adjust reproductive investment (clutch size). Then, the possible effects of food supplementation on female reproductive investment could be mediated by other variables related to parental quality, such as nest size in magpies. In the present study, we explore if higher food availability in a magpie territory affected both male sexually selected traits (i.e. nest size) and female reproductive investment (laying date, egg size, clutch size). We performed a food supplementation experiment in which we experimentally increased food availability in several magpie territories, keeping others as controls. In food-supplemented territories, males built significantly larger nests and females significantly increased egg size by 4.1% compared to control females. Results suggest that the continuous provisioning of protein rich food allowed magpie females to increase egg size. However, laying date and clutch size did not differ between control and food-supplemented magpie pairs. Food availability also affected the relationship between female reproductive investment and nest size. In control territories, females decreased their egg size in response to a larger nest, whereas a tendency for the opposite relationship was revealed in food-supplemented territories. We discuss the possibility that magpie females adopt different strategies for reproductive investment according to food availability.     

Differences in the pre‐diapause and pre‐oviposition accumulation of critical nutrients in adult females of the beetle Colaphellus bowringi

In many insect species, the differentiation of development between diapause and reproduction first becomes obvious during the diapause preparation (pre‐diapause) and pre‐oviposition phases. However, the differentiation of nutrient accumulation between these two phases remains unclear. We compared the weights of pre‐diapause and reproductive adult female Colaphellus bowringi Baly (Coleoptera: Chrysomelidae), and measured their triacylglycerol (TAG), protein, and carbohydrate content from emergence until they had fed for 4 days post‐eclosion. We also compared the ovarian development and accumulation of lipid droplets between pre‐diapause and reproductive adult females in order to determine whether we could visually detect differences in nutrient allocation. The weights of both pre‐diapause and reproductive females increased with duration of feeding. The fresh weight and water content of pre‐diapause females was significantly lower than that of reproductive females after feeding for 3 days post‐eclosion. Pre‐diapause females channeled their reserves into TAG in the fat body, whereas reproductive females converted nutrients into proteins and carbohydrates for egg development. These results quantify differences in nutrient accumulation between pre‐diapause and reproductive adult female C. bowringi, and provide clues for understanding the molecular mechanisms underlying differences in the allocation of nutrients between diapause and reproduction in insects.     

Dietary essential amino acids affect the reproduction of the keystone herbivore Daphnia pulex

Recent studies have indicated that nitrogen availability can be an important determinant of primary production in freshwater lakes and that herbivore growth can be limited by low dietary nitrogen availability. Furthermore, a lack of specific essential nitrogenous biochemicals (such as essential amino acids) might be another important constraint on the fitness of consumers. This might be of particular importance for cladoceran zooplankton, which can switch between two alternative reproductive strategies--the production of subitaneously developing and resting eggs. Here, we hypothesize that both the somatic growth and the type of reproduction of the aquatic keystone herbivore Daphnia is limited by the availability of specific essential amino acids in the diet. In laboratory experiments, we investigated this hypothesis by feeding a high quality phytoplankton organism (Cryptomonas) and a green alga of moderate nutritional quality (Chlamydomonas) to a clone of Daphnia pulex with and without the addition of essential amino acids. The somatic growth of D. pulex differed between the algae of different nutritional quality, but not dependent on the addition of dissolved amino acids. However, in reproduction experiments, where moderate crowding conditions at saturating food quantities were applied, addition of the essential amino acids arginine and histidine (but not lysine and threonine) increased the total number and the developmental stage of subitaneous eggs. While D. pulex did not produce resting eggs on Cryptomonas, relatively high numbers of resting eggs were released on Chlamydomonas. When arginine and histidine were added to the green algal diet, the production of resting eggs was effectively suppressed. This demonstrates the high, but previously overlooked importance of single essential amino acids for the reproductive strategy of the aquatic keystone herbivore Daphnia.     

Male genotype influences female reproductive investment in Drosophila melanogaster

In many species, males can influence the amount of resources their mates invest in reproduction. Two favoured hypotheses for this observation are that females assess male quality during courtship or copulation and alter their investment in offspring accordingly, or that males manipulate females to invest heavily in offspring produced soon after mating. Here, we examined whether there is genetic variation for males to influence female short-term reproductive investment in Drosophila melanogaster, a species with strong sexual selection and substantial sexual conflict. We measured the fecundity and egg size of females mated to males from multiple isofemale lines collected from populations around the globe. Although these traits were not strongly influenced by the male's population of origin, we found that 22 per cent of the variation in female short-term reproductive investment was attributable to the genotype of her mate. This is the first direct evidence that male D. melanogaster vary genetically in their proximate influence on female fecundity, egg size and overall reproductive investment.     

Adult diet affects lifespan and reproduction of the fruit‐feeding butterfly Charaxes fulvescens

Fruit‐feeding butterflies are among the longest lived Lepidoptera. While the use of pollen‐derived amino acids by Heliconius butterflies has been interpreted as important for the evolution of extended lifespans, very little is known about the life‐history consequences of frugivory. This issue is addressed by investigating effects of four adult diets (sugar, sugar with amino acids, banana, and moistened banana) on lifespan and reproduction in the fruit‐feeding butterfly Charaxes fulvescens Aurivillius (Lepidoptera: Nymphalidae). Female butterflies were collected from Kibale National Park, Uganda, and kept individually in cages near their natural habitat and data were collected on lifespan, oviposition, and hatching of eggs. Lifespan in captivity was longer for the sugar and the amino acid cohort, than for the banana cohorts. The longitudinal pattern of oviposition was erratic, with many days without oviposition and few periods with high numbers of eggs laid. Butterflies typically did not lay eggs during their 1st week in captivity and the length of the period between capture and first reproduction was significantly shorter for butterflies fed moistened banana. The length of the reproduction period (first reproduction–last reproduction in captivity) and the reproduction rate (total number of eggs/length of the reproduction period) did not differ significantly between the diet treatments. Those fed with amino acid and moistened banana had significantly higher egg hatchability than those fed with sugar and banana. We found no evidence for a lifespan cost of reproduction. Our results show that (1) female C. fulvescens can use amino acids in their diet for laying fertile eggs, (2) more wing‐wear does correlate with lower survival in captivity (indicating aging in the wild), but not with intensity of reproduction (providing no evidence for reproductive aging), and (3) fruit‐feeding butterflies may be dietary restricted in the field.     

Thermal and nutritional environments during development exert different effects on adult reproductive success in Drosophila melanogaster

Environments experienced during development have long‐lasting consequences for adult performance and fitness. The “environmental matching” hypothesis predicts that individuals perform best when adult and developmental environments match whereas the “silver spoon” hypothesis expects that fitness is higher in individuals developed under favorable environments regardless of adult environments. Temperature and nutrition are the two most influential determinants of environmental quality, but it remains to be elucidated which of these hypotheses better explains the long‐term effects of thermal and nutritional histories on adult fitness traits. Here we compared how the temperature and nutrition of larval environment would affect adult survivorship and reproductive success in the fruit fly, Drosophila melanogaster. The aspect of nutrition focused on in this study was the dietary protein‐to‐carbohydrate (P:C) ratio. The impact of low developmental and adult temperature was to improve adult survivorship. High P:C diet had a negative effect on adult survivorship when ingested during the adult stage, but had a positive effect when ingested during development. No matter whether adult and developmental environments matched or not, females raised in warm and protein‐enriched environments produced more eggs than those raised in cool and protein‐limiting environments, suggesting the presence of a significant silver spoon effect of larval temperature and nutrition. The effect of larval temperature on adult egg production was weak but persisted across the early adult stage whereas that of larval nutrition was initially strong but diminished rapidly after day 5 posteclosion. Egg production after day 5 was strongly influenced by the P:C ratio of the adult diet, indicating that the diet contributing mainly to reproduction had shifted from larval to adult diet. Our results highlight the importance of thermal and nutritional histories in shaping organismal performance and fitness and also demonstrate how the silver spoon effects of these aspects of environmental histories differ fundamentally in their nature, strength, and persistence.     

Food quality controls reproduction of the zebra mussel (Dreissena polymorpha)

Species such as Dreissena polymorpha sometimes contribute substantially in the transfer of primary to secondary production. During the ontogenetic cycle, the reproductive investment of adult mussels is one of the main parameters that affect recruitment success. We studied how food quality and temperature affect the reproductive investment in term of egg mass of D. polymorpha in a lake by sampling mussels monthly from 4 m and 15 m depths. Temperature affected reproduction directly and also indirectly through the food. To assess whether temperature and/or food conditions led to the differences observed in mussels sampled from the two depths, mussels were reared in the laboratory under two different temperature regimes for 3 months, simulating the temperature of the lake at 4 m and 15 m depth. Possible effects of food quality were tested at each temperature using four diets differing in fatty acid composition. Temperature played an important role as a trigger for spawning, and the type of diet clearly affected the reproductive investment. When the heterokont chromophyte alga Nannochloropsis limnetica, which is rich in polyunsaturated fatty acids (PUFAs) and long-chained PUFAs (>C18), was fed to mussels, an increased egg mass was obtained. This result was in contrast to that found when the green alga Scenedesmus obliquus and the cyanobacterium Aphanothece sp., both of which are deficient in long-chained PUFAs, were offered as food to the mussels. Such a PUFA-dependent food quality may affect reproduction in lakes. Food quality effects vary seasonally in a lake and may be most important in summer, when low-food-quality green algae and cyanobacteria are abundant. The low biochemical quality of these blooms may affect at least the later period of gametogenesis of D. polymorpha, which reproduces from June to August.     

Female canaries produce eggs with greater amounts of testosterone when exposed to preferred male song

Male birdsong has a great influence in the stimulation of female reproduction. However, female physiological responsiveness to song may depend on the degree of complexity of male song. This is expected because females of iteroparous organisms may increase their fitness by matching their reproductive investment to the predicted value of each reproductive attempt. To the extent that the expression of male ornaments is a signal of male quality, we expect females to increase their investment when paired to highly ornamented males. However, female investment may be cryptic and difficult to detect, such as androgen content in the eggs. In this study, we exposed female canaries (Serinus canaria) to attractive and unattractive song repertoires using a crossover design. As predicted, females invested greater concentrations of testosterone in their eggs when exposed to attractive repertoires than when exposed to unattractive repertoires. This implies that song repertoires convey important information about the reproductive value of a given male and suggests that testosterone deposition in egg yolk may be costly.