Boaz Yuval

Nutritional correlates of reproductive success of male Mediterranean fruit flies (Diptera: Tephritidae)

We examined the hypothesis that adult diet affects the reproductive success of male Mediterranean fruit flies. In particular we determined whether protein-fed males copulated more frequently than protein-deprived males. Furthermore, we determined whether the nutritional status of their first sexual partner affects the renewal of female receptivity. Males fed no protein copulated at a significantly lower rate than did males fed protein. In both diet groups, size was significantly associated with copulatory success. Protein-deprived males transferred significantly more sperm to their mates than did protein-fed males. However, significantly more females mated to protein-deprived males re-mated on the following day. We conclude that male diet is a significant factor in determining male reproductive success. Male diet affects the ability to gain copulations with virgin females, and the receptivity of these females to further copulations.

Nutritional reserves regulate male participation in Mediterranean fruit fly leks

1. The mating system of Mediterranean fruit flies (Ceratitis capitata, Diptera: Tephritidae), is based on male leks that form on the foliage of trees. Following observations that not all males participate in leks, the hypotheses that (a) small males are absent from leks and (b) males with inadequate nutrient reserves are unable to participate in leks were examined.

Enterobacteria-mediated nitrogen fixation in natural populations of the fruit fly Ceratitis capitata

Nitrogen, although abundant in the atmosphere, is paradoxically a limited resource for multicellular organisms. In the Animalia, biological nitrogen fixation has solely been demonstrated in termites. We found that all individuals of field‐collected Mediterranean fruit flies (Ceratitis capitata) harbour large diazotrophic enterobacterial populations that express dinitrogen reductase in the gut. Moreover, nitrogen fixation was demonstrated in isolated guts and in live flies and may significantly contribute to the flys nitrogen intake. The presence of similar bacterial consortia in additional insect orders suggests that nitrogen fixation occurs in vast pools of terrestrial insects. On such a large scale, this phenomenon may have a considerable impact on the nitrogen cycle.

Postcopulatory sexual selection in Mediterranean fruit flies: advantages for large and protein-fed males.

Previous laboratory studies of Mediterranean fruit flies, Ceratitis capitata (medflies), have identified large size and protein feeding as positive influences on the ability of males to secure copulations. In this study, we investigated whether large and protein-fed males experience additional advantages in terms of amount and distribution of sperm stored by mates. We also examined relationships between copula duration and sperm storage. Mates of large and protein-fed males were more likely to store sperm and to store more sperm than mates of small and protein-deprived males. Probability of sperm storage was associated with copula duration; all copulations lasting less than 100 min failed whereas 98% lasting longer than 100 min succeeded. Copulations involving sperm storage were longer if males were small or protein deprived or if the female was large, although there was no evidence of a relationship between copula duration and total sperm storage. Evidence from related studies suggests that variation in latency until sperm transfer, caused by size and diet, is a likely explanation for varying copula duration. Sperm tended to be stored asymmetrically between the females two spermathecae, consistent with a mating system in which females maintain isolated populations of sperm from different males and later select between them. Storage was less asymmetric when large numbers of sperm were stored but there was little evidence that male size or diet affected this asymmetry. It is uncertain whether postcopulatory advantages of large and protein-fed male medflies arise from female preferences or male dominance through coercion or force. Copyright 1999 The Association for the Study of Animal Behaviour.

Diet and size influence sexual advertisement and copulatory success of males in Mediterranean fruit fly leks

1. The objective of the work reported here was to test the hypothesis that in insects that invest considerable energy in sexual displays and courtship, foraging successfully for food affects their subsequent performance and copulatory success in leks. Accordingly, the interactions between body size and diet on initiation of lekking behaviour and copulatory success in male Mediterranean fruit flies Ceratitis capitata (Diptera: Tephritidae) were investigated.

Effects of larval diet on development rates and reproductive maturation of male and female Mediterranean fruit flies

Abstract Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae) larvae are capable of developing in one of many hosts that may vary greatly in quality. We hypothesized that they will respond to the larval environment in a manner beneficial to their subsequent reproductive performance. Accordingly, we investigated the effects of various larval diets (varying in the amount of protein and sugar they contain) on the size, development time, nutritional status and reproductive maturation (ovarian development and onset of sexual behaviour) of females and males. We found that flies which undergo larval development in artificial host fruit that contain sugar and protein (‘protein‐fed’) were larger, developed faster and emerged with more nutritional reserves than flies that were protein‐deprived as larvae. Protein‐fed males, regardless of their size, became sexually active before males that developed in hosts with no protein. Protein‐fed females produced more mature eggs than protein‐deprived ones. Moreover, protein‐fed females tended to copulate sooner than females that developed in hosts with no protein. In addition, regardless of female larval diet, females with more mature eggs tended to copulate sooner than females with less mature eggs. In light of these results, the importance of the larval environment for adult reproductive success is discussed.

Energy budget of swarming male mosquitoes

Abstract. 1 The objective of this study was to determine, in the field, the energetic costs of swarming for male Anopheles freeborni (Diptera: Culicidae). By comparing the caloric contents of resting males to marked males captured after swarming, we established when sugar feeding takes place, what energy source is used to fuel swarming flight, and how much energy is invested in this activity. 2 Sugar‐feeding takes place sometime during the night after swarming is concluded. Nectar sugars are therefore not immediately available to fuel flight. Stored sugars (trehalose and glucose) and glycogen are the primary sources of energy for flight. Lipids are not used to fuel flight but may be used in resting metabolism. 3 Male size is not related to feeding success. For males of all sizes, swarming consumes more than 50% of available calories. Accordingly, the ability of an individual to find and exploit nectar sources will greatly affect reproductive success.

Bringing back the fruit into fruit fly–bacteria interactions

Female Mediterranean fruit flies (Ceratitis capitata) oviposit in fruits, within which the larvae develop. This development is associated with rapid deterioration of the fruit, and frequently with invasion by secondary pests. Most research on the associations between medflies and microorganisms has focused on the bacteria inhabiting the digestive system of the adult fly, while the role of the fruit in mediating, amplifying or regulating the fruit fly microflora has been largely neglected. In this study, we examine the hypothesis that the host fruit plays a role in perpetuating the fly‐associated bacterial community. Using direct and cultured‐based approaches, we show that this community is composed in its very large majority of diazotrophic and pectinolytic Enterobacteriaceae. Our data suggest that this fly‐associated enterobacterial community is vertically transmitted from the female parent to its offspring. During oviposition, bacteria are transferred to the fruit, establish and proliferate within it, causing its decay. These results show that the host fruit is indeed a central partner in the fruit fly–bacterial interaction as these transmitted bacteria are amplified by the fruit, and subsequently maintained throughout the flys life. This enterobacterial community may contribute to the flys nitrogen and carbon metabolism, affecting its development and ultimately, fitness.

Regulation of sexual receptivity of female Mediterranean fruit flies: old hypotheses revisited and a new synthesis proposed.

The objective of this study was to examine the relative contributions of copula duration and sperm transfer to the inhibition of sexual receptivity of female Mediterranean fruit flies (Ceratitis capitata, Diptera: Tephritidae). Females choosing to remate had significantly fewer sperm in their spermathecae than females who chose not to remate. Duration of a females first copulation did not affect her subsequent receptivity. Furthermore, on the first day following copulation significantly more females whose first mate was sterile and from a laboratory strain (sterile males transfer fewer sperm than wild males) chose to copulate than did females whose mate was fertile and recently derived from wild stock. Finally, we offer a synthesis of the available information on remating in this species, and suggest that while females are facultatively polyandrous, copula duration, sperm transfer and male accessory gland secretions act in succession to inhibit female receptivity.

Post-Teneral Protein Feeding Improves Sexual Competitiveness But Reduces Longevity of Mass-Reared Sterile Male Mediterranean Fruit Flies (Diptera: Tephritidae)

Abstract The sterile insect technique is gaining an increasing role in the control of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), populations. In the current study, we examine how post-teneral nutrition during the first 4–8 d after adult emergence affects performance and copulatory success in leks of mass-reared sterile (TSL strain) males. We found that protein and sugar fed males were significantly more likely to emit pheromone (call) in leks, and more likely to copulate, than males fed only sugar. Sterile males, who had access to water and apples after 4 d of feeding on protein and sugar, or sugar alone, were significantly more likely to copulate than their starved competitors who had access to water alone. However, after 24 h of starvation, 4-d protein-fed males suffered a higher mortality than sugar-fed males. More work is necessary to determine the optimal protein formulation that will maintain a balance between hastened mortality and increased sexual competitiveness of sterile males.