Appetite for self-destruction: suicidal biting as a nest defense strategy in Trigona stingless bees

Self-sacrificial behavior represents an extreme and relatively uncommon form of altruism in worker insects. It can occur, however, when inclusive fitness benefits are high, such as when defending the nest. We studied nest defense behaviors in stingless bees, which live in eusocial colonies subject to predation. We introduced a target flag to nest entrances to elicit defensive responses and quantified four measures of defensivity in 12 stingless bee species in São Paulo State, Brazil. These included three Trigona species, which are locally known for their aggression. Species varied significantly in their attack probability (cross species range = 0–1, P < 0.001), attack latency (7.0–23.5 s, P = 0.002), biting duration of individual bees (3.5–508.7 s, P < 0.001), and number of attackers (1.0–10.8, P < 0.001). A “suicide” bioassay on the six most aggressive species determined the proportion of workers willing to suffer fatal damage rather than disengage from an intruder. All six species had at least some suicidal individuals (7–83 %, P < 0.001), reaching 83 % in Trigona hyalinata. Biting pain was positively correlated with an index of overall aggression (P = 0.002). Microscopic examination revealed that all three Trigona species had five sharp teeth per mandible, a possible defensive adaptation and cause of increased pain. Suicidal defense via biting is a new example of self-sacrificial altruism and has both parallels and differences with other self-sacrificial worker insects, such as the honey bee. Our results indicate that suicidal biting may be a widespread defense strategy in stingless bees, but it is not universal

Working-class royalty: bees beat the caste system

The struggle among social classes or castes is well known in humans. Here, we show that caste inequality similarly affects societies of ants, bees and wasps, where castes are morphologically distinct and workers have greatly reduced reproductive potential compared with queens. In social insects, an individual normally has no control over its own fate, whether queen or worker, as this is socially determined during rearing. Here, for the first time, we quantify a strategy for overcoming social control. In the stingless bee Schwarziana quadripunctata, some individuals reared in worker cells avoid a worker fate by developing into fully functional dwarf queens

Body image perception in scholars of a school in the brazilian north region

Introduction: In the adolescence period, an individual experiences biopsychosocial changes and dissatisfaction with body image is quite prevalent at this stage. Objective: To investigate the prevalence of body image dissatisfaction and its association with demographic and psychosocial factors, sexual maturity, nutritional condition and lifestyle. Method: Cross-sectional study with a sample representing 831 eighth grade students from Porto Velho, Rondônia, Brazil, stratified into clusters. The data were obtained by questi onnaires - the Body Shape Questionnaire and Global School-based Student Health Survey - and anthropometry. The associations of interest were tested in a multivariate analysis with Cox regression adjusted for cross-sectional studies. Results: The prevalence of body image dissatisfaction was 22 per cent. The outcome was signifi cantly more prevalent among girls (PR: 4.69; CI: 95%: 3.09 – 7.12), young Caucasians (PR: 1.32; CI: 95%: 1.02 – 1.72), those who used tobacco (RP: 1.53; CI: 95%: 1.12 – 2.09), who were overweight or obese (PR: 2.77; CI: 95%: 2.18 – 3.51), and who reported feelings of sadness (PR: 1.35; CI: 95%: 1.05 – 1.73) and loneliness (PR: 1.66; CI: 95%: 1.30 – 2.11). The students with lower weight were more satisfied with their image. Conclusion: The results point to the need for parents, educators and health professionals to act jointly in developing actions that reinforce the positive qualities of youth, especially in girls. Encouraging physical activity and healthy habits can promote overall health, improving satisfaction with body image

Bee Pollination Highly Improves Oil Quality in Sunflower

Sunflower is a pollinator-dependent crop and one of the most cultivated oilseeds in the world, supporting important sectors of the agricultural industry, such as the food supply, because it is an important source of vitamin E and unsaturated fatty acids for human health. Although it is well stablished that bee pollination improves sunflower seed set, it is still unknown if pollinators influence the nutritional composition. Considering the economic importance of sunflowers for several Brazilian agricultural sectors, the aim of this study was to evaluate the effect of the bee community for (1) achene quality (weight and nutritional composition) and (2) market value. Exclusion experiments were performed with hybrid sunflowers and showed that bee pollination enhanced the achene weight by 91 %, the levels of vitamin E by 45 % and unsaturated fatty acids by 0.3 %. Also, it was estimated that due to the pollination services provided by bees, the grower of the sunflower cultivar used in this study nearly duplicates the sale value of the achenes per hectare of cultivated area. Thus, the current study highlights the importance of bees as providers of cross- and self-pollination to nutritional quality of sunflower achenes and provides useful baseline figures to further evaluations of the effects of pollinators on human diets and health

Molecular Marker to Identify Two Stingless Bee Species: Tetragonisca angustula and Tetragonisca fiebrigi (Hymenoptera, Meliponinae)

Tetragonisca angustula and T. fiebrigi esterases were biochemically characterized by their inhibition pattern and thermostability. Workers of both species were collected from nests at the State University of Maringa. In T. fiebrigi three esterases were observed: EST-1 (β-esterase, cholinesterase I), EST-2 (α-esterase, cholinesterase II) and EST-4 (αβ-esterase, carboxylesterase). In T. angustula two esterases were detected: EST-3 (β-esterase, acetylesterase) e EST-4 (αβ-esterase, carboxylesterase). T. angustula EST-3 showed the highest thermostability, and it was not observed above 54°C, while in T. fiebrigi EST- 1 and EST-2 were not detected above 52°C. Through this characterization, it was observed that EST-4 of T. angustula and T. fiebrigi showed identical biochemical characteristics, and probably those esterases are encoded by the same gene in the two species. Together, the biochemical characterization and molecular markers show that the two species are differentiated and secondary contact between the populations can still be occurring.

Quality versus quantity: foraging decisions in the honeybee (Apis mellifera scutellata) feeding on wildflower nectar and fruit juice

Foraging animals must often decide among resources which vary in quality and quantity. Nectar is a resource that exists along a continuum of quality in terms of sugar concentration and is the primary energy source for bees. Alternative sugar sources exist, including fruit juice, which generally has lower energetic value than nectar. We observed many honeybees (Apis mellifera scutellata) foraging on juice from fallen guava (Psidium guajava) fruit near others foraging on nectar. To investigate whether fruit and nectar offered contrasting benefits of quality and quantity, we compared honeybee foraging performance on P. guajava fruit versus two wildflowers growing within 50 m, Richardia brasiliensis and Tridax procumbens. Bees gained weight significantly faster on fruit, 2.72 mg/min, than on either flower (0.17 and 0.12 mg/min, respectively). However, the crop sugar concentration of fruit foragers was significantly lower than for either flower (12.4% vs. 37.0% and 22.7%, respectively). Fruit foragers also spent the most time handling and the least time flying, suggesting that fruit juice was energetically inexpensive to collect. We interpret honeybee foraging decisions in the context of existing foraging models and consider how nest-patch distance may be a key factor for central place foragers choosing between resources of contrasting quality and quantity. We also discuss how dilute solutions, such as fruit juice, can help maintain colony sugar–water balance. These results show the benefits of feeding on resources with contrasting quality and quantity and that even low-quality resources have value

Bourgeois behavior and freeloading in the colonial orb web spider Parawixia bistriata (Araneae, Araneidae)

Spiders of the tropical American colonial orb weaver Parawixia bistriata form a communal bivouac in daytime. At sunset, they leave the bivouac and construct individual, defended webs within a large, communally built scaffolding of permanent, thick silk lines between trees and bushes. Once spiders started building a web, they repelled other spiders walking on nearby scaffolding with a "bounce" behavior. In nearly all cases (93%), this resulted in the intruder leaving without a fight, akin to the "bourgeois strategy," in which residents win and intruders retreat without escalated contests. However, a few spiders (6.5%) did not build a web due to lack of available space. Webless spiders were less likely to leave when bounced (only 42% left) and instead attempted to "freeload," awaiting the capture of prey items in nearby webs. Our simple model shows that webless spiders should change their strategy from bourgeois to freeloading satellite as potential web sites become increasingly occupied