196 research outputs found
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 SĂŁo Paulo State, Brazil. These included three Trigona species, which are locally known for their aggression. Species varied significantly in their attack probability (cross species rangeâ=â0â1, Pâ<â0.001), attack latency (7.0â23.5 s, Pâ=â0.002), biting duration of individual bees (3.5â508.7 s, Pâ<â0.001), and number of attackers (1.0â10.8, Pâ<â0.001). A âsuicideâ 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 (7â83 %, Pâ<â0.001), reaching 83 % in Trigona hyalinata. Biting pain was positively correlated with an index of overall aggression (Pâ=â0.002). 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
A Novel Feature Selection Method for Uncertain Features: An Application to the Prediction of Pro-/Anti- Longevity Genes
Understanding the ageing process is a very challenging problem for biologists. To help in this task, there has been a growing use of classification methods (from machine learning) to learn models that predict whether a gene influences the process of ageing or promotes longevity. One type of predictive feature often used for learning such classification models is Protein-Protein Interaction (PPI) features. One important property of PPI features is their uncertainty, i.e., a given feature (PPI annotation) is often associated with a confidence score, which is usually ignored by conventional classification methods. Hence, we propose the Lazy Feature Selection for Uncertain Features (LFSUF) method, which is tailored for coping with the uncertainty in PPI confidence scores. In addition, following the lazy learning paradigm, LFSUF selects features for each instance to be classified, making the feature selection process more flexible. We show that our LFSUF method achieves better predictive accuracy when compared to other feature selection methods that either do not explicitly take PPI confidence scores into account or deal with uncertainty globally rather than using a per-instance approach. Also, we interpret the results of the classification process using the features selected by LFSUF, showing that the number of selected features is significantly reduced, assisting the interpretability of the results. The datasets used in the experiments and the program code of the LFSUF method are freely available on the web at http://github.com/pablonsilva/FSforUncertainFeatureSpaces
Revelar-se homossexual: percepçÔes de jovens adultos brasileiros
Considering the new perspectives on male and female homosexuality and the coming out process, the aim of this study was to investigate the perceptions of young Brazilian homosexuals about the coming out on the family relationships. This is a study of multiple cases supported by the qualitative research approach. Eight homosexuals (five gays and three lesbians) were interviewed, with an average age of 26 years old. The interviews were submitted to content analysis, in which categories were constructed a posteriori, highlighting similarities and differences between the cases. In front of coming out process in a heterosexist context, the individual can make this event a moment of silence and shame, as well as deal with guilt. Family and friends constituted the main support network in front of homosexual disclosure, considered fundamental after coming out.En vista de las nuevas perspectivas sobre la homosexualidad masculina y femenina y del processo de coming out, el objetivo de este estudio fue investigar las percepciones de jĂłvenes homosexuales brasileños sobre la revelaciĂłn de la orientaciĂłn sexual en el contexto familiar. Se trata de un estudio de casos mĂșltiples apoyado en el enfoque cualitativo. Fueron entrevistados ocho homosexuales (cinco gays y tres lesbianas), con edad media de 26 años. Las entrevistas fueron sometidas a anĂĄlisis de contenido, en el que las categorĂas se construyeron a posteriori, destacando las similitudes y diferencias entre los casos. Ante el processo de coming out en un contexto heterosexista, el individuo puede hacer de ese evento un momento de silenciamiento y vergĂŒenza, asĂ como lidiar con el sentimiento de culpa. La familia y los amigos constituyeron la principal red de apoyo ante la revelaciĂłn de la homosexualidad, red Ă©sta considerada fundamental despuĂ©s del coming out.Considerando as novas perspectivas acerca da homossexualidade masculina e feminina e do processo de coming out, o objetivo do presente estudo foi investigar as percepçÔes de jovens homossexuais brasileiros acerca do processo de revelação da orientação sexual no contexto familiar. Trata-se de um estudo de casos mĂșltiplos qualitativo. Foram entrevistados oito homossexuais (cinco gays e trĂȘs lĂ©sbicas), com idade mĂ©dia de 26 anos. As entrevistas foram submetidas Ă anĂĄlise de conteĂșdo, na qual foram construĂdas categorias a posteriori, destacando-se semelhanças e diferenças entre os casos. Diante do processo de coming out em um contexto heterossexista, o indivĂduo pode fazer desse evento um momento de silenciamento e vergonha, alĂ©m de lidar com o sentimento de culpa. A famĂlia e os amigos constituĂram a principal rede de apoio diante da revelação da homossexualidade, rede esta considerada fundamental apĂłs o coming out
On an accidental degeneracy in the 31P{ÂčH} NMR chemical shifts in ruthenium diphosphine complexes
The [RuCl(bipy)(dppb)(4-pic)]PF6 complex was prepared and fully characterized. The X-ray crystal structure of this complex was determined in order to make an unambiguous distinction between the two possible positions of the 4-methylpyridine ligand (4-pic) in the compound: trans to phosphorus atom or trans to nitrogen atom. The [RuCl(bipy)(dppb)(4-pic)]PF6 complex exhibits an unusual temperature-dependent accidental degeneracy of the 31P chemical shifts in its solution NMR spectrum
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
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Pyrazines from bacteria and ants: convergent chemistry within an ecological niche
Ants use pheromones to coordinate their communal activity. Volatile pyrazines, for instance, mediate food resource gathering and alarm behaviors in different ant species. Here we report that leaf-cutter ant-associated bacteria produce a family of pyrazines that includes members previously identified as ant trail and alarm pheromones. We found that L-threonine induces the bacterial production of the trail pheromone pyrazines, which are common for the host leaf-cutter ants. Isotope feeding experiments revealed that L-threonine along with sodium acetate were the biosynthetic precursors of these natural products and a biosynthetic pathway was proposed
Cellular Automata Applications in Shortest Path Problem
Cellular Automata (CAs) are computational models that can capture the
essential features of systems in which global behavior emerges from the
collective effect of simple components, which interact locally. During the last
decades, CAs have been extensively used for mimicking several natural processes
and systems to find fine solutions in many complex hard to solve computer
science and engineering problems. Among them, the shortest path problem is one
of the most pronounced and highly studied problems that scientists have been
trying to tackle by using a plethora of methodologies and even unconventional
approaches. The proposed solutions are mainly justified by their ability to
provide a correct solution in a better time complexity than the renowned
Dijkstra's algorithm. Although there is a wide variety regarding the
algorithmic complexity of the algorithms suggested, spanning from simplistic
graph traversal algorithms to complex nature inspired and bio-mimicking
algorithms, in this chapter we focus on the successful application of CAs to
shortest path problem as found in various diverse disciplines like computer
science, swarm robotics, computer networks, decision science and biomimicking
of biological organisms' behaviour. In particular, an introduction on the first
CA-based algorithm tackling the shortest path problem is provided in detail.
After the short presentation of shortest path algorithms arriving from the
relaxization of the CAs principles, the application of the CA-based shortest
path definition on the coordinated motion of swarm robotics is also introduced.
Moreover, the CA based application of shortest path finding in computer
networks is presented in brief. Finally, a CA that models exactly the behavior
of a biological organism, namely the Physarum's behavior, finding the
minimum-length path between two points in a labyrinth is given.Comment: To appear in the book: Adamatzky, A (Ed.) Shortest path solvers. From
software to wetware. Springer, 201
Life history and chemical ecology of the Warrior wasp Synoeca septentrionalis (Hymenoptera : Vespidae, Epiponini)
Swarm-founding âWarrior waspsâ (Synoeca spp.) are found throughout the tropical regions of South America, are much feared due to their aggressive nest defence and painful sting. There are only five species of Synoeca, all construct distinctive nests that consist of a single sessile comb built onto the surface of a tree or rock face, which is covered by a ribbed envelope. Although locally common, research into this group is just starting. We studied eight colonies of Synoeca septentrionalis, a species recently been described from Brazil. A new colony is established by a swarm of 52 to 140 adults that constructs a colony containing around 200 brood cells. The largest colony collected containing 865 adults and over 1400 cells. The number of queenâs present among the eight colonies varied between 3 and 58 and no clear association between colony development and queen number was detected. Workers and queens were morphologically indistinguishable, but differences in their cuticular hydrocarbons were detected, particularly in their (Z)-9-alkenes. The simple cuticular profile, multiple queens, large size and small number of species makes the âWarrior waspsâ an excellent model group for further chemical ecology studies of swarm-founding wasps
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