Surface lipids of queen-laid eggs do not regulate queen production in a fission-performing ant

In animal societies, most collective and individual decision making depends on the presence of reproductive individuals. The efficient transmission of information among reproductive and non-reproductive individuals is therefore a determinant of colony organization. In social insects, the presence of a queen modulates multiple colonial activities. In many species, it negatively affects worker reproduction and the development of diploid larvae into future queens. The queen mostly signals her presence through pheromone emission, but the means by which these chemicals are distributed in the colony are still unclear. In several ant species, queen-laid eggs are the vehicle of the queen signal. The aim of this study was to investigate whether queen-laid eggs of the ant Aphaenogaster senilis possess queen-specific cuticular hydrocarbons and/or Dufour or poison gland compounds, and whether the presence of eggs inhibited larval development into queens. Our results show that the queen- and worker-laid eggs shared cuticular and Dufour hydrocarbons with the adults; however, their poison gland compounds were not similar. Queen-laid eggs had more dimethylalkanes and possessed a queen-specific mixture of cuticular hydrocarbons composed of 3,11?+?3,9?+?3,7-dimethylnonacosane, in higher proportions than did worker-laid eggs. Even though the queen-laid eggs were biochemically similar to the queen, their addition to experimentally queenless groups did not prevent the development of new queens. More studies are needed on the means by which queen ant pheromones are transmitted in the colony, and how these mechanisms correlates with life history traits.     

Larval regulation of worker reproduction in the polydomous ant Novomessor cockerelli

The Science of Nature - Many insects use chemical defence mechanisms to defend themselves against predators. However, defensive secretions are costly to produce and should thus only be used in...     

Tolerating an infection: an indirect benefit of co-founding queen associations in the ant Lasius niger

Pathogens exert a strong selection pressure on organisms to evolve effective immune defences. In addition to individual immunity, social organisms can act cooperatively to produce collective defences. In many ant species, queens have the option to found a colony alone or in groups with other, often unrelated, conspecifics. These associations are transient, usually lasting only as long as each queen benefits from the presence of others. In fact, once the first workers emerge, queens fight to the death for dominance. One potential advantage of co-founding may be that queens benefit from collective disease defences, such as mutual grooming, that act against common soil pathogens. We test this hypothesis by exposing single and co-founding queens to a fungal parasite, in order to assess whether queens in co-founding associations have improved survival. Surprisingly, co-foundresses exposed to the entomopathogenic fungus Metarhizium did not engage in cooperative disease defences, and consequently, we find no direct benefit of multiple queens on survival. However, an indirect benefit was observed, with parasite-exposed queens producing more brood when they co-founded, than when they were alone. We suggest this is due to a trade-off between reproduction and immunity. Additionally, we report an extraordinary ability of the queens to tolerate an infection for long periods after parasite exposure. Our study suggests that there are no social immunity benefits for co-founding ant queens, but that in parasite-rich environments, the presence of additional queens may nevertheless improve the chances of colony founding success.     

大连湾挥发性有机污染物挥发速率常数估算

本文采用气－液双膜模型和大连湾水文参数，对大连湾检测出的挥发性有机物的挥发速率常数进行估算。结果表明，三氯乙烯等１４种挥发性有机物在大连湾海域中的挥发速率常数在８．０×１０＾－３ｈ－１－１．４×１０＾－２×＾－１之间，挥发半衰期在５０ｈ＝８０ｈ之间。因此，挥发至大气是这些在机物主要归宿。     

Exceptionally high levels of multiple mating in an army ant

Most species of social insects have singly mated queens, although there are notable exceptions. Competing hypotheses have been proposed to explain the evolution of high levels of multiple mating, but this issue is far from resolved. Here we use microsatellites to investigate mating frequency in the army ant Eciton burchellii and show that queens mate with an exceptionally large number of males, eclipsing all but one other social insect species for which data are available. In addition we present evidence that suggests that mating is serial, continuing throughout the lifetime of the queen. This is the first demonstration of serial mating among social hymenoptera. We propose that high paternity within colonies is most likely to have evolved to increase genetic diversity and to counter high pathogen and parasite loads.     

Biogenic amine levels, reproduction and social dominance in the queenless ant Streblognathus peetersi

Social harmony often relies on ritualised dominance interactions between society members, particularly in queenless ant societies, where colony members do not have developmentally predetermined castes but have to fight for their status in the reproductive and work hierarchy. In this behavioural plasticity, their social organisation resembles more that of vertebrates than that of the “classic” social insects. The present study investigates the neurochemistry of the queenless ant species, Streblognathus peetersi, to better understand the neural basis of the high behavioural plasticity observed in queenless ants. We report measurements of brain biogenic amines [octopamine, dopamine, serotonin] of S. peetersi ants; they reveal a new set of biogenic amine influences on social organisation with no common features with other “primitively organised societies” (bumble bees) and some common features with “highly eusocial” species (honey bees). This similarity to honey bees may either confirm the heritage of queenless species from their probably highly eusocial ancestors or highlight independent patterns of biogenic amine influences on the social organisation of these highly derived species.     

Alternative mating behaviors of the queen polymorphic ant <Emphasis Type="Italic">Temnothorax longispinosus</Emphasis>

Mating behaviors of ants fall into two categories: female calling, in which a female alate releases pheromones that attract males, and male swarming, in which large male aggregations attract females. Female calling is common in species with queens that return to their natal nest to found colonies dependently after mating, while male swarming is common in species with queens that disperse to found independently. In some species that display both founding strategies, a queen-size polymorphism has evolved in which dependent-founding queens are smaller than independent-founding queens. Dependent founding is likely difficult if gynes (virgin queens) are mating in distant swarms. Therefore, a queen may adopt one or the other mating strategy based on its size and founding behavior. We investigated mating behaviors in the queen-polymorphic ant, Temnothorax longispinosus. Observations in laboratory mating arenas indicated that small gynes exhibited significantly lower flight activity than large gynes. Both forms mated in male swarms, and neither form exhibited female calling. The reduced flight activity of the small morph may facilitate returning to the natal nest after mating, provided the mating swarm is located nearby. Therefore, alternative colony-founding behaviors may be possible without the evolution of female-calling behavior; however, the reduced flight activity of small morphs may require that mating swarms are not distant from the natal nest.     

Reclaiming the crown: queen to worker conflict over reproduction in <Emphasis Type="Italic">Aphaenogaster cockerelli</Emphasis>

In many social taxa, reproductively dominant individuals sometimes use aggression to secure and maintain reproductive status. In the social insects, queen aggression towards subordinate individuals or workers has been documented and is predicted to occur only in species with a small colony size and a low level of queen–worker dimorphism. We report queen aggression towards reproductive workers in the ant species Aphaenogaster cockerelli, a species with a relatively large colony size and a high level of reproductive dimorphism. Through analysis of cuticular hydrocarbon profiles, we show that queens are aggressive only to reproductively active workers. Non-reproductive workers treated with a hydrocarbon typical for reproductives are attacked by workers but not by queens, which suggests different ways of recognition. We provide possible explanations of why queen aggression is observed in this species.     

No evidence for an afrotherian-like delayed dental eruption in South American notoungulates

The fossil South American ungulates are of great interest relative to the new phylogenetic framework elaborated for living placental mammals. In particular, studies on these endemic taxa can allow for testing congruence between southern placental phylogeny and plate tectonics, beyond what has already been suggested in the Atlantogenata hypothesis based on extant afrotherians and xenarthrans. The presence of delayed dental eruption relative to skull growth is one feature characterizing the extant afrotherians and possibly the xenarthrans. Late dental eruption has been mentioned previously in South American notoungulates, thus suggesting possible resemblance with afrotherians and perhaps xenarthrans. We provide here a detailed study of the dental eruption pattern relative to the skull growth in the notoungulates. In contrast to previous statements, our results demonstrate that there is currently no evidence for an afrotherian-like delayed dental eruption in this group. For now, the inferred absence of a delayed dental eruption in notoungulates does not support atlantogenatan/afrotherian affinities for the Notoungulata, but other atlantogenatan/afrotherian characteristics remain to be explored in more detail in this group and other South American ungulates.     

Sex mosaics in a male dimorphic ant Cardiocondyla kagutsuchi

Gynandromorphy, or the development of organisms with a combination of male and female morphological features, is common in Hymenoptera. The underlying mechanism is likely associated with the sex-determination system, and studying this phenomenon should lead to a deeper understanding of both embryonic development and sex determination. The reproductive capabilities of gynandromorphs (hereafter, sex mosaics) remain unclear. We studied gynandromorphy in the Malaysian ant Cardiocondyla kagutsuchi, which has sex mosaics of queens (gynandromorphs; mosaic of queens and winged male) and workers (ergatandromorphs; mosaic of worker and wingless ergatoid male). These sex mosaics were classified into seven morphological categories. Most individuals had more male than female body areas. Behavioral observations revealed that sex mosaics behave more in accordance with the “sex” of their brain than that of the reproductive organs (gaster). Relative DNA quantities showed that both female and male regions contained haploid and diploid nuclei, irrespective of their phenotypic appearance, indicating that external appearance did not reflect internal tissues. Nearly one third of the adults were sex mosaics and they were not infected with Wolbachia. Our results suggest that the production of sex mosaics in this species does not pose a substantial cost to colonies and that the underlying causes are therefore not strongly selected against.