Microgynous Queens in the Paleartic Ant, Manica rubida: Dispersal Morphs or Social Parasites?

In many ant species, queen size is dimorphic, with small microgynes and large macrogynes, which differ, for example, in size, insemination rate, ovary development, and dispersal tactics. These polymorphic queens often correspond with alternative reproductive strategies. The Palearctic ant, Manica rubida (Latreille) (Hymenoptera: Formicidae), lives mostly in mountainous regions in either monogynous colonies, containing one macrogynous queen or polygynous colonies, containing a few large macrogynous queens. In 1998, a colony of M. rubida was discovered containing macrogynes and many small alate microgynes that did not engage in a nuptial flight but, instead, stayed in the home nest the following winter. These microgynes were studied more closely by investigating their size, behavior, and spermatheca in relation to M. rubida macrogynes and workers. Mitochondrial DNA of macrogynes, microgynes and workers from four nests was sequenced to detect possible genetic differences between them. The microgynes were significantly smaller than the macrogynes, and the head width of the gynes was completely bimodal. The microgynes behaved like workers of the macrogynes in every experiment tested. Furthermore, the microgynes had a normal spermatheca and could be fecundated, but rarely (only one in several years). Finally, all the individuals were genetically identical, except three workers that differed by only one codon position. Because these microgynes have features of both queens and workers, their functional significance in the colony is not yet clear

Association between Repeated Unpredictable Chronic Mild Stress (UCMS) Procedures with a High Fat Diet: A Model of Fluoxetine Resistance in Mice

Major depressive disorder is a debilitating disease. Unfortunately, treatment with antidepressants (ADs) has limited therapeutic efficacy since resistance to AD is common. Research in this field is hampered by the lack of a reliable natural animal model of AD resistance. Depression resistance is related to various factors, including the attendance of cardiovascular risk factors and past depressive episodes. We aimed to design a rodent model of depression resistance to ADs, associating cardiovascular risk factors with repeated unpredicted chronic mild stress (UCMS). Male BALB/c mice were given either a regular (4% fat) or a high fat diet (45% fat) and subjected to two 7-week periods of UCMS separated by 6 weeks. From the second week of each UCMS procedure, vehicle or fluoxetine (10 mg/kg, i.p.) was administrated daily. The effects of the UCMS and fluoxetine in both diet conditions were assessed using physical (coat state and body weight) and behavioural tests (the reward maze test and the splash test). The results demonstrate that during the second procedure, UCMS induced behavioural changes, including coat state degradation, disturbances in self-care behaviour (splash test) and anhedonia (reward maze test) and these were reversed by fluoxetine in the regular diet condition. In contrast, the high-fat diet regimen prevented the AD fluoxetine from abolishing the UCMS-induced changes. In conclusion, by associating UCMS—an already validated animal model of depression—with high-fat diet regimen, we designed a naturalistic animal model of AD resistance related to a sub-nosographic clinical entity of depression

Earwig mothers consume the feces of their juveniles during family life

International audienceMany animals consume the feces of their conspecifics. This allo-coprophagy can have benefits, such as access to nutrients and symbionts, but also risks for consumers, mainly due to direct contact with pathogens that develop on feces. In the European earwig Forficula auricularia, mothers and juveniles live in nests lined with their feces. This surprising habit allows juveniles to consume the feces of their siblings during family life and provides them with nutritional benefits when mothers provide low care. However, it was unclear whether earwig mothers also practice allo-coprophagy, and whether this behaviour is motivated by their nutritional needs. Here, we set up four types of experimental families in which we manipulated the nutritional needs of mothers and/or juveniles and measured the effects on the production of feces by the juveniles, and the consumption of these feces by the mothers. Our results first show that fed juveniles produced more feces pellet in presence of fed compared to food-deprived mothers. We also found that, overall, about 50% of the mothers consumed juveniles feces. This consumption was both more likely and larger when the feces were produced by fed compared to food-deprived juveniles, while the proportion of feces pellets eaten was larger in fooddeprived compared to fed mothers. Overall, our results reveal that allo-coprophagy involves every family member and suggest that it can have both nutritional and non-nutritional benefits for earwig mothers. Allo-coprophagy could thus favour the maintenance of mothers in the nest and, more generally, promote the early evolution of family life

Love them all: mothers provide care to foreign eggs in the European earwig Forficula auricularia

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Data sets

Data sets of the three main question

Data from: Love them all: mothers provide care to foreign eggs in the European earwig Forficula auricularia

The rejection of foreign individuals is considered a central parameter in the evolution of social life. Within family units, parents are typically thought to reject foreign offspring to ensure that their investment into care is directed towards their own descendants. Whereas selection for such kin bias is expected to be high when parental care is extended and involves numerous and energetically costly behaviours, it can be reduced when the acceptance of foreigners provide subsequent benefits to offspring and when alternative parental strategies limit the risk of clutch parasitism. In this study, we investigated the outcome of these conflicting selection pressures in the European earwig. Our results overall demonstrate that mothers do not eliminate foreign eggs, provide the same level of care to both foreign and own eggs (egg grooming, egg defense and maternal return) and pay the same costs of care in terms of weight loss and immunity when tending each type of eggs. We also show that foreign and own eggs exhibit similar development time, hatching success and lead to comparable juvenile quality. Interestingly, our results reveal that tending eggs (of any origin) reduces mothers’ weight loss during this long period, possibly due to egg cannibalism. Hence, these findings emphasize the difficulty to predict the occurrence of kin bias, and stress the need to broaden our knowledge on the net benefits of egg rejection for parents to better understand the general importance of kin bias in the evolution of pre-hatching parental care

Relations entre endosymbiotes Blochmannia et leur hôte, la fourmi Camponotus fellah avec hydrocarbures cuticulaires et mélanisation

International audienceCarpenter ants (genus Camponotus) have mutualistic, endosymbiotic bacteria of the genus Blochmannia whose main contribution to their hosts is alimentary. It was also recently demonstrated that they play a role in improving immune function as well. In this study, we show that treatment with an antibiotic produces a physiological response inducing an increase in both the quantity of cuticular hydrocarbons and in the melanization of the cuticle probably due to a nutritive and immunological deficit. We suggest that this is because it enhances the protection the cuticle provides from desiccation and also from invasions by pathogens and parasites. Nevertheless, the cuticular hydrocarbon profile is not modified by the antibiotic treatment, which indicates that nestmate recognition is not modified

Regulation of worker egg laying by larvae in a fission-performing ant

International audienceAnts provide one of the best examples of the division of labour in animal societies. In many species, although workers still have ovaries, they refrain from laying (haploid) eggs when a queen is present in the colony and, instead, dedicate themselves exclusively to domestic tasks. In monogynous species, workers generally begin laying eggs once the queen dies, which allows the colony's remaining resources to be invested in the workers' offspring. However, we found that in the fission-performing ant Aphae-nogaster senilis, worker reproduction was also inhibited by brood pheromones; the presence of larvae, irrespective of their ploidy or origin, inhibited egg laying by orphaned workers in a dose-dependent manner. The end result was that workers allocated resources to the larvae that were present in the colony before starting to lay their own eggs. We also found that, while the number of workers reared was proportional to the number of larvae provided, the number of queens reared tended to plateau at six, regardless of the number of totipotent larvae present. This finding concurs with what has been observed in colonies in the field and fits with what the theory of local resource competition predicts. One explanation is that one of the queens produced is likely to mate and replace her dead mother as the head of the colony. Therefore, by rearing the queen's brood after her death, workers may have an opportunity to prolong the life of the colony