Yves Quinet

Spatial specialization of the foragers and foraging strategy in Lasius fuliginosus (Latreille) (Hymenoptera, Formicidae)

SummaryThe spatial specialization inLasius fuliginosus was investigated in the field by a mass-marking of foragers with colors. In the spring, summer and autumn, foragers exhibit a high degree of persistence, with coefficients of fidelity between 83 and 96%, in using a particular foraging trail, in visiting a particular tree or shrub housing aphid colonies, and even micro-sites like a particular branch. A high degree of fidelity to particular temporary hunting ground areas has also been shown. Trail and aphid site fidelity persist for at least 1 to 3 months and are preserved through the hibernation period (about 5 months). However, in early spring, a period during which food sources are scarce, trail fidelity is lower (coefficient of fidelity: 57%).Spatial specialization develops quickly in foragers recruited to a new permanent food source. Once acquired, the specialization is not rigid since specialized honeydew collectors can shift from a no more rewarding aphid site to other aphid sites of the same trail on which they develop a secondary specialization.The ecological and behavioral aspects of the spatial specialization inL. fuliginosus are discussed with reference to the resource structure of the habitat.

Transcriptome Analysis in Venom Gland of the Predatory Giant Ant Dinoponera quadriceps: Insights into the Polypeptide Toxin Arsenal of Hymenopterans

Background Dinoponera quadriceps is a predatory giant ant that inhabits the Neotropical region and subdues its prey (insects) with stings that deliver a toxic cocktail of molecules. Human accidents occasionally occur and cause local pain and systemic symptoms. A comprehensive study of the D. quadriceps venom gland transcriptome is required to advance our knowledge about the toxin repertoire of the giant ant venom and to understand the physiopathological basis of Hymenoptera envenomation. Results We conducted a transcriptome analysis of a cDNA library from the D. quadriceps venom gland with Sanger sequencing in combination with whole-transcriptome shotgun deep sequencing. From the cDNA library, a total of 420 independent clones were analyzed. Although the proportion of dinoponeratoxin isoform precursors was high, the first giant ant venom inhibitor cysteine-knot (ICK) toxin was found. The deep next generation sequencing yielded a total of 2,514,767 raw reads that were assembled into 18,546 contigs. A BLAST search of the assembled contigs against non-redundant and Swiss-Prot databases showed that 6,463 contigs corresponded to BLASTx hits and indicated an interesting diversity of transcripts related to venom gene expression. The majority of these venom-related sequences code for a major polypeptide core, which comprises venom allergens, lethal-like proteins and esterases, and a minor peptide framework composed of inter-specific structurally conserved cysteine-rich toxins. Both the cDNA library and deep sequencing yielded large proportions of contigs that showed no similarities with known sequences. Conclusions To our knowledge, this is the first report of the venom gland transcriptome of the New World giant ant D. quadriceps. The glandular venom system was dissected, and the toxin arsenal was revealed; this process brought to light novel sequences that included an ICK-folded toxins, allergen proteins, esterases (phospholipases and carboxylesterases), and lethal-like toxins. These findings contribute to the understanding of the ecology, behavior and venomics of hymenopterans.

Defensive behaviour and biological activities of the abdominal secretion in the ant Crematogaster scutellaris (Hymenoptera: Myrmicinae).

Using bioassays, the defensive behaviour of Crematogaster scutellaris and the biological activities of its abdominal secretion were investigated. Beside classical aggressive behaviours such as grips, C. scutellaris workers performed frequent characteristic gaster flexions during interspecific encounters, sometimes tempting to apply their abdominal secretion topically on the enemy. The toxicity of the venom of C. scutellaris to other ants greatly differed among the species tested, some being killed after the topical application of only three droplets, while others were quite resistant to a dose of 90 droplets. All ant species tested were strongly and immediately repelled by a contact between their antennae or mouthparts with the venom of C. scutellaris. Abdominal secretion was never used during intraspecific interference and workers were resistant to a topical application of the venom of their own species. Intraspecific repellency was significant but moderate compared to interspecific one. Workers of C. scutellaris were never seen using their venom during prey capture. In conclusion, the main biological activity of the abdominal secretion of C. scutellaris seems to be its repellency to other ant species. This is supported by field experiments showing that Pheidole pallidula foragers were efficiently repelled at coexploited baits, allowing the monopolization of most prey by C. scutellaris.

Explosive food recruitment as a competitive strategy in the ant Myrmica sabuleti (Hymenoptera, Formicidae)

Summary:Myrmica sabuleti forms mature colonies of about one thousand workers and a few queens. Although living in dry and sunny biotopes, this species avoids foraging during the warmer hours of the day which correspond to the period of the maximum foraging activity of two sympatric species, Formica fusca and F. cunicularia. M. sabuleti is the most frequently observed species on the extrafloral nectaries of Vicia sativa, even during the warmer hours of the day, whereas F. fusca is the most frequent species during those hours at tubes of 1M sucrose solutions placed on the ground. In spite of this temporal segregation, the foraging activity of M. sabuleti and F. fusca overlaps two times a day (10:00‐11:00 am and 5:00‐8:00 pm). Newly discovered large food sources are exploited by M. sabuleti through an explosively increasing recruitment, whereas workers of F. fusca forage mainly individually. Interference between M. sabuleti and F. fusca was studied when offering sucrose solutions, large dead insects unretrievable by individual foragers of either species (cockroaches), medium-sized insects retrievable by single foragers of F. fusca but not by single M. sabuleti(larvae of Calliphora erythrocephala) and small insects (Drosophila) retrievable by individual foragers of both species. Owing to its rapid recruitment, M. sabuleti is able to displace F. fusca from sucrose solution and large dead prey during the overlaping of the activity cycles of both species. When medium-sized corpses are offered, the issue depends on the speed of the events. F. fusca is able to take the prey away only if it discovers it before M. sabuleti has recruited nestmates. Small dead prey do not lead to interference, but is taken by the first worker that finds it.

Furanocembranoid Diterpenes as Defensive Compounds in the Dufour Gland of the Ant Crematogaster brevispinosa rochai

Abstract Two new furanocembranoid diterpenes, crematofuran [(1R∗,11R∗,12R∗)-6,19:11,12-bisepoxycembra-3,6,8(19),15-tetraene] (1) and isocrematofuran [(1R∗,3S∗,4S∗)-3,4:6,19-bisepoxycembra-6,8(19),11,15-tetraene] (2), have been isolated from the Dufour gland secretion of the Brazilian ant Crematogaster brevispinosa rochai. Their structures, including the relative configuration, have been determined by a combination of NMR and molecular mechanics methods. The toxicity of 1 towards other ants is on the same level as that of nicotine. This is the first report of cembranoid diterpenes as defensive compounds in an ant.

Food recruitment as a component of the trunk-trail foraging behaviour of Lasius fuliginosus (Hymenoptera: Formicidae).

Field investigations showed that the ant Lasius fuliginosus combines stable foraging behaviour based on long-term memory and spatial specialization with more flexible actions, based on food recruitment. The use of food recruitment varies according to the season and the type of food. Baits of meat or large prey elicited recruitment during the major part of the year, except in the autumn, while baits of sugar elicited recruitment only in early spring, before the aphid colonies developed. A permanent trunk trail was established after a recruitment towards a newly discovered and stable source of carbohydrate food. This happened in early spring when the food sources were scarce or when spring migrating aphids were produced.

Five new furanocembrenoids from the venom of the ant Crematogaster brevispinosa ampla from Brazil

Abstract Five new furanocembrenoids (3–7) were isolated from the Dufour gland secretion of the Brazilian ant Crematogaster brevispinosa ampla. The structure of the major component was established by a detailed high-field 1D and 2D NMR study as the dibutanoate 3. Compounds 4 and 5 were shown to be the two isomeric monoacetate monobutanoates corresponding to 3, whereas 6 and 7 are the two isomeric monohydroxy monobutanoates.

(13E,15E,18Z,20Z)-1-Hydroxypentacosa-13,15,18,20-tetraen-11-yn-4-one 1-acetate, from the venom of a Brazilian Crematogaster ant

Abstract (13E,15E,18Z,20Z)-1-hydroxypentacosa-13,15,18,20-tetraen-11-yn-4-one 1-acetate, a new polyfunctionalized long chain derivative, was isolated from the venom of an as yet undetermined Crematogaster ant species from Brazil, and its structure established by a detailed high-field 1D and 2D NMR study.

The effects of the Brazilian antDinoponera quadriceps venom on chemically induced seizure models

Arthropod venoms are potential sources of neuroactive substances, providing new tools for the design of drugs. The aim of this study was to evaluate the effects of Dinoponera quadriceps venom (DqV) on seizure models in mice induced by pentylenetetrazole (PTZ), pilocarpine, and strychnine. In the PTZ model, intraperitoneal treatment with DqV (0.5mg/kg) increased the time until the first seizure and the percentage of survival (155.4±27.7s/12.5%, p<0.05) compared to the control group (79.75±3.97s/0%), whereas endovenous treatment (0.1 and 0.5mg/kg) decreased the time until the first seizure (0.1mg/kg: 77.83±5.3s versus 101.0±3.3s in the control group; 0.5mg/kg: 74.43±3.9s versus 101.0±3.3s for the control group, p<0.05). We did not observe significant changes in the pilocarpine- and strychnine-induced seizure models. In assays that measured oxidative parameters in the PTZ model, intraperitoneal treatment with DqV (0.5 and 2.0mg/kg) only decreased the levels of MDA and nitrite in the cortex. However, endovenous treatment with DqV (0.1 and 0.5mg/kg) increased the levels of MDA in the cortex and hippocampus and at a dose of 0.5mg/kg in the striatum. Moreover, increased in nitrite content was observed in all three of the brain regions analyzed. Taken together, the D. quadriceps venom caused both neuroprotective and neurotoxic effects in a PTZ-induced seizure model, and this effect was dependent on the route of administration used.

Trail following and stowaway behaviour of the myrmecophilous staphylinid beetle, Homoeusa acuminata, during foraging trips of its host Lasius fuliginosus (Hymenoptera: Formicidae)

SummaryThe behaviour of adultHomoeusa acuminata on trails of its hostLasius fuliginosus was investigated both in the field and in the laboratory. The beetles were active from May to September, accurately following the foraging trails of their hosts up to 20 metres from the nest. Most of the time, they were ignored by the ants, but if attacked they raised their abdomen as a possible appeasement or defensive behaviour. On trails the beetles most probably act as food robbers, feeding on prey collected by ants. The following method, called stowaway behaviour, was used by the beetles: when a beetle encountered an ant carrying a prey back to the nest it jumped on the prey, probably feeding on it while being transported.Laboratory experiments on circular artificial trails demonstrated thatH. acuminata follows a water extract of hindguts of the ants, the source of the trail pheromone. Both beetles and ants responded to an artificial trail of 0.03 hindgut equivalent per cm, but the mean distance followed by the beetles was about twelve times higher than that covered by the ants themselves. In contrast, experiments with solutions of the six fatty acids reported as the active components of the trail pheromone showed that the beetles did not respond at all, and that the ants only respond to the fatty acids at a very high concentration.