Paralyzing Action from a Distance in an Arboreal African Ant Species

Due to their prowess in interspecific competition and ability to catch a wide range of arthropod prey (mostly termites with which they are engaged in an evolutionary arms race), ants are recognized as a good model for studying the chemicals involved in defensive and predatory behaviors. Ants' wide diversity of nesting habits and relationships with plants and prey types implies that these chemicals are also very diverse. Using the African myrmicine ant Crematogaster striatula as our focal species, we adopted a three-pronged research approach. We studied the aggressive and predatory behaviors of the ant workers, conducted bioassays on the effect of their Dufour gland contents on termites, and analyzed these contents. (1) The workers defend themselves or eliminate termites by orienting their abdominal tip toward the opponent, stinger protruded. The chemicals emitted, apparently volatile, trigger the recruitment of nestmates situated in the vicinity and act without the stinger having to come into direct contact with the opponent. Whereas alien ants competing with C. striatula for sugary food sources are repelled by this behavior and retreat further and further away, termites defend their nest whatever the danger. They face down C. striatula workers and end up by rolling onto their backs, their legs batting the air. (2) The bioassays showed that the toxicity of the Dufour gland contents acts in a time-dependent manner, leading to the irreversible paralysis, and, ultimately, death of the termites. (3) Gas chromatography-mass spectrometry analyses showed that the Dufour gland contains a mixture of mono- or polyunsaturated long-chain derivatives, bearing functional groups like oxo-alcohols or oxo-acetates. Electrospray ionization-mass spectrometry showed the presence of a molecule of 1584 Da that might be a large, acetylated alkaloid capable of splitting into smaller molecules that could be responsible for the final degree of venom toxicity

A Non-lethal Water-based Removal-reapplication Technique for Behavioral Analysis of Cuticular Compounds of Ants

International audienc

Chemical characterization of contact semiochemicals for host-recognition and host-acceptance by the specialist parasitoid Cotesia plutellae (Kurdjumov)

Cotesia plutellae is a specialist parasitoid of Plutella xylostella. This specificity is potentially under the control of several factors before and after oviposition. Thereby, the stimuli that lead female parasitoids to host locations and to oviposition, might be at the basis of the specificity. We explore here the response of C. plutellae females exposed to host cuticular lipids. A total cuticular lipid extract of host caterpillars was fractionated into a hydrocarbon fraction and a non-hydrocarbon fraction. Neither fraction alone had any effect on oviposition behaviour in C. plutellae but the hydrocarbon fraction alone did seem to have a positive effect on the rate of antennal contact by the females. To induce oviposition behaviour, both fractions were necessary and reflect cooperation between at least one compound in each fraction. Identification of cuticular lipids shows that hydrocarbons were dominant (77%). Non-hydrocarbon compounds were mainly represented by 15-nonacosanone (18% of the total lipid extract). This ketone is rare in insect cuticle lipids and is thought to originate from the cabbage epicuticle where it is dominant with n-C29 and 14- and 15-nonacosanol also found among the cuticular lipids of the host caterpillar. (Résumé d'auteur

1-(3-Phenyl-1H-pyrazol-5-yl)-1,2,3,4-tetrahydroquinoxaline-2,3-dione

In the title compound, C17H12N4O2, the mean plane of the pyrazole ring is nearly perpendicular to that of the tetrahydroquinoxalinedione moiety [dihedral angle = 86.92 (7)°]. The phenyl ring is disordered over two orientations in a 0.556 (4):0.444 (4) ratio. In the crystal, molecules are connected by bifurcated N—H...(N,O) and N—H...(O,O) hydrogen bonds, generating (100) sheets. Aromatic π–π stacking [shortest centroid–centroid separation = 3.5307 (8) Å] links the sheets into a three-dimensional network. A short N...O contact [2.8198 (19) Å] is present

ESI-MS/MS Analysis of Phenolic Compounds from Aeonium arboreum Leaf Extracts and Evaluation of their Antioxidant and Antimicrobial Activities

Aeonium is a genus of succulents belonging to the Crassulaceae family. Their importance in traditional medicine has stimulated both pharmacological and chemical research. In this study, we optimized extraction, separation, and analytical conditions using a high performance liquid chromatographic method coupled with electrospray ionization mass spectrometry by the negative mode (HPLC-ESI-MS) in order to, for the first time, determine thirty-four compounds from Aeonium arboreum leaves. Twenty-one of them are assigned among which are sixteen flavonoids and five phenolic acids. FRAP, TAC, DPPH, and ABTS•+ radical scavenging were used to evaluate antioxidant activity. The obtained IC50 values ranged from 0.031 to 0.043 mg.mL−1 for DPPH and between 0.048 and 0.09 mg·mL−1 for ABTS•+. Antimicrobial activity was also assessed. The obtained minimum inhibitory concentrations (MIC) of these extracts ranged from 12.5 to 50 µg·mL−1 against Micrococcus luteus, Listeria ivanovii, Staphylococcus aureus, Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, and Fusarium oxysporum, and from 25 to 50 µg·mL−1 against Candida albicans. Therefore, these extracts can be considered as a potential source of biological active compounds

Host-Specific Myrmecophily and Myrmecophagy in the Tropical Coccinellid Diomus thoracicus in French Guiana

International audienc

Comparison of the effect of time and doses of the <i>Crematogaster striatula</i> Dufour gland extracts applied topically on termite workers.

<p>The doses correspond to the equivalent of one, three or six Dufour gland extracts (N: normal state of the termites that are active; P = paralysis; D: Death). Statistical comparison. Friedman χ² = 20.8; df = 3; P = 0.00011; <i>Post-hoc</i> tests; control <i>vs</i>. 1 gland: NS; control <i>vs</i>. 3 glands: P = 0.0011; control <i>vs</i>. 6 glands: P = 0.0002.</p

Mass of the peaks from Fig. 2 and the corresponding identification according to Daloze et al. 1987, 1991 [33], [34].

<p>Note that several components have similar masses and fragmentations.</p