Biology subjects

Karpati, Z.

Publications and source records attributed to Karpati, Z..

3 recordsLinked to original sources

bioRxiv2024

A chemically defined oviposition attractant and repellent of Black Soldier Flies (Hermetia illucens)

Black Soldier Flies (BSF), Hermetia illucens, are industrially important species. They can consume large amounts of spoilt organic material as larvae and bio-convert it to more useful biomass. Female BSF lay eggs in crevices adjacent to spoilt organic materials that serve as an oviposition attractant. These kairomones are central to maximising rearing efforts, yet the composition and origin of oviposition cues remain undefined, and no synthetic oviposition attractants are currently available. This work aimed to identify key components of naturally occurring oviposition attractants and to formulate an effective synthetic alternative for BSF. We have developed a novel oviposition assay and found larval food- and frass-based attractants to be the most effective at centralizing egg laying. We have identified the volatile compounds in the headspaces of putative attractants and established that the antennae of the female flies respond to some of these compounds. Behavioural validation using synthetic compounds allowed us to generate a mixture of 5 compounds (p-cresol, decanal, sulcatone, pentanoic acid, acetophenone) that cues oviposition as efficiently as currently used natural oviposition attractants. We also identified a synthetic mixture that deters oviposition in BSF. The synthetic attractant and repellent we generated are likely to simplify BSF rearing in research and industrial settings.

neuroscience↗

bioRxiv2022

The alarm pheromone and alarm response of the clonal raider ant

Ants communicate via an arsenal of different pheromones produced in a variety of exocrine glands. For example, ants release alarm pheromones in response to danger to alert their nestmates and to trigger behavioral alarm responses. Here we characterize the alarm pheromone and the alarm response of the clonal raider ant Ooceraea biroi, a species that is amenable to laboratory studies but for which no pheromones have been identified. During an alarm response, ants quickly become unsettled, leave their nest pile, and are sometimes initially attracted to the source of alarm, but ultimately move away from it. We find that the alarm pheromone is released from the head of the ant and identify the putative alarm pheromone as a blend of two compounds found in the head, 4-methyl-3-heptanone and 4-methyl-3-heptanol. These compounds are sufficient to induce alarm behavior alone and in combination. They elicit similar, though slightly different behavioral features of the alarm response, with 4-methyl-3-heptanone being immediately repulsive and 4-methyl-3-heptanol being initially attractive before causing ants to move away. The behavioral response to these compounds in combination is dose-dependent, with ants becoming unsettled and attracted to the source of alarm pheromone at low concentrations and repulsed at high concentrations. While 4-methyl-3-heptanone and 4-methyl-3-heptanol are known alarm pheromones in other more distantly related ant species, this is the first report of the chemical identity of a pheromone in O. biroi, and the first alarm pheromone identified in the genus Ooceraea. Identification of a pheromone that triggers a robust, consistent, and conserved behavior, like the alarm pheromone, provides an avenue to dissect the behavioral and neuronal mechanisms underpinning chemical communication.

animal behavior and cognition↗

bioRxiv2018

Trace impurities in test stimuli can seriously compromise chemosensory studies

The discovery of olfactory receptors and major technological advances have greatly accelerated our understanding of chemosensory mechanisms. However, some of this rapid progress may be compromised by inadequate knowledge or characterization of the purity of chemical stimuli used to challenge olfactory or other chemoreceptors when mapping their response profiles. Here, we provide strong evidence that the presence of trace impurities in test stimuli can completely obscure true ligand-receptor relationships. DmOR7a, an olfactory receptor of the vinegar fly (Drosophila melanogaster) has been reported to respond to several long-chain aliphatic ligands such as a putative Drosophila pheromone1, the pheromone of the silkworm moth Bombyx mori2, and a common fatty acid, linoleic acid3. By contrast, we show that DmOR7a responds with high sensitivity to volatile impurities and degradation products present in minute quantities in authentic standards of those compounds, but not to the standards themselves. Responses to impurities can easily go unnoticed due to two main factors. First, the sensitivity of receptors to key ligands may be greater than that of analytical chemistry instruments used to check sample purity. Second, the concentration of highly volatile impurities in an odour puff may be orders of magnitude higher than the main component of a sample, due to the large differences in vapour pressures between the impurities and the main component. Issues concerning impurities are not limited to studies on olfaction that use odour puffs to characterize receptor-ligand interactions, but may affect all studies on chemosensation, from molecular biology and in-silico predictions to behaviour. Purity, which is crucial in receptor-ligand studies, is always implied, but rarely checked rigorously. To avoid misinterpretations, a proper account of all compounds present in test stimuli and an unequivocal confirmation of ligand affinity should accompany chemosensory studies.

neuroscience↗