Linoleic acid as corpse recognition signal in a social aphid

Pollen-Derived Fatty Acids and Amino Acids Mediate Variance in Pollinator Visitation

Pollinators help maintain functional landscapes and are sensitive to floral nutritional quality. Both proteins and lipids influence pollinator foraging, but the role of individual biochemical components in pollen remains unclear. We conducted an experiment comprising common garden plots of six plant species (Asteraceae, Rosaceae, Onagraceae, Boraginaceae, and Plantaginaceae). These plots were treated with low concentrations of agrochemicals, including fertilizer, herbicide, and a combination of both to induce intra-specific variation in floral chemistry. We recorded insect visitation to inflorescences over two years and eight sites in Dublin, Ireland. We analyzed the pollen amino acid and fatty acid content, quantifying the concentrations of 51 fatty acids and 17 amino acids of the six focal plant species across the four agrochemical treatments. We tested relationships between the pollen composition and the insect visitation matrix as well as an insect trait matrix including sociality, body size, nesting behavior, and whether the insect was a bee or hoverfly. We found: (i) the agrochemical treatments did not affect the biochemical composition of the pollen; (ii) there were many strong associations between fatty acids, amino acids, insect traits, and visitation; and (iii) specific compounds with strong associations (montanic acid, cysteine, and proline) explained more of the variance in insect abundance (honeybees, bumble bees, and hoverflies) than the total amino acid or fatty acid concentrations in the pollen. Our results suggest it is important to evaluate the contribution of individual biochemical compounds in pollen to insect visitation, and also that different insect species respond to different pollen compounds.

Social aphids: emerging model for studying insect sociality

Sociality is also evolved in parthenogenetic herbivorous hemipteran aphids, encompassing species with complex life history traits and significant social diversity. Owing to their interesting biological characteristics comparing to other social insect groups, social aphids can be a good model for studying insect sociality. Here, we review the species, behavior, and trait diversity of social aphids, and present recent findings on environmental, physiological, and molecular regulations of caste differentiation and behavior in social aphids. We propose the unique value of social aphids in investigating the evolution and mechanisms of insect sociality as well as future research directions using the social aphid model, including social evolution, caste differentiation, behavioral polymorphism, morphological plasticity, physical mechanics, and interspecific interactions.

Oleic acid triggers burial behavior in a termite population through an odorant binding protein

Social insects maintain hygienic conditions through their social immunity behaviors. Among these behaviors, burial behavior of termites is central for protecting healthy individuals from corpses. Many factors trigger burial behavior, and it is generally believed that chemicals released by corpses, such as oleic acid, are the most important cues for triggering burial behavior in termites. However, the contribution of the olfactory system to this behavior remains unclear. Here we report an odorant binding protein (OBP) that transports oleic acid and triggers burial behavior in Coptotermes formosanus Shiraki. We demonstrated that CforOBP7 is highly expressed in the antennae of workers. Fluorescent competition binding experiments exhibited that CforOBP7 has a strong affinity for oleic acid. Furthermore, the antennal response to oleic acid was significantly reduced, and oleic acid-triggered burial behavior was also inhibited in CforOBP7-silenced termites. We conclude that CforOBP7 governs the burial behavior of C. formosanus triggered by oleic acid.