Behavioural responses to amino acids and related compounds, including propionic acid, by adult Biomphalaria glabrata (Say), a snail host of Schistosoma mansoni

Volatile Foraging Kairomones in the Littoral Zone: Attraction of an Herbivorous Freshwater Gastropod to Algal Odors

Volatile organic compounds (VOCs) produced by algae and cyanobacteria are primarily responsible for odors in fresh waters. Among other functions, VOCs may serve as important infochemicals in biofilms of benthic primary producers. VOCs liberated by benthic, mat-forming cyanobacteria can be used as habitat-finding cues by insects, nematodes, and possibly other organisms. We developed a new gastropod behavioral assay that allows detection of food preference without offering food, thus allowing the distinction between taste, which requires direct contact with the food source, and the detection of odorous infochemicals, which work over distance. We demonstrated that VOCs released from disintegrated cells of a benthic, mat-forming, green alga (Ulothrix fimbriata) are food-finding cues ("foraging kairomones") that attract the herbivorous freshwater snail Radix ovata. A mixture of three C5 lipoxygenase compounds and 2(E),4(E)-heptadienal that mimic the major VOCs released by U. fimbriata attracted the snails, whereas neither the mixture of C5 compounds nor 2(E),4(E)-heptadienal were effective when given alone. This study suggests that VOCs can play a steering role as infochemicals in freshwater benthic habitats, as has been established for many organismic interactions in terrestrial ecosystems.

Chemotaxis of Caenorhabditis elegans during simultaneous presentation of two water-soluble attractants, l-lysine and chloride ions

Lysine and chloride ions are water-soluble attractants for Caenorhabditis elegans. When chemotaxis behavior to either of these attractants was assayed separately, the radial concentration gradients of 3 M lysine and 0.1 M ammonium chloride had similar potencies for attracting worms. However, when the concentration gradients of lysine and ammonium chloride at these concentrations were presented simultaneously, worms preferred lysine to ammonium chloride more than expected from the results obtained in separate experiments, suggesting the presence of an interaction between these two sensory information pathways within the nervous system. Chemotaxis behavior toward the radial concentration gradient of one of these attractants superimposed on a uniform concentration of the other attractant showed that the chemotaxis was augmented or attenuated by the ammonium chloride background depending on the background concentration, and attenuated by the lysine background, further supporting the interaction between the two sensory information pathways.