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Strangers in the dark: behavioral and biochemical evidence for trail pheromones in Hawaiian tree snails

Holland, Brenden S., Gousy‐Leblanc, Marianne, Yew, Joanne Y.
Invertebrate biology 2018 v.137 no.2 pp. 124-132
adults, chemical communication, insects, juveniles, long chain fatty acids, mammals, mass spectrometry, snails, threatened species, trail pheromones
The importance of pheromones in insect and mammal social systems is well documented, but few studies have addressed the role of pheromones in land snail behavior. In this investigation, we used a series of behavioral trials and direct analysis in real time mass spectrometry (MS) to test the hypothesis that land snails use mucous trails in orientation and chemical communication. We worked with six endemic Hawaiian land snail species in four genera, three subfamilies, and two families. We tested conspecific trail following in five of these species, and trail following occurred at a statistically significant frequency for each of the species tested (n=181, p‐values ranged <0.0001–0.0494). Percentage of conspecific trials that showed trail following ranged 66.7–94.1%. None of the interspecific tests revealed evidence of trail following among species (n=105, with p‐values of 0.0577–0.5000). Juvenile achatinelline snails did not follow trails of conspecific juveniles (n=30, p=0.5722) or adults (n=30, p=0.4278), nor did adults follow juvenile trails (n=30, p=0.5722). Comparative MS analysis of adult and juvenile trails showed distinct chemical signatures in the two groups. Signals corresponding to medium‐ and long‐chain fatty acids and other unidentified small molecules were present in adult but not in juvenile trails. Considered together, these results support the hypotheses that trail following could serve an important social and reproductive function. This discovery provides evidence for the presence of an ephemeral tree snail pheromone, which could have important implications for the conservation of these increasingly rare and threatened species.