Meeting Abstract
Chemical signals are increasingly recognized as triggers of defensive traits; however, less is known about their role in triggering changes in offensive traits. We explored the role of chemical signals in the induction of an herbivore offense, the morphology of radular teeth in Lacuna spp. Lacuna produce pointed teeth when consuming macroalgae and blunt teeth when consuming diatom epiphytes on eelgrasses. To determine whether L. vincta and L. variegata produce a default radular tooth type in the absence of chemical cues, we fed snails artificial diets amended with freeze-dried ground kelps, diatoms, eelgrass or Romaine lettuce. Snails fed diets containing lettuce, kelp, and eelgrass produced pointed teeth. Only snails fed diets with diatoms switched from pointed to blunt-shaped teeth, suggesting that pointed teeth are the default morphology and that a chemical cue originating from diatoms triggers the production of the alternate morphology. To confirm the latter, diatom epiphytes from eelgrass were extracted and partitioned into polar and non-polar fractions. L. vincta with pointed teeth were maintained in filtered seawater, fed Romaine lettuce, and exposed to polar or non-polar fractions. Non-polar fractions did not affect the number of snails producing blunt teeth. However, blunt teeth were produced more frequently in animals exposed to high concentrations of polar fractions, confirming that a waterborne polar chemical from diatoms can trigger the alternate morphology in L. vincta. Further work is needed to identify the signaling molecule and determine if it cues morphological changes in other gastropods.
