Preliminary characterization of response-eliciting components of earthworm extract

Abstract

Fifteen garter snakes ( Thamnophis sirtalis) reliably spent more time and tongue flicked more frequently at a dish containing earthworm extract than a dish containing distilled water when these were presented simultaneously for two minute intervals. The discriminability of the earthworm extract was directly related to its concentration. Garter snakes with their vomeronasal ducts sutured closed did not respond differentially to earthworm extract and water under these test conditions. Thus their ability to discriminate earthworm extract from water in this bioassay was dependent upon a functional vomeronasal system. Earthworm extract retains its biological activity after boiling at 100°C for 15 minutes and after lyophilization. Its effectiveness is not altered by changes in pH. Snakes continued to respond differentially to extracts with pH 2, 5–6 or 11. Chloroform extractions of the acid, neutral and alkaline earthworm extract yielded activity primarily in the water layer. The small amount of activity in the chloroform layer was removed by use of a drying agent. Bradford dye-binding tests indicated the presence of protein in the active fractions.