Experimental demonstration of close‐range olfaction and contact chemoreception in the Brazilian harvestman,Iporangaia pustulosa

Abstract

AbstractWe studied the ability to detect food by close‐range olfaction and contact chemoreception in the harvestmanIporangaia pustulosaMello‐Leitão (Opiliones: Laniatores: Gonyleptidae). We first tested the reaction of individuals towards tasteless (pure agar), aversive (agar with salt), and food‐intake stimulating substrates (agar with saccharose). Only the substrate containing saccharose was consumed. Contact (mainly with legs II) was necessary for detection of the agar and, before ingestion, the stimulus was always tapped with legs I. In the second experiment, we observed the behavior of individuals in an arena with a screened plastic box containing pieces ofTenebrio molitorL. (Coleoptera: Tenebrionidae) larvae. Individuals spent more time on the box containing food than on the control. In the third experiment, in an arena identical to that used in Experiment 2, we introduced a live but motionlessT. molitorlarva in the box. There was no difference between experimental and control treatments. We also observed the behavior ofI. pustulosain an arena containing live isopods. In first capture attempts, isopods were only detected upon contact, mainly with legs I. Our results suggest that (i)I. pustulosais capable of detecting food only by its chemical properties; (ii) food with weak odor may not be detected by close‐range olfaction; and (iii) legs I and II are important for food detection but, before ingestion, legs I are used to examine potential food items.