Chemical communication in competitive interactions among tropical stream detritivores

Abstract

The role of chemical communication among competitors in streams is virtually unknown, especially in tropical streams. In this study, we experimentally examined the ability of four tropical invertebrate shredders (Anisocentropus kirramus Neboiss 1980, Lectrides varians Mosely 1953, Triplectides gonetalus Moser & Neboiss 1982 and Atalophlebia sp.) to detect and respond to chemical cues from competitors of the same species (conspecifics) or other species (heterospecifics — the other three species plus the crayfish Cherax cairnsensis Riek 1969). Behavioural trials indicated a shortterm response (a reduction in activity) to the addition of conspecific chemical cues but not to those of heterospecifics, including the crayfish. Litter breakdown experiments showed no mid-term effects of chemical cues from conspecifics or heterospecifics on breakdown rates. Our results indicate that chemical communication among tropical stream shredders is weak, suggesting that hydrodynamic cues and physical contact may be primary mechanisms mediating competitive interactions among these organisms.