LONG-TERM AND SHORT-TERM EFFECT OF CUCURBITACIN CONSUMPTION ON ACALYMMA-VITTATUM (COLEOPTERA, CHRYSOMELIDAE) FITNESS

Efforts to explain the evolution of cucurbitacin phagostimulation in m any luperine Chrysomelidae have focused primarily on the ecological be nefits derived from consuming these bitter compounds. Little attention has been given to the physiological costs that may result from ingest ing cytotoxic triterpenes. To understand the current factors that stab ilize the response of luperines to cucurbitacins we quantified the eff ect of cucurbitacin consumption on larval growth rate and survivorship , adult longevity, age at Ist reproduction; and fecundity in Acalymma vittatum (F.), the striped cucumber beetle. Larvae that fed on roots h igh in cucurbitacins gained weight more quickly than, and survived as well as, larvae that developed on roots with only trace amounts of bit terness. We found no significant differences in the fitness traits of females reared from eclosion until death on diets excluding cucurbitac ins, featuring 1 short pulse of cucurbitacins, consisting of a choice between cucurbitacin-laden and cucurbitacin-free food, and containing only foods rich in cucurbitacins, However, males fed 1 short pulse of dietary cucurbitacins lived significantly longer than males that ate n o cucurbitacins or males that ate cucurbitacins throughout their adult lives. The data suggest that the physiological costs associated with cucurbitacin consumption in A. vittatum are minimal and are counteract ed by advantages from short-term consumption of cucurbitacins. This is consistent with observations of a marked gustatorial sensitivity towa rd cucurbitacins that disappears after beetles have consumed enough co mpound to embitter their tissues.