Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>) |
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Authors: | Carmen?Rossini Alexander?Bezzerides Andrés?González Maria?Eisner Email author" target="_blank">Thomas?EisnerEmail author |
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Institution: | (1) Facultad de Química, Universidad de la República, General Flores 2124, 1157 Montevideo, Uruguay;(2) Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA |
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Abstract: | Summary. Evidence is presented that pyrrolizidine alkaloid acquired
by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva
from Crotalaria foodplants is incorporated in part into the scales
of the adult. A single forewing of a male or female moth may contain in
the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2%
of the moths systemic monocrotaline content. Based on estimates of the number
of scales per forewing, the monocrotaline content of individual scales is calculated
to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale,
respectively. This amounts to concentrations of about 1 and 3%, values roughly at
a par with the average systemic concentration (0.5-0.6%) previously determined
for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid
in the moths scale coating could account for the promptness with which adult Utetheisa are
rejected by spiders. It is suggested further that chemical impregnation of scales with substances
deterrent to predators may be more widespread among insects than generally assumed. |
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Keywords: | Chemical defense Arctiidae pyrrolizidine alkaloid moth scales spider predation |
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