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. 1999 May 11;96(10):5570-4.
doi: 10.1073/pnas.96.10.5570.

Sexually Transmitted Chemical Defense in a Moth (Utetheisa Ornatrix)

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Free PMC article

Sexually Transmitted Chemical Defense in a Moth (Utetheisa Ornatrix)

A González et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

The arctiid moth Utetheisa ornatrix is protected against predation by pyrrolizidine alkaloids (PA) that it sequesters as a larva from its food plant. Earlier work had shown that males transmit PA to the female with the sperm package and that the female bestows part of this gift on the eggs, protecting these against predation as a result. We now show that the female herself derives protection from the gift. Females deficient in PA are vulnerable to predation from spiders (Lycosa ceratiola and Nephila clavipes). If mated with a PA-laden male, the females become unacceptable as prey. The effect takes hold promptly and endures; females are unacceptable to spiders virtually from the moment they uncouple from the male and remain unacceptable as they age. Chemical data showed that the female allocates the received PA quickly to all body parts. We predict that other instances will be found of female insects being rendered invulnerable by receipt of sexually transmitted chemicals.

Figures

Figure 1
Figure 1
(A) Female Utetheisa emitting defensive froth. (Bar = 1 mm.) (B) Outcome of an encounter between a L. ceratiola spider and a PA-free Utetheisa from the − ♀ (− ♂) category. (Bar = 1 cm.)
Figure 2
Figure 2
Fate of Utetheisa moths in N. clavipes webs. Numbers above bars indicate sample sizes.
Figure 3
Figure 3
Fate of Utetheisa females in laboratory tests with L. ceratiola. All females were raised to be PA-free and were mated either with PA-laden males [− ♀ (+ ♂); solid bars] or with PA-free males [− ♀ (− ♂); open bars]. Numbers above bars give sample sizes. The discrimination against the [− ♀ (+ ♂)] females is significant (G test on pooled data; P < 0.0001).
Figure 4
Figure 4
Total PA content (A) and PA concentration (B) in three body components of 24 − ♀ (+ ♂) Utetheisa females whose only PA was that received at mating. The females were dissected within 0–2 h after mating. (B) The PA is shown to be equitably distributed in the three body components [single-factor ANOVA; P = 0.32].

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