Pheromonal advertisement of a nuptial gift by a male moth (Utetheisa ornatrix).

Abstract

Male Utetheisa ornatrix produce a courtship pheromone (hydroxydnaidal) that they derive from systemic pyrrolizidine alkaloid of planit origin. Pheromone titers in males correlate with systemic levels of alkalid and with the quantity of alkaloid tr itted to the female at mating. The male's emission of pheromone during courtship may therefore communicate his possession of protective akaloids and his capacity to provision the female. By mating preferentially with males endowed with hydroxydanaidal, females may ensure their acquisition of an alkaloid f git for use in egg defense. OH H O-C\ C-_.In many insect species, males contribute resources to the female at mating (2). Benefits to the female from these nuptial gifts include increased fecundity (3-5) and enhanced offspring survivorship (6). When male donations are of variable quality, females may assess the gifts and mate preferentially with males able to bestow the most worthy offerings. Precopulatory gift assessment by the female can occur visually when offerings are presented overtly, as in the form of prey items (3, 7). But if gifts are bestowed covertly, by transfer with the spermatophore, their prenuptial evaluation becomes problematic.Covert gift presentation occurs in the arctiid moth Utetheisa ornatrix, in which the males transmit protective pyrrolizidine alkaloids (for example, monocrotaline; structure I) to the females by seminal infusion (6). Mated females transfer alkaloid thus received, together with systemic alkaloid of their own, to the eggs, which are protected against predation as a result (6). Both males and females obtain their alkaloid from their larval food plants (Crotalaria spp.), thereby acquiring protection both for themselves (8,9) and their offspring. Males, in addition, use the alkaloid metabolically to produce a pheromone, hydroxydanaidal (structure H), that they emit from a pair of brushes (coremata) everted during close-range precopulatory interaction with the female (10). Males endowed with hydroxydanaidal have a higher mating success than those devoid of the pheromone (10). The females possess antennal chemoreceptors by which they could gauge hydroxydanaidal (11).The finding that hydroxydanaidal mediates male acceptance in courtship led to the suggestion that female Utetheisa might assess their suitor's defensive vigor (that is, their alkaloid content), as well as the male's alkaloid donating capacity, by quantitative appraisal of the pheromone (6,8,10). If so, males should contain pheromone titers proportional both to their intrinsic alkaloid load and to the quantity of alkaloid they bestow upon females. We here present laboratory data demonstrating that these quantitative relations hold and that males do indeed advertise their alkaloidal "worth" in the context of courtship. I II MATERIALS AND METHODSOur approach involved rearing males on diets containing various levels of monocrotaline and then assaying chemically for (i) the hydroxydanaidal content of the coremata, (ii) the quantity of monocrotaline transferred to femal...

Identification and Biosynthetic Studies of the Hydrocarbon Sex Pheromone in Utetheisa ornatrix

“…Larvae were reared on a pinto-bean diet mixed with seeds of the host plant, Crotalaria mucronata (Leguminoseae), as described (Dussourd et al 1991) in an environmental chamber under a L:D14:10 at 26°C at the University of Kansas. Pupae were shipped to Iowa State University, where they were sexed and allowed to emerge separately.…”

Temporal patterns of nutrition dependence in secondary sexual traits and their varying impacts on male mating success

“…avian plumage) or after maturation, but nutrition intake prior to maturation can affect the resources available to produce pigmentation or ornamentation (Ohlsson, Smith, Raberg, & Hasselquist, 2002;Taylor, Clark, & McGraw, 2011;Uetz, Papke, & Kilinc, 2002). On the other hand, energetically demanding behaviors such as elaborate courtship displays may be more strongly affected by adult (or current) diet, which has an impact on available energetic resources (Brown, 2011;Droney, 1996Droney, , 1998Dussourd, Harvis, Meiwald, & Eisner, 1991;Kolluru & Grether, 2004;Wedell, 1994). However, these trends in dietary life-history effects on behavioral and morphological traits are far from universal.…”

Sexually transmitted chemical defense in a moth (Utetheisa ornatrix)

“…An interesting feature of the mating strategy of Utetheisa is that the female does not accept males at random but shows preference for those of high PA content, which are able to bestow large alkaloidal gifts (19,20). She is capable of discerning such males, because they produce higher titers of a courtship pheromone.…”