Chemical defense: Bestowal of a nuptial alkaloidal garment by a male moth on its mate

Abstract

Males of the moth Cosmosoma myrodora (Arctiidae) acquire pyrrolizidine alkaloid by feeding on the excrescent fluids of certain plants (for instance, Eupatorium capillifolium). They incorporate the alkaloid systemically and as a result are protected against spiders. The males have a pair of abdominal pouches, densely packed with fine cuticular filaments, which in alkaloid-fed males are alkaloid laden. The males discharge the filaments on the female in bursts during courtship, embellishing her with alkaloid as a result. The topical investiture protects the female against spiders. Alkaloid-free filaments, from alkaloid-deprived males, convey no such protection. The males also transmit alkaloid to the female by seminal infusion. The systemic alkaloid thus received, which itself may contribute to the female's defense against spiders, is bestowed in part by the female on the eggs. Although paternal contribution to egg defense had previously been demonstrated for several arctiid moths, protective nuptial festooning of a female by its mate, such as is practiced by C. myrodora, appears to be without parallel among insects.pyrrolizidine alkaloid ͉ paternal investment ͉ predation ͉ Arctiidae ͉ Cosmosoma myrodora H ere we describe the behavior of a moth in which acquisition of pyrrolizidine alkaloid (henceforth, for simplicity, sometimes called alkaloid) plays a crucial role in defense. We demonstrate that the alkaloid is initially procured by the male from plants, and that the male derives protection against spiders (Nephila clavipes) as a result. We demonstrate further that the male allocates some of the acquired alkaloid to a cottony mass of cuticular filaments that he keeps tucked away in the abdomen and that he discharges on the female in bursts during courtship. We show that the alkaloid-laden filaments thus bestowed by the males protect the female against N. clavipes, whereas alkaloidfree filaments from control males that had no access to alkaloid provide no such protection. We show further that the female receives additional alkaloid from the male through seminal infusion, an endowment that can itself contribute to her defense and that she shares with the eggs. The moth, Cosmosoma myrodora, known as the scarlet-bodied wasp moth, is a stunningly beautiful member of the family Arctiidae (Fig. 1A) (1).The study was undertaken at a field site, the Archbold Biological Station, Lake Placid, Highlands County, FL, and in our laboratories.Henceforth we refer to the moth by its generic designation. For the male's mass of filaments, we adopt the term flocculent. Materials and MethodsCosmosoma. Field-collected moths were obtained at the Archbold Station by baiting with air-dried roots of Eupatorium capillifolium (Asteraceae), a plant that we found to contain pyrrolizidine alkaloids (see below). We had previously noted Cosmosoma to be attracted to such bait. The roots were hung in clusters, about 1.5 m above the ground, and were kept moistened. They were inspected intermittently throughout the night for visiting Cosmosoma that h...

Diet-Mediated Pheromones and Signature Mixtures Can Enforce Signal Reliability

“…Females benefit from mating with males that produce high amounts of the alkaloid, because the male then transfers some of the stored alkaloid to the female during mating, and this is incorporated into her eggs protecting them from predation (see also Eisner and Meinwald, 2003). Additionally, male Cosmosoma myrodora moths cover female mates with a sequestered alkaloid during coupling, providing both partners with protection from predators, such as spiders, during lengthy copulations (Conner et al, 2000). The role of this alkaloid as a pheromone is unclear, but like other species where a pheromonal role of the alkaloid has been established (see above examples), C. myrodora females receive male-sequestered alkaloids via semen and transfer some of the alkaloid to their eggs for protection.…”

Effectiveness of tiger moth (Lepidoptera, Arctiidae) chemical defenses against an insectivorous bat (Eptesicus fuscus)

“…The IGs, PAs and CGs are sequestered from plants as the larvae feed on allelochemically laden tissues (Rothschild et al 1970;Black 1976;Conner et al 1981;Bowers 1991;NickischRosenegk & Wink 1993;Wink & Nickisch-Rosenegk 1997;Eisner & Meinwald 2003). Some PAs are collected by adults through plant visitation (Beebe 1955;Pliske 1975;Goss 1979;Boppré 1990;Conner et al 2000). Defensive chemicals may also be transferred between the sexes, male to female and transovarianly from mother to offspring (Dussourd et al 1988;González et al 1999;Conner et al 2000;Rossini et al 2001;Bezzerides & Eisner 2002;Hartmann et al 2004).…”

“…Some PAs are collected by adults through plant visitation (Beebe 1955;Pliske 1975;Goss 1979;Boppré 1990;Conner et al 2000). Defensive chemicals may also be transferred between the sexes, male to female and transovarianly from mother to offspring (Dussourd et al 1988;González et al 1999;Conner et al 2000;Rossini et al 2001;Bezzerides & Eisner 2002;Hartmann et al 2004). Sequestered defense compounds may be altered to special insect forms (Hartmann et al 2003;Hartmann et al 2004).…”

Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth ( Utetheisa ornatrix )

“…At the very least, one would expect other species of Arctiidae that also acquire PA from the diet (Hartmann 1999;Conner et al 2000;Hartmann & Ober 2000) to conform to the example set by Utetheisa. But it is conceivable that entirely different substances, both of exogenous and of endogenous origin, will also be found to be used as scale additives.…”