The chemistry of sexual selection.

Abstract

The moth Utetheisa ornatrix (Lepidoptera: Arctiidae) is protected against predation by pyrrolizidine alkaloids that it sequesters as a larva from its foodplants. At mating, the male transfers alkaloid to the female with the spermatophore, a gift that the female supplements with alkaloid of her own and transmits to the eggs. Eggs are protected as a result. The male produces a pheromone, hydroxydanaidal, that he derives from the alkaloid and emits from a pair of extrusible brushes (coremata) during precopulatory interaction with the female. Males rendered experimentally alkaloid-free fail to produce the pheromone and are less successful in courtship. The male produces the pheromone in proportion both to his alkaloid load and to the amount of alkaloid he transfers to the female. The pheromone could thus serve as an indication of male "worth" and provide a basis for female choice. Utetheisa females are promiscuous and therefore are able to accrue multiple nuptial gifts (alkaloid and nutrient, both transmitted with the spermatophore). They use sperm selectively, favoring those of larger males. Larger males in nature are also richer in alkaloid. Females therefore reinforce after copulation the choice mechanism they already exercise during courtship.

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

“…After being attracted to the female, through the long distance sex pheromone, the male courts the female by releasing hydroxydanaidal, derived from host plant pyrrolizidine alkaloids, obtained during larval feeding on seeds of Crotalaria spp. (Eisner and Meinwald 1995). The alkaloids are toxic, and female U. ornatrix may derive protection from predators by receiving these additional alkaloids during mating (Conner and Weller 2004).…”

Cognition in Invertebrates

“…Airborne sound and substrate vibration are most important signals for all three behavioral conditions of communication (intersex, predator-prey, social interactions;Cocroft and Rodriguez, 2005). Although the sensory, ecological, and evolutionary aspects of these communication systems have been often studied in great detail in invertebrates (e.g., sound communication in insects: Henry (1994), Gerhardt and Huber (2002); substrate vibration in spiders: Barth (2002), and in insects: Hö lldobler and Roces (2000), Cocroft (2003); visual signaling in butterflies: Eisner and Aneshansley (1973); chemical signaling: (Hö lldobler and Wilson (1990), Eisner and Meinwald (1995); see also Section 1.26.2), very little is known about the cognitive dimensions of these communication systems, for example, how the innate mechanisms interact with experience-dependent developmental processes, how the innate mechanisms are related to internal and external context conditions, whether learning shapes the communication process, and if communication leads to individual recognition (see discussion below). More is known in these respects about the ritualized movements ('waggle dance') used by honeybees to communicate distance and direction from the hive or the swarm to important places (potential nest sites, feeding, water or resin places).…”

Gene-silencing reveals the functional significance of pheromone biosynthesis activating neuropeptide receptor (PBAN-R) in a male moth

“…In general, moth male-produced pheromones are considered to have many functions, such as aphrodisiacs to stimulate female receptivity during courtship (11,14); inducing calling behavior (15); as an arrestant of females to enable copulation (16,17); or as a male-to-male competition inhibitor (12,(18)(19)(20). Close-range male chemical cues have also been proposed as a trait used by females to assess male quality (21).…”