Mayolenes: Labile defensive lipids from the glandular hairs of a caterpillar ( Pieris rapae )

Abstract

Larvae of the European cabbage butterfly, Pieris rapae (Pieridae), are beset with glandular hairs, bearing droplets of a clear oily secretion at their tip. The fluid consists primarily of a series of chemically labile, unsaturated lipids, the mayolenes, which are derived from 11-hydroxylinolenic acid. In bioassays with the ant Crematogaster lineolata, the secretion was shown to be potently deterrent, indicating that the fluid plays a defensive role in nature.chemical defense ͉ predation ͉ Lepidoptera ͉ Formicidae T he European cabbage butterfly, Pieris rapae, is a widely distributed insect. Native to Eurasia and North Africa, it was accidentally introduced into Canada in about 1860, from where it spread over most of North America. It also has become established in Bermuda, Australia, Hawaii, and other Pacific Islands (1). As a larva, it prefers plants of the crucifer and caper families (Brassicaceae, Capparidaceae), and it is a common pest on cabbage, Brussel sprouts, and cauliflower (1). Pursuant to a study of the defenses of a number of larval insects, we noted the caterpillars of P. rapae to be beset with glandular hairs, such as pierid larvae had been reported to possess (2), but had never been investigated. In P. rapae, these hairs are arranged in rows along the full length of the body. Their product is a clear oily fluid that collects as droplets at the tip of the hairs (Fig. 1). On the assumption that this secretion might be protective and responsible in part for P. rapae's extraordinary adaptive fitness, we looked into both the repellency and chemistry of the fluid. We found the secretion to be potently deterrent to ants, and to consist primarily of a series of unsaturated lipids, which we named the mayolenes. Here, we present these results.** Materials and Methods P. rapae. Secretion was obtained from larvae of a laboratory population of P. rapae maintained on cabbage plants (Brassica oleraceae). The larvae used in the ant bioassays stemmed either from laboratory-laid or field-collected eggs.Crematogaster lineolata. The ant of choice is one we maintain in the laboratory specifically for predation purposes. Colonies were collected in eastern Connecticut, including at the Trinity College Field Station at Church Farm, Ashford.Ant Bioassay l (Acceptability of P. rapae Larvae and Tenebrio Molitor Larvae). Trials were carried out in individual Petri dishes (5 cm diameter), the floor of which was roughened by sand-blasting to provide for an improved locomotory surface (the sides of the dish were Teflon-coated and thereby rendered escape-proof). An individual ant was first introduced by itself into the dish, and its behavior was videotaped (with time track) for 5 min (the control period), providing a record of its spontaneous cleaning activities [antennal wiping with forelegs (Fig. 2E); foreleg wiping with mouthparts (Fig. 2F); dragging of mouthparts against substrate; regurgitating]. A P. rapae larva (of measured length; second instar) was then introduced, having been transferred into the dish on a small piece...

Pinoresinol: A lignol of plant origin serving for defense in a caterpillar

“…1 H-NMR-spectroscopic analyses of crude, unfractionated larval-secretion samples showed that the secretion consisted largely of the mayolenes described earlier (11). In addition, the spectra reproducibly showed several signals that appeared to belong to a lessabundant, previously unidentified component (Fig.…”

“…We had noted the fluid to contain a series of structurally labile linolenic acid derivatives, the mayolenes (6 in Fig. 3), which we demonstrated to be protective against ants (Crematogaster lineolata) (11). We have found pinoresinol itself to also be deterrent to ants (bioassay with Formica exsectoides), indicating that the compound could be part of the armamentarium of the larva.…”

“…We here report the presence of pinoresinol in the defensive secretion of a caterpillar, the larva of Pieris rapae, the cabbage butterfly, one of the world's most familiar lepidopterans (10). We had earlier reported on the composition of this secretion, produced as droplets by glandular hairs on the back and flanks of the larva (11) (Fig. 2).…”

The Prosternal Gland in Pacific Northwest Butterfly Larvae with Preliminary Chemical Analyses of Emissions

“…Larval chemical defense in many pierid species is attributable to oily droplets attached to the tips of dorsal setae. Smedley et al (2002) showed that in Pieris rapae (L.) these droplets contain unsaturated lipids (mayolenes) that repel ants. Neophasia menapia larvae do not carry oily droplets on their setae (James & Nunnallee 2011) and may rely instead upon the prosternal gland for defense.…”

Composition and antimicrobial activity of fatty acids detected in the hygroscopic secretion collected from the secretory setae of larvae of the biting midge Forcipomyia nigra (Diptera: Ceratopogonidae)

“…In other insects, similar dorsal glandular setae or spines bearing viscous, oily droplets that are not antimicrobial. In lepidopteran larvae and hemipteran nymphs the secreted substances provide a form of defence (Carver, 1991;Smedley et al, 2002;Shiojiri and Takabayashi, 2005;Schroeder et al, 2006) or help in the search for the host-plant (Takabayashi et al, 2000).…”