Loss of gustatory responses to pyrrolizidine alkaloids after their extensive ingestion in the polyphagous caterpillar Estigmene acrea

Abstract

SUMMARY Electrophysiological recordings from taste sensilla of the caterpillar Estigmene acrea with the pyrrolizidine alkaloid (PA) seneciphylline N-oxide demonstrated that extensive feeding on plants rich in PAs caused a loss in response of the PA-sensitive cell in the lateral styloconic sensillum on the galea. The effect could be repeated using pure PAs fed to the insect in synthetic diets and by injection of PA into the hemolymph. The sensitivity loss lasted for approximately two hours and was less pronounced in individuals that had been reared on PA-containing food. Behavioral experiments and field observations demonstrate a parallel reduction in responsiveness to PAs and to PA-containing plants.

Complex effects of parasitoids on pharmacophagy and diet choice of a polyphagous caterpillar

“…First, we collected 120 late-instar G. incorrupta caterpillars from a natural population near Oracle, AZ, USA in April 2007. Because of the caterpillars' varied and unknown feeding histories prior to collection and the possibility that the PA feeding experience modifies subsequent feeding response to PAs (Bernays et al 2003), we manipulated their feeding experience prior to the feeding assay by individually confining the caterpillars in 162.7 ml plastic cups, with half randomly assigned to Senecio longilobus (PA-containing plant), and the other 60 assigned to Malva parviflora (PA-free plant) for 24 h. Next, we placed all caterpillars that had fed on their assigned host plant (N = 116) individually into clean cups, each with an impaled PA-treated glass fiber disc (as described above), and allowed them to feed for 24 h. After this PA-feeding assay period, the glass fiber discs were removed for drying and weighing (as described above), and the caterpillars were weighed, dissected, and examined under 509 magnification for the presence of endoparasitoids. Dissections mostly revealed caterpillars lacking any signs of parasitism (N = 96), a set of caterpillars containing a single early-instar tachinid larva surrounded by melanized tissue and often in conjunction with a single macrotype tachinid egg on the caterpillar's outer exoskeleton (N = 7), and a set of caterpillars harboring a single macrotype tachinid egg but no embedded tachinid larva (N = 13).…”

Enemies lost: parallel evolution in structural defense and tolerance to herbivory of invasive Jacobaea vulgaris

“…Qualitative defenses (toxins such as alkaloids and glucosinolates) act against generalist herbivores and are cheaper to produce, but specialist herbivores are often adapted to these defenses (Berryman 1988;Strauss et al 2002). Specialist herbivores often use these compounds as a cue to locate their host plant, as an oviposition and feeding stimulant, and may sequester the qualitative plant defense compounds for their own defense (van der Meijden 1996;Hay et al 1990;Müller et al 2001;Bernays et al 2003;Macel and Vrieling 2003;Nieminen et al 2003). In the invasive area where specialist herbivores are absent, plant can shift their allocation to produce more of the cheap qualitative defenses against generalist herbivores without having the side effect of attracting the specialist herbivores.…”

Gustatory Sensitivity and Food Acceptance in Two Phylogenetically Closely Related Papilionid Species: Papilio hospiton and Papilio machaon

“…Medial and lateral sensilla were tested with KCl (50 mM), NaCl (1, 10, 100, 500 mM), nicotine (0.1, 1, 10 mM), myo -inositol (0.1, 1, 10 mM), glucose, fructose and sucrose (1, 10, 100, 250 mM). Although a higher concentration of salt stimulates deterrent cells and induces aversive behaviour in the two species, 50 mM KCl was used to dissolve all compounds except for NaCl, with the aim of optimizing recording conditions and signal-noise ratio for better spike identification [4], [6], [10]–[12], [14], [21]–[36].…”