20-Hydroxyecdysone Deters Oviposition and Larval Feeding in the European Grapevine Moth, Lobesia botrana

Abstract

European grapevine moth females (Lobesia botrana, Lepidoptera Tortricidae) select an oviposition site by tasting the host plant surface and then gluing a single egg on berries from grapes or from several other host plant species. In doing so, females should avoid ovipositing on plants that are detrimental to their progeny. Do they sense the same deterrent compounds as larvae, despite the fact that they do not have access to the same compartments of the plants? We tested this hypothesis with 20-hydroxyecdysone (20E), purified from Leuzea carthamoides. Phytoecdysteroids are usually found inside plant tissues and accessible to larvae in an aqueous phase, while adults would access them only through the epicuticular wax. We first confirmed that larvae avoid feeding on 20E and that they taste 20E with their lateral sensilla styloconica, at a threshold of 10(-6) M. Then, we tested whether adult females avoid ovipositing on glass spheres sprayed with 20E. When given a choice, females avoided laying eggs on a treated surface, at a threshold of 8 ng/cm(2). In addition, they deposited significantly fewer eggs in the presence of 20E. Presuming that legs play an important role in assessing the oviposition substrate, we assessed the sensitivity of their taste receptors. In females, 14 taste sensilla are located on the ventral side of the last tarsus of the prothoracic leg. One group of these sensilla house one neuron that is sensitive to 20E, with a detection threshold of about 10(-7) M. The same molecule is thus sensed both in larvae and adults of L. botrana where it respectively inhibits feeding and oviposition.

Physiological responses of theDrosophilalabellum to amino acids

“…However, declining spike rates at higher tastant concentrations have been observed in several other insect species (Marion-Poll et al , 2002; Calas et al , 2006). All of these experiments followed a standard protocol in which sensilla are stimulated successively with progressively greater doses of tastant, and it is possible that these apparent declines represent adaptation of neurons during the course of the experiments.…”

Egg-laying rhythm in Drosophila melanogaster

“…Further, application of the JH analogue methoprene is found to mimic the SP-mediated stimulation of vitellogenic oocyte progression in sexually mature virgin females (Soller et al 1999). 20HE is known to deter oviposition, and females avoid laying eggs in the presence of 20HE (Calas et al 2006(Calas et al , 2007. Apoptosis is induced by 20HE in nurse cells of egg chambers at physiological concentrations (10 −7 M) (Soller et al 1999).…”

Level and distribution of 20-hydroxyecdysone during Pfaffia glomerata development

“…The potential ecological importance of 20E may be illustrated by several observations: (i) 20E deters oviposition and larval feeding (Calas et al, 2006); (ii) monophagous or oligophagous species feeding on host plants containing exogenous 20E were either deterred from feeding or showed abnormalities in growth and development (Blackford and Dinan, 1997); (iii) during sexual activity of the spider Tegenaria atrica 20E inhibits cannibalism and changes sex pheromone production (Trabalon et al, 2005); (iv) anomalous molting, immobility, reduced invasion, impaired development, and death were observed in nematodes exposed to 20E (Soriano et al, 2004);and, (v) 20E concentration increases in response to mechanical damage (Schmelz et al, 1998), insect herbivory (Schmelz et al, 1999), and application of methyl jasmonate (Schmelz et al, 1999). These findings suggest that the induction of PEs may protect plants from insect attack (Schmelz et al, 2002).…”