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Experience-based behavioral and chemosensory changes in the generalist insect herbivore Helicoverpa armigera exposed to two deterrent plant chemicals.

Zhou D, van Loon JJ, Wang CZ - J. Comp. Physiol. A Neuroethol. Sens. Neural. Behav. Physiol. (2010)

Bottom Line: In dual-choice cotton leaf disk and pepper fruit disk arena assays, caterpillars reared on a normal artificial diet were strongly deterred by strychnine and strophanthin-K.Electrophysiological tests revealed that the deterrent-sensitive neurons in taste sensilla on the maxillae of caterpillars reared on each deterrent-containing diet displayed reduced sensitivity to the two chemicals compared with the caterpillars reared on normal diets.We conclude that the experience-dependent behavioral plasticity was partly based on the reduced sensitivity of taste receptor neurons and that the desensitization of taste receptor neurons contributed to the cross-habituation to the two chemicals.

View Article: PubMed Central - PubMed

Affiliation: Institute of Zoology, The Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China.

ABSTRACT
Behavioral and electrophysiological responses of larvae of the polyphagous moth species Helicoverpa armigera to two plant-derived allelochemicals were studied, both in larvae that had been reared on a diet devoid of these compounds and in larvae previously exposed to these compounds. In dual-choice cotton leaf disk and pepper fruit disk arena assays, caterpillars reared on a normal artificial diet were strongly deterred by strychnine and strophanthin-K. However, caterpillars reared on an artificial diet containing strychnine were insensitive to strychnine and strophanthin-K. Similarly, caterpillars reared on an artificial diet containing strophanthin-K were also desensitized to both deterrent chemicals. Electrophysiological tests revealed that the deterrent-sensitive neurons in taste sensilla on the maxillae of caterpillars reared on each deterrent-containing diet displayed reduced sensitivity to the two chemicals compared with the caterpillars reared on normal diets. We conclude that the experience-dependent behavioral plasticity was partly based on the reduced sensitivity of taste receptor neurons and that the desensitization of taste receptor neurons contributed to the cross-habituation to the two chemicals.

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a Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. b Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. c Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. d Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. e Spike frequencies (spikes/s; mean ± SE, n = 12) of the two different neurons activated by 1 mM strophanthin-K of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. Bar values that have no letters in common differ significantly (t test, P < 0.05)
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Fig2: a Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. b Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. c Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. d Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. e Spike frequencies (spikes/s; mean ± SE, n = 12) of the two different neurons activated by 1 mM strophanthin-K of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. Bar values that have no letters in common differ significantly (t test, P < 0.05)

Mentions: Strychnine and strophanthin-K elicited relatively weak responses from the lateral sensilla styloconica. Response frequency of strychnine increased significantly from 0.01 to 0.1 mM; the response frequency of strophanthin-K increased significantly from 0.1 to 1 mM. The two chemicals elicited strong responses from the medial sensilla styloconica of the normal diet-reared caterpillars (Figs. 2a, b, 4b, e, respectively), demonstrating that this sensillum contains deterrent neurons that are considerably more sensitive to strychnine and strophanthin-K than neurons in the lateral sensillum. The deterrent neurons in the medial sensilla styloconica of caterpillars reared on artificial diet containing strychnine were significantly less sensitive to strychnine than in those of caterpillars reared on normal artificial diet when tested at 0.1, 1 and 2 mM (P < 0.05, Figs. 2c, 4c). Deterrent taste neurons of caterpillars reared on artificial diet containing strophanthin-K also produced significantly weaker responses to 0.1 and 1 mM strychnine than caterpillars reared on normal artificial diet (P < 0.01, P < 0.05, respectively, Figs. 2c, 4d). Similarly, H. armigera reared on artificial diet containing strychnine were significantly less sensitive to 1 and 2 mM strophanthin-K compared with caterpillars reared on normal artificial diet (P < 0.05, P < 0.001, respectively; Figs. 2d, 4f). Caterpillars reared on artificial diet containing strophanthin-K also had significantly weaker responses to 0.1, 1 and 2 mM strophanthin-K compared with caterpillars reared on normal artificial diet (P < 0.01, P < 0.05, P < 0.01, respectively; Figs. 2d, 4g). Furthermore, strychnine elicited responses from only one neuron in medial sensilla styloconica (Fig. 4b). However, strophanthin-K elicited responses from two neurons in medial sensilla styloconica, a more abundant larger amplitude spike type and a less abundant smaller amplitude spike type (Fig. 4e). The mixture of strychnine and strophanthin-K also elicited responses in which the same two spike types were observed, demonstrating that the neuron producing the more abundant and larger amplitude of the two spike types activated by strophanthin-K is the neuron responding to strychnine (Fig. 4b, e, h). Further analysis showed that the spike frequency of the neuron responsive to strychnine in the caterpillars reared on strychnine or strophanthin-K diet was significantly decreased when compared with normal diet-reared caterpillars (P < 0.01; Fig. 2e). However, the spike frequency of the neuron producing the less abundant smaller amplitude spikes did not differ significantly between caterpillars reared on normal diet and those reared on the diets containing the deterrents (P > 0.05; Fig. 2e). Sucrose elicited equally strong responses from the lateral sensilla styloconica irrespective of the diet to which the caterpillars had been exposed (Fig. 3). Similarly, responses of the inositol-sensitive neuron in the medial sensilla styloconica were equal for the caterpillars reared on the three different diets (Figs. 3, 4).Fig. 2


Experience-based behavioral and chemosensory changes in the generalist insect herbivore Helicoverpa armigera exposed to two deterrent plant chemicals.

Zhou D, van Loon JJ, Wang CZ - J. Comp. Physiol. A Neuroethol. Sens. Neural. Behav. Physiol. (2010)

a Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. b Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. c Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. d Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. e Spike frequencies (spikes/s; mean ± SE, n = 12) of the two different neurons activated by 1 mM strophanthin-K of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. Bar values that have no letters in common differ significantly (t test, P < 0.05)
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Related In: Results  -  Collection

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Fig2: a Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. b Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neurons in the two sensilla styloconica of H. armigera caterpillars reared on normal artificial diet from neonate to fifth instar. c Dose-response curves for strychnine; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. d Dose-response curves for strophanthin-K; spike frequencies (spikes/s; mean ± SE, n = 12) of the deterrent neuron in medial sensilla styloconica of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. e Spike frequencies (spikes/s; mean ± SE, n = 12) of the two different neurons activated by 1 mM strophanthin-K of H. armigera caterpillars reared on normal artificial diet, artificial diet containing strychnine or artificial diet containing strophanthin-K during development to the fifth instar. Bar values that have no letters in common differ significantly (t test, P < 0.05)
Mentions: Strychnine and strophanthin-K elicited relatively weak responses from the lateral sensilla styloconica. Response frequency of strychnine increased significantly from 0.01 to 0.1 mM; the response frequency of strophanthin-K increased significantly from 0.1 to 1 mM. The two chemicals elicited strong responses from the medial sensilla styloconica of the normal diet-reared caterpillars (Figs. 2a, b, 4b, e, respectively), demonstrating that this sensillum contains deterrent neurons that are considerably more sensitive to strychnine and strophanthin-K than neurons in the lateral sensillum. The deterrent neurons in the medial sensilla styloconica of caterpillars reared on artificial diet containing strychnine were significantly less sensitive to strychnine than in those of caterpillars reared on normal artificial diet when tested at 0.1, 1 and 2 mM (P < 0.05, Figs. 2c, 4c). Deterrent taste neurons of caterpillars reared on artificial diet containing strophanthin-K also produced significantly weaker responses to 0.1 and 1 mM strychnine than caterpillars reared on normal artificial diet (P < 0.01, P < 0.05, respectively, Figs. 2c, 4d). Similarly, H. armigera reared on artificial diet containing strychnine were significantly less sensitive to 1 and 2 mM strophanthin-K compared with caterpillars reared on normal artificial diet (P < 0.05, P < 0.001, respectively; Figs. 2d, 4f). Caterpillars reared on artificial diet containing strophanthin-K also had significantly weaker responses to 0.1, 1 and 2 mM strophanthin-K compared with caterpillars reared on normal artificial diet (P < 0.01, P < 0.05, P < 0.01, respectively; Figs. 2d, 4g). Furthermore, strychnine elicited responses from only one neuron in medial sensilla styloconica (Fig. 4b). However, strophanthin-K elicited responses from two neurons in medial sensilla styloconica, a more abundant larger amplitude spike type and a less abundant smaller amplitude spike type (Fig. 4e). The mixture of strychnine and strophanthin-K also elicited responses in which the same two spike types were observed, demonstrating that the neuron producing the more abundant and larger amplitude of the two spike types activated by strophanthin-K is the neuron responding to strychnine (Fig. 4b, e, h). Further analysis showed that the spike frequency of the neuron responsive to strychnine in the caterpillars reared on strychnine or strophanthin-K diet was significantly decreased when compared with normal diet-reared caterpillars (P < 0.01; Fig. 2e). However, the spike frequency of the neuron producing the less abundant smaller amplitude spikes did not differ significantly between caterpillars reared on normal diet and those reared on the diets containing the deterrents (P > 0.05; Fig. 2e). Sucrose elicited equally strong responses from the lateral sensilla styloconica irrespective of the diet to which the caterpillars had been exposed (Fig. 3). Similarly, responses of the inositol-sensitive neuron in the medial sensilla styloconica were equal for the caterpillars reared on the three different diets (Figs. 3, 4).Fig. 2

Bottom Line: In dual-choice cotton leaf disk and pepper fruit disk arena assays, caterpillars reared on a normal artificial diet were strongly deterred by strychnine and strophanthin-K.Electrophysiological tests revealed that the deterrent-sensitive neurons in taste sensilla on the maxillae of caterpillars reared on each deterrent-containing diet displayed reduced sensitivity to the two chemicals compared with the caterpillars reared on normal diets.We conclude that the experience-dependent behavioral plasticity was partly based on the reduced sensitivity of taste receptor neurons and that the desensitization of taste receptor neurons contributed to the cross-habituation to the two chemicals.

View Article: PubMed Central - PubMed

Affiliation: Institute of Zoology, The Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, People's Republic of China.

ABSTRACT
Behavioral and electrophysiological responses of larvae of the polyphagous moth species Helicoverpa armigera to two plant-derived allelochemicals were studied, both in larvae that had been reared on a diet devoid of these compounds and in larvae previously exposed to these compounds. In dual-choice cotton leaf disk and pepper fruit disk arena assays, caterpillars reared on a normal artificial diet were strongly deterred by strychnine and strophanthin-K. However, caterpillars reared on an artificial diet containing strychnine were insensitive to strychnine and strophanthin-K. Similarly, caterpillars reared on an artificial diet containing strophanthin-K were also desensitized to both deterrent chemicals. Electrophysiological tests revealed that the deterrent-sensitive neurons in taste sensilla on the maxillae of caterpillars reared on each deterrent-containing diet displayed reduced sensitivity to the two chemicals compared with the caterpillars reared on normal diets. We conclude that the experience-dependent behavioral plasticity was partly based on the reduced sensitivity of taste receptor neurons and that the desensitization of taste receptor neurons contributed to the cross-habituation to the two chemicals.

Show MeSH