On the island of Sardinia the lepidopteran Papilio hospiton uses Ferula com- munis as exclusive host plant. However, on the small island of Tavolara, adult females lay eggs on Seseli tortuosum, a plant confined to the...On the island of Sardinia the lepidopteran Papilio hospiton uses Ferula com- munis as exclusive host plant. However, on the small island of Tavolara, adult females lay eggs on Seseli tortuosum, a plant confined to the island. When raised in captivity on Seseli only few larvae grew beyond the first-second instar. Host specificity of lepidopterans is determined by female oviposition preferences, but also by larval food acceptance, and adult and larval taste sensitivity may be related to host selection in both cases. Aim of this work was： （i） to study the taste sensitivity of larvae and ovipositing females to saps of Ferula and Seseli; （ii） to cross-compare the spike activity of gustatory receptor neurons （GRNs） to both taste stimuli; （iii） to evaluate the discriminating capability between the two saps and determine which neural code/s is/are used. The results show that： （i） the spike responses of the tarsal GRNs of adult females to both plant saps are not different and therefore they cannot discriminate the two plants; （ii） larval L-lat GRN shows a higher activity in response to Seseli than Ferula, while the opposite occurs for the phagostimulant neurons, and larvae may discriminate between the two saps by means of multiple neural codes; （iii） the number of eggs laid on the two plants is the same, but the larval growth performance is better on Ferula than Seseli. Taste sensitivity differences may explain the absence of a positive relationship between oviposition preferences by adult females and plant acceptance and growth performance by larvae.展开更多
A morphofunctional investigation of the different neuronal subpopulations projecting through each of the nerves IV-VI emerging bilaterally from the terminal ab- dominal ganglion （TAG） was correlated with the octopam...A morphofunctional investigation of the different neuronal subpopulations projecting through each of the nerves IV-VI emerging bilaterally from the terminal ab- dominal ganglion （TAG） was correlated with the octopaminergic activity in the ganglion that controls the ovipositor movements associated with caUing behavior in the female gypsy moth Lymantria dispar. Tetramethylrodamine-dextran backfills from nerve stumps resulted in a relatively low number of TAG projections, ranging from 12 to 13 for nerve pair IV, 12 to 14 for nerve pair V, and 8 to 9 for nerve pair VI. Furthermore, as assessed by electrophysiological recordings, a number of fibers within each of these nerves displays spontaneous tonic activity, also when the ganglion is fully disconnected from the ventral nerve cord （VNC）. Octopamine （OA） applications to the TAG strongly enhanced the activ- ity of these nerves, either by increasing the firing rate of a number of spontaneously firing units or by recruiting new ones. This octopaminergic activity affected calling behavior, and specifically the muscle activity leading to cycling extensions of the intersegmental membrane （IM） between segments VIII and IX （ovipositor）. Our results indicate that in the female gypsy moth the octopaminergic neural activity of the TAG is coupled with ex- tensions and retractions oflM for the purpose of releasing pheromone, where motor units innervated by nerve pair IV appear antagonistic with respect to those innervated by nerve pair V.展开更多
文摘On the island of Sardinia the lepidopteran Papilio hospiton uses Ferula com- munis as exclusive host plant. However, on the small island of Tavolara, adult females lay eggs on Seseli tortuosum, a plant confined to the island. When raised in captivity on Seseli only few larvae grew beyond the first-second instar. Host specificity of lepidopterans is determined by female oviposition preferences, but also by larval food acceptance, and adult and larval taste sensitivity may be related to host selection in both cases. Aim of this work was： （i） to study the taste sensitivity of larvae and ovipositing females to saps of Ferula and Seseli; （ii） to cross-compare the spike activity of gustatory receptor neurons （GRNs） to both taste stimuli; （iii） to evaluate the discriminating capability between the two saps and determine which neural code/s is/are used. The results show that： （i） the spike responses of the tarsal GRNs of adult females to both plant saps are not different and therefore they cannot discriminate the two plants; （ii） larval L-lat GRN shows a higher activity in response to Seseli than Ferula, while the opposite occurs for the phagostimulant neurons, and larvae may discriminate between the two saps by means of multiple neural codes; （iii） the number of eggs laid on the two plants is the same, but the larval growth performance is better on Ferula than Seseli. Taste sensitivity differences may explain the absence of a positive relationship between oviposition preferences by adult females and plant acceptance and growth performance by larvae.
文摘A morphofunctional investigation of the different neuronal subpopulations projecting through each of the nerves IV-VI emerging bilaterally from the terminal ab- dominal ganglion （TAG） was correlated with the octopaminergic activity in the ganglion that controls the ovipositor movements associated with caUing behavior in the female gypsy moth Lymantria dispar. Tetramethylrodamine-dextran backfills from nerve stumps resulted in a relatively low number of TAG projections, ranging from 12 to 13 for nerve pair IV, 12 to 14 for nerve pair V, and 8 to 9 for nerve pair VI. Furthermore, as assessed by electrophysiological recordings, a number of fibers within each of these nerves displays spontaneous tonic activity, also when the ganglion is fully disconnected from the ventral nerve cord （VNC）. Octopamine （OA） applications to the TAG strongly enhanced the activ- ity of these nerves, either by increasing the firing rate of a number of spontaneously firing units or by recruiting new ones. This octopaminergic activity affected calling behavior, and specifically the muscle activity leading to cycling extensions of the intersegmental membrane （IM） between segments VIII and IX （ovipositor）. Our results indicate that in the female gypsy moth the octopaminergic neural activity of the TAG is coupled with ex- tensions and retractions oflM for the purpose of releasing pheromone, where motor units innervated by nerve pair IV appear antagonistic with respect to those innervated by nerve pair V.
