Neurophysiological and behavioural evidence for an olfactory function for the dorsal organ and a gustatory one for the terminal organ in Drosophila melanogaster larvae

Abstract

Multicellular electrophysiological responses from the dorsal organ on the cephalic lobes of third instar Drosophila melanogaster larvae (wild-type Canton S) stimulated with a cold-trapped banana volatile extract showed that this structure has an olfactory function in the fruit fly. Responses of the dorsal organ were also recorded to constituents of the banana volatile extract as they eluted from a gas chromatographic column (GC-coupled dorsal organ electrophysiology). The active chemostimulants were identified as 2-heptanone, isoamyl alcohol, hexyl acetate, hexanol and hexyl butyrate by gas chromatography-coupled mass spectrometry. Applying the same recording system to the terminal organ sensilla, no responses were obtained to either the banana volatile bouquet or its constituents. By contrast, high frequency multicellular responses were recorded in response to touching the terminal organ with the gustatory stimuli KCl and grapefruit juice; responses were absent on similar stimulation of the dorsal organ with either NaCl or KCl. This suggests a role for olfaction by the dorsal organ and for gustation by the terminal organ in Drosophila larvae.In a 7-mm high wind tunnel with a thin 1.2% agar floor, the Drosophila larvae showed odour-conditioned upwind responses in an air stream of 0.1 m/s bearing banana volatiles. Drosophila larvae responded best to the odour of cut bananas. A 1:1 mixture of the banana odour constituents 2-heptanone and hexanol (at either 50 or 100 µg source dose each) proved as attractive as the known larval attractants propionic acid and isoamyl acetate on their own at 100 µg, whereas hexanol and 2-heptanone on their own at a 100 µg source dose were less attractive. The stronger behavioural response to the banana volatile bouquet and to the binary mixture serves to underline the multireceptor nature of the dorsal organ response to food odour in Drosophila.

Oriented responses of grapevine moth larvae Lobesia botrana to volatiles from host plants and an artificial diet on a locomotion compensator

“…1-Hexanol caused a dose dependent increase in attraction and was the compound that induced the highest target vector response values from Lobesia larvae. This attraction indicates that 1-hexanol plays a fundamental role in the olfactory responses of these larvae, as has also been found for Drosophila melanogaster larvae (Cobb and Domain, 2000;Oppliger et al, 2000). 1-Hexanol was also tested here in 1:1 (v/v) binary mixtures with host plant compounds of other chemical classes.…”

Preliminary characterization of two atypical soluble guanylyl cyclases in the central and peripheral nervous system ofDrosophila melanogaster

“…Gyc-88E stained one neuron in each of the two terminal ganglia while Gyc-89Db stained 2-5 neurons in each of the terminal ganglia and 4-5 neurons in each of the two dorsal ganglia. The terminal ganglion innervates the maxillary organ, which is known to serve a gustatory function and has at least six different types of sensilla (Stocker, 1994;Heimbeck et al, 1999;Oppliger et al, 2000). The dorsal ganglion innervates the dorsal or antennal organ, which consists of seven different sensilla and is the main olfactory organ in larval Drosophila (Stocker, 1994;Heinbeck et al, 1999;Oppliger et al, 2000).…”

A microfluidics-based method for measuring neuronal activity in Drosophila chemosensory neurons

“…This method enables sensitive measurements of action potential patterns and shows whether responses are excitatory or inhibitory, but drawing final conclusions about the individual firing neuron is difficult, as each sensillum contains two to four neurons 14 . In the larva, multicellular electrophysiological measurements of the taste system have been performed, but this method is technically challenging and it is not clear how many taste neurons are housed in which sensillum 15 .…”

“…This method enables sensitive measurements of action potential patterns and shows whether responses are excitatory or inhibitory, but drawing final conclusions about the individual firing neuron is difficult, as each sensillum contains two to four neurons 14 . In the larva, multicellular electrophysiological measurements of the taste system have been performed, but this method is technically challenging and it is not clear how many taste neurons are housed in which sensillum 15 .Microfluidic devices have been used previously to image command interneurons (AVA) and sensory neurons (ASH) in the nematode Caenorhabditis elegans and for studies of axotomy in peripheral sensory neurons of Drosophila larvae [16][17][18] . To implement a similar strategy for Drosophila larval chemosensation, we developed a simple and widely applicable microfluidic chip.…”