The Drosophila antenna: ultrastructural and physiological studies in wild-type and lozenge mutants

Abstract

The physiology and ultrastructure of the antenna in Drosophila melanogaster have been examined in wild-type and lozenge mutants. Scanning electron microscopy (SEM) of sensilla on the antennal surface has revealed that in the wild-type the basiconic sensilla contain linear arrays of pores connected by longitudinal furrows and transected by shorter furrows. Sensilla trichodea also are shown to have pores, as revealed by examining transverse sections by transmission electron microscopy (TEM); these data directly address a longstanding controversy. Coeloconic sensilla, previously described as "pit sensilla" and as "grooved" sensilla, are shown to rise directly from the antennal surface, as opposed to lying below the antennal surface in pits; the previously observed grooves correspond to the junctions between bundled, finger-like projections. This description of coeloconic sensilla is supported by analysis of lz mutants, in which the projections of coeloconic sensilla splay apart. Coeloconic sensilla are also shown to undergo duplication on the lz3 antenna. Physiological recordings from the antenna show that responses to all odorants tested are severely decreased in lz mutants. Measurements made from different parts of the antenna show similar defects. Evidence is provided that both the physiological and ultrastructural defects map to the lz locus.

Odorant response of individual sensilla on theDrosophila antenna

“…These data showed that s. basiconica fell into different functional types, with different types responding to different subsets of odors, and distributed in different subregions of the antennal surface. There are few if any data from s. trichodea and s. coeloconica of Drosophila, and in fact until recently there has been controversy as to whether s. trichodea were likely to have olfactory function (Venkatesh and Singh, 1984;Stocker, 1994;Riesgo-Escovar, et al, 1997).…”

“…The -220 s. basiconica fall into two morphological subtypes: large s. basiconica are 2-3.5 ~um in diameter (Venkatesh and Singh, 1984) and approximately 10 ~um in height (Riesgo-Escovar et al, 1997); small s. basiconica are approximately 1.7 ~um in diameter and 8 jam in height (Riesgo-Escovar et al, 1997). Both classes of s. basiconica contain pores through which odors are believed to pass, and they contain either 2 or 4 neurons.…”

“…The anatomy of these sensilla has been described in some detail (Venkatesh and Singh, 1984;Stocker, 1994;Riesgo-Escovar et al, 1997). The -220 s. basiconica fall into two morphological subtypes: large s. basiconica are 2-3.5 ~um in diameter (Venkatesh and Singh, 1984) and approximately 10 ~um in height (Riesgo-Escovar et al, 1997); small s. basiconica are approximately 1.7 ~um in diameter and 8 jam in height (Riesgo-Escovar et al, 1997).…”

Drosophila as a focus in olfactory research: Mapping of olfactory sensilla by fine structure, odor specificity, odorant receptor expression, and central connectivity

“…The surface of the funiculus bears three major types of sensilla: the conspicuous, sharp-tipped trichoid sensilla, the translucent, club-shaped basiconic sensilla, and the tiny, coeloconic sensilla with prominent sockets (Fig. 1) (Link, 1983;Mindek, 1968;Riesgo-Escovar et al, 1997b;Venkatesh and Singh, 1984). Electrophysiological recordings have assigned an olfactory function to all of them (Clyne et al, 1997;de Bruyne et al, 2001;Siddiqi, , 1991see below).…”

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

“…Some mutants show morphological deficiencies, such as those on the lozenge gene implicated in the development of the antennae and palps. These mutants show a complete absence of basiconic sensilla on the antenna (Riesgo-Escovar et al, 1997a), along with a reduction in size and absence of pores on the basiconic sensilla on the palps (Riesgo-Escovar et al, 1997b). Electrophysiological responses from the palps and antennae, as well as behavioural responses to olfactory stimulants in lozenge mutants are strongly reduced compared to wild-type flies (Venard and Stocker, 1991;Riesgo-Escovar et al, 1997a,b).…”