I.Tomassini Barbarossa

Influence of age on the electroantennogram response of the female blowfly (Phormia regina) (Diptera: Calliphoridae)

Abstract By means of electroantennogram recording techniques, we have monitored the antennal olfactory sensitivity, from the time of eclosion until complete egg maturation, of female blowflies (Phormia regina) fed either a protein diet or a protein free one. The tested stimuli were swormlure-4 (SL-4) which is a potent lure for calliphorid flies, 1-hexanol as a reference stimulus and air as a control. After taking the electroantennograms, egg and ovarian development were evaluated. Stimulation with SL-4 and 1-hexanol evoked electroantennograms increasing in amplitude with age regardless of whether or not flies were fed protein during the first 5 days of adult life. In the protein-fed flies eggs were fully developed whereas those of the no-protein group remained undeveloped. The peak olfactory sensitivity occurs at a time when the female fly begins to search for an oviposition substrate.

Morphology and EAG mapping of the antennal olfactory receptors in Dacus oleae

EAGs were recorded from various locations on the flagellar surface of the antennae of the olive fly Dacus oleae stimulated with compounds of behavioural significance to this species. This information was compared with data on the typology and distribution patterns of the olfactory sensilla. Results showed that: a) 3 types of olfactory sensilla are present on the antennae: long basiconica, short grooved basiconica and trichodea; b) 1‐hexanol, ethanol and volatiles belonging to the oily fraction of the olive pulp are the strongest stimuli, while those of the water fraction are little or not effective; c) EAG amplitude values vary as a function of the recording location on the flagellar surface; d) a significant correlation was found, for 2 stimuli of the oily fraction, between EAG amplitude and population density of long sensilla basiconica, thus suggesting this type as specifically responding to these substances.

Reflex cardiac response to various olfactory stimuli in the blowfly, Protophormia terraenovae

In the present investigation it is shown that a reflex change in the heart activity of Protophormia flies is evoked by olfactory stimulation with several volatile substances, and particularly with those which are repellent for blowflies. Among these, i-pentanal and hexanal vapours evoked a fast, highly persistent cardiac response, whereas in the case of hexanol and ammonia vapours the response resulted slower and could be suppressed as a function of repeated stimulation.

Effects of ATP and cAMP on salt and sugar (responses of chemosensilla in the blowfly)

Abstract 1. 1. The addition of cAMP to stimulating solutions of NaCl, fructose (furanose sugar), sucrose, or glucose (pyranose sugars) decreases the responsiveness of labellar chemosensilla in Phormia . 2. 2. The addition of ATP, while decreasing the responsiveness to NaCl or fructose enhances the responsiveness to glucose and sucrose. 3. 3. The inhibiting effect of ATP on NaCl or fructose responses is suppressed by GDPsS, an inhibitor of adenylate cyclase (and thus of cAMP synthesis); moreover GDPsS further enhances the increase in response due to ATP when added to the sucrose or glucose solutions. 4. 4. Results suggest a possible involvement of cAMP and ATP in the taste reception mechanism in the blowfly.

Effects of octopaminergic substances on the labellar lobe spreading response in the blowfly Protophormia terraenovae.

The effectiveness of labellar taste input in evoking the feeding response of labellar lobe spreading in Protophormia was greatly increased by injecting flies with clonidine or DL-octopamine. This effect was suppressed when either drug was administered together with yohimbine; when injected alone, the latter determined a strong decrease in the feeding responses. Drug treatment did not determine variations in labellar taste input or evoke spontaneous activity in the denervated muscle. These results suggest that the injected substances lower the feeding-related reflex threshold at the CNS level.

Sensitivity to albumin and its terminal amino acids of labellar taste chemoreceptors in Protophormia terraenovae (Diptera: Calliphoridae)

Abstract Stimulation with bovine serum albumin (BSA) evokes spikes discharges from three receptor cells of the labellar chemosensilla in Protophormia , the “sugar” cell being the most sensitive. Confrontation of the spike frequency profiles across all three chemoreceptor cells by the vector space analysis suggests that l -alanine (the C-terminal amino acid of the BSA molecule), but not l -aspartic acid (N-terminal amino acid), may account for the stimulator effectiveness of BSA.

GTP and cGMP both enhance, while cAMP depresses, the response to a furanose sugar of taste chemosensilla in the blowfly Protophormia terraenov ae

Abstract 1. 1. The stimulatory effect of a fructose (furanose sugar) solution on labellar taste chemosensilla in the blowfly Protophormia terraenovae is enhanced in the presence of GTP or cGMP. 2. 2. The increase in stimulating effectiveness due to cGMP is double with respect to that due to GTP. 3. 3. Chemosensillar responsiveness to the fructose solution is enhanced by the addition of an adenylate cyclase inhibitor, but is decreased by the addition of a phosphodiesterase inhibitor; these results are consistent with an inhibitory effect of cAMP.

EFFECTS OF ATP ON THE INTERACTION OF ALBUMIN AND ITS C-TERMINAL AMINO-ACID L-ALANINE WITH THE SUGAR RECEPTOR CELL IN PROTOPHORMIA-TERRAENOVAE (DIPTERA, CALLIPHORIDAE)

Abstract Stimulation with bovine serum albumin (BSA) and its C-terminal amino acid l -alanine evokes spike activity from the “sugar” cell of the labellar chemosensilla in Protophormia. The presence of ATP in the BSA solution strongly enhances this effect, but is pH-dependent. On the contrary, addition of ATP to the l -alanine solution inhibits the “sugar” cell response regardless of pH. Reception mechanisms for BSA and l -alanine are discussed.

Effects of GTP, cGMP and cAMP on the salt response of taste labellar chemosensilla in the blowfly, Protophormia terraenovae

Abstract 1. 1. The addition of GTP and cGMP to an NaCl stimulating solution has an inhibitory effect on “cation” receptor cell responsiveness of taste chemosensilla in the blowfly, Protophormia terraenovae. 2. 2. The responsiveness of the same taste sensilla to an NaCl solution is enhanced by the addition of an adenylate cyclase inhibitor, but decreased by the addition of a phosphodiesterase inhibitor; this confirms the inhibitory effect of cAMP.

Variations in salt sensitivity related to type and position of labellar chemosensilla in Protophormia terraenovae

Abstract Electrophysiological responses to NaCl in the concentration range 1–1000 mM were obtained from each of the 11 intermediate and 13 large labellar chemosensilla in the blowfly Protophormia terraenovae . Up to three of the four chemoreceptor cells associated with each chemosensillum responded to NaCl in both sensillum types; the spike discharges of two of these cells were analysed and cross-compared. Differences in chemoreceptor sensitivity and response pattern resulted between intermediate and large sensilla. Sensitivity differences were found, by means of the cluster analysis, within each sensillum type in relation to sensillar topology and are discussed in the light of a possible spatial contribution to the sensory coding process.