Pedal peptide/orcokinin-type neuropeptide signaling in a deuterostome: The anatomy and pharmacology of starfish myorelaxant peptide in Asterias rubens.

Pedal peptide (PP) and orcokinin (OK) are related neuropeptides that were discovered in protostomian invertebrates (mollusks, arthropods). However, analysis of genome/transcriptome sequence data has revealed that PP/OK-type neuropeptides also occur in a deuterostomian phylum-the echinoderms. Furthermore, a PP/OK-type neuropeptide (starfish myorelaxant peptide, SMP) was recently identified as a muscle relaxant in the starfish Patiria pectinifera. Here mass spectrometry was used to identify five neuropeptides (ArPPLN1a-e) derived from the SMP precursor (PP-like neuropeptide precursor 1; ArPPLNP1) in the starfish Asterias rubens. Analysis of the expression of ArPPLNP1 and neuropeptides derived from this precursor in A. rubens using mRNA in situ hybridization and immunohistochemistry revealed a widespread pattern of expression, with labeled cells and/or processes present in the radial nerve cords, circumoral nerve ring, digestive system (e.g., cardiac stomach) and body wall-associated muscles (e.g., apical muscle) and appendages (e.g., tube feet and papulae). Furthermore, our data provide the first evidence that neuropeptides are present in the lateral motor nerves and in nerve processes innervating interossicular muscles. In vitro pharmacological tests with SMP (ArPPLN1b) revealed that it causes dose-dependent relaxation of apical muscle, tube foot and cardiac stomach preparations from A. rubens. Collectively, these anatomical and pharmacological data indicate that neuropeptides derived from ArPPLNP1 act as inhibitory neuromuscular transmitters in starfish, which contrasts with the myoexcitatory actions of PP/OK-type neuropeptides in protostomian invertebrates. Thus, the divergence of deuterostomes and protostomes may have been accompanied by an inhibitory-excitatory transition in the roles of PP/OK-type neuropeptides as regulators of muscle activity.

Investigation of titania nanoparticles on behaviour and mechanosensory organ of Drosophila melanogaster.

Titania nanoparticles are used in food, cosmetic, medicine, paint and many more domestic items. Its extensive use has raised the threat to the physiological system and thus the functioning of the body. In the current study, the toxicity of TiO2 is checked by adding it in food and using Drosophila melanogaster as a model organism. Various concentrations of TiO2 (50, 100, 200, 250mg·L-1) toxicity was assessed via oral route exposure. Survivability, life-cycle, mechanosensory behaviour and structure of various mechanosensory organs were monitored as a read out of nanoparticle toxicity. TiO2 NPs generate reactive oxygen species which can modify multiple signalling pathways and thus can alter the development and behavioural pattern of the fly.

Chopper-stabilized gas chromatography-electroantennography: Part I. background, signal processing and example.

A new method that can improve gas-chromatography-electroantennographic detection (GC-EAD) by orders of magnitude through a technique known as chopper stabilization combined with matched filtering in colored noise is presented. The EAD is a physiological recording from the antenna of an insect which can be used to find compounds in the GC effluent that the antenna is able to detect, having important applications for pest control and understanding of chemical communication in nature. The new method is demonstrated with whole-animal male Helicoverpa zea antennal preparations for detection of major pheromone component (cis-11-hexadecenal) and compared to results obtained using traditional EAD recording techniques. Results indicate that chopper stabilization under these circumstances can increase odorant detection performance by a factor of approximately 10(4) over traditional methods. The time course of the response of the antenna is also better resolved under chopped conditions. Although the degree of improvement is expected to vary with insect species, odor, and insect preparation, under most circumstances a more sensitive and robust GC-EAD instrument will result from the application of this technique.

Functionally redundant peg sensilla on the scorpion pecten.

All scorpions have two mid-ventral organs called pectines. Each pecten has thousands of pore-tipped sensilla sensitive to a variety of volatile organic and water-based stimulants. However, it was previously unknown whether individual sensilla were functionally identical or different. The information enhancement hypothesis predicts that all sensilla have similar chemosensitivities such that each is a unit of a parallel processing system. The information segmentation hypothesis states that sensilla differ in their chemosensitivities, a functional arrangement akin to the glomeruli-specific chemical detection system in the moth or human olfactory sense. In this study, we tested these hypotheses by extracellularly tip-recording sensillar responses to three aqueous tastants: 0.01 M KCl, 0.1 M citric acid, and 40% ethanol by volume. We isolated stimulation to one sensillum at a time and compared the chemoresponses. Sensilla appeared to respond similarly to the same stimulant (i.e., sensillar tip-recordings revealed activity of the same cell types), although sometimes a few sensilla responded with higher spike rates than the others. We conclude that our data primarily support the information enhancement hypothesis but for future tests of sensillar function we suggest a new hybrid model, which proposes that a few specialized sensilla exist among a mostly uniform field of identical sensilla.

Identification of early requirements for preplacodal ectoderm and sensory organ development.

Preplacodal ectoderm arises near the end of gastrulation as a narrow band of cells surrounding the anterior neural plate. This domain later resolves into discrete cranial placodes that, together with neural crest, produce paired sensory structures of the head. Unlike the better-characterized neural crest, little is known about early regulation of preplacodal development. Classical models of ectodermal patterning posit that preplacodal identity is specified by readout of a discrete level of Bmp signaling along a DV gradient. More recent studies indicate that Bmp-antagonists are critical for promoting preplacodal development. However, it is unclear whether Bmp-antagonists establish the proper level of Bmp signaling within a morphogen gradient or, alternatively, block Bmp altogether. To begin addressing these issues, we treated zebrafish embryos with a pharmacological inhibitor of Bmp, sometimes combined with heat shock-induction of Chordin and dominant-negative Bmp receptor, to fully block Bmp signaling at various developmental stages. We find that preplacodal development occurs in two phases with opposing Bmp requirements. Initially, Bmp is required before gastrulation to co-induce four transcription factors, Tfap2a, Tfap2c, Foxi1, and Gata3, which establish preplacodal competence throughout the nonneural ectoderm. Subsequently, Bmp must be fully blocked in late gastrulation by dorsally expressed Bmp-antagonists, together with dorsally expressed Fgf and Pdgf, to specify preplacodal identity within competent cells abutting the neural plate. Localized ventral misexpression of Fgf8 and Chordin can activate ectopic preplacodal development anywhere within the zone of competence, whereas dorsal misexpression of one or more competence factors can activate ectopic preplacodal development in the neural plate. Conversely, morpholino-knockdown of competence factors specifically ablates preplacodal development. Our work supports a relatively simple two-step model that traces regulation of preplacodal development to late blastula stage, resolves two distinct phases of Bmp dependence, and identifies the main factors required for preplacodal competence and specification.

The dynein-tubulin motor powers active oscillations and amplification in the hearing organ of the mosquito.

The design principles and specific proteins of the dynein-tubulin motor, which powers the flagella and cilia of eukaryotes, have been conserved throughout the evolution of life from algae to humans. Cilia and flagella can support both motile and sensory functions independently, or sometimes in parallel to each other. In this paper we show that this dual sensory-motile role of eukaryotic cilia is preserved in the most sensitive of all invertebrate hearing organs, the Johnston's organ of the mosquito. The Johnston's organ displays spontaneous oscillations, which have been identified as being a characteristic of amplification in the ears of mosquitoes and Drosophila. In the auditory organs of Drosophila and vertebrates, the molecular basis of amplification has been attributed to the gating and adaptation of the mechanoelectrical transducer channels themselves. On the basis of their temperature-dependence and sensitivity to colchicine, we attribute the molecular basis of spontaneous oscillations by the Johnston's organ of the mosquito Culex quinquefasciatus, to the dynein-tubulin motor of the ciliated sensillae. If, as has been claimed for insect and vertebrate hearing organs, spontaneous oscillations epitomize amplification, then in the mosquito ear, this process is independent of mechanotransduction.

Olfactory perception of oviposition-deterring fatty acids and their methyl esters by the Asian corn borer, Ostrinia furnacalis.

Olfactory perception of myristic, palmitic, stearic and oleic acids and their corresponding methyl esters by Asian corn borer moths, Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae) was investigated. It was found that mated females with both antennae amputated, in contrast to intact females and females with one antenna removed, could not discriminate between simultaneously provided control filter papers and filters treated with a blend of oviposition-deterring fatty acids. Oviposition by mated females exhibited a very marked periodicity, with all egg masses deposited during the scotophase and most egg masses laid before midnight. According to the peak and trough period of oviposition, electroantennogram (EAG) responses from both mated females and males to the four fatty acids and four methyl esters were tested within two two-hour periods from 3 to 5 hours after the start of darkness and from 1 to 3 hours after light onset, respectively. Significant EAG responses above solvent and background were elicited by all test chemicals from females, and by most of the test compounds from males. EAG values of all test chemicals from mated females were not statistically different between the two test periods except for methyl myristate. Conversely, EAG responses from mated males to myristic acid, stearic acid and their methyl esters significantly differed between the two test periods.

A K(+)/H (+) P-ATPase transport in the accessory cell membrane of the blowfly taste chemosensilla sustains the transepithelial potential.

An electrogenic K(+) transport in the tormogen cell of insect chemosensilla is involved in the generation and maintenance of the transepithelial potential (TEP). To gain more information about the K(+) transport system underlying the TEP generation and the location of its components in the plasma membrane of the tormogen cell, we studied the effects of inhibitors of K(+)/H(+) P-ATPase (bafilomycin A1, omeprazole and Na-orthovanadate), of K(+)/Cl(-) co-transport (bumetanide), of Cl(-) channels (NPPB) and of a K(+) channel blocker (BaCl(2)). The relationship between TEP amplitude and spike firing activity was also studied. Experiments were performed on the labellar chemosensilla of the blowfly Protophormia terraenovae using a modified tip-recording technique. Results show that: (a) K(+)/H(+) P-ATPase inhibitors significantly decrease the TEP, when properly applied to the labellum for 20 min, so as to reach the basolateral side of the plasma membrane, while no effect was detected when applied to the apical side, (b) bumetanide, NPPB and BaCl(2) decrease the TEP value only when administered to the apical side, (c) spike activity is positively correlated with the TEP. A model is proposed of the active and passive K(+) transports sustaining the TEP associated with the blowfly chemosensilla.

Clonidine effects on protein and carbohydrate electrophysiological responses of labellar and tarsal sensilla in Phormia regina.

The electrophysiological response of labellar and tarsal chemosensilla in the blowfly Phormia regina was studied in response to a complex stimulus naturally encountered by flies such as sheep faeces, and to beef liver, a proteinaceous feeding source. Responses were investigated both before or after injection of clonidine, an octopamine agonist previously shown to enhance sucrose ingestion, while decreasing that of proteins. As assessed by single sensillum recordings, the four different chemosensory - "salt", "sugar", "deterrent" and "water" - cells were all activated by both stimuli, regardless of sex and sensillum type, the "sugar" one being in all cases the most sensitive to beef liver before clonidine injection. Clonidine treatment affected neither labellar nor tarsal sensitivity to sucrose. Conversely, clonidine-injected flies showed a significant increase in the activity of the "deterrent" cell to beef liver, thus accounting for a decrease in protein ingestion. This study for the first time provides evidence of a key role of a clonidine-sensitive peripheral taste sensitivity in down-regulation of protein ingestion in blowflies. Correlation between peripheral sensitivity and behavioural output is discussed.

Modulation of olfactory information processing in the antennal lobe of Manduca sexta by serotonin.

The nervous system copes with variability in the external and internal environment by using neuromodulators to adjust the efficacy of neural circuits. The role of serotonin (5HT) as a neuromodulator of olfactory information processing in the antennal lobe (AL) of Manduca sexta was examined using multichannel extracellular electrodes to record the responses of ensembles of AL neurons to olfactory stimuli. In one experiment, the effects of 5HT on the concentration-response functions for two essential plant oils across a range of stimulus intensities were examined. In a second experiment, the effect of 5HT on the ability of ensembles to discriminate odorants from different chemical classes was examined. Bath application of 5HT enhanced AL unit responses by increasing response duration and firing rate, which in turn increased the amount of spike time cross-correlation and -covariance between pairs of units. 5HT had the greatest effect on overall ensemble activation at higher odorant concentrations, resulting in an increase in the gain of the dose-response function of individual units. Additionally, response thresholds shifted to lower odorant concentrations for some units, suggesting that 5HT increased their sensitivity. Serotonin enhanced ensemble discrimination of different concentrations of individual odorants as well as discrimination of structurally dissimilar odors at the same concentration. Given the known circadian fluctuations of 5HT in the AL of this species, these findings support the hypothesis that 5HT periodically enhances sensitivity and responsiveness in the AL of Manduca to maximize efficiency when the requirement for olfactory acuity is the greatest.

Identification of human-derived volatile chemicals that interfere with attraction of Aedes aegypti mosquitoes.

It is known that human individuals show different levels of attractiveness to mosquitoes. In this study, we investigated the chemical basis for low attractiveness. We recorded behaviors of Aedes aegypti toward the hands of human volunteers and toward the volatile chemicals produced by their bodies. Some individuals, and their corresponding volatiles, elicited low upwind flight, relative attraction, and probing activity. Analyzing the components by gas chromatography coupled to electrophysiological recordings from the antennae of Aedes aegypti, enabled the location of 33 physiologically relevant compounds. The results indicated that higher levels of specific compounds may be responsible for decreased "attractiveness." In behavioral experiments, five of the compounds caused a significant reduction in upwind flight of Aedes aegypti to attractive human hands. Thus, unattractiveness of individuals may result from a repellent, or attractant "masking," mechanism.

Characterization of Aplysia Alb-1, a candidate water-borne protein pheromone released during egg laying.

Pheromones are known to be important to the innate behavior of marine animals. Attraction in Aplysia involves the long-distance water-borne protein pheromones attractin, enticin, temptin and seductin, which are released from the albumen gland during egg laying. Other pheromones are predicted to act in concert with these pheromones, but their identities are unknown. To identify additional pheromone candidates, we employed differential library screening of an albumen gland cDNA library, RT-PCR, recombinant protein expression, rhinophore contraction bioassays and immunocytochemistry. Alb-1 is expressed in the Aplysia californica albumen gland and encodes a novel protein that does not share significant sequence identity with any proteins in the database. RT-PCR analysis detected Alb-1 transcripts in the albumen gland, exocrine atrial gland and ovotestis. The Alb-1 precursor has a signal peptide sequence followed by a predicted 101-residue protein sequence containing eight cysteine residues. Recombinant protein expression, RP-HPLC, microsequence analysis and MALDI mass spectrometry analyses demonstrated that mature recombinant Alb-1 was processed at a paired basic residue site to generate an N-terminal and C-terminal protein fragment; this was consistent with immunoblot observations on purified albumen gland extracts. In rhinophore contraction (twitch) bioassays, the recombinant N-terminal protein induced rhinophore contractions whereas the C-terminal protein did not. An antibody generated to the N-terminal protein was used for immunocytochemical and immunoblot analyses and demonstrated that this protein is present in albumen gland secretory cells, egg cordons and egg eluates. Overall, the data suggest that Alb-1 may be processed in the albumen gland and that the Alb-1 1-56 protein released during egg laying may serve a pheromonal function in concert with attractin, enticin, temptin and seductin.

Identification of a sex pheromone produced by sternal glands in females of the caddisfly Molanna angustata curtis.

In the caddisfly Molanna angustata, females produce a sex pheromone in glands with openings on the fifth sternite. Gas chromatographic analyses of pheromone gland extracts with electroantennographic detection revealed four major compounds that stimulated male antennae. These compounds were identified by means of gas chromatography-mass spectrometry and enantioselective gas chromatography as heptan-2-one, (S)-heptan-2-ol, nonan-2-one, and (S)-nonan-2-ol in the approximate ratio of 1:1:4:10, respectively. Field tests showed that the mixture of the two alcohols was attractive to males whereas addition of the corresponding ketones reduced trap catches. The sex pheromone of M. angustata, a species in the family Molannidae within the suborder Integripalpia, is similar to the pheromones or pheromone-like compounds previously reported from six other trichopteran families, including members of the basal suborder Annulipalpia. This suggests that minimal evolutionary change of the pheromone chemistry has taken place within the leptoceroid branch of integripalpian Trichoptera compared to the ancestral character state.

New sex attractant composition for the click beetle Agriotes proximus: similarity to the pheromone of Agriotes lineatus.

While testing traps baited with a blend of geranyl octanoate and geranyl butanoate (pheromone components previously identified for Agriotes lineatus, Coleoptera, Elateridae) in Portugal and Bulgaria, large numbers of the closely related Agriotes proximus were captured. In the literature, two different compounds, (E,E)-farnesyl acetate and neryl isovalerate had previously been identified as pheromone components of A. proximus. Subsequent field tests, conducted in several European countries, revealed that A. proximus was weakly attracted to geranyl butanoate on its own, while A. lineatus was weakly attracted to geranyl octanoate on its own. However, the largest catches for both species were observed with a blend of both compounds. No A. proximus was caught in traps baited with the blend of (E,E)-farnesyl acetate and neryl isovalerate at any of the test sites. In electroantennographic studies, antennae of male A. proximus and A. lineatus both gave greater responses to geranyl butanoate than to geranyl octanoate, suggesting that the perception of these two compounds was similar for both species. A 1:1 blend of geranyl octanoate and geranyl butanoate can be used as a bait in traps for the detection and monitoring of both A. lineatus and A. proximus in many European countries.

Floral odors of Silene otites: their variability and attractiveness to mosquitoes.

Inflorescence scent samples from nine populations of dioecious Silene otites, a plant pollinated by moths and mosquitoes, were collected by dynamic headspace extraction. Sixty-three scent samples were analyzed by gas chromatography-mass spectrometry. Out of 38 found, 35 compounds were identified, most of which were monoterpenoids, fatty acid derivatives, and benzenoids. Phenyl acetaldehyde was the most dominant compound in the majority of samples. The variability in scent composition was high, and population and sex differences were found. Nevertheless, wind tunnel experiments proved similar attraction of Culex pipiens pipiens biotype molestus mosquitoes to the inflorescence odor of S. otites of different populations, indicating that different blends are similarly attractive to mosquitoes. The electrophysiological responses of mosquitoes to the 12 most common and abundant odor compounds of S. otites differed. Linalool oxide (furanoid) and linalool evoked the strongest responses in male and female mosquitoes, and (Z)-3-hexenyl acetate was strongly active in females. Medium responses were evoked in males by (Z)-3-hexenyl acetate, in females by benzaldehyde and methyl salicylate, and in both sexes by lilac aldehyde, lilac alcohol, and linalool oxide (pyranoid).

Morphology and electrophysiology of water receptors on legs of the cricket Gryllus bimaculatus.

To identify the sensory organs that are sensitive to water stimuli in the cricket Gryllus bimaculatus, cuticular structures on the legs and the number of sensory neurons innervating them were studied. Some small hair sensilla on the legs were innervated by 2-5 sensory neurons. All such sensilla had a tiny pore at the tip of their hairs. The diameter of the pore was approximately 0.2 mum. These findings suggest that these are chemosensitive hairs (LCS: leg chemosensillum). Of the three pairs of legs, the anterior legs (forelegs) possessed the largest number of LCSs. Of the five leg segments (i.e., coxa, trochanter, femur, tibia and tarsus), the tarsus possessed the largest number of LCSs on each leg. Electrophysiological investigation by tip recording revealed that some of the LCSs contained water-receptor cells. Because the basitarsus possessed a larger number of LCSs than the other tarsomeres, the distribution of water-receptor-containing LCSs in the basitarsus of a foreleg was investigated morphologically and electrophysiologically. LCSs that contained water-receptor cells were mainly distributed on the ventral surface of the basitarsus. There were two types of water receptor that showed different response patterns to a stimulus, that is, phasic- and tonic-type water receptors. From the distribution of LCSs on the legs, the roles of these different types of water receptors in behavioral selection, that is, the initiation of swimming and the inhibition of flying, will be discussed.

Taste and pheromone perception in the fruit fly Drosophila melanogaster.

Taste is an essential sense for detection of nutrient-rich food and avoidance of toxic substances. The Drosophila melanogaster gustatory system provides an excellent model to study taste perception and taste-elicited behaviors. "The fly" is unique in the animal kingdom with regard to available experimental tools, which include a wide repertoire of molecular-genetic analyses (i.e., efficient production of transgenics and gene knockouts), elegant behavioral assays, and the possibility to conduct electrophysiological investigations. In addition, fruit flies, like humans, recognize sugars as a food source, but avoid bitter tasting substances that are often toxic to insects and mammals alike. This paper will present recent research progress in the field of taste and contact pheromone perception in the fruit fly. First, we shall describe the anatomical properties of the Drosophila gustatory system and survey the family of taste receptors to provide an appropriate background. We shall then review taste and pheromone perception mainly from a molecular genetic perspective that includes behavioral, electrophysiological and imaging analyses of wild type flies and flies with genetically manipulated taste cells. Finally, we shall provide an outlook of taste research in this elegant model system for the next few years.

Sensory cell proliferation within the olfactory epithelium of developing adult Manduca sexta (Lepidoptera).

BACKGROUND: Insects detect a multitude of odors using a broad array of phenotypically distinct olfactory organs referred to as olfactory sensilla. Each sensillum contains one to several sensory neurons and at least three support cells; these cells arise from mitotic activities from one or a small group of defined precursor cells. Sensilla phenotypes are defined by distinct morphologies, and specificities to specific odors; these are the consequence of developmental programs expressed by associated neurons and support cells, and by selection and expression of subpopulations of olfactory genes encoding such proteins as odor receptors, odorant binding proteins, and odor degrading enzymes. METHODOLOGY/PRINCIPAL FINDINGS: We are investigating development of the olfactory epithelium of adult M. sexta, identifying events which might establish sensilla phenotypes. In the present study, antennal tissue was examined during the first three days of an 18 day development, a period when sensory mitotic activity was previously reported to occur. Each antenna develops as a cylinder with an outward facing sensory epithelium divided into approximately 80 repeat units or annuli. Mitotic proliferation of sensory cells initiated about 20-24 hrs after pupation (a.p.), in pre-existing zones of high density cells lining the proximal and distal borders of each annulus. These high density zones were observed as early as two hr. a.p., and expanded with mitotic activity to fill the mid-annular regions by about 72 hrs a.p. Mitotic activity initiated at a low rate, increasing dramatically after 40-48 hrs a.p.; this activity was enhanced by ecdysteroids, but did not occur in animals entering pupal diapause (which is also ecdysteroid sensitive). CONCLUSIONS/SIGNIFICANCE: Sensory proliferation initiates in narrow zones along the proximal and distal borders of each annulus; these zones rapidly expand to fill the mid-annular regions. These zones exist prior to any mitotic activity as regions of high density cells which form either at or prior to pupation. Mitotic sensitivity to ecdysteroids may be a regulatory mechanism coordinating olfactory development with the developmental choice of diapause entry.

Odour-evoked responses to queen pheromone components and to plant odours using optical imaging in the antennal lobe of the honey bee drone Apis mellifera L.

The primordial functional role of honey bee males (drones) is to mate with virgin queens, a behaviour relying heavily on the olfactory detection of queen pheromone. In the present work I studied olfactory processing in the drone antennal lobe (AL), the primary olfactory centre of the insect brain. In drones, the AL consists of about 103 ordinary glomeruli and four enlarged glomeruli, the macroglomeruli (MG). Two macroglomeruli (MG1 and MG2) and approximately 20 ordinary glomeruli occupy the anterior surface of the antennal lobe and are thus accessible to optical recordings. Calcium imaging was used to measure odour-evoked responses to queen pheromonal components and plant odours. MG2 responded specifically to the main component of the queen mandibular pheromone, 9-ODA. The secondary components HOB and HVA each triggered activity in one, but not the same, ordinary glomerulus. MG1 did not respond to any of the tested stimuli. Plant odours induced signals only in ordinary glomeruli in a combinatorial manner, as in workers. This study thus shows that the major queen pheromonal component is processed in the most voluminous macroglomerulus of the drone antennal lobe, and that plant odours, as well as some queen pheromonal components, are processed in ordinary glomeruli.

Phototactic behaviour correlates with gustatory responsiveness in honey bees (Apis mellifera L.).

The response threshold hypothesis of division of labour in honey bees assumes that individuals differ in their responsiveness to different stimulus modalities. However, previous experiments have shown that responsiveness to gustatory stimuli correlates with responsiveness to odours, pollen and tactile stimuli. Evaluation of these stimuli involves sensory receptors on the antenna. We tested whether responsiveness to gustatory stimuli correlates with responsiveness to visual stimuli in a phototaxis experiment, which is independent of antennal input. Gustatory responsiveness was measured using the proboscis extension response to antennal stimulation with water and different sucrose concentrations. Phototaxis was quantified by measuring the walking times a bee needed to reach light sources of different intensities. Walking behaviour in the darkness was measured to test for differences in locomotor behaviour. The walking time towards a light stimulus, the path length, and the walking speed depended on the intensity of the light stimulus. Responsiveness to visual stimuli correlated significantly with gustatory responsiveness. Bees displaying a high gustatory responsiveness were also very sensitive to light. Locomotor activity did not correlate with gustatory responsiveness. This shows that gustatory responsiveness is a good indicator of sensitivity for visual stimuli, which are not perceived by the antenna.