The pteropod mollusc Clione limacina feeds on shelled pteropods capturing them with 3 pairs of oral appendages, called buccal cones. A group of electricallycoupled putative motoneurons (A neurons) has been identified in the cerebral ganglia, whose activation induces opening of the oral skin folds and extrusion of the buccal cones. These cells are normally silent and have one or two axons in the ipsilateral head nerves. Electrical coupling between A neurons is relatively weak and normally does not produce 1∶1 spike synchronization. Coupling coefficients ranged from 0.05 to 0.25. A second type of putative motoneurons (B neurons) controls retraction and withdrawal of buccal cones. B neurons show spontaneous spike activity which maintains the buccal cones in a continuous retracted state. All B neurons have one axon running into the head nerves. Ipsilateral B motoneurons are electrically coupled to each other. A neurons strongly inhibit B neurons, however, seven identified A motoneurons which were specifically tested do not form monosynaptic contacts with B motoneurons. Appropriate stimuli from the prey activate A motoneurons, which in turn inhibit B motoneurons and evoke extrusion of the buccal cones. One mechanism promoting the speed of this extremely rapid reaction is brief co-activation of antagonistic A and B neuron groups, which provides a notable increase in fluid pressure inside the head. Mechanical stimulation of buccal cones provides excitatory inputs to A motoneurons. Similar stimulation from captured prey would serve to prolong buccal cone protraction during the manipulatory phase of feeding.
For optimal visual control of compensatory eye movements during locomotion it is necessary to distinguish the rotational and translational components of the optic flow field. Optokinetic eye movements can reduce the rotational component only, making the information contained in the translational flow readily available to the animal. We investigated optokinetic eye rotation in the marble rock crab, Pachygrapsus marmoratus, during translational movement, either by displacing the animal or its visual surroundings. Any eye movement in response to such stimuli is taken as an indication that the system is unable to separate the translational and the rotational components in the optic flow in a mathematically perfect way. When the crabs are translated within a pseudo-natural environment, eye movements are negligible, especially during sideways translation. When, however, crabs were placed in a gangway between two elongated rectangular sidewalls carrying dotted patterns which were translated back and forth, marked eye movements were elicited, depending on the translational velocity. To resolve this discrepancy, we tested several hypotheses about mechanisms using detailed analysis of the optic flow or whole-field integration. We found that the latter are sufficient to explain the efficient separation of translation and rotation of crabs in quasi-natural situations.
The stepping patterns of intact, amputated and leg restrained first instar stick insects were examined by analysing video tape records of their free walking behaviour. Amputation produced changes in the relative timing of protraction movements both along and across the body axis. Restraint of individual front or rear legs produced walking behaviour similar to that of the amputee animal but restraint of middle legs caused a breakdown in the coordination of front and rear legs. The changes in behaviour produced by leg autotomy and restraint were used to test certain assumptions of a model for generating the step pattern of these insects and to investigate how the tonic influence of proprioceptive input might be incorporated into the model.
DOI : 10.1007/BF00605519 Anahtar Kelimeler :
Relative Timing, Tape Record, Body Axis, Video Tape, Stick Insect
ISSN: 1432-1351 Cilt: 116 Sayı: 1 Sayfa: 91-116
The butterfly Papilio xuthus has acute tetrachromatic color vision. Its eyes are furnished with eight spectral classes of photoreceptors, situated in three types of ommatidia, randomly distributed in the retinal mosaic. Here, we investigated early chromatic information processing by recording spectral, angular, and polarization sensitivities of photoreceptors and lamina monopolar cells (LMCs). We identified three spectral classes of LMCs whose spectral sensitivities corresponded to weighted linear sums of the spectral sensitivities of the photoreceptors present in the three ommatidial types. In ~ 25% of the photoreceptor axons, the spectral sensitivities differed from those recorded at the photoreceptor cell bodies. These axons showed spectral opponency, most likely mediated by chloride ion currents through histaminergic interphotoreceptor synapses. The opponency was most prominent in the processes of the long visual fibers in the medulla. We recalculated the wavelength discrimination function using the noise-limited opponency model to reflect the new spectral sensitivity data and found that it matched well with the behaviorally determined function. Our results reveal opponency at the first stage of Papilio’s visual system, indicating that spectral information is preprocessed with signals from photoreceptors within each ommatidium in the lamina, before being conveyed downstream by the long visual fibers and the LMCs.
The osmotic pressure (OP) of the incubation medium directly affects synthesis and release of prolactin byPoecilia andAnguilla pituitariesin vitro. There is an inverse relationship between the OP of the medium and the amount of prolactin released into the medium (Pigs. 1, 2; Tables 1, 3). Release of newly-synthesised prolactin is similarly related to OP of the medium (Pigs. 3,4; Table 3). Histometric data of prolactin cells also suggests that hormone synthesis is reduced in high OP media (Table 2). Release and synthesis of putative growth hormone (GH) byPoecilia pituitaries is not influenced by OP of the medium (Table 4), butAnguilla pituitaries release more GH in low OP media (Table 5).
Removal of the pineal gland modifies the entrainment behavior of house sparrows. Abnormal entrainment occurs in pinealectomized sparrows exposed to ‘skeleton’ photoperiods (light cycles composed of 2 pulses of light per 24-h cycle). This abnormal entrainment depends upon the state of the locomotor activity (rhythmic or arrhythmic) before exposure to the light cycle, and upon the interval between the 2 pulses of light which constitute the skeleton photoperiod. The conditions that produce abnormal entrainment in pinealectomized birds are strongly correlated with those that produce 2 stable phases of entrainment to skeleton photoperiods in normal birds (‘bistability phenomenon’). These results suggest that after pinealectomy, there remains a population of oscillators whose combined output is reflected in the locomotor activity of individual sparrows.
Small songbirds have a difficult analysis problem: their head is small compared to the wavelengths of sounds used for communication providing only small interaural time and level differences. Klump and Larsen (1992) measured the physical binaural cues in the European starling (Sturnus vulgaris) that allow the comparison of acoustical cues and perception. We determined the starling’s minimum audible angle (MAA) in an operant Go/NoGo procedure for different spectral and temporal stimulus conditions. The MAA for broadband noise with closed-loop localization reached 17°, while the starling’s MAA for open-loop localization of broadband noise reached 29°. No substantial difference between open-loop and closed-loop localization was found in 2 kHz pure tones. The closed-loop MAA improved from 26° to 19° with an increase in pure tone frequency from 1 to 4 kHz. This finding is in line with the physical cues available. While the starlings can only make use of interaural time difference cues at lower frequencies (e.g., 1 and 2 kHz), additional interaural level difference cues become available at higher frequencies (e.g., 4 kHz or higher, Klump and Larsen 1992). An improvement of the starling’s MAA with an increasing number of standard stimulus presentations prior to the test stimulus has important implications for determining relative (MAA) localization thresholds.
Although nectar feeding in insects has long been studied, the knowledge of the effect of nectar energy content on the ingestion dynamics separately from the viscosity of the fluid is very limited. To determine the effects of both factors on the feeding behavior of the hovering hawk moth Macroglossum stellatarum, we developed a method to independently manipulate sucrose concentrations and viscosity. The intake rate was analyzed as a function of sucrose concentration, the concentration at constant viscosity (kept constant by adding tylose, an inert polysaccharide), and of the different viscosities of a 30% weight/weight (w/w) sucrose solution (by adding different amounts of tylose). By increasing the concentration, and thus its viscosity, the solution intake rate (in µl s–1) decreased beyond a 20% w/w sucrose solution. For a 30% sucrose solution, the intake rate decreased with increasing viscosity. At constant viscosity, the solution intake rate decreased beyond a 30% w/w sucrose solution. However, if we considered the quantity of sucrose ingested per unit time (sucrose intake rate), the same fitted maximum was attained for both series in which the sucrose concentration changed (33.6% w/w). Results suggest that the gustatory input affects the dynamics of fluid ingestion separately from the viscosity.
Performance of a bout of courtship behaviour has a cumulative decremental effect on subsequent bouts in males of the parasitic waspNasonia vitripennis. Bout length recovers as a function of time since the previous bout. The rate of recovery is independent of temperature. However, a 10-min exposure to an extremely low temperature (−30 °C) temporarily increased bout length as if a complete recovery had been achieved. The results are explained by temporal removal of an inhibition.
Orientation in the geomagnetic field is essential for many animal species. As yet, the interaction mechanisms of this weak field with the organisms are understood only incompletely. One mechanism in question is the interaction with the photochemical reaction in the retina. We show that the visual sensitivity of man is influenced by periodic sinusoidal inversion of the vertical component of the geomagnetic field. This effect indicates visual fixation in north-south direction and shows a pronounced resonance at a period duration of 110 s. These findings should be helpful in identifying in detail the mechanisms which are influenced by the geomagnetic field.
Effects of food supply on daily periodic locomotor activity in the ground beetle Carabus auronitens were recorded in the laboratory with the animals exposed to natural daylight and photoperiod. Inspection of individual actograms exhibits that in most cases feeding leads to strongly reduced and more or less irregularly distributed activity for a period of up to 4 days. In terms of quantitative parameters, the animals respond to food supply by an immediate reduction of mean amounts of daily activity. This is achieved through the reduction of duration (as a consequence of reduced burstlengths instead of burstnumber) and, less distinctly, the reduction of intensity. The initial levels of parameters are reattained after 4 days. Direct comparison by means of standardized (i.e. level-independent) relative parameter functions demonstrates close concordance between the amount and duration of daily activity; however, distinct synchronous change of intensity is apparent as a consequence of food supply only. This means that any variation of activity amounts is due to changing duration rather than to intensity variation. In analogy to the feeding-dependent parameter dynamics, also the proportion of animals with strong synchronization to the natural light/dark cycle is considerably reduced by food supply. The feeding-dependent reduction of activity is paralleled by temporarily reduced activity of proteolytic enzymes in the beetles. It is argued that, for the purpose of energy saving, the animals will remain inactive as long as reduced enzyme activity inhibits further consumption and digestion of food.
Background noise evokes a similar suite of adaptations in the acoustic structure of communication calls across a diverse range of vertebrates. Echolocating bats may have evolved specialized vocal strategies for echolocating in noise, but also seem to exhibit generic vertebrate responses such as the ubiquitous Lombard response. We wondered how bats balance generic and echolocation-specific vocal responses to noise. To address this question, we first characterized the vocal responses of flying free-tailed bats (Tadarida brasiliensis) to broadband noises varying in amplitude. Secondly, we measured the bats’ responses to band-limited noises that varied in the extent of overlap with their echolocation pulse bandwidth. We hypothesized that the bats’ generic responses to noise would be graded proportionally with noise amplitude, total bandwidth and frequency content, and consequently that more selective responses to band-limited noise such as the jamming avoidance response could be explained by a linear decomposition of the response to broadband noise. Instead, the results showed that both the nature and the magnitude of the vocal responses varied with the acoustic structure of the outgoing pulse as well as non-linearly with noise parameters. We conclude that free-tailed bats utilize separate generic and specialized vocal responses to noise in a context-dependent fashion.
The ability of Sternopygus, a South American electric fish, to track longitudinal motion of its surround was studied. Tracking responses were elicited by moving plexiglass enclosures which these fish readily occupy. The longitudinal position of these ‘shuttles’ was varied over time in a sinusoidal or linear fashion. The objectives were to quantify the metrics of longitudinal tracking responses and the roles of the various sensory modalities in this behavior. The following results were obtained:
DOI : 10.1007/BF00213075 Anahtar Kelimeler :
Electric fish, Electromotor response, Pursuit movements, Motor function, Sensory processing
ISSN: 1432-1351 Cilt: 171 Sayı: 6 Sayfa: 791-798
Pregnant Syrian hamsters with lesions of the suprachiasmatic nucleus (SCN) received single injections of melatonin or the D1-dopamine receptor agonist, SKF 38393 on day 15 of gestation (1 day before birth). Pups were weaned on postnatal day 20 and their freerunning activity rhythms recorded for 3–4 weeks. The pups phases on the day of weaning were significantly clustered in both of the treatment groups, but the average phases differed by approximately 180°. The results demonstrate that a single prenatal stimulus is sufficient to set the phases of the hamsters rhythms and that the phase established depends on the stimulus. Both c-fos mRNA and Fos protein were expressed in the fetal SCN after SKF 38393 injection but neither were expressed after melatonin injection. Simulations showed that a single stimulus could produce the observed synchrony from a population of uniformally distributed phases if the phase shifts were three to four times the magnitude of the adult hamster light phase response curve (PRC). A light pulse PRC mimicked the effect of an SKF 38393 injection and a dark-pulse PRC mimicked the effects of a melatonin injection. Together these results suggest that dopamine and melatonin either are, or mimic, maternal entraining signals that represent day and night.
Sharks and rays are highly sensitive to chemical stimuli in their natural environment but several hypotheses predict that hammerhead sharks, with their expanded head and enlarged olfactory epithelium, have particularly acute olfactory systems. We used the electro-olfactogram (EOG) technique to compare the relative response of the scalloped hammerhead shark (Sphyrna lewini) olfactory epithelium to 20 proteinogenic amino acids and determine the sensitivity for 6 amino acids. At micromolar concentrations, cysteine evoked the greatest EOG response which was approximately twice as large as that of alanine. The weakest response was obtained for proline followed by aspartic acid and isoleucine. The olfactory epithelium showed adaptation to sequential stimulation, and recovery was related to the inter-stimulus time period. Estimated EOG response thresholds were in the sub-nanomolar range for both alanine (9.2 × 10−11 M) and cysteine (8.4 × 10−10 M) and in the micromolar range for proline and serine. These thresholds from 10−10 to 10−6 M for the scalloped hammerhead shark are comparable or lower than those reported for other teleost and elasmobranch species. Future work should focus on binary and more complex compounds to test for competition and cross-adaptation for different classes of peripheral receptors, and their responses to molecules found in biologically relevant stimuli.
indica and Argyreus
hyperbius frequently forage on flower nectar, but the former also utilizes tree sap and rotting fruits. Compared to flower nectar, these rotting foods are characterized by low sugar concentrations and the presence of fermentation products (ethanol and acetic acid). We suspected that gustatory responses by the receptors on the proboscis might differ in these species. Among the three sugars tested, sucrose elicited the greatest probing (behavioral) responses and was followed by fructose and glucose. A. hyperbius showed higher sugar sensitivity than V. indica in probing responsiveness. In electrophysiological responses of the proboscis sensilla, V. indica was slightly more sensitive than A. hyperbius to glucose and lower concentrations of the other sugars. The sugar reception in A. hyperbius was strongly inhibited by fermentation products, particularly acetic acid at natural concentrations. In contrast, V. indica was noticeably less susceptible to them than A. hyperbius, and its behavioral and sensory responses to sucrose were enhanced by 5–20% (w/v) ethanol. Thus, V. indica not only possesses tolerance to fermentation products but may perceive them as synergists for sugar reception. To utilize rotting foods, such tolerance might be more necessary than high sugar sensitivity.
Polarisation sensitivity is based on the regular alignment of dichroic photopigment molecules within photoreceptor cells. In crustaceans, this is achieved by regularly stacking photopigment-rich microvilli in alternating orthogonal bands within fused rhabdoms. Despite being critical for the efficient detection of polarised light, very little research has focused on the detailed arrangement of these microvilli bands. We report here a number of hitherto undescribed, but functionally relevant changes in the organisation of microvilli banding patterns, both within receptors, and across the compound eye of fiddler crabs. In all ommatidia, microvilli bands increase in length from the distal to the proximal ends of the rhabdom. In equatorial rhabdoms, horizontal bands increase gradually from 3 rows of microvilli distally to 20 rows proximally. In contrast, vertical equatorial microvilli bands contain 15–20 rows of microvilli in the distal 30 µm of the rhabdom, shortening to 10 rows over the next 30 µm and then increase in length to 20 rows in parallel with horizontal bands. In the dorsal eye, horizontal microvilli occupy only half the cross-sectional area as vertical microvilli bands. Modelling absorption along the length of fiddler crab rhabdoms suggests that (1) increasing band length assures that photon absorption probability per band remains constant along the length of photoreceptors, indicating that individual bands may act as units of transduction or adaptation; (2) the different organisation of microvilli bands in equatorial and dorsal rhabdoms tune receptors to the degree and the information content of polarised light in the environment.
Treatment of the labellar chemosensory setae of the fruit fly,Drosophila melanogaster, with 0.1 % papain for 3 min induced a complete elimination of the taste nerve response to fructose (Fig. 1). Responses to other sugars examined were not affected (Table 1). Responses to 20 mM LiCl and 0.1 M NaCl also remained unchanged by the treatment. The experiment on the time-dependency of the papain treatment showed a clear difference in the proteasesensitivity between the response to fructose and to glucose and sucrose (Fig. 2). The treatment with 0.005% trypsin for 3 min produced the same results. The response to fructose which was eliminated with the papain treatment, was restored after 3 hrs. These findings reveal the presence of a specific receptor site for fructose and its protease-sensitive nature and suggest the involvement of multiple receptor proteins in the sugar receptor ofDrosophila.
We recently identified changes in amine-receptor gene expression in the antennae of the honey bee that correlate with shifts in the behavioural responsiveness of worker bees towards queen mandibular pheromone. Here we examine whether variations in expression of amine-receptor genes are related to age and/or to behavioural state. Colonies with a normal age structure were used to collect bees of different ages, as well as pollen foragers of unknown age. Single- and double-cohort colonies were established also to generate nurses and pollen foragers of the same age. Amdop1 was the only gene examined that showed no significant change in expression levels across the age groups tested. However, expression of this gene was significantly higher in 6-day-old nurses than in pollen foragers of the same age. Levels of expression of Amdop2 were very variable, particularly during the first week of adult life, and showed no correlation with nursing or foraging behaviour. Amdop3 and Amtyr1 expression levels changed dramatically with age. Interestingly, Amtyr1 expression was significantly higher in 15-day-old pollen foragers than in same-age nurses, whereas the opposite was true for Amoa1. While Amoa1 expression in the antennae was lower in 6- and 15-day-old pollen foragers than in nurses of the same age, differences in gene expression levels between nurses and pollen foragers could not be detected in 22-day-old bees. Our data show dynamic modulation of gene expression in the antennae of worker bees and suggest a peripheral role for biogenic amines in regulating behavioural plasticity in the honey bee.
Bees have ultraviolet (UV), blue and green photoreceptor types in their compound eyes with which they locate food sources in landscapes that change continuously in cues emanating from plants and backgrounds against which they are perceived. The complexity of bee vision has been elucidated through studies examining individual species under laboratory conditions. Here, we used a bee-attractive fluorescent blue trap as a model for analyzing visual signals in operation outdoors, and across bee species. We manipulated trap color (appearance to humans under light with weak UV component) and UV-induced fluorescence emission, and aligned field capture results with bee vision models. Our studies show that the bees were attracted to traps that under solar illumination exhibited strong fluorescence emission exclusively in the blue spectral region. Through quantitative analysis, we established that strong spectral overlap of trap emittance with the photosensitivity characteristic of the blue receptor type and minimal overlap with those of the other two receptor types is the most critical property of attractive traps. A parameter has been identified which predicts the degree of attractiveness of the traps and which captures trends in the field data across wild bee species and for a diversity of backgrounds.
The distribution of frequencies along the basilar papilla of the barn owl (Tyto alba) was studied by labelling small groups of primary auditory neurones of defined frequency response and tracing them to their peripheral innervation sites. The exact location of marked neurones was determined in cochlear wholemounts with the aid of a special surface preparation technique. The average basilar papilla length (in fixed, embedded specimens) was 10.74 mm. The resulting frequency map shows the basic vertebrate pattern with the lowest frequencies represented apically and increasingly higher frequencies mapped at progressively more basal locations. However, the length of basilar papilla devoted to different frequency ranges, i.e. the space per octave, varies dramatically in the barn owl. The lower frequencies (up to 2 kHz) show values between about 0.35 and 1 mm/octave, which are roughly equivalent to values reported for other birds. Above that, the space increases enormously, the highest octave (5–10 kHz) covering about 6 mm, or more than half of the length of the basilar papilla. Such an overrepresentation of a narrow, behaviourally very important frequency band is also seen in some bats, where it has been termed an acoustic or auditory fovea.
DOI : 10.1007/BF00213066 Anahtar Kelimeler :
Hearing, Birds, Basilar papilla, Frequency map, Barn owl
ISSN: 1432-1351 Cilt: 171 Sayı: 6 Sayfa: 695-704