Behavioural responses to visual stimuli by the snails Tectarius muricatus,Turbo castanea, and Helix aspersa

The visual responses of three gastropods were studied for comparison with data previously obtained for the marsh periwinkle, Littorina irrorata. Turbo castanea, an archeogastropod inhabiting subtidal grass beds, had the lowest response thresholds for bar width (0.3–1.4⁰) and shape reflectance (83%), and showed significant preferences in two binary-choice tests. Tectarius muricatus, a littorinid inhabiting hard substrate in the supratidal zone, had slightly higher response thresholds (1.4–6.5^o; 75%) than T. castanea, and showed a significant preference in only one binary-choice test. Helix aspersa, a terrestrial pulmonate primarily active e at night, had much higher response thresholds (14.5–24.6°; 19%) than T. castanea and T. muricatus, and showed no significant preferences in binarychoice tests. Assuming that these response threshold estimates approximate actual sensory thresholds, then T. castanea can see slightly better than T. muricatus, and both species can see much better than H. aspersa. This conclusion coincides with expectations based on the light intensities and complexity of visual stimuli present in the habitats of these snails.     

Ecology of the intertidal snail Littorina acutispira Smith

Littorina acutispira Smith, a minute gastropod of < 3 mm shell height, lives at great densities in pools and on rock-surfaces at the highest levels of sea-shores in New South Wales. Populations from pools and dry areas were sampled on two shores for 18 months to investigate seasonal changes in density, size-structure, rates of growth and reproductive biology of the snails. Densities of snails increased between February and May, due to an influx of juveniles, and then declined until the following February, when they increased again. The decrease in density was due to the death of the largest snails at the end of summer, and the mortality of medium-sized snails between June and January. Longevity was estimated as 1–2 yr, but most individuals died by ≈ 16 months from settlement on the shore. Newly-settled snails grew to merge in size with those of the previous year's population by winter. During the summer months, the rate of growth of snails from a sheltered shore was greater than that of snails on a shore exposed to wave-action. Laboratory experiments revealed that this could be attributed to the presence of better quality food, or food in greater abundance on the sheltered shore, compared with the exposed shore.During winter months, but not during the summer, snails from dry areas grew more slowly than those from pools. An experiment demonstrated that some snails from dry areas might be able to compensate for reduced periods of feeding by being able to feed faster when submersed. This could not explain the differences in natural rates of growth.L. acutispira bred from October–November to March–April. Spawning in the laboratory was greatest during late summer (January to March). The percentage of mature oocytes in the gonads was small in winter and increased in early summer. Among the largest-sized snails, females outnumbered males. Two experiments, on unsexed and pre-sexed snails, demonstrated that the biased sex-ratio of the largest snails was due to faster growth by females.There was a greater density of snails on the exposed shore, which was correlated with the presence of barnacles. When barnacles were removed from experimental areas, the density of the snails declined within 24 h. This suggested that barnacles provided a refuge from wave-shock, rather than shelter from desiccation or high temperature. In laboratory experiments, snails were exposed to higher temperatures and less humidity than they would normally encounter on the shore. There was negligible mortality of small or large snails after 24 h of these conditions.This minute species grows quickly, recruits annually and has a short life-span. This type of life-history is discussed in comparison with similar small species from other habitats.     

Behavioural responses to visual stimuli following posterior dorsal telencephalic ablations in Gallus domesticus

The behaviour of chickens following posterior dorsal telencephalic ablations was studied in response to humans, strange hens, aerial predators, ground predators and a visual startle stimulus. The ablations had no effect on the birds' response to either the aerial or ground predator but there was a significant reduction in pacing after the visual startle stimulus. Following posterior telencephalic ablation the birds showed significantly fewer attacks and threats in encounters with unfamiliar hens but showed exaggerated escape/avoidance behaviour to humans in both their home pens and in experimental testing cages. The reasons for this avoidance behaviour to humans are discussed but no definite conclusions could be drawn.     

Behavioural responses of diverse insect groups to electric stimuli

Anecdotal evidence suggests that cockroaches respond to electrical appliances or outlets. Our objectives were to determine the effect of field‐inducing sources and field attributes on attraction of German cockroaches, Blattella germanica (L.) (Blattodea: Blattellidae), and to test those parameters found effective for attraction of B. germanica for attraction of other groups of insects. In two‐choice, large‐arena experiments, significantly more female, but not nymphal, B. germanica settled in or near electrified coils with static or fluctuating electromagnetic fields produced by low‐level direct current (DC) or alternating current (AC) sources than in control coils without current. Electromagnetic fields with the magnetic, but not the electric, component of the field nulled still attracted B. germanica, suggesting that the electric component of the field may contribute to the attraction or arrestment response of B. germanica. DC‐powered coils with static electromagnetic fields also attracted/arrested brown‐banded cockroaches, Supella longipalpa (Fabricius) (Blattodea: Blattellidae), common silverfish, Lepisma saccharina (L.), firebrats, Thermobia domestica (Packard) (both Thysanura: Lepismatidae), and European earwigs, Forficula auricularia (L.) (Dermaptera: Forficulidae), but they repelled American cockroaches, Periplaneta americana (L.) (Blattodea: Blattidae). If proven in field experiments, electrified coils as trap baits may offer non‐toxic alternatives to pesticides for selective insect control in urban environments.     

Neural responses to salient visual stimuli.

The neural mechanisms involved in the selective processing of salient or behaviourally important stimuli are uncertain. We used an aversive conditioning paradigm in human volunteer subjects to manipulate the salience of visual stimuli (emotionally expressive faces) presented during positron emission tomography (PET) neuroimaging. Increases in salience, and conflicts between the innate and acquired value of the stimuli, produced augmented activation of the pulvinar nucleus of the right thalamus. Furthermore, this pulvinar activity correlated positively with responses in structures hypothesized to mediate value in the brain right amygdala and basal forebrain (including the cholinergic nucleus basalis of Meynert). The results provide evidence that the pulvinar nucleus of the thalamus plays a crucial modulatory role in selective visual processing, and that changes in perceptual salience are mediated by value-dependent plasticity in pulvinar responses.     

Unit responses of the squirrel visual cortex to shaped visual stimuli

Visual cortical unit responses of the squirrelSciurus vulgaris to shaped visual stimuli (stationary and moving spots and bands) were studied. Neurons responding selectively to the direction of stimulus movement and orientation of lines and those not responding selectively to these features were distinguished. Many neurons, whether responding selectively or not to movement direction, were specifically sensitive to high speeds of movement, of the order of hundreds of degrees per second. This selectivity in neurons responding selectively to movement direction persisted at these high speeds, despite the short time taken by the stimulus to move across the receptive field. Neurons responding selectively to line orientation were sensitive to lower speeds of stimulus movement — from units to tens of degrees per second. Neuronal sensitivity to high speeds of stimulus movement is achieved through rapid summation of excitation from large areas of the receptive field crossed by the fast-moving stimulus. Selectivity of the response to movement direction is produced under these conditions with the aid of directed short-latency inhibition, inhibiting unit activity for stimulus movement in "zero" direction.     

Behavioural responses to female sex pheromone components in Periplaneta americana

Female American cockroaches, Periplaneta americana, release two sex pheromones, periplanone-A and periplanone-B, each of which is perceived by a specialized receptor type on the male antennae. This study investigates whether male behavioural responses to both components may differ qualitatively or quantitatively. Running, upwind orientation and wing-raising were evoked by stimulation with either component. The intensity of running increased with stimulus concentration in much the same way for both substances. However, the relative effectiveness of periplanone-A was 30 times lower in behavioural assays than in the electroantennogram. Behavioural responses to periplanone-B declined faster and were more easily adapted by repeated stimulation than those to periplanone-A. It is hypothesized that periplanone-B is responsible for long distance attraction while periplanone-A influences male behaviour near the female.     

Classical conditioning to visual stimuli in the housefly, Musca domestica

In the housefly, Musca domestica, classical conditioning to monochromatic light was demonstrated by using a proboscis extension response to labellar stimulation with sucrose solution as an unconditioned response. Sequential and temporal relationships between the conditioned stimulus (CS) and unconditioned stimulus (UCS) to form conditioning were studied; conditioning occurred most readily when the CS was presented before the UCS without an interstimulus interval. Spectral response curves, which were obtained by examining the responsiveness of flies conditioned for one colour to other colours, were divided into two groups; one was that of 462 nm-conditioned flies and the other those of 516 nm-, 579 nm-, and 642 nm-conditioned flies.     

Behavioural responses of the yellow emitting annelid Tomopteris helgolandica to photic stimuli

In contrast to most mesopelagic bioluminescent organisms specialised in the emission and reception of blue light, the planktonic annelid Tomopteris helgolandica produces yellow light. This unusual feature has long been suggested to serve for intraspecific communication. Yet, this virtually admitted hypothesis has never been tested. In this behavioural study of spectral colour sensitivity, we first present an illustrated repertoire of the postures and action patterns described by captive specimens. Then video tracking and motion analysis are used to quantify the behavioural responses of singled out worms to photic stimuli imitating intraspecific (yellow) or interspecific (blue) bioluminescent signals. We show the ability of T. helgolandica to react and to contrast its responses to bioluminescent‐like blue and yellow light signals. In particular, the attractive effect of yellow light and the variation of angular velocity observed according to the pattern of yellow stimuli (flashes versus glows) support the intraspecific communication hypothesis. However, given the behavioural patterns of T. helgolandica, including mechanically induced light emission, the possibility that bioluminescence may be part of escape/defence responses to predation, should remain an open question.     

Optic nerve responses to visual stimuli in squid

Summary Single unit optic nerve responses were studied in isolated eye-optic lobe preparations ofLoligo opalescens. Units could be classified as fast or slow. Fast units were invariably receptor cell axons; slow units might be either receptor cell axons or centrifugal axons.On, on-off, andoff units could be found within these classes. A given unit was not stable with respect to these latter attributes which depended greatly on the history and level of illumination. The curve which relates quantal content of a brief flash to number of spikes in the response has a logarithmic phase, but it saturates as brightness is increased further. An inhibitory component has been demonstrated following the response to a flash. It is probably responsible for the non-monotonic relationship between frequency and light intensity which is observed for sustained stimuli. Background light or previous illumination can lead to a facilitation of the response to a flash.The authors share equally in credit and responsibility for this paper and for the research reported here. We thank Dr. A. Hurley and Dr. T. H. Bullock for valuable comments and suggestions and L. Ball and S. St. John for technical assistance. This research was supported by PHS grants NS 09342 to GDL and EY 29405 to PHH, by a grant from the Sloan Foundation to the group in Neurosciences at UCSD and NSF grants GB 24816 and GD 28838 to the Scripps Institution of Oceanography for operation of the Alpha Helix Research Program.     

Neurophysiological and behavioral responses to olfactory stimuli in the snail Helix pomatia L

Some aspects of olfactory sensitivity in the pulmonate Helix pomatia L. were studied by means of neurophysiological and behavioral methods. Single fiber recordings were carried out in the olfactory nerve of the posterior tentacles. Olfactory stimulations with different odors were performed by means of a continuous air stream. The order of neuronal sensitivity to different odors was as follows: ethanol > or = ethyl acetate > pentanol > hexanol > octanol > or = diethyl malonate > vanillin. Furthermore, the results revealed a relative specificity for some substances. A comparison between neurophysiological and behavioral data shows that those substances, which cause the highest increases in impulse frequency, also evoke a behavioral avoidance reaction.     

Behavioural evidence for visual recognition of predators by the mangrove climbing crab Sesarma leptosoma

The climbing crab Sesarma leptosoma colonizes the mangrove roots and canopy of East African mangrove swamps, an intricate three-dimensional habitat in which it orients itself visually. To ascertain if vision helps this tree crab to detect dangers such as predators, we used dummy objects: (1) a preserved specimen of its predator, the crab Epixanthus dentatus in its typical ambush posture; (2) a piece of wood with real E. dentatus claws attached to it, the same size as, and painted to resemble (to the human eye), this predator; and (3) a piece of wood the same size and colour as a live crab but without claws. When these dummies were presented to migrating S. leptosoma in the field, they stopped their normal migratory flow only when they were able to see the open claws of the predator. Thus S. leptosoma showed a considerable ability to perceive shape, being able to distinguish motionless objects of different shapes but similar size and to associate the detected shapes with the presence of danger.     

Behavioural and physiological responses to conflicting oviposition stimuli in a synovigenic parasitoid

The behavioural and physiological responses of the synovigenic parasitoid, Dinarmus basalis (Rond.) (Hymenoptera: Pteromalidae), were investigated whilst the wasps were submitted to conflicting oviposition stimuli: an environment which induced them to restrict egg-laying and a physiological factor, egg-load pressure, which induced them to lay eggs. When individual females depleted patches containing hosts parasitized 24 h or 72 h beforehand, they laid preferentially on unparasitized hosts and the number of eggs laid decreased significantly. Although they remained for several days in such patches, egg-load pressure did not lead them to modify their strategy (i.e. to accept all the available hosts including the already parasitized ones). In this synovigenic species, the oviposition constraint resulted in the retention of oocytes. Dissection and histological observation showed that the unlaid eggs are resorbed, a reproductive regulatory process which has seldom previously been reported in the presence of unparasitized hosts. This physiological response was induced by the mere presence of the parasitized hosts rather than their density. The females’ response was also influenced by the presence of conspecifics. They still avoided laying on parasitized hosts but the number of eggs laid daily became comparable to that observed in patches containing only unparasitized hosts. Thus, D. basalis females adapted their strategy in response to their environment, in which the most significant factor seemed to be the quality of the hosts provided, and their physiology. The originality and the importance of these results are discussed.     

Parvalbumin-expressing interneurons linearly transform cortical responses to visual stimuli

The response of cortical neurons to a sensory stimulus is shaped by the network in which they are embedded. Here we establish a role of parvalbumin (PV)-expressing cells, a large class of inhibitory neurons that target the soma and perisomatic compartments of pyramidal cells, in controlling cortical responses. By bidirectionally manipulating PV cell activity in visual cortex we show that these neurons strongly modulate layer 2/3 pyramidal cell spiking responses to visual stimuli while only modestly affecting their tuning properties. PV cells' impact on pyramidal cells is captured by a linear transformation, both additive and multiplicative, with a threshold. These results indicate that PV cells are ideally suited to modulate cortical gain and establish a causal relationship between a select neuron type and specific computations performed by the cortex during sensory processing.     

Responses to computer-generated visual stimuli by the male praying mantis, Sphodromantis lineola (Burmeister)

We tested male mantis' responses to square, computer-generated visual stimuli of various sizes to determine the stimulus parameters that affect their striking behaviour. Males in a high-hunger group displayed a sharp preference for solid black 12×12-degree squares moving linearly against a white background, especially when the squares moved downward (versus horizontally). Males in a low-hunger group visually tracked but, with rare exception, did not strike at any linearly moving squares. In contrast, when solid black squares moved erratically around visual field centre, males struck regularly at them irrespective of hunger level, even when the squares were as large as 47×47 degrees. Males also recognized black-and-white Julesz-patterned square stimuli moving against a similarly patterned background, indicating that they recognized the synchronous movement of a group of stimulus elements as a single moving object. Finally, we compared allometric and life history data between male and females S. lineola to elucidate the possible reasons for the differences between male response patterns and previously published data on females. These comparisons suggest that males employ a different behavioural strategy than do females when faced with large, erratically moving visual stimuli.     

Neuronal responses in the tectum opticum ofSalamandra to visual prey stimuli

Summary In the tectum opticum ofSalamandra salamandra neurons were recorded that showed different selectivity to visual prey stimulus parameters. 21 of 80 neurons responded stronger to rectangles oriented horizontally (wormlike configuration) than to the same patterns oriented vertically. With increasing stimulus velocity, however, these neurons showed non-uniform response characteristics. Although there are partial similarities between behavior and neuronal activity, no response curve of tectal neurons corresponds strictly to response curves of salamander preycapture behavior. So none of the neuron types can be called a prey detector.Supported by the Deutsche Forschungsgemeinschaft     

Body temperature and desiccation constrain the activity of Littoraria irrorata within the Spartina alterniflora canopy

Behavioral patterns of motile ectotherms are often constrained by their microclimate conditions. For intertidal ectotherms, thermal and desiccation stresses are primary limiting factors. In this study, we developed and tested a steady-state heat budget model to calculate the duration of time that the salt marsh snail, Littoraria irrorata (Say), would maintain active behaviors (crawling or attached on stalks of marsh grass Spartina alterniflora) before switching to an inactive state (retracted and glued with a mucus holdfast on the stalks) due to desiccation. The snails' water loss tolerance limit was found to be 43.6±16.0 mg in a laboratory experiment using 5 temperature treatments (25-45 °C in 5 °C increments) with a vapor density (VD) deficit of ∼15 g/m³ (saturated VD-air VD). We found that snails attached to S. alterniflora at lower heights in the canopy had higher body temperatures during daytime hours but lower water loss rates. Furthermore, we found that calculated activity times generally matched daily and seasonal patterns of life history behaviors reported in the literature. If tidal emersion began at night (∼20:00-4:00 h), calculated activity times were much higher than if emersion began in the daytime. The total monthly activity times for 2005-2010 were the highest in May, the lowest in July, and increased from July to September. Therefore, L. irrorata's behaviors appear to be constrained by microclimate conditions within the S. alterniflora canopy as predicted by the heat budget model. The extent to which the snails' life history traits are controlled by environmental conditions will have important implications for their population dynamics as climate change progresses, and heat budget models can help to predict future changes in behavioral responses.     

Behavioural responses to food addition by hedgehogs

We conducted a field experiment at a 4-ha sports ground in Oxford between May and August 1992 to analyse the role of learning and social organization m the short-term responses of hedgehogs Erinaceus europaeus to manipulations of food availability On six nights we uniformly distnbuted 36 'prey' (cat food chunks) twice a night in an 70 × 70 m area (the 'patch') Prey were placed at sites marked with small flags In a subsequent experiment lasting five nights, non-marked and randomly distributed prey were provided We regularly mapped the position of individuals, before, during and after both food supplementation treatments Hedgehogs showed a stable pattern of spatial utilisation of the habitat during the non-hibernation months prior to experimental perturbation Addition of food to parts of the habitat significantly and rapidly changed these patterns a) Hedgehog density increased in food supplemented pans of the habitat b) Hedgehogs learned to associate visual cues with the presence of food c) Hedgehogs learned the spatial location of patches d) Hedgehogs probably engaged in 'area restricted' searching Hedgehogs had overlapping home ranges but showed a uniform distribution within patches and avoided conspecifics at distance < 30 m The number of different individuals visiting the area decreased throughout the experiment Food addition did not significantly change the mean density of hedgehogs, perhaps because social interactions placed an upper limit on density in the areas with supplementary food