Memory use in insect visual navigation

The navigational strategies that are used by foraging ants and bees to reach a goal are similar to those of birds and mammals. Species from all these groups use path integration and memories of visual landmarks to navigate through familiar terrain. Insects have far fewer neural resources than vertebrates, so data from insects might be useful in revealing the essential components of efficient navigation. Recent work on ants and bees has uncovered a major role for associative links between long-term memories. We emphasize the roles of these associations in the reliable recognition of visual landmarks and the reliable performance of learnt routes. It is unknown whether such associations also provide insects with a map-like representation of familiar terrain. We suggest, however, that landmarks act primarily as signposts that tell insects what particular action they need to perform, rather than telling them where they are.     

Cuttlefish use visual cues to determine arm postures for camouflage

To achieve effective visual camouflage, prey organisms must combine cryptic coloration with the appropriate posture and behaviour to render them difficult to be detected or recognized. Body patterning has been studied in various taxa, yet body postures and their implementation on different backgrounds have seldom been studied experimentally. Here, we provide the first experimental evidence that cuttlefish (Sepia officinalis), masters of rapid adaptive camouflage, use visual cues from adjacent visual stimuli to control arm postures. Cuttlefish were presented with a square wave stimulus (period = 0.47 cm; black and white stripes) that was angled 0°, 45° or 90° relative to the animals' horizontal body axis. Cuttlefish positioned their arms parallel, obliquely or transversely to their body axis according to the orientation of the stripes. These experimental results corroborate our field observations of cuttlefish camouflage behaviour in which flexible, precise arm posture is often tailored to match nearby objects. By relating the cuttlefishes' visual perception of backgrounds to their versatile postural behaviour, our results highlight yet another of the many flexible and adaptive anti-predator tactics adopted by cephalopods.     

Cattle use visual cues to track food locations

We tested the hypothesis that cattle aided by visual cues would be more efficient than uncued animals in locating and consuming foods placed in either fixed or variable locations within a 0.64-ha experimental pasture. Eight yearling steers were randomly selected and trained to associate traffic barricades and traffic cones with high- (oat-barley mixture) and low- (straw) quality foods, respectively. Initially steers were randomly assigned to 1 of 4 food location/visual cue treatments: fixed locations/with cues (F/C), variable locations/with cues (V/C), fixed locations/no cues (F/NC), or variable locations/no cues (V/NC). High- and low-quality foods and their respective cue (or no cue) were placed in the experimental pasture. Individual animals were allowed to explore the pasture for 10 min twice per day every other day for 1 week. Minutes until feeding, first feed type consumed (i.e., high-quality, low-quality, or no food consumed), animal location and activity (i.e., feeding, standing, or moving), and total intake of high- and low-quality feed were recorded during each 10-min trial. At the end of each week, location/visual cue treatments were randomly assigned to another 2 steers, which permitted an independent test of each animal in each treatment over a 4-week period. Animals in the F/C and V/C treatments took about 2 min to initially locate and consume a food, compared to F/NC and V/NC animals who took nearly 4 and 6 min, respectively. The high-quality food was the first food located and consumed by F/C, V/C, F/NC, and V/NC animals during 79, 77, 67, and 54% of sampling occasions, respectively. Cued animals typically spent more time feeding (P=0.0004) and less time standing (P=0.005) than uncued animals. Cued animals had a higher mean intake than uncued animals of high- (P=0.001) and low- (P=0.04) quality food. Mean high-quality intake for F/C, V/C, F/NC, and V/NC treatments was 266, 245, 214, and 126 (+/-22) g, respectively; mean low-quality intake for the same treatments was 36, 32, 12, and 10 (+/-10) g. Cued animals also consumed more food per distance traveled than uncued animals (P=0.005). Animals located food quicker (P=0.03) and consumed more high-quality food (P=0.02) when food locations were constant than when they were variable. Our data strongly indicate that cattle can learn to associate visual cues with disparate food qualities and use this information to forage more efficiently in both fixed and variable foraging environments.     

Cuttlefish use visual cues to control three-dimensional skin papillae for camouflage

Cephalopods (octopus, squid and cuttlefish) are known for their camouflage. Cuttlefish Sepia officinalis use chromatophores and light reflectors for color change, and papillae to change three-dimensional physical skin texture. Papillae vary in size, shape and coloration; nine distinct sets of papillae are described here. The objective was to determine whether cuttlefish use visual or tactile cues to control papillae expression. Cuttlefish were placed on natural substrates to evoke the three major camouflage body patterns: Uniform/Stipple, Mottle and Disruptive. Three versions of each substrate were presented: the actual substrate, the actual substrate covered with glass (removes tactile information) and a laminated photograph of the substrate (removes tactile and three-dimensional information because depth-of-field information is unavailable). No differences in Small dorsal papillae or Major lateral mantle papillae expression were observed among the three versions of each substrate. Thus, visual (not tactile) cues drive the expression of papillae in S. officinalis. Two sets of papillae (Major lateral mantle papillae and Major lateral eye papillae) showed irregular responses; their control requires future investigation. Finally, more Small dorsal papillae were shown in Uniform/Stipple and Mottle patterns than in Disruptive patterns, which may provide clues regarding the visual mechanisms of background matching versus disruptive coloration.     

Do terrestrial gastropods use olfactory cues to locate and select food actively?

Having been investigated for over 40 years, some aspects of the biology of terrestrial gastropod’s olfactory system have been challenging and highly contentious, while others still remain unresolved. For example, a number of terrestrial gastropod species can track the odor of food, while others have no strong preferences toward food odor; rather they find it by random encounter. Here, while assessing the most recent findings and comparing them with earlier studies, the aspects of the food selection based on olfactory cues are examined critically to highlight the speculations and controversies that have arisen. We analyzed and compared the potential role of airborne odors in the feeding behavior of several terrestrial gastropod species. The available results indicate that in the foraging of most of the terrestrial gastropod species odor cues contribute substantially to food finding and selection. The results also suggest, however, that what they will actually consume largely depends on where they live and the species of gastropod that they are. Due to the voluminous literature relevant to this object, this review is not intended to be exhaustive. Instead, I selected what I consider to be the most important or critical in studies regarding the role of the olfaction in feeding of terrestrial gastropods.     

The use of visual cues in host evaluation by aphidiid wasps

We examined host evaluation behaviour in three species of aphid parasitoids, Ephedrus californicus Baker, Monoctonus paulensis (Ashmead), and Praon pequodorum Viereck (Hymenoptera: Aphidiidae). Mated females were provided with pairwise choices among three kinds of hosts in the laboratory: (green) pea aphid, Acyrthosiphon pisum (Harris), and a green and a pink colour morph of alfalfa aphid, Macrosiphum creelii Davis. Patterns of attack and host acceptance were species-specific. Females of E. californicus did not respond to the presence of aphids prior to making antennal contact. Variations in rates of parasitization (pea aphid>green alfalfa aphid>pink alfalfa aphid) were consistent with differences in aphid defensive behaviours; no ‘preference’ for any host type was evident when aphids were anaesthetized with carbon dioxide. In M. paulensis, the order of preference (pea aphid>green alfalfa aphid>pink alfalfa aphid) did not vary when aphids were immobilized, or presented in the dark, or both. Host movement did not influence the rate of attack by M. paulensis. In contrast, the ranked order of preference in P. pequodorum varied with circumstance. In the light, females attacked pea aphid and green alfalfa aphid with equal frequency, but parasitized significantly more of the former; both kinds of aphids were attacked and parasitized at higher rates than pink alfalfa aphid. In the dark, P. pequodorum females parasitized green and pink alfalfa aphids equally and at higher rates than pea aphids. Whereas E. californicus was more successful ovipositing in immobilized hosts, P. pequodorum females attacked and laid more eggs in normal than anaesthetized aphids. Patterns of host recognition and evaluation are compared across six species representing four genera in the family Aphidiidae.     

Velarium control and visual steering in box jellyfish

Directional swimming in the box jellyfish Tripedalia cystophora (cubozoa, cnidaria) is controlled by the shape of the velarium, which is a thin muscular sheet that forms the opening of the bell. It was unclear how different patterns of visual stimulation control directional swimming and that is the focus of this study. Jellyfish were tethered inside a small experimental tank, where the four vertical walls formed light panels. All four panels were lit at the start of an experiment. The shape of the opening in the velarium was recorded in response to switching off different combinations of panels. We found that under the experimental conditions the opening in the velarium assumed three distinct shapes during a swim contraction. The opening was (1) centred or it was off-centred and pocketed out either towards (2) a rhopalium or (3) a pedalium. The shape of the opening in the velarium followed the direction of the stimulus as long as the stimulus contained directional information. When the stimulus contained no directional information, the percentage of centred pulses increased and the shape of the off-centred pulses had a random orientation. Removing one rhopalium did not change the directional response of the animals, however, the number of centred pulses increased. When three rhopalia were removed, the percentage of centred pulses increased even further and the animals lost their ability to respond to directional information.     

Controlling airborne cues to study small animal navigation

Small animals such as nematodes and insects analyze airborne chemical cues to infer the direction of favorable and noxious locations. In these animals, the study of navigational behavior evoked by airborne cues has been limited by the difficulty of precisely controlling stimuli. We present a system that can be used to deliver gaseous stimuli in defined spatial and temporal patterns to freely moving small animals. We used this apparatus, in combination with machine-vision algorithms, to assess and quantify navigational decision making of Drosophila melanogaster larvae in response to ethyl acetate (a volatile attractant) and carbon dioxide (a gaseous repellant).     

Honeybee navigation: following routes using polarized-light cues

While it is generally accepted that honeybees (Apis mellifera) are capable of using the pattern of polarized light in the sky to navigate to a food source, there is little or no direct behavioural evidence that they actually do so. We have examined whether bees can be trained to find their way through a maze composed of four interconnected tunnels, by using directional information provided by polarized light illumination from the ceilings of the tunnels. The results show that bees can learn this task, thus demonstrating directly, and for the first time, that bees are indeed capable of using the polarized-light information in the sky as a compass to steer their way to a food source.     

A simple visual system without neurons in jellyfish larvae

Earlier detailed studies of cnidarian planula larvae have revealed a simple nervous system but no eyes or identifiable light sensing structures. Here, we describe the planula of a box jellyfish, Tripedalia cystophora, and report that these larvae have an extremely simple organization with no nervous system at all. Their only advanced feature is the presence of 10-15 pigment-cup ocelli, evenly spaced across the posterior half of the larval ectoderm. The ocelli are single cell structures containing a cup of screening pigment filled with presumably photosensory microvilli. These rhabdomeric photoreceptors have no neural connections to any other cells, but each has a well-developed motor-cilium, appearing to be the only means by which light can control the behaviour of the larva. The ocelli are thus self-contained sensory-motor entities, making a nervous system superfluous.     

Spatial navigation on the radial maze with trial-unique intramaze cues and restricted extramaze cues

We investigated the use of extramaze and intramaze cues on the eight-arm radial maze. The rats received daily training consisting of forced-choice visits to four baited arms, a retention interval, and the availability of all eight arms with baits available at arms that did not appear in the forced-choice phase. The radial maze was placed in a featureless octagonal enclosure to minimize the availability of extramaze cues. Intramaze cues were provided at the distal end of each arm by placing a small object in front of the food trough; unique objects were randomly sampled from a large pool of objects. The use of extramaze and intramaze cues was assessed by rotating the objects, after the retention interval, on occasional non-rewarded probes, thereby dissociating the location of extramaze and intramaze cues. The rats used extramaze rather than intramaze cues. Implications for spatial representations are discussed.     

The use of chemical and visual cues in female choice in the butterfly Bicyclus anynana

Investigating the relative importance of multiple cues for mate choice within a species may highlight possible mechanisms that led to the diversification of closely related species in the past. Here, we investigate the importance of close-range pheromones produced by male Bicyclus anynana butterflies and determine the relative importance of these chemical cues versus visual cues in sexual selection by female choice. We first blocked putative androconial organs on the fore- and hindwings of males, while also manipulating the ability of females to perceive chemical signals via their antenna. We found that male chemical signals were emitted by both fore- and hindwing pairs and that they play an important role in female choice. We subsequently tested the relative importance of these chemical cues versus visual cues, previously identified for this species, and found that they play an equally important role in female choice in our laboratory setting. In addition, females will mate with males with only one signal present and blocking both androconial organs on males seems to interfere with male to male recognition. We discuss the possible functions of these signals and how this bimodal system may be used in intra- and interspecific mate evaluation.     

Memory: obstacle avoidance without visual cues

Avoiding obstacles is essential when we move about the world, yet little is known about how we do this when visual cues are not present to guide us. Recent evidence from behavioural studies in cats suggests that working memory may be crucial.     

Readiness to attend to visual foreground cues

Nonhuman primate genera are differentially inclined to attend to stimuli of the immediate foreground. When great apes were trained to a criterion on each of a series of two-choice visual discrimination problems and then given critical test trials with irrelevant visual cues ($\text{1}\text{2}$ in wire mesh) positioned immediately in front of each problem's objects, accuracy of performance was significantly more disrupted in orang-utans (Pongo) than in chimpanzees (Pan) and gorillas (Gorilla). Two groups of chimpanzees known to differ profoundly in complex-learning skills did not differ in their readiness to attend to irrelevant foreground cues; hence, it is concluded that the observed differences among the three genera of great apes must be species related and associated with how arboreal/terrestial they are in their natural habitats.     

Identification of visual paternity cues in humans

Understanding how individuals identify their relatives has implications for the evolution of social behaviour. Kinship cues might be based on familiarity, but in the face of paternity uncertainty and costly paternal investment, other mechanisms such as phenotypic matching may have evolved. In humans, paternal recognition of offspring and subsequent discriminative paternal investment have been linked to father–offspring facial phenotypic similarities. However, the extent to which paternity detection is impaired by environmentally induced facial information is unclear. We used 27 portraits of fathers and their adult sons to quantify the level of paternity detection according to experimental treatments that manipulate the location, type and quantity of visible facial information. We found that (i) the lower part of the face, that changes most with development, does not contain paternity cues, (ii) paternity can be detected even if relational information within the face is disrupted and (iii) the signal depends on the presence of specific information rather than their number. Taken together, the results support the view that environmental effects have little influence on the detection of paternity using facial similarities. This suggests that the cognitive dispositions enabling the facial detection of kinship relationships ignore genetic irrelevant facial information.     

Operant conditioning of rat navigation using electrical stimulation for directional cues and rewards

Operant conditioning is often used to train a desired behavior in an animal. The contingency between a specific behavior and a reward is required for successful training. Here, we compared the effectiveness of two different mazes for training turning behaviors in response to directional cues in Sprague-Dawley rats. Forty-three rats were implanted with electrodes into the medial forebrain bundle and the left and right somatosensory cortices for reward and cues. Among them, thirteen rats discriminated between the left and right somatosensory stimulations to obtain rewards. They were trained to learn ipsilateral turning response to the stimulation of the left or right somatosensory cortex in either the T-maze (Group T) or the maze (Group W). Performance was measured by the navigation speed in the mazes. Performances of rats in Group T were enhanced faster than those in Group W. A significant correlation between performances during training and performance in final testing was observed in Group T starting with the fifth training session while such a correlation was not observed in Group W until the tenth training session. The training mazes did not however affect the performances in the final test. These results suggest that a simple maze is better than a complicated maze for training animals to learn directions and direct cortical stimulation can be used as a cue for direction training.     

Memory for location and visual cues in white-eared hummingbirds Hylocharis leucotis

In nature hummingbirds face floral resources whose availability,quality and quantity can vary spatially and temporally.Thus,they must constantly make foraging d...