Field evidence of compass orientation in migrating juvenile grunts (Haemulidae)

Juvenile French and white grunts, Haemulon flavolineatum (Desmarest) and H. plumieri (Lacé-pède), were captured during their daily migrations between diurnal resting sites on coral patch reefs and nocturnal feeding grounds in seagrass beds. Grunts captured during morning and evening migrations were released on the route and after displacement up to 100 m or 5 km away. Grunts generally moved in the direction which would have taken them back towards their home reef or to their accustomed feeding sites, indicating that familiar landmarks are not essential for orientation. The spatial precision of migration may serve to partition the feeding area most efficiently. The timing of migrations is also very precise, and appears to be adapted to reduce the vulnerability of grunts to predation near their home reef.     

The nature and role of learning in the orientation and migratory behavior of fishes

Synopsis Fish migration may be viewed as the product of two processes; the selection and tracking of optimal environmental conditions through time and space, and the use of predictive information about environmental structure to bias movements towards a goal. The establishment and maintenance of directional bias is based on the interaction of experience and instinct. The preoccupation of much fish orientation research with innate fixed patterns of behavior on one hand and hydrodynamics on the other has led us to underestimate the possibility that orientation is a flexible process relying on developmental sequences, calibration of the motor-sensory interaction based on experience and the learning of environmental pattern. Evidence illustrating how experience and learning may influence the direction of movement and how the goal is recognized is presented according to two general categories: (a) imprinting and early experience and (b), spatial learning, including the social transmission of migratory routes and directions. In the first category, the olfactory hypothesis of salmon homing is briefly reviewed and new data presented describing olfactory imprinting in Atlantic salmon,Salmo salar. In the second category, evidence is presented demonstrating the modifiability of sun-compass orientation and the ability of some fish species to learn the spatial distribution of landmarks. The role of social transmission in the migration of coral reef fishes is reviewed. The possible role of these learning phenomena in the formation of familiar area maps, route-based and location-based navigation and the critical distance factor is considered. The relationship between life history and the nature of learning in migratory orientation is discussed     

Goldfish use the visual angle of a familiar landmark to locate a food source

Three goldfish were trained to search for food buried 20 cm from a perspex tower. In the absence of food, all fish still searched in the correct location, revealing that fish can use a landmark to locate food. Halving either the width or height of the landmark resulted in searches significantly closer to the tower, suggesting that fish determined their position relative to the landmark using its horizontal and vertical visual angles.     

Hydrodynamic orientation of crayfish (Procambarus clarkii) to swimming fish prey

Reversibly blindfolded crayfish (Procambarus clarkii) react to small swimming fish (Astyanax fasciatus mexicanus) approaching or passing nearby with antennal and cheliped movements and body turns (Fig. 3). We studied the accuracy and dynamics of crayfish orientation responses to the previously analyzed hydrodynamic disturbances caused by the fish, mostly produced by tail flicks.Antennal and cheliped movements started slightly before the onset of turning responses (Fig. 4). Antennal sweeps were performed most rapidly. 50% of the appendage sweeps resulted in contacts with the fish (Fig. 5).Most turns were directed toward the stimulus (Fig. 6). Response amplitudes increased with increasing stimulus angle. Turns were accurate for small stimulus angles, but smaller than expected for larger ones. Sweeps of ipsilateral antennae and chelipeds were generally directed backwards, while those of contralateral appendages were smaller and directed forwards. The amplitudes of appendage sweeps first increased with increasing stimulus angle and then decreased again for more caudal stimulus directions. Lateral stimuli (60°–120°) from opposite sides were usually significantly distinguished. The amplitudes of the different elements of orientation behaviour were highly correlated with each other, indicating that they were directed by the same sensory input.     

How to calculate the optimal density of food for fish larvae

Synopsis The optimal density of plankton required for the growth and development ofCoregonus lavaretus (L.) larvae is calculated on the basis of the volume of water searched, the probability of successful feeding responses, and the results of experimental growth studies. This amounts to 200–260 individual food organisms 1^–1 (individual plankton 0.004 mg), or 14–17 individuals 1^–1 (individual plankton 0.057 mg). The feeding optimum depends on water temperature and the time at which feeding begins.     

How swimming fish use slow and fast muscle fibers: implications for models of vertebrate muscle recruitment

We quantified the intensity and duration of electromyograms (emgs) from the red and white axial muscles in five bluegill sunfish (Lepomis macrochirus) which performed three categories of behavior including steady swimming and burst and glide swimming at moderate and rapid speeds. Steady swimming (at 2 lengths/s) involved exclusively red muscle activity (mean posterior emg duration = 95 ms), whereas unsteady swimming utilized red and white fibers with two features of fiber type recruitment previously undescribed for any ectothermic vertebrate locomotor muscle. First, for moderate speed swimming, the timing of red and white activity differed significantly with the average onset time of white lagging behind that of red by approximately 40 ms. The durations of these white emgs were shorter than those of the red emgs (posterior mean = 82 ms) because offset times were effectively synchronous. Second, compared to steady and moderate speed unsteady swimming, the intensity of red activity during rapid unsteady swimming decreased while the intensity of white muscle activity (mean white emg duration = 33 ms) increased. Decreased red activity associated with increased white activity differs from the general pattern of vertebrate muscle recruitment in which faster fiber types are recruited in addition to, but not to the exclusion of, slower fiber types.     

Cytoskeletal organization and collagen orientation in the fish scales

Summary Immunofluorescence and electron microscopy were used to analyze the relationships between the organization of collagen fibrils in elasmoid scales, and the orientation of microtubules and actin microfilaments in the scleroblasts producing this collagenous stroma. Attention was focused on the basal plate of the scales because of the highly ordered three-dimensional arrangement of the collagen fibrils in superimposed plies forming an acellular plywood-like structure. The collagen fibrils are synthesized by the scleroblasts forming a monolayered pseudo-epithelium, the hyposquama, at the lowest surface of the scale. Fully developed scales with a low collagen deposition rate were compared with regenerating scales active in fibrillogenesis. When an ordered array of the collagen fibrils is found, the innermost collagen fibrils are coaligned with microtubules and actin microfilaments. Thus, because of this coalignment, microtubules and actin microfilaments of the hyposquamal scleroblasts are subjected to consecutive alterations during the formation of the plies of the basal plate. The sequence of events when the collagen fibrils change their direction from one ply to the other in the basal plate is deduced from immunofluorescence and phase-contrast-microscopic observations. During the formation of the orthogonal plywood-like structure in the regenerating scales, first microtubules may change their curse with a rotating angle of about 90°; then, actin microfilaments are disorganized and reorganized by interacting mechanically with the microtubules with which they are coaligned. Collagen fibrils are synthesized in a direction that is roughly perpendicular to that of the preceding ply. The unknown signals inducing the change in direction of the cytoskeleton may be transmitted throughout the hyposquama via gap junctions.This work is dedicated to the memory of Jacques Escaig     

How synapses in the auditory system wax and wane: theoretical perspectives

Spike-timing-dependent synaptic plasticity has recently provided an account of both the acuity of sound localization and the development of temporal-feature maps in the avian auditory system. The dynamics of the resulting learning equation, which describes the evolution of the synaptic weights, is governed by an unstable fixed point. We outline the derivation of the learning equation for both the Poisson neuron model and the leaky integrate-and-fire neuron with conductance synapses. The asymptotic solutions of the learning equation can be described by a spectral representation based on a biorthogonal expansion.     

昆虫定向机制研究进展

许多昆虫具有定向运动的行为。对部分社会性昆虫和迁飞性昆虫定向行为的大量研究已经初步阐明太阳、地磁场、天体、风及地面标志物等都可能成为昆虫返巢和迁飞定向的线索。社会性昆虫具有对不同定向线索进行整合而实现精确导航的能力。日间迁飞性昆虫利用时间补偿太阳罗盘进行定向的机制亦已明确,但夜间迁飞昆虫的定向机制尚需深入研究。迁飞性害虫定向机制的明确将有助于判断害虫迁飞路径及降落区域,为迁飞害虫的准确预测提供科学依据。本文对昆虫的定向机制研究进展进行了综述。     

Learning and solar orientation in the mole cricket Gryllotalpa gryllotalpa (Orthoptera: Gryllidae)

The ecologically efficient escape direction assumed by Gryllotalpa gryllotalpais learned by the larvae after they leave the maternal nest. Nonetheless, larvae hatched in the laboratory are innately capable of using the sun to maintain a set escape direction. The species can also modify the set point of its sun compass to conform to topographical changes encountered during its wanderings.     

Use of water flow direction to provide spatial information in a small-scale orientation task

Experiments were designed to investigate whether three-spined sticklebacks Gasterosteus aculeatus can use direction of water flow as an orientation cue. The fish had to learn the location of a food patch in a channel where water flow direction was the only reliable indicator of the food patch position. Fish from two ponds and two rivers were trained and tested in the spatial task to determine whether river three-spined sticklebacks are more adept at using water flow as a spatial cue than fish from ponds. All fish were able to use water flow to locate the food patch but one of the two river groups was significantly faster at learning the patch location. When the task was reversed so that fish that had formerly been trained to swim downstream now had to learn to swim upstream and vice versa both river groups learned the reversed task faster than the two pond groups. In a second experiment, to investigate whether fish from ponds or rivers vary in the type of spatial cue that they prefer to use, fish from one pond and one river were given a choice between two different types of spatial cue: flow direction or visual landmarks. A test trial in which these two cues were put into conflict revealed that the river population showed a strong preference for flow direction whilst the pond population preferred to use visual landmarks.     

Coral reef fish communities: a compromise view

Synopsis The fishes associated with coral reefs offer excellent opportunities for the study of the factors that determine the species composition of complex, highly interactive communities. Amenable to sampling and direct observations many patch reefs are small enough to be studied as entire units and yet diverse enough to include a wide range of interactions.Coral reef fishes appear to be highly specialized in morphology, color, behavior and life cycles and yet colonization experiments and repeated censusing have shown a surprisingly high variation in the fishes that are associated in similar habitats or in the same habitat at different times. This has led to two different views: (i) the chaos view that holds that the species composition is due to random factors and chance colonization, and (ii) the order view that resource sharing adaptations determine which species can live together.This paper reviews some of the obvious adaptations of reef fishes. An examination of the maximum sizes reached by infaunal reef dwellers shows that the largest individual of each species differs by a constant proportion from the next larger and next smaller species. This suggests growth limitations by interspecies competition. A hypothetical model showing how this might work is offered and it is shown that as long as there are more species than can be accommodated in the community at any one time the number of combinations is great enough to give the appearance of randomness even though the individual species may have precise environmental requirements.This paper forms part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N.Y., 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Hellman, ed.).     

Correspondences in visual imaging and spatial orientation in dreaming and film viewing.

New directions in film and media theory have begun to focus on precognitive, embodied aspects of film viewing. Drawing on these recent theoretical approaches, this article examines correspondences between the brain–mind state of the dreamer and the film viewer and formal similarities between the cinematic image and dream images. First, the study asks whether cinema's evolution toward the production of images that are more easily processed by the brain has also made film images easily accessible during dream-sleep. Then it shows how the cinematic image and the visual imaging of dreams depend on a similar construction of navigable space. The analysis suggests that the bodily systems for simulating movement and establishing spatial orientation function in a similar manner during dreaming and film viewing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Making learning easy: the acquisition of visual information during the orientation flights of social wasps

The flights of individual wasps (Vespula) were recorded as they approached a small feeder on the ground that was marked by a black cylinder ca 15 cm away. Two navigational strategies are used in these approaches. Initially, the wasp aims at the cylinder, treating it as a beacon and fixating it with frontal retina. In the last stage of the flight, the wasp assumes a preferred orientation so that the cylinder takes up a constant, more peripheral retinal position as the wasp nears the feeder. Path guidance by image-matching is likely to be limited to this final segment of the return. Wasps could gain the information needed for these distinct navigational strategies during the learning flights that they perform on their initial departures from the feeder. They fly away from the feeder in a series of arcs while turning at a mean angular velocity of 226°/s. The cylinder tends to be viewed with frontal retina during the arcs suggesting that the information required for aiming at the cylinder is acquired then. For image matching, the appearance of the cylinder needs to be learnt when the wasp is in the orientation that it adopts close to the feeder on its return flight. Wasps tend to assume this orientation during learning flights while they face the feeder. Such inspections of the feeder occur at the ends of arcs when a wasp's turning velocity is low.     

Balken orientation in three coleopteran cuticles

The cuticles of three beetles of differing habit have been examined, and the disposition of the Balken (fibre bundles) found to be appropriate to functional requirements. Crossed Balken are present in the body generally, but longitudinal orientation of Balken provides suitable reinforcement where bending stresses may be expected to be high, as in the femur of the hind limbs of Cybister and G eotrupes , and in the horns of Golofa .     

The dinoflagellates Pfiesteria shumwayae and Luciella masanensis cause fish kills in recirculation fish farms in Denmark

Fish kills in two geographically separate fish farms in northern Denmark in 2012, one using marine, the other brackish water ‘Recirculation Aquaculture Systems’ (RAS), were found to be caused by Pfiesteria shumwayae and Luciella masanensis, two species of dinoflagellates belonging to the family Pfiesteriaceae. There were no other harmful algae present in either of the aquaculture plants. Serious fish kills in the US have been attributed to Pfiesteria during the past 20 years, but this type of mortality has not been documented elsewhere. L. masanensis, described recently from Korea and USA, has not been previously reported to be the source of fish kills. In the marine farm, the affected fish was rainbow trout, in the brackish water farm pikeperch. Light microscopy is presently insufficient to discriminate between the approx. 20 species of the family Pfiesteriaceae described. Identification of the two algal species was therefore based on molecular sequencing of nuclear-encoded LSU rDNA, confirmed by scanning electron microscopy and, eventually, also by examination of the very thin amphiesmal plates of the flagellates by calcofluor-stained cells in a fluorescence microscope.Although the two fish farms differed in light and salinity conditions, both farms used re-circulating water in closed circuit systems. The dinoflagellates were examined in detail and shown to feed on organic material such as live, damaged nematodes, as described for the single pfiesteriacean flagellate known from freshwater, Tyrannodinium edax. Algal cells were observed to attach to their prey by an attachment filament and subsequently used a peduncle to suck up the food. Fish farms utilizing water recirculation technology are gaining popularity due to their reduced effect on the environment. The two cases from Denmark are apparently the first RAS farms in which serious fish kills have been reported. In the marine farm (Luciella) fish mortality increased dramatically despite treatment of the water with peracetic acid and chloramine-T. The plant was temporarily closed down pending investigation into the cause of mortality and subsequently to determine a method of management to control the dinoflagellate and avoid future fish kills. In the brackish water farm (Pfiesteria), water was treated with chloramine-T, which caused the dinoflagellates to disappear temporarily from the water column, apparently forming temporary cysts. The treatment was repeated after a few days to a week, when the temporary cysts appeared to germinate and the dinoflagellates reappeared in the water column.     

Moon orientation in adult and young sandhoppers

In the last 30 years, lunar orientation has received little attention from students of animal orientation. Even in Talitrus saltator, the first animals in which the lunar compass was demonstrated, research did not continue. Our studies have demonstrated that: 1) chronometrically compensated lunar orientation is independent of the earth's magnetic field (an ever present non-chronometric orientation reference); 2) lunar orientation is independent of the lunar shape; and 3) the lunar compass is also used by young animals born in the laboratory (without experience in nature). Accepted: 30 September 1998