Impact of magnetic fields generated by AC/DC submarine power cables on the behavior of juvenile European lobster (Homarus gammarus).

The number of submarine power cables using either direct or alternating current is expected to increase drastically in coming decades. Data concerning the impact of magnetic fields generated by these cables on marine invertebrates are scarce. In this context, the aim of this study was to explore the potential impact of anthropogenic static and time-varying magnetic fields on the behavior of recently settled juvenile European lobsters (Homarus gammarus) using two different behavioral assays. Day-light conditions were used to stimulate the sheltering behavior and facilitate the video tracking. We showed that juvenile lobsters did not exhibit any change of behavior when submitted to an artificial magnetic field gradient (maximum intensity of 200 µT) compared to non-exposed lobsters in the ambient magnetic field. Additionally, no influence was noted on either the lobsters' ability to find shelter or modified their exploratory behavior after one week of exposure to anthropogenic magnetic fields (225 ±â€¯5 µT) which remained similar to those observed in control individuals. It appears that static and time-varying anthropogenic magnetic fields, at these intensities, do not significantly impact the behavior of juvenile European lobsters in daylight conditions. Nevertheless, to form a complete picture for this biological model, further studies are needed on the other life stages as they may respond differently.

An Enriched Environment Promotes Shelter-Seeking Behaviour and Survival of Hatchery-Produced Juvenile European Lobster (Homarus gammarus).

The high loss of newly released hatchery-reared European lobster (Homarus gammarus) juveniles for stock enhancement is believed to be the result of maladaptive anti-predator behaviour connected to deprived stimuli in the hatchery environment. Our objective was to learn if an enriched hatchery environment enhances shelter-seeking behaviour and survival. In the "naïve" treatment, the juveniles were raised in single compartments without substrate and shelter whereas juveniles in the "exposed" treatment experienced substrate, shelter and interactions with conspecifics. Three experiments with increasing complexity were conducted. Few differences in shelter-seeking behaviour were found between treatments when one naïve or one exposed juvenile were observed alone. When observing interactions between one naïve and one exposed juvenile competing for shelter, naïve juveniles more often initiated the first aggressive encounter. The third experiment was set up to simulate a release for stock enhancement. Naïve and exposed juveniles were introduced to a semi-natural environment including substrate, a limited number of shelters and interactions with conspecifics. Shelter occupancy was recorded three times during a period of 35 days. Exposed juveniles occupied more shelters, grew larger and had higher survival compared with naïve juveniles. Our results demonstrate that experience of environmental complexity and social interactions increase shelter-seeking ability and survival in hatchery reared lobster juveniles.

Ordinary and Extraordinary Movement Behaviour of Small Resident Fish within a Mediterranean Marine Protected Area.

It is important to account for the movement behaviour of fishes when designing effective marine protected areas (MPAs). Fish movements occur across different spatial and temporal scales and understanding the variety of movements is essential to make correct management decisions. This study describes in detail the movement patterns of an economically and commercially important species, Diplodus sargus, within a well-enforced Mediterranean MPA. We monitored horizontal and vertical movements of 41 adult individuals using passive acoustic telemetry for up to one year. We applied novel analysis and visualization techniques to get a comprehensive view of a wide range of movements. D. sargus individuals were highly territorial, moving within small home ranges (< 1 km2), inside which they displayed repetitive diel activity patterns. Extraordinary movements beyond the ordinary home range were observed under two specific conditions. First, during stormy events D. sargus presented a sheltering behaviour, moving to more protected places to avoid the disturbance. Second, during the spawning season they made excursions to deep areas (> 50 m), where they aggregated to spawn. This study advances our understanding about the functioning of an established MPA and provides important insights into the biology and management of a small sedentary species, suggesting the relevance of rare but important fish behaviours.

Response, use and habituation to a mouse house in C57BL/6J and BALB/c mice.

Animal welfare depends on the possibility to express species-specific behaviours and can be strongly compromised in socially and environmentally deprived conditions. Nesting materials and refuges are very important resources to express these behaviours and should be considered as housing supplementation items. We evaluated the effects of one item of housing supplementation in standard settings in laboratory mice. C57BL/6JOlaHsd (B6) and BALB/cOlaHsd (BALB) young male and female mice, upon arrival, were housed in groups of four in standard laboratory cages and after 10 days of acclimatization, a red transparent plastic triangular-shaped Mouse House™ was introduced into half of the home cages. Animals with or without a mouse house were observed in various contexts for more than one month. Body weight gain and food intake, home cage behaviours, emotionality and response to standard cage changing procedures were evaluated. The presence of a mouse house in the home cage did not interfere with main developmental and behavioural parameters or emotionality of BALB and B6 male and female mice compared with controls. Both strains habituated to the mouse house in about a week, but made use of it differently, with BALB mice using the house more than the B6 strain. Our results suggest that mice habituated to the mouse house rather quickly without disrupting their home cage activities. Scientists can thus be encouraged to use mouse houses, also in view of the implementation of the EU Directive (2010/63/EU).

Insect-inspired navigation algorithm for an aerial agent using satellite imagery.

Humans have long marveled at the ability of animals to navigate swiftly, accurately, and across long distances. Many mechanisms have been proposed for how animals acquire, store, and retrace learned routes, yet many of these hypotheses appear incongruent with behavioral observations and the animals' neural constraints. The "Navigation by Scene Familiarity Hypothesis" proposed originally for insect navigation offers an elegantly simple solution for retracing previously experienced routes without the need for complex neural architectures and memory retrieval mechanisms. This hypothesis proposes that an animal can return to a target location by simply moving toward the most familiar scene at any given point. Proof of concept simulations have used computer-generated ant's-eye views of the world, but here we test the ability of scene familiarity algorithms to navigate training routes across satellite images extracted from Google Maps. We find that Google satellite images are so rich in visual information that familiarity algorithms can be used to retrace even tortuous routes with low-resolution sensors. We discuss the implications of these findings not only for animal navigation but also for the potential development of visual augmentation systems and robot guidance algorithms.

Impaired path integration and grid cell spatial periodicity in mice lacking GluA1-containing AMPA receptors.

The hippocampus and the parahippocampal region have been proposed to contribute to path integration. Mice lacking GluA1-containing AMPA receptors (GluA1(-/-) mice) were previously shown to exhibit impaired hippocampal place cell selectivity. Here we investigated whether path integration performance and the activity of grid cells of the medial entorhinal cortex (MEC) are affected in these mice. We first tested GluA1(-/-) mice on a standard food-carrying homing task and found that they were impaired in processing idiothetic cues. To corroborate these findings, we developed an L-maze task that is less complex and is performed entirely in darkness, thereby reducing numerous confounding variables when testing path integration. Also in this task, the performance of GluA1(-/-) mice was impaired. Next, we performed in vivo recordings in the MEC of GluA1(-/-) mice. MEC neurons exhibited altered grid cell spatial periodicity and reduced spatial selectivity, whereas head direction tuning and speed modulation were not affected. The firing associations between pairs of neurons in GluA1(-/-) mice were stable, both in time and space, indicating that attractor states were still present despite the lack of grid periodicity. Together, these results support the hypothesis that spatial representations in the hippocampal-entorhinal network contribute to path integration.

Maternal genotype influences behavioral development of 3×Tg-AD mouse pups.

Transgenic mice are a valuable tool in the investigation of neurodegenerative disorders such as Alzheimer's disease. The triple transgenic mouse (3×Tg-AD) is a model of Alzheimer's disease that possesses age-related amyloid beta plaques, neurofibrillary tangles and cell death as well as cognitive decline. Because maternal effects may interact with pup genotype in determining behavior phenotypes, we used a cross-fostering paradigm to investigate the effects of maternal genotype on behavioral development of the 3×Tg-AD mouse model and its wildtype control (B6129S1F2) from 2 to 24 days of age. Developmental patterns of behavior were influenced by both pup and maternal genotype. The 3×Tg-AD mice were delayed in sensory reflexes, showed less activity and poorer habituation to a novel object, but showed advanced development of motor reflexes compared to wildtype pups. While there were no differences in levels of maternal care between transgenic and control mothers, maternal genotype affected the development of several pup reflexes (body weight, hindlimb grasp reflex, loss of crossed extensor reflex, vibrissae response, righting reflex) and the number of horizontal and vertical beam breaks in an open field. This study is the first to examine neurobehavioral development and maternal behavior in a mouse model of Alzheimer's disease, and highlights the importance of investigating the consequences of early environmental experience as well as genetic manipulation on behavioral development.

Path integration: how the head direction signal maintains and corrects spatial orientation.

Head-direction cells have frequently been regarded as an internal 'compass' that can be used for navigation, although there is little evidence showing a link between their activity and spatial behavior. In a navigational task requiring the use of internal cues to return to a home location without vision (path integration), we found a robust correlation between head-direction cell activity and the rat's heading error in the rat's homing behavior. We observed two different correction processes that rats used to improve performance after an error. The more frequent one consists of 'resetting' the cell whenever the rat returns to the home location. However, we found that when large errors occur, the head-direction system has the ability to 'remap' and set a new reference frame, which is then used in subsequent trials. We also offer some insight into how these two correction processes operate when rats make an error.

Participation of the homing pigeon thalamofugal visual pathway in sun-compass associative learning.

The ascending thalamofugal visual pathway in pigeons (Columba livia) terminates in the telencephalic wulst. Characterizing the role of this pathway in visually guided behaviour has remained a challenge. To determine whether this pathway, and in particular the wulst, may participate in sun-compass-guided behaviour in homing pigeons, intact, ectostriatum-lesioned or wulst-lesioned pigeons were trained to use their sun compass to locate the direction of a food reward in an outdoor, octagonal arena. Control and ectostriatum-lesioned pigeons learned the task well, and orientated appropriately during the first trial of the last three training sessions and after a phase-shift manipulation. In contrast, the wulst-lesioned pigeons learned the task but they took more sessions to learn, and their directional choices were more scattered during the first trial of the last three training sessions and after the phase-shift manipulation. A subsequent regression analysis indicated that deeper layers of the wulst might have made more of a contribution to the observed behavioural impairments. The data indicate that the homing pigeon wulst participates in visually guided behaviour when the sun compass is used to learn the directional location of a goal.