Distance Of Animals Research Articles

Object-centered population coding in CA1 of the hippocampus

Objects and landmarks are crucial for guiding navigation and must be integrated into the cognitive map of space. Studies of object coding in the hippocampus have primarily focused on activity of single cells. Here, we record simultaneously from large numbers of hippocampal CA1 neurons to determine how the presence of a salient object in the environment alters single-neuron and neural-population activity of the area. The majority of the cells showed some change in their spatial firing patterns when the object was introduced. At the neural-population level, these changes were systematically organized according to the animal's distance from the object. This organization was widely distributed across the cell sample, suggesting that some features of cognitive maps-including object representation-are best understood as emergent properties of neural populations.

Atrazine and Diuron Effects on Survival, Embryo Development, and Behavior in Larvae and Adult Zebrafish.

Atrazine and Diuron are widely used herbicides. The use of pesticides contaminates the aquatic environment, threatening biodiversity and non-target organisms such as fish. In this study, we investigated the effects of acute exposure for 96 h hours to atrazine and diuron commercial formulations in zebrafish (Danio rerio, wild-type AB) embryos and larvae and adult stages. We observed a significant concentration-dependent survival decrease and hatching delays in animals exposed to both herbicides and in the frequency of malformations compared to the control groups. Morphological defects included cardiac edema, tail reduction, and head malformation. At 7 days post-fertilization (dpf), atrazine exposure resulted in a reduction in the head length at 2, 2.5, and 5 mg/L and increased the ocular distance at 1, 2, 2.5, and 5 mg/L atrazine when compared to controls. At the same age, diuron increased the ocular distance in animals exposed to diuron (1.0 and 1.5 mg/L) and no effects were observed on the head length. We also evaluated a behavioral repertoire in larvae at 7 dpf, and there were no significant differences in distance traveled, mean speed, time in movement, and thigmotaxis for atrazine and diuron when animals were individually placed in a new environment. The cognitive ability of the larvae was tested at 7 dpf for avoidance and optomotor responses, and neither atrazine nor diuron had significant impacts when treated groups were compared to their corresponding controls. Adults’ behavior was evaluated 7 and 8 days after the end of the acute herbicide exposure. Exploration of a new environment and associated anxiety-like parameters, social interaction, and aggressiveness were not altered. Our results highlight the need for further studies on the sublethal effects of both herbicides and the consideration of the effects of commercial formulas vs. isolated active ingredients. It also emphasizes the need to take sublethal effects into consideration when establishing the environmental limits of residues.

Estimating effective detection area of static passive acoustic data loggers from playback experiments with cetacean vocalisations

AbstractPassive acoustic monitoring (PAM) is used for many vocal species. However, few studies have quantified the fraction of vocalisations captured, and how animal distance and sound source level affect detection probability. Quantifying the detection probability or effective detection area (EDA) of a recorder is a prerequisite for designing and implementing monitoring studies, and essential for estimating absolute density and abundance fromPAMdata.We tested the detector performance of cetacean click loggers (C‐PODs) using artificial and recorded harbour porpoise clicks played at a range of distances and source levels. Detection rate of individual clicks and click sequences (or click trains) was calculated. A Generalised Additive Model (GAM) was used to create a detection function and estimate the effective detection radius (EDR) andEDAfor both types of signals.Source level and distance from logger influenced the detection probability. Whilst differences between loggers were evident, detectability was influenced more by the deployment site than within‐logger variability. Maximum distance for detecting real recorded porpoise clicks was 566 m. MeanEDRfor artificial signals with source level 176dBre 1 μPa @ 1m was 187 m., and for a recorded vocalisation with source level up to 182dBre 1 μPa was 188 m. For detections classified as harbour porpoise click sequences the meanEDRwas 72 m.The analytical methods presented are a valid technique for estimating theEDAof any logger used in abundance estimates. We present a practical way to obtain data with a cetacean click logger, with the caveat that artificial playbacks cannot mimic real animal behaviour and are at best able to account for some of the variability in detections between sites, removing logger and propagation effects so that what remains is density and behavioural differences. If calibrated against real‐worldEDAs (e.g., from tagged animals) it is possible to estimate site‐specific detection area and absolute density. We highlight the importance of accounting for both biological and environmental factors affecting vocalisations so that accurate estimates of detection area can be determined, and effective monitoring regimes implemented.

A Genetic Network for Systemic RNA Silencing in Plants.

Non-cell autonomous RNA silencing can spread from cell to cell and over long distances in animals and plants. However, the genetic requirements and signals involved in plant mobile gene silencing are poorly understood. Here, we identified a DICER-LIKE2 (DCL2)-dependent mechanism for systemic spread of posttranscriptional RNA silencing, also known as posttranscriptional gene silencing (PTGS), in Nicotiana benthamiana Using a suite of transgenic DCL RNAi lines coupled with a GFP reporter, we demonstrated that N. benthamiana DCL1, DCL2, DCL3, and DCL4 are required to produce microRNAs and 22, 24, and 21nt small interfering RNAs (siRNAs), respectively. All investigated siRNAs produced in local incipient cells were present at low levels in distal tissues. Inhibition of DCL2 expression reduced the spread of gene silencing, while suppression of DCL3 or DCL4 expression enhanced systemic PTGS. In contrast to DCL4 RNAi lines, DCL2-DCL4 double-RNAi lines developed systemic PTGS similar to that observed in DCL2 RNAi. We further showed that the 21 or 24 nt local siRNAs produced by DCL4 or DCL3 were not involved in long-distance gene silencing. Grafting experiments demonstrated that DCL2 was required in the scion to respond to the signal, but not in the rootstock to produce/send the signal. These results suggest a coordinated DCL genetic pathway in which DCL2 plays an essential role in systemic PTGS in N. benthamiana, while both DCL4 and DCL3 attenuate systemic PTGS. We discuss the potential role of 21, 22, and 24 nt siRNAs in systemic PTGS.

In Utero Exposure to Dioxins and Dioxin-like Compounds and Anogenital Distance in Newborns and Infants

Background: Anogenital distance in animals is used as a measure of fetal androgen action. Prenatal exposure to dioxins and dioxin-like compounds in rodents causes reproductive changes in male offspring and decreases anogenital distance.Objective: We assessed whether in utero exposure to dioxins and dioxin-like compounds adversely influences anogenital distance in newborns and young children (median age, 16 months; range, 1–31 months).Methods: We measured anogenital distance among participants of the “Rhea” mother–child cohort study in Crete and the Hospital del Mar (HMAR) cohort in Barcelona. Anogenital distance (AGD; anus to upper penis), anoscrotal distance (ASD; anus to scrotum), and penis width (PW) were measured in 119 newborn and 239 young boys; anoclitoral (ACD; anus to clitoris) and anofourchetal distance (AFD; anus to fourchette) were measured in 118 newborn and 223 young girls. We estimated plasma dioxin-like activity in maternal blood samples collected at delivery with the Dioxin-Responsive Chemically Activated LUciferase eXpression (DR CALUX®) bioassay.Results: Anogenital distances were sexually dimorphic, being longer in males than females. Plasma dioxin-like activity was negatively associated with AGD in male newborns. The estimated change in AGD per 10 pg CALUX®–toxic equivalent/g lipid increase was –0.44 mm (95% CI: –0.80, –0.08) after adjusting for confounders. Negative but smaller and nonsignificant associations were observed for AGD in young boys. No associations were found in girls.Conclusions: Male infants may be susceptible to endocrine-disrupting effects of dioxins. Our findings are consistent with the experimental animal evidence used by the Food and Agriculture Organization/World Health Organization to set recommendations for human dioxin intake.

Keeping returns optimal: gain control exerted through sensitivity adjustments in the harbour porpoise auditory system

Animals that use echolocation (biosonar) listen to acoustic signals with a large range of intensities, because echo levels vary with the fourth power of the animal's distance to the target. In man-made sonar, engineers apply automatic gain control to stabilize the echo energy levels, thereby rendering them independent of distance to the target. Both toothed whales and bats vary the level of their echolocation clicks to compensate for the distance-related energy loss. By monitoring the auditory brainstem response (ABR) during a psychophysical task, we found that a harbour porpoise (Phocoena phocoena), in addition to adjusting the sound level of the outgoing signals up to 5.4 dB, also reduces its ABR threshold by 6 dB when the target distance doubles. This self-induced threshold shift increases the dynamic range of the biosonar system and compensates for half of the variation of energy that is caused by changes in the distance to the target. In combination with an increased source level as a function of target range, this helps the porpoise to maintain a stable echo-evoked ABR amplitude irrespective of target range, and is therefore probably an important tool enabling porpoises to efficiently analyse and classify received echoes.

Effects of Selective iNOS Inhibitor on Spatial Memory in Recovered and Non-Recovered Ketamine Induced Anesthesia.

Nitric oxide (NO) is thought to be involved in spatial learning and memory in several brain areas such as hippocampus. This study examined the effects of post-training intrahippocampal microinjections of 1400W as a selective iNOS inhibitor on spatial memory, in anesthetized and non-anesthetized situations in rats. In the present work, 4-day training trials of animals were conducted. Spatial memory was tested 48 hours after the drug infusions. For microinjection of 1400W into CA1 region of the hippocampus in conscious animals, guide cannula was implanted into the CA1 area and 1400W was infused after recovery from surgical anesthesia. In anesthetized animals, 1400W was microinjected directly into CA1 region by Hamilton syringe during anesthesia. After completion of training, 1400W (10, 50 and 100 μM/side) were microinjected bilaterally (1 μL/side) and testing trials were performed 48 h after drug infusions in both groups of cannulated and non-cannulated rats. Significant reduction was observed in escape latency and traveled distance in animals that received 1400W (100 μM/side, *p < 0.05) via cannula after recovery in comparison with control group. Also, microinjection of 1400W (100 μM/side) in post recovery phase caused a significant (***p < 0.001) reduction in time and distance of finding the hidden platform in comparison with anesthetized situation. These findings suggest that 1400W has a significant improvement on spatial memory and memory enhancement induced by iNOS inhibitor can be affected by anesthesia in a period of time.

Predator‐hunting success and prey vulnerability: quantifying the spatial scale over which lethal and non‐lethal effects of predation occur

1. The shape of the function linking predator-attack success rate with distance to predator-concealing cover, or prey refuge, will affect population dynamics, distribution patterns and community trophic structure. Theory predicts that predator-attack success should decline exponentially with distance from predator-concealing cover, resulting in a threshold distance value above which there is little change in risk. Animals should then completely avoid areas of otherwise suitable habitat below this threshold, except when starvation risk exceeds predation risk. 2. We measured the shape of the function linking attack success with distance from cover in a system of Eurasian Sparrowhawks Accipiter nisus attacking (n = 445) and killing (n = 71) Redshanks Tringa totanus. We then determined if there was a threshold value and whether redshanks avoided areas below this threshold. 3. Sparrowhawk success rate with distance to predator-concealing cover declined exponentially with a threshold value of approximately 30 m. Redshanks used habitat above the threshold according to profitability and only fed below it, on average, in cold weather when starvation risk can be imminently high. Above about 5 degrees C, 26% of available habitat was avoided. 4. Our data support the hypothesis that predators create discrete areas with respect to cover that are avoided by prey. Large areas of suitable habitat may be unused, except in times of high starvation risk, when such areas may provide a foraging reserve, with large implications for population distribution and dynamics. 5. Our results are generated from a system in which predators attack their prey from concealing cover. But in the theoretically identical reverse scenario where the prey animal's distance from protective cover determines predation risk, such non-lethal effects will be equally important, especially in heavily fragmented landscapes.

Effects of Selective iNOS Inhibitor on Spatial Memory in Recovered and Non-recovered Ketamine Induced-anesthesia in Wistar Rats.

Nitric oxide (NO) is thought to be involved in spatial learning and memory in several brain areas such as hippocampus. This study examined the effects of post-training intrahippocampal microinjections of 1400W as a selective inducible nitric oxide synthase (iNOS) inhibitor on spatial memory, in both anesthetized and non-anesthetized situations in rats. In the present work, 4-day training trials of animals were conducted. Spatial memory was tested 48 h after the drug infusions. For microinjection of 1400W into CA1 region of the hippocampus in conscious animals, guide cannula was implanted into the CA1 area and 1400W was infused after recovery from surgical anesthesia. In anesthetized animals, 1400W was microinjected directly into CA1 region by Hamilton syringe during anesthesia. After completion of training, 1400W (10, 50 and 100 μM/side) were microinjected bilaterally (1 μL/side) and testing trials were performed 48 h after drug infusions in both groups of cannulated and non-cannulated rats. Significant reduction was observed in escape latency and traveled distance in animals that received 1400W (100 μM/side, * P < 0.05) via cannula after recovery in comparison with control group. Moreover, microinjection of 1400W (100 μM/side) in post recovery phase also caused a significant (*** P < 0.001) reduction in time and distance of finding the hidden platform in comparison with anesthetized situation. These results suggest that 1400W has a significant improvement on spatial memory, and memory enhancement induced by iNOS inhibitor can be affected by anesthesia in a period of time.

Direct Evidence for Distance Measurement via Flexible Stride Integration in the Fiddler Crab

While on foraging excursions, fiddler crabs track their burrow location despite having no visual contact with it . They do this by path integration, a common navigational process in which motion vectors (the direction and distance of animals' movements) are summed to form a single "home vector" linking the current location with the point of origin. Here, we identify the mechanism by which the integrator measures distance, by decoupling motor output from both inertial and visual feedback. Fiddler crabs were passively translated to a position such that the home vector lay across an acetate sheet on the ground. After being frightened, crabs tried to escape but slipped as they did so. Detailed high-speed video analysis reveals that crabs measure distance by integrating strides, rather than linear acceleration or optic flow: the number of steps they took depended on both the length of the home vector and how large their steps were, whether they slipped and fell short or not. This is the most direct evidence to date of a stride integrator that is flexible enough to account for significant variation in stride length and frequency.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

A Close Keeper–Nonhuman Animal Distance Does Not Reduce Undesirable Behavior in Contact Yard Goats and Sheep

This study investigated the relation between zookeeper-nonhuman animal distance and the undesirable behavior goats and sheep exhibited toward visitors of Zoo Atlanta's contact yard. It hypothesized that a close distance between keeper and animal would be associated with a lower rate of undesirable behavior than would a distant keeper-animal distance. The study recorded rate of undesirable behavior exhibited, number of visitors in the yard, and number of times visitors touched an animal under near and distant keeper-animal distances. Seven African pygmy goats (Capra hircus) and 4 Romanov sheep (Ovis aries) were the subjects. The study used linear regression methods to analyze approximately 48 hr of behavioral data collected using a focal sampling technique. Findings indicated a familiar animal keeper nearby was not associated with lower rates of undesirable behavior toward visitors. Higher rates of undesirable behavior occurred when keepers were nearby than when they were distant. The study also found that undesirable behavior increased as visitors' touching of the animals increased. Applying the study's findings may improve human-animal interactions and increase animal well-being in a contact yard through animal management techniques.

Effect of variable moderate chronic stress on ligature‐induced periodontal disease in Wistar rats

The aim of this investigation was to study the impact of stress on ligature‐induced periodontal disease in rats by means of a variable moderate chronic stress model. Thirty male Wistar rats were randomly assigned to six groups. Control groups received only ligatures around the second maxillary molars, while experimental groups were exposed to stress in additional. Stress was imposed by means of flashing light, isolation, rat blood smelling, new environment exposure, immobilization in cold temperature and immobilization at room temperature. Stress was applied randomly, thereby diminishing adaptation of the animals to the model. The animals were killed after 29, 43, and 57 days. The distance between the cementum‐enamel junction and the alveolar bone (CEJ‐AB) was measured. Alveolar bone loss was statistically different between stressed and control animals, whereas differences were not observed between experimental periods. The mean CEJ‐AB distance in animals exposed to stress was 154.50 μm smaller than the corresponding distance in the controls. It might be concluded that variable moderate chronic stress decreased alveolar bone loss in a ligature‐induced periodontal disease model.

Stimulus control of defensive behaviors of garter snakes (Thamnophis sirtalis): Effects of eye spots and movement.

The purpose of these experiments was to examine the effects of eye spots and stimulus movement as mediators of antipredator responses in garter snakes. In Experiment 1, 13 Eastern garter snakes (Thamnophis sirtalis) at 6-8 weeks of age were confronted with a series of threatening models that varied in the configuration of the eyes (artificial glass eyes, circular black spots, elongated black bars, or no eyespots). There were significant differences in the number of strikes elicited by the models, and the model with realistic glass eyes elicited the most strikes. In Experiment 2, we examined the effects of erratic and consistent stimulus movement on defensive behavior in 12 garter snakes at 12-16 weeks of age. The snakes delivered significantly more strikes to an erratically moving model than to a model oscillated at a regular rate. Animals of most species are prey for other animals, and it is critical that they can identify potential predators at a distance. Although a wide variety of cues are used in predator recognition (e.g., Edmunds, 1974; Endler, 1986), the involvement of visual cues has received most attention. (See Curio, 1993, for a comprehensive review.) Eyes and eyelike markings play a particularly important role in interactions between predator and prey. For example, eyelike stimuli have been shown to prolong tonic immobility in a number of species under laboratory conditions (e.g., Gagliardi, Gallup, & Boren, 1976; Gallup, 1971; Hennig, 1977) and produce increased flight distances in animals tested in nature (Burger, Gochfeld & Murray, 1991, 1992). Despite the apparent importance of the eyes of predators as a trigger of defensive responses, there has been little research on the role of eye markings as releasers of defensive behavior in snakes. Burghardt and Greene (1988) found that direct gaze by a human experimenter potentiated deathfeigning response in neonate hog-nosed snakes. Herzog and Bern (1992) recently reported that juvenile garter snakes direct a disproportionate number of strikes toward the eyes of predator models. Herzog, Bowers, and Burghardt (1989) found that the size and movement of a threat stimulus affect antipredator responses of neonate and juvenile garter snakes and that realistic models elicited higher levels of defensive strikes than nonrealistic models. In this study we examine the role of eye markings in mediating antipredator responses. In Experiment 1, we tested the hypothesis that eyespots would enhance a model's ability to

Spatial firing patterns of hippocampal complex-spike cells in a fixed environment

A TV/computer technique was used to simultaneously track a rat's position in a simple apparatus and record the firing of single hippocampal complex-spike neurons. The primary finding is that many of these neurons behave as "place cells," as first described by O'Keefe and Dostrovsky (1971) and O'Keefe (1976). Each place cell fires rapidly only when the rat is in a delimited portion of the apparatus (the cell's "firing field"). In agreement with O'Keefe (1976) and many other authors, we have seen that the firing of place cells is highly correlated with the animal's position and is remarkably independent of other aspects of the animal's behavioral state. Several properties of firing fields were characterized. Firing fields are stable over long time intervals (days) if the environment is constant. They come in several shapes when the animal is in a cylindrical apparatus; moreover, the set of field shapes is different when the animal is in a rectangular apparatus. It also seems that a single cell may have more than one field in a given apparatus. By collecting a sample of 40 place cells in a fixed environment, it has been possible to describe certain features of the place cell population, including the spatial distribution of fields within the apparatus, the average size of fields, and the "intensity" of fields (as measured by maximum firing rate). We also tested the hypothesis that the firing rate of each place cell signals the animal's distance from a point (the field center) so that a weighted average of the firing of the individual cells encodes the animal's position within the apparatus. The animal's position, calculated according to this "distance hypothesis," is systematically different from the animal's true position; this implies that the hypothesis in its simplest form is wrong.

Comparison of Navigating and Recording Systems for Aerial Moose Surveys

right-angle distances of animals from the center of the transect. Such surveys can be biased by inaccurate estimation of that distance (Robinette et al. 1974, Caughley et al. 1976, Anderson et al. 1979). In Ontario and elsewhere (e.g., Caughley et al. 1976), the edges of an aerial transect are often determined by reference to streamers or tape on the window or wing strut of an aircraft. These markers correspond to a particular lateral distance at a fixed height. The census involves counting all animals inside the transect. Visibility of moose (Alces alces) varies with the open or closed nature of the habitat and weather conditions (LeResche and Rausch 1974, Gasaway et al. 1978). Therefore, it is often desirable to fly at various altitudes depending on vegetation type. This frequently requires returning to a fixed altitude to determine whether an animal was on or off the transect. In Ontario, plots or transects are usually marked on 1:50,000-scale topographic maps for navigation purposes and to establish borders. Although these can sometimes be used to pinpoint the location of animals, doubt still remains for many observations near the edges. The objective of this study was to compare counts of moose and time to fly transects, using topographic maps and aerial-photograph mosaics to determine transect borders.