Incubation feeding as a male tactic for early hatching

Male marsh tits, Parus palustris, regularly feed their mates from the beginning of nest building until hatching. Over three periods (the 15 days preceding egg formation, egg formation/laying and incubation) the number of food passes by the male to the female increased significantly. There was a significant negative relationship between the frequency with which the male fed the female in the nest during incubation and the length of the incubation period. Female blue tits, Parus caeruleus, experimentally supplied with food in the nestbox during incubation had a significantly shorter incubation period than control females. Clutches of experimentally fed females also tended to hatch more successfully. It is concluded that feeding of the female by the male is a nutritional contribution and that the shorter incubation period and increased hatching success enhance the fitness of both parents. However, the male should balance the benefits against the costs in time and energy and therefore not necessarily work at a maximal level. In accordance with this is the finding that the male's provisioning rate increased when ambient temperatures decreased. Adverse weather may jeopardize the whole or large proportions of the clutch, thereby significantly reducing the benefit from the current breeding attempt.     

Asymmetry of movement direction of Myrmica rubra ants during maze learning motivated by food

Asymmetry in direction of motion was found in Myrmica rubra ants at their learning in a symmetrical multi-alternative maze in conditions of "social" alimentary motivation. It was manifested in the form of preferable stay in the right half of the maze and was significant by several parameters: total number of motions, approaches to "false" spots and right turns. Unequal degrees of spatial-motor asymmetry (individual and for the whole sample) was revealed by various parameters. Most clearly the right-sided spatial preference was seen in the insects which had more approaches to goal with reinforcement taking than "exploratory" approaches. It is suggested that the parameters of motion direction asymmetry in ants learning in the maze depend on the level of alimentary "social" motivation.     

Disparate movement behavior and feeding ecology in sympatric ecotypes of Atlantic cod

Coexistence of ecotypes, genetically divergent population units, is a widespread phenomenon, potentially affecting ecosystem functioning and local food web stability. In coastal Skagerrak, Atlantic cod (Gadus morhua) occur as two such coexisting ecotypes. We applied a combination of acoustic telemetry, genotyping, and stable isotope analysis to 72 individuals to investigate movement ecology and food niche of putative local “Fjord” and putative oceanic “North Sea” ecotypes—thus named based on previous molecular studies. Genotyping and individual origin assignment suggested 41 individuals were Fjord and 31 were North Sea ecotypes. Both ecotypes were found throughout the fjord. Seven percent of Fjord ecotype individuals left the study system during the study while 42% of North Sea individuals left, potentially homing to natal spawning grounds. Home range sizes were similar for the two ecotypes but highly variable among individuals. Fjord ecotype cod had significantly higher δ¹³C and δ¹⁵N stable isotope values than North Sea ecotype cod, suggesting they exploited different food niches. The results suggest coexisting ecotypes may possess innate differences in feeding and movement ecologies and may thus fill different functional roles in marine ecosystems. This highlights the importance of conserving interconnected populations to ensure stable ecosystem functioning and food web structures.     

Egg-depositing behavior as a predator avoidance tactic of Yezonychus sapporensis Ehara (Acari, Tetranychidae)

Spider mites are very small phytophagous organisms living on plant leaves. They possess a diverse array of life types. Such diversity in life type has been supposed to be a result of coevolution between predator and prey, although there is little concrete evidence to support this concept. In Yezonychus sapporensis inhabiting the leaves of a dwarf bamboo, Sasa senanensis, all quiescent stages including eggs appear on the tips of the host leaf hairs during the summer season, and this habit is thought to be a kind of predator avoidance trait. To confirm this, the survival rates of Y. sapporensis eggs deposited on natural sites and experimentally manipulated sites were observed for eight co-occurring predator species. The results clearly showed that the oviposition behavior of Y. sapporensis has a function in avoiding predator attack, at least under experimental conditions. Received: October 26, 2000 / Accepted: December 19, 2000     

Sociality as a life-history tactic of ground squirrels

Summary Multi-variate analysis of life-history traits of 18 species of burrowing sciurids indicates that reproductive effort is determined by body-size energetics. Other traits, such as age adult weight reached, age of dispersal, length of time of gestation, were significantly correlated with body size. A principal component analysis suggested that the complex of life-history traits could be reduced to four components: body size (=weight), seasonality, specific reproductive effort, and maturity. The variation in the sociality index was best explained by age of first reproduction and age adult weight reached. Generally, species are more social when large body size combined with a relatively short growing season is associated with delayed dispersal and occurs in those species typically breeding for the first time at age two or older. Sociality in these species may have evolved through retention of daughters within the maternal home range as a means of continuing reproductive investment beyond weaning.     

Hypothalamic huntingtin-associated protein 1 as a mediator of feeding behavior

The hypothalamus responds to circulating leptin and insulin in the control of food intake and body weight. A number of neurotransmitters in the hypothalamus, including gamma-aminobutyric acid (GABA), also have key roles in feeding. Huntingtin-associated protein 1 (Hap1) is expressed more abundantly in the hypothalamus than in other brain regions, and lack of Hap1 in mice leads to early postnatal death. Hap1 is also involved in intracellular trafficking of the GABA(A) receptor. Here, we report that fasting upregulates the expression of Hap1 in the rodent hypothalamus, whereas intracerebroventricular administration of insulin downregulates Hap1 by increasing its degradation through ubiquitination. Decreasing the expression of mouse hypothalamic Hap1 by siRNA reduces the level and activity of hypothalamic GABA(A) receptors and causes a decrease in food intake and body weight. These findings provide evidence linking hypothalamic Hap1 to GABA in the stimulation of feeding and suggest that this mechanism is involved in the feeding-inhibitory actions of insulin in the brain.     

Trophic ecology of red roach (Rutilus arcasii) in a seasonal stream; an example of detritivory as a feeding tactic

1. Diel feeding activity and diet of red roach (Rutilus arcasii) were determined on five occasions (February, April, June, August and November 1985) in a seasonal, fluctuating stream subject to severe summer droughts and cold winter floods. 2. Except in June, the two age groups of the population (1 + and >1+) fed mainly on detritus and showed no significant differences either in their feeding intensity or in the relative contribution of the main diet components (detritus, plants and invertebrates). 3. The size, abundance and availability of drifting invertebrates influenced red roach feeding. When drift was scarce or inaccessible, both age groups fed on detritus, plants, or a combination of the two. These niche shifts were a trophic tactic aimed at maintaining feeding when other, more nutritional and energetically valuable foods were scarce. 4. A comparison with other populations suggested that a detritus-based diet had no major cost in the life history of the red roach. We hypothesize that the highly opportunistic trophic strategy of this Iberian endemic cyprinid is an adaptative response to seasonal Mediterranean streams.     

Adaptation effects in the analyzer of movement direction

A prolonged observation of a point-like stimulus moving in a given direction influences the perception of movement direction of subsequent stimuli. The prolonged observation of the same stimulus results in a subjective drift of the perceived movement towards horizontal or vertical direction depending on which of these directions is nearer to the stimulus trajectory. If, however, the stimulus moves in vertical, diagonal and horizontal directions its perception does not change under prolonged observation.     

Leptin leads hypothalamic feeding circuits in a new direction

A decade ago, leptin (from the greek lepto meaning 'thin') was identified as the product of the ob gene.1 This adipocyte-derived hormone was found to suppress feeding and stimulate thermogenesis, and was thus proposed as a mediator in a negative feedback loop that controls body adiposity. This discovery led to a rapid revolution in the understanding of neurobiological mechanisms regulating obesity. However, while leptin's first life was as an adipostat, it is now known to have a wide range of additional neuroendocrine, metabolic and behavioural functions in the CNS and periphery. Remarkably, the pleiotropic nature of the hormone continues to be extended with the recent publication of two papers that expand on leptin's neurobiological actions in the CNS.2,3 They indicate novel regulatory roles for the hormone in both synaptic plasticity and axon guidance. Crucially, in light of the rising incidence of obesity in modern society, both of the studies reveal leptin-mediated links between nutrition and neurodevelopment, findings that have further implications for leptin's role in the regulation of energy homeostasis.     

The preference for movement direction in a T-maze in planarians

Characteristics of spatial orientation in T-maze were studied in 1768 Planaria of following types: Dugesia tigrina (sexless and sexual race), Dugesia lugubris, Ijmia tenuis, Bdellacephala punctata. It was shown that from one third to one half of individuals were characterized by asymmetry of movement direction preference. The preference of right turning was typical for Dugesia tigrina; Dugesia lugubris, Ijmia tenuis, Bdellacephala punctata preferred left turning. The asymmetry described is considered as a primitive form of species functional asymmetry.     

Phencyclidine produces aggressive behavior in rapid eye movement sleep-deprived rats

This study examined effects of acute doses of phencyclidine (PCP; 0.025, 0.05, 0.10, and 0.20 mg/kg intraperitoneally) on intra-specific aggressive behavior and muricide in normal rats and rats deprived of rapid eye movement (REM) sleep. Dose-related changes in intra-specific aggression and muricide occurred in REM sleep-deprived rats only. Dose-response curves are inverted-U shaped with the .05 mg/kg dose producing increases in aggression. Intra-specific and muricide may serve as models of PCP-induced aggression in humans.     

Using strategic movement to calibrate a neural compass: a spiking network for tracking head direction in rats and robots

The head direction (HD) system in mammals contains neurons that fire to represent the direction the animal is facing in its environment. The ability of these cells to reliably track head direction even after the removal of external sensory cues implies that the HD system is calibrated to function effectively using just internal (proprioceptive and vestibular) inputs. Rat pups and other infant mammals display stereotypical warm-up movements prior to locomotion in novel environments, and similar warm-up movements are seen in adult mammals with certain brain lesion-induced motor impairments. In this study we propose that synaptic learning mechanisms, in conjunction with appropriate movement strategies based on warm-up movements, can calibrate the HD system so that it functions effectively even in darkness. To examine the link between physical embodiment and neural control, and to determine that the system is robust to real-world phenomena, we implemented the synaptic mechanisms in a spiking neural network and tested it on a mobile robot platform. Results show that the combination of the synaptic learning mechanisms and warm-up movements are able to reliably calibrate the HD system so that it accurately tracks real-world head direction, and that calibration breaks down in systematic ways if certain movements are omitted. This work confirms that targeted, embodied behaviour can be used to calibrate neural systems, demonstrates that 'grounding' of modelled biological processes in the real world can reveal underlying functional principles (supporting the importance of robotics to biology), and proposes a functional role for stereotypical behaviours seen in infant mammals and those animals with certain motor deficits. We conjecture that these calibration principles may extend to the calibration of other neural systems involved in motion tracking and the representation of space, such as grid cells in entorhinal cortex.     

Neural coding of movement direction in the healthy human brain

Neurophysiological studies in monkeys show that activity of neurons in primary cortex (M1), pre-motor cortex (PMC), and cerebellum varies systematically with the direction of reaching movements. These neurons exhibit preferred direction tuning, where the level of neural activity is highest when movements are made in the preferred direction (PD), and gets progressively lower as movements are made at increasing degrees of offset from the PD. Using a functional magnetic resonance imaging adaptation (fMRI-A) paradigm, we show that PD coding does exist in regions of the human motor system that are homologous to those observed in non-human primates. Consistent with predictions of the PD model, we show adaptation (i.e., a lower level) of the blood oxygen level dependent (BOLD) time-course signal in M1, PMC, SMA, and cerebellum when consecutive wrist movements were made in the same direction (0° offset) relative to movements offset by 90° or 180°. The BOLD signal in dorsolateral prefrontal cortex adapted equally in all movement offset conditions, mitigating against the possibility that the present results are the consequence of differential task complexity or attention to action in each movement offset condition.     

Numerical study of coding of the movement direction by a population in the motor cortex

The fundamental statistical aspects of population coding of the movement direction in the motor cortex are studied numerically. The activity of neurons in a population is simulated using pseudorandom numbers so that the directional selectivity of the neurons is similar to that observed experimentally. Accuracy of the coding, which is evaluated by the root-mean-square (rms) error, is analyzed for various population sizes, degrees of variability of neuronal activity, and degrees of nonuniformity of distribution of the preferred directions. The dependence of the rms error on the population size shows a good fit to the inverse square-root law, from which it is estimated that a single population must contain around 10 000 neurons in order to attain the accuracy that allows 1 deg rms error, for example. The coding is studied further for populations with different types of tuning function. The results support the hypothesis proposed by Georgopoulos et al. (1988) except that the tuning function must be tuned in the sense that the average value of the function for movements with components in the preferred direction is larger than for movements away from the preferred direction.