African grey parrots (Psittacus erithacus) use inference by exclusion to find hidden food

Exclusion allows the detection of hidden food when confronted with the choice between an empty and a potentially baited food location. However, exclusion may be based on avoidance of the empty location without drawing inferences about the presence of the food in the baited location. So far, such inferences have been demonstrated in the great apes only: after seeing an experimenter eating one of two food types, which both had been hidden previously in two boxes, the apes were able to choose the box that still contained the other food type. African grey parrots are capable of exclusion, and we here assessed if they are capable of inference by exclusion. In our task, two different but equally preferred food items were hidden in full view of the birds under two opaque cups. Then, an experimenter secretly removed one food type and showed it to the bird. Similarly to the apes, one out of seven parrots significantly preferred the baited cup; control conditions rule out that its choice was based on associative learning or the use of olfactory cues. Thus, we conclude that-like the apes-some grey parrots are able to infer the location of a hidden food reward.     

Frogs use retinal elevation as a cue to distance

Summary We have investigated the role that retinal elevation plays in a frog's (Rana pipiens) estimate of prey distance. We dissociated retinal elevation from other depth cues by artificially increasing the height of the frogs' eyes above the ground. Frogs then snapped short of their prey in their ventral visual field as if their estimate of distance were determined primarily by the retinal elevation of the image of the prey. The data suggest that the frog assumes its eyes to be about 3 cm above the ground. Other cues modify depth judgements when targets are close to this assumed groundplane.     

Pattern discrimination by the honeybee: disruption as a cue

The discrimination of pattern disruption in freely flying honeybees (Apis mellifera) was examined. Bees were trained to discriminate at a fixed distance between a regularly repeated black/white pattern and the same pattern at a different magnification in targets of the same angular size. The locations of areas of black were regularly shuffled to make them useless as cues. The results of the experiments indicate that the bees discriminate the disruption of the pattern as a whole, irrespective of the actual pattern. Bees trained to prefer a larger period transfer to an even larger period, when given a forced choice with a pair of patterns of differing disruption from those they were trained on, as if their spontaneous preference has not been overcome. Bees trained to prefer a smaller period, however, prefer the former negative pattern rather than transfer to an even smaller period. These results show that the bees do not rely solely on learning the absolute period of a pattern nor the relative disruption of two patterns, and they are confused when these two cues conflict in tests with unfamiliar targets. Bees can discriminate between fields of view that differ in average disruption as a generalized cue, irrespective of pattern. Accepted: 7 April 1997     

Fourteen-month-old infants use interpersonal synchrony as a cue to direct helpfulness

Musical behaviours such as dancing, singing and music production, which require the ability to entrain to a rhythmic beat, encourage high levels of interpersonal coordination. Such coordination has been associated with increased group cohesion and social bonding between group members. Previously, we demonstrated that this association influences even the social behaviour of 14-month-old infants. Infants were significantly more likely to display helpfulness towards an adult experimenter following synchronous bouncing compared with asynchronous bouncing to music. The present experiment was designed to determine whether interpersonal synchrony acts as a cue for 14-month-olds to direct their prosocial behaviours to specific individuals with whom they have experienced synchronous movement, or whether it acts as a social prime, increasing prosocial behaviour in general. Consistent with the previous results, infants were significantly more likely to help an experimenter following synchronous versus asynchronous movement with this person. Furthermore, this manipulation did not affect infant''s behaviour towards a neutral stranger, who was not involved in any movement experience. This indicates that synchronous bouncing acts as a social cue for directing prosociality. These results have implications for how musical engagement and rhythmic synchrony affect social behaviour very early in development.     

Social aphids use their antennae to perceive density cue for soldier production

In social insects, local interactions among colony members facilitate information transfer, and allow the whole colony to regulate division of labor and task allocation in an integrated and coordinated manner. In particular, regulation of caste differentiation in response to external cues is important for sustaining social insect colonies. The social aphid Tuberaphis styraci exhibits a caste polyphenism, producing second‐instar soldiers and non‐soldiers. Previous studies using an artificial diet rearing system identified high aphid density as a crucial cue for soldier production, which acts on embryos in the maternal body and newborn first‐instar nymphs to induce soldier differentiation. While direct contact stimuli from live non‐soldiers were suggested to mediate the density effect, how the aphids perceive the stimuli has been unknown. Here we investigated how antennal removal of adult females affects the soldier production in T. styraci. Under a high density condition, intact females produced the highest percentage of soldiers, females deprived of both antennae produced the lowest percentage of soldiers, and females deprived of one antenna exhibited an intermediate percentage of soldiers. Scanning electron microscopic observations of the aphids revealed the existence of sensory organs for chemoreception and tactile sensation on the antennae of the mother aphids. These results indicate that T. styraci females use their antennae to perceive soldier‐inducing density cue, suggesting that maternal perception of density cue is involved in regulation over caste phenotype of their offspring.     

Surfacing activity and food utilisation in the obligatory air-breathing fish ophiocephalus striatus as a function of body weight

Reared in cylindrical aquaria containing different depths of water (2.5 to 70 cm) the obligatory air-breathing fish Ophiocephalus striatus, belonging to different weight classes (0.1, 0.75, 10, 20 and 41 g), was forced to swim vertically a longer or shorter distance per surfacing. Surfacing frequency was a depth-dependent, activity in individuals weighing less than 20 g in all weight classes, the frequency was nearly 2 times more in the series fed ad libitum on fish muscle, than in the one where the fish were starved. Owing to the sustained surfacing activity and the consequent fatigue, the test individuals hung to the surface for a definite period. Neither frequency nor duration of hanging was depth-dependent. Mean hanging durations for the feeding series were 1.1, 3.8, 5.9, 7.9 and 8.8 hr/day in the 0.1, 0.75, 10, 20 and 41 g weight classes, respectively; the corresponding values for the starving series were 1.3, 15.0, 13.0, 12.7 and 12.8 hr/day. The distance swum by the feeding fish increased from 57 to 681 m/day and from 61 to 507 m/day in the 0.1 and 41 g individuals exposed to the minimum and maximum aquarium depths. Feeding rate, which was a depth-dependent activity, decreased from 280 to 113 g cal/g live fish/day with increasing weight. Rate and efficiency of conversion also decreased with increasing body weight; in larger fish conversion was dependent on volume rather than on depth of the aquarium. O₂ uptake of feeding fish was about 6 times higher than the starving ones of the tested weight classes at different aquarium depths.This paper is part of a thesis submitted by the author (from A.P.A. College, PALNI) to Madurai University in partial fulfillment of the requirement of the Ph. D. degree. Contribution No. 12 under a research scheme granted to Dr. T. J. Pandian by the UGC (New Delhi). The author is grateful to Dr. T. J. Pandian for valuable guidance, financial support and encouragements.     

Rats' memory for event duration: differential effects of delaying the discriminative choice cue as opposed to the opportunity to execute the choice response

Rats were trained to discriminate short or long durations of houselight illumination using a choice procedure. During the test phase of each trial, the left and right levers were presented with an auditory cue above one of them on (cued lever) while the other was off (uncued lever). The auditory cue was presented immediately after sample offset and the levers were inserted after the auditory cue had been presented for 2 s. For half of the rats, the correct response following the short sample was to press the cued lever, while following the long sample, it was to press the uncued lever. This was reversed for the remaining rats. Following acquisition of the discrimination, two different types of delay tests were administered. In the first set, the delay between offset of the sample and onset of the auditory cue was manipulated (Cue Delay Test). In the second set, the delay between onset of the auditory cue and entry of the levers into the chamber was manipulated (Response Delay Test). Cue Delay testing resulted in a choose-long bias at the longer delays. Response Delay testing did not result in a systematic response bias and there was little forgetting over the delay interval. These data suggest that the rats did not stop the internal clock when the nominal sample was offset, but allowed it to keep running until the auditory cue was presented. The data from the Response Delay Test indicate that either a response decision was made based on the clock reading as soon as the auditory cue was presented, or the clock reading itself was retained over the delay with no subjective shortening and little forgetting.     

Neuropeptides,food intake and body weight regulation: a hypothalamic focus

Energy homeostasis is controlled by a complex neuroendocrine system consisting of peripheral signals like leptin and central signals, in particular, neuropeptides. Several neuropeptides with anorexigenic (POMC, CART, and CRH) as well as orexigenic (NPY, AgRP, and MCH) actions are involved in this complex (partly redundant) controlling system. Starvation as well as overfeeding lead to changes in expression levels of these neuropeptides, which act downstream of leptin, resulting in a physiological response. In this review the role of several anorexigenic and orexigenic (hypothalamic) neuropeptides on food intake and body weight regulation is summarized.     

Brown (Eulemur fulvus) and ring-tailed lemurs (Lemur catta) use human head orientation as a cue to gaze direction in a food choice task

Whilst the ability to follow human gaze has been demonstrated in monkeys and apes, there is little evidence that prosimians share this ability. The current study used a food choice paradigm to assess whether captive brown (Eulemur fulvus) and ring-tailed lemurs (Lemur catta) use human gaze direction as a cue when choosing between an attending or non-attending human. Four experiments assessed the use of body, head and eye cues by the lemurs. In experiment 1, the non-attending human stood with her back to a food item; 3 of the 5 lemurs preferentially chose the attending human with an equivalent food item in view. In experiments 2 and 3, which used head angles of 90°, 4 out of 5 lemurs preferentially chose the attending human. In experiment 4, in which the humans differed only by whether their eyes were open or shut, no significant preferences were found. This study provides the first tentative evidence that lemurs are capable of discriminating human gaze direction and can use both body and head direction to do so.     

Plumage coloration can be perceived as a multiple condition‐dependent signal by Great Tits Parus major

The evolution of multiple signals can be explained because they enhance the perception of a general message by recipients. Plumage coloration frequently acts as a condition‐dependent signal, so that species displaying different colour patches have the potential to transmit information on condition through a multiple signalling system. The Great Tit Parus major exhibits plumage colour patches generated by the main types of colour production, some of which, particularly those based on melanins and carotenoids, are known to be related to body condition. However, the colour expressions of all of the different colour types have never been investigated simultaneously to determine whether they function as multiple signals of condition. In addition, visual perception models have never been applied to a multiple signalling system in a wild population of birds. Here I present information that links body condition with the colour expression of almost all of the different plumage patches of male Great Tits captured during the winter. Birds in better condition had greater reflectance values at short wavelengths in all plumage patches, and this was especially so in the white (i.e. structural) colour of the cheeks. Plumage colour characteristics were calculated by means of avian visual models, suggesting that Great Tits have the capacity to perceive information contained in the plumage coloration of conspecifics. These results show that short‐wavelength reflectance has great potential to transmit biologically significant information on the body condition of birds, even in achromatic plumage patches.     

Percent ash‐free dry weight as a robust method to estimate energy density across taxa

Determining how energy flows through ecosystems reveals underlying ecological patterns that drive processes such as growth and food web dynamics. Models that assess the transfer of energy from producers to consumers require information on the energy content or energy density (ED) of prey species. ED is most accurately measured through bomb calorimetry, but this method suffers from limitations of cost, time, and sample requirements that often make it unrealistic for many studies. Percent dry weight (DW) is typically used as a proxy for ED, but this measure includes an indigestible portion (e.g., bones, shell, salt) that can vary widely among organisms. Further, several distinct models exist for various taxonomic groups, yet none can accurately estimate invertebrate, vertebrate and plant ED with a single equation. Here, we present a novel method to estimate the ED of organisms using percent ash‐free dry weight (AFDW). Using data obtained from 11 studies diverse in geographic, temporal and taxonomic scope, AFDW, DW as well as percent protein and percent lipid were compared as predictors of ED. Linear models were produced on a logarithmic scale, including dummy variables for broad taxonomic groups. AFDW was the superior predictor of ED compared to DW, percent protein content and percent lipid content. Model selection revealed that using correction factors (dummy variables) for aquatic animals (AA) and terrestrial invertebrates (TI) produced the best‐supported model—log₁₀(ED) = 1.07*log₁₀(AFDW) ? 0.80 (R² = 0.978, p < .00001)—with an intercept adjustment of 0.09 and 0.04 for AA and TI, respectively. All models including AFDW as a predictor had high predictive power (R² > 0.97), suggesting that AFDW can be used with high degrees of certainty to predict the ED of taxonomically diverse organisms. Our AFDW model will allow ED to be determined with minimal cost and time requirements and excludes ash‐weight from estimates of digestible mass. Its ease of use will allow for ED to be more readily and accurately determined for diverse taxa across different ecosystems.     

A two-year randomized weight loss trial comparing a vegan diet to a more moderate low-fat diet

Objective: The objective was to assess the effect of a low‐fat, vegan diet compared with the National Cholesterol Education Program (NCEP) diet on weight loss maintenance at 1 and 2 years. Research Methods and Procedures: Sixty‐four overweight, postmenopausal women were randomly assigned to a vegan or NCEP diet for 14 weeks, and 62 women began the study. The study was done in two replications. Participants in the first replication (N = 28) received no follow‐up support after the 14 weeks, and those in the second replication (N = 34) were offered group support meetings for 1 year. Weight and diet adherence were measured at 1 and 2 years for all participants. Weight loss is reported as median (interquartile range) and is the difference from baseline weight at years 1 and 2. Results: Individuals in the vegan group lost more weight than those in the NCEP group at 1 year [?4.9 (?0.5, ?8.0) kg vs. ?1.8 (0.8, ?4.3); p < 0.05] and at 2 years [?3.1 (0.0, ?6.0) kg vs. ?0.8 (3.1, ?4.2) kg; p < 0.05]. Those participants offered group support lost more weight at 1 year (p < 0.01) and 2 years (p < 0.05) than those without support. Attendance at meetings was associated with improved weight loss at 1 year (p < 0.001) and 2 years (p < 0.01). Discussion: A vegan diet was associated with significantly greater weight loss than the NCEP diet at 1 and 2 years. Both group support and meeting attendance were associated with significant weight loss at follow‐up.     

Critical evaluation of the use of bioinformatics as a theoretical tool to find high-potential sources of ACE inhibitory peptides

A bioinformatics analysis to screen for high-potential sources of angiotensin converting enzyme (ACE) inhibitory peptides was conducted in the area of insect muscle proteins. Vertebrate muscle proteins are reported as good sources of ACE inhibitory peptides, while the research on invertebrate muscle proteins is limited. A phylogenetic tree constructed with actin sequences of both vertebrate and invertebrate species indicated a high homology. Furthermore, a quantitative in silico ACE inhibition analysis suggested that actin proteins of invertebrates have potentials as new sources of ACE inhibitory peptides. On one insect, Bombyx mori, a more detailed in silico analysis was done followed by a small experimental study. The in silico analysis indicated B. mori as a high-potential source of ACE inhibitory peptides and this was supported by the ACE inhibitory activity of the partially purified actin preparation. In conclusion, in food science, in silico analysis can be used as fast initial screening tool to look for high-potential sources of ACE inhibitory peptides and other peptidic bioactivities.     

A bacterial pathogen uses dimethylsulfoniopropionate as a cue to target heat-stressed corals

Diseases are an emerging threat to ocean ecosystems. Coral reefs, in particular, are experiencing a worldwide decline because of disease and bleaching, which have been exacerbated by rising seawater temperatures. Yet, the ecological mechanisms behind most coral diseases remain unidentified. Here, we demonstrate that a coral pathogen, Vibrio coralliilyticus, uses chemotaxis and chemokinesis to target the mucus of its coral host, Pocillopora damicornis. A primary driver of this response is the host metabolite dimethylsulfoniopropionate (DMSP), a key element in the global sulfur cycle and a potent foraging cue throughout the marine food web. Coral mucus is rich in DMSP, and we found that DMSP alone elicits chemotactic responses of comparable intensity to whole mucus. Furthermore, in heat-stressed coral fragments, DMSP concentrations increased fivefold and the pathogen''s chemotactic response was correspondingly enhanced. Intriguingly, despite being a rich source of carbon and sulfur, DMSP is not metabolized by the pathogen, suggesting that it is used purely as an infochemical for host location. These results reveal a new role for DMSP in coral disease, demonstrate the importance of chemical signaling and swimming behavior in the recruitment of pathogens to corals and highlight the impact of increased seawater temperatures on disease pathways.     

Concerning the use of empirical methods for determining the molecular weight of a small glycopeptide cleaved from bovine rhodopsin

The molecular weight of a glycopeptide cleaved enzymatically from bovine rhodopsin was investigated by a variety of techniques, such as gel filtration, sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence and absence of urea, and gel filtration in 6 guanidinium chloride after reduction and carboxymethylation. Great variation in the estimation of the molecular weight between the several techniques was observed. When compared to an estimate of 9000 based on amino acid analysis and considerations of its carbohydrate content, values ranging between 4500 and 18,000 were obtained by the other methods. Thus, while the molecular weight of the glycopeptide remains unresolved, the resultant ambiguity in evaluating this property may exemplify the limitations inherent in applying empirical methods to the determination of the molecular weight of small glycopeptides.     

Refuge use by fish as a function of body weight changes

Refuge use provides a good model for the study of trade-offs between the benefits of predator avoidance and the costs of lost feeding opportunities. We manipulated the latter costs by subjecting similar-sized three-spine sticklebacks to 2 days of food deprivation followed by a 2-day re-feeding period and recorded associated changes in body weight and refuge use. Food deprivation resulted in a decrease and re-feeding in an increase in the duration of refuge use by fish. Emergence times of fish from the refuge were extremely variable (with a ratio of 1:127 between the shortest and the longest ones) but individual ranks were highly consistent between different days of testing, suggesting that emergence times were individually characteristic. Percentage weight change of fish in response to the experimental treatments also showed a high level of inter-individual variation ranging from 0–17%. A significant positive correlation was found between the percentage weight lost and the percentage decrease in emergence time from a refuge after food deprivation and similarly between the percentage weight gained and the percentage increase in refuge use after re-feeding. The relationship between energy turnover and behavioural strategies is discussed. Received: 13 December 1998 / Received in revised form: 2 May 1999 / Accepted: 7 June 1999     

The dry weight estimate of chaoborus flavicans (Meigen) as a function of length and instars

Regression equations relating length to dry weight have been derived for the four larval instars of Chaoborus flavicans (Meigen). A general equation, in which all instars are lumped, was also developed, but produces biased results outside a rather narrow central interval.The rate of increase, in terms of weight, is minimal in first instar larvae and maximal in fourth instar larvae, while the second and third instars are both intermediate and very closely related to one another.Three critical points have been defined, corresponding to body lengths at which a particular instar has to molt in order to be able to continue growing optimally.

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Résumé Des équations de régression longueur-poids sec ont été établies pur les différents stades aquatiques de développement de Chaoborus flavicans (MEIGEN).La croissance pondérale, minimale pour les larves de premier stade, est maximale au cours du quatrième stade; les larves de deuxième et de troisième stade présentent des croissances comparables.L'emploi des équations propres à chaque stade est préférable à celui de l'équation moyenne établie pour l'ensemble des quatre stades larvaires.

     

Captive cotton‐top tamarins' (Saguinus oedipus oedipus) use of landmarks to localize hidden food items

Seventeen captive cotton‐top tamarins (Saguinus oedipus oedipus) were individually tested on their use of spatial relationships between landmarks to locate multiple hidden food items. In two experiments, the tamarins were presented with a spatial‐foraging task in which positions of hidden food rewards were fixed in relation to an array of visual cues. In Experiment 1, the cues+hidden food configuration was rotated 90° and the tamarins were successful in locating the food items significantly above chance levels (P<0.01). In Experiment 2 the cues+hidden food configuration was translated (up, down or sideways) from the previously learned configuration, and the monkeys successfully localized the hidden food items (P<0.001). Results indicate that the tamarins relied on the spatial relationship between the multiple landmarks to locate hidden food items rather than on an associative or beacon strategy. The results of these experiments support the contention that when contextually appropriate these captive New World monkeys have the capacity to rely on the spatial relationship or positions of several cues as an array to localize points in their environment. Am. J. Primatol. 71:316–323, 2009. © 2009 Wiley‐Liss, Inc.