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PubMed2007

Interactions between mosquito larvae and species that share the same trophic level.

Ecological theory predicts, and empirical research shows, that species sharing the same trophic level as a target species (hereafter controphic species) can have large direct and indirect effects on the target species by sharing resources and/or by serving as alternative prey to predators. Yet, the roles of controphic species of mosquito larvae in affecting mosquito populations have received little attention. Published empirical evidence, although scarce, suggests that controphic species such as zooplankton and anuran larvae compete with mosquito larvae, can positively affect mosquito larvae by consuming bacteria that are pathogenic to mosquito larvae, reduce predation on mosquito larvae by serving as alternative prey, and ultimately cause increased predation on mosquito larvae by causing a numerical response in the predator. We conclude that more extensive theoretical and empirical studies in elucidating the roles of controphic species will better allow us to predict mosquito population dynamics and allow for better management of mosquitoes.

Animals↗

PubMed1999

Relative medial and dorsal cortex volume in relation to foraging ecology in congeneric lizards.

The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species. This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory.

Animals↗

PubMed2002

Evolutionary convergence in nervous systems: insights from comparative phylogenetic studies.

Over the past 20 years, cladistic analyses have revolutionized our understanding of brain evolution by demonstrating that many structures, some of which had previously been assumed to be homologous, have evolved many times independently. These and other studies demonstrate that evolutionary convergence in brain anatomy and function is widespread. Although there are relatively few neuroethological studies in which brain and behavior have be studied within an evolutionary framework, three relatively well studied cases are reviewed here: electric communication among gymnotiform and mormyriform fishes, prey capture among frogs, and sound localization among owls. These three examples reveal similar patterns of brain evolution. First, it is clear that novel abilities have evolved many times independently in taxa whose common ancestors lack these abilities. Second, it is apparent that small changes in neural pathways can lead to dramatic changes in an organism's abilities. Brain evolution at this small scale is quite common. The behavioral importance of small scale changes on one hand, and the pervasiveness of convergent evolution on the other, have several implications for understanding brain evolution. First, similar abilities may be conferred by convergent rather than homologous circuits, even among closely related species. Furthermore, closely related species may use the same information in different ways, or they may use different means to obtain the same information. One reason that convergence is so common in the biological world may be that the evolutionary appearance of novel functions is associated with constraints, for example in the algorithms used for a given neural computation. Convergence in functional organization may thus reveal basic design features of neural circuits in species that possess unique evolutionary histories but use similar algorithms to solve basic computational problems.

Animals↗

PubMed1993

Chemical delivery to the vomeronasal organs and functional domain of squamate chemoreception.

While evidence exists that many squamate behaviors are released by chemical stimuli, the specific sensory system that detects such stimuli and mediates subsequent behavior has been determined infrequently. Techniques and experimental approaches that have been used to determine the roles that the main olfactory and vomeronasal systems play in mediation of specific behaviors are discussed.

Animals↗

PubMed2006

Dolphin foraging sounds suppress calling and elevate stress hormone levels in a prey species, the Gulf toadfish.

The passive listening hypothesis proposes that dolphins and whales detect acoustic signals emitted by prey, including sound-producing (soniferous) fishes. Previous work showed that bottlenose dolphins (Tursiops truncatus) behaviorally orient toward the sounds of prey, including the advertisement calls of male Gulf toadfish (Opsanus beta). In addition, soniferous fishes constitute over 80% of Tursiops diet, and toadfishes alone account for approximately 13% of the stomach contents of adult bottlenose dolphins. Here, we used both behavioral (vocalizations) and physiological (plasma cortisol levels) parameters to determine if male Gulf toadfish can, in turn, detect the acoustic signals of bottlenose dolphins. Using underwater playbacks to toadfish in their natural environment, we found that low-frequency dolphin sounds (;pops') within the toadfish's range of hearing dramatically reduce toadfish calling rates by 50%. High frequency dolphin sounds (whistles) and low-frequency snapping shrimp pops (ambient control sounds) each had no effect on toadfish calling rates. Predator sound playbacks also had consequences for circulating stress hormones, as cortisol levels were significantly elevated in male toadfish exposed to dolphin pops compared with snapping shrimp pops. These findings lend strong support to the hypothesis that individuals of a prey species modulate communication behavior in the presence of a predator, and also suggest that short-term glucocorticoid elevation is associated with anti-predator behavior.

Acoustics↗

PubMed1986

Motor correlates of learning behaviour: feeding on novel prey by pumpkinseed sunfish (Lepomis gibbosus).

The functional basis of learning in prey capture was investigated in the pumpkinseed sunfish (Lepomis gibbosus). Feeding performance of sunfishes was assessed when the fish were first fed a novel, elusive prey (guppies) and compared with their performance after several weeks of experience with capturing guppies. During these feedings electromyographic recordings were made to document the pattern of activity in four jaw muscles at the strike. With experience, the L. gibbosus improved their ability to capture guppies, and several changes in the pattern of muscle activity were associated with this improved performance. Average duration and maximum amplitude of activity in all muscles increased between trials. Previous studies of muscle activity modulation in fishes indicate that these changes could improve feeding performance on an elusive prey. Thus, specific modifications of muscle activity appear to be one functional determinant of feeding success in fishes.

Animals↗

PubMed1995

The kinematics and mechanism of prey capture in the African pig-nosed frog (Hemisus marmoratum): description of a radically divergent anuran tongue.

High-speed videography and muscle denervation experiments were used to quantify the feeding kinematics of Hemisus marmoratum and to test hypotheses of muscle function. The feeding behavior of H. marmoratum, which feeds on ants and termites, differs radically from that of other frogs that have been studied. During feeding in H. marmoratum, the tongue 'telescopes' straight out of the mouth, as opposed to the 'flipping' tongue trajectory observed in most other frogs. At the time of prey contact, two lateral lobes of tissue at the tongue tip envelop the prey. These lateral lobes are capable of applying significant pulling forces to the prey and the tongue is, therefore, described as prehensile. The trajectory of the tongue can be adjusted throughout protraction so that the frog can 'aim' its tongue in all three dimensions; distance, azimuth and elevation. Bilateral denervation of the genioglossus muscles results in a complete lack of tongue protraction, indicating that the genioglossus muscle is the main tongue protractor in H. marmoratum, as in other frogs. Thus, H. marmoratum provides strong evidence of functional conservatism of the genioglossus muscle within anurans. Bilateral denervation of the hyoglossus muscle indicates that although the hyoglossus is involved in several aspects of normal tongue retraction, including the prehensile capability of the tongue tip, it is not necessary for tongue retraction. Unilateral denervation of the genioglossus muscle causes significant deviation of the tongue towards the denervated side, providing evidence for a mechanism of lateral tongue aiming. On the basis of the kinematics of prey capture, the anatomy of the tongue and the results of the denervation experiments, we propose that H. marmoratum uses a hydraulic mechanism to protract its tongue.

Animals↗

PubMed2006

Effects of larval competitors and predators on oviposition site selection of Anopheles gambiae sensu stricto.

We examined whether predators and competitors influence selection of oviposition sites by Anopheles gambiae Giles. Mosquitoes in cages laid significantly fewer eggs in rainwater conditioned with a predator (backswimmers, Notonecta sp.) than in unconditioned rainwater. Rainwater conditioned with a putative competitor (tadpoles, Xenopus sp.) also had fewer eggs than unconditioned rainwater. Similarly, mosquitoes laid significantly fewer eggs in rainwater conditioned with five and 50 An. gambiae larvae than in unconditioned rainwater. When larvae were present, significantly more eggs were laid in containers with five larvae than in containers with higher densities, but the differences in number of eggs laid were not significant among the densities of 40, 70, and 100 larvae. This study demonstrated that caged An. gambiae females avoid oviposition in habitats with supposed competitors and predators.

Analysis of Variance↗

PubMed2000

A preliminary assessment of the potential of the Muschovy duck (Cairina maschata) as a biocontrol agent of schistosomiasis intermediate host snails.

OBJECTIVE: To assess the impact of Muschovy ducks on snail populations. DESIGN: Populations of four different snail species were monitored in nine ponds for a period of 32 weeks. Zero, one and two ducks were randomly introduced to a set of three ponds in the 16th, 20th and 24th week. SETTING: Nine fenced ponds at De Beers Research Laboratory, Chiredzi. MAIN OUTCOME MEASURES: Reduction in snail population following introduction of ducks. RESULTS: Mean counts for the intervention period showed that more intermediate host snails (Bulinus globosus and Biomphalaria pfeifferi) were present in ponds where ducks were not introduced (control) than in ponds where either one or two ducks were introduced. In control ponds the mean counts for intermediate host snails were 1.37, 1.03 and 1.02 for control, treatment with one duck and treatment with two ducks respectively. Similar observations were made for Physa acuta, with mean counts of 1.10, 0.64 and 0.67 for control, treatment with one duck and treatment with two ducks, respectively. No differences were observed in snail counts of Melanoides turbeculata where 2.40 snails were collected from the control pond and 2.37 snails in both treatment ponds. There was no significant difference in number of snails in ponds with one or two ducks. CONCLUSION: The study demonstrated that Muschovy ducks significantly reduce snail populations in a pond environment. Further studies are required in large natural ponds before conclusive recommendations are made on the use of Muschovy ducks as biological control agents of schistosomiasis intermediate host snails can be drawn.

Animals↗

PubMed2005

Diseases and mortality in free-ranging brown bear (Ursus arctos), gray wolf (Canis lupus), and wolverine (Gulo gulo) in Sweden.

Ninety-eight brown bears (Ursus arctos), 20 gray wolves (Canis lupus), and 27 wolverines (Gulo gulo), all free-ranging, were submitted to the National Veterinary Institute, Uppsala, Sweden, during 1987-2001 for investigation of diseases and causes of mortality. The most common cause of natural death in brown bears was infanticide. Infanticide also was observed in wolverines but not in wolves. Traumatic injuries, originating from road or railway accidents, were the most common cause of death in wolves and occurred occasionally in brown bears. Most wolverines were submitted as forensic cases in which illegal hunting/poaching was suspected. Sarcoptic mange was observed in several wolves but not in brown bears or wolverines. Sarcoptic mange most likely was acquired from infected red foxes (Vulpes vulpes) that were killed by wolves. Other parasites and infectious diseases were only found sporadically.

Animal Diseases↗

PubMed2002

[The effect on other individual presentations of the goldfish by FG7142 injection].

To research the emotional effects on goldfish shoaling behavior, the change in time spent by the stimulus shoal sizes (0, 1, 2, and 5) was investigated. Consequently, as for shoaling behavior, a difference was seen only in the presence of a shoal, independent of size. The experimental goldfish were then injected with beta-carboline (FG7142, N-Methyl-beta-carboline-3-carboxyamide at 0.1, 1, 2, or 4 mg/kg) or the vehicle and exposed to the stimulus fish (1). In the beta-carboline group with the 1 and 2 mg/kg dose, the time spent within 10 cm of the stimulus fish increased compared with the vehicle, and this increase was maintained throughout the trial. In contrast, the time spent was unchanged in the high-dose group (4 mg/kg). The subject fish motility was unchanged in all dose groups. These results are discussed in their relationship to predator avoidance.

Animals↗

PubMed2006

[Competitive mechanism of non - predator - prey metapopulation system based on competition and dispersal ability].

Species competition is one of the important ecological courses that influence the evolvement of ecosystem. To an ecosystem of predator - prey, competition is always bidirectional, that is there is competitive infection on superior species and inferior species. Without regarding to the destruction of habitat, the bidirectional competitive mechanism was introduced, Tilman' unilateral competitive model was extended to bidirectional competitive model of metapopulation. At the same time, the competitive dynamics of the 6- metapopulation species are simulated on computer. The results showed that at the equilibrium, the coexistence condition of population competition is migratory ability and competition ability take on exponential negative correlation, the outcome of competition makes the superior and inferior sequence changed, the exclusion and coexistence of species competition was affected by migratory ability and competition ability, the metapopulations which are excluded in local patches can exist in regional scale, that is escaping coexistence.

Animals↗

PubMed1978

A semi-Markovian model for predator-prey interactions.

In the study of population dynamics, the predator-prey system is recognized as a vitally important aspect in natural population control. On aspect of predator-prey interactions is studied in this paper. The attack cycle of a predator is assumed to consist of four different activities, namely, search, pursuit, handle and eat, and digestion. A semi-Markovian model is proposed to obtain the number of prey devoured by a predator during the activity of a day. The advantages of a new semi-Markovian model to the queueing model developed by Curry and DeMichele (1977) is demonstrated, as the results from the semi-Markovian model are closer to Holling's (1966) experimental data than their results, which were based entirely on Poisson assumptions.

Animals↗

PubMed1975

[Observations, analyses and experiments on the use of the hand in Callithrix jacchus Erxleben, 1777. Part II. Fine analysis of prehensive behavior].

The use of the hand of the common marmoset (Callithrix jacchus Erxleben, 1777) was analysed on the basis of observations and experiments conducted on 56 animals of all age. During arboreal locomotion Callithrix jacchus makes use of the hands for support and for grasping to maintain its balance, The palmar region serves as the main means of support, while the findgers in the locomotor grip also contribute to maintaining balance and support. The greater the need for maintaining balance, for example, during vertikal climbing or in movement along the narow branches, the mre complete the djustment of the hand form on the surface and the more complete the alignment of the hand on the branch will be. Additional support is supplied by the longitudinal palm furrow, caused by the radio-ulnar adduction of the hand edges and by the clinging properties of the volar pads...

Age Factors↗

PubMed2005

Sublethal effects of cadmium on prey choice and capture efficiency in juvenile brook trout (Salvelinus fontinalis).

Prey choice in juvenile brook trout (Salvelinus fontinalis) was investigated under sublethal Cd stress in the presence of alternative prey types. Following 30-d exposures to either 0, 0.5, or 5.0 microg/L Cd, individual fish held in artificial stream channels were presented with both motile (Baetis tricaudatus) and nonmotile (Chironomus tentans) prey items and their foraging behavior and capture success was observed. The Cd-exposed trout were found to express a significant preference for C. tentans larvae as alternative prey to B. tricaudatus nymphs. Nevertheless, these preliminary findings indicate that, irrespective of prey choice, the capture efficiency of Cd-stressed trout declined by 20 to 55% with increasing Cd concentration when compared with control fish, and the activity of individual trout increased by 25% over controls, although these responses were not statistically significant. Cadmium significantly affected fish condition factors: The condition factor of control fish increased by 34% over the 30-d period, and Cd-exposed fish declined in condition by 12 to 18%. It is hypothesized that such a switch by fish to feeding on benthic prey under natural exposure conditions and their proximity to contaminated sediment may further exacerbate the sublethal effects of Cd on these individuals by intensifying or prolonging Cd exposure through a combination of trophic transfer and altered foraging behavior.

Animals↗

PubMed2000

Sleeping site preferences in tufted capuchin monkeys (Cebus apella nigritus).

The characteristics and availability of the sleeping sites used by a group of 27 tufted capuchin monkeys (Cebus apella nigritus) were studied during 17 months at the Iguazu National Park, Argentina. We tested different hypotheses regarding possible ultimate causes of sleeping-site selection. Most sleeping sites were located in areas of tall, mature forest. Of the 34 sleeping sites the monkeys used during 203 nights, five were more frequently used than the others (more than 20 times each, constituting 67% of the nights). Four species of tree (Peltophorum dubium, Parapiptadenia rigida, Copaifera langsdorfii and Cordia trichotoma) were the most frequently used. They constituted 82% of all the trees used, though they represent only 12% of the trees within the monkeys' home range which had a diameter at breast height (DBH) > 48.16 cm (1 SD below the mean DBH of sleeping trees). The sleeping trees share a set of characteristics not found in other trees: they are tall emergent (mean height +/- SD = 31.1+/-5.2 m) with large DBH (78.5+/-30.3 cm), they have large crown diameter (14+/-5.5 m), and they have many horizontal branches and forks. Adult females usually slept with their kin and infants, while peripheral adult males sometimes slept alone in nearby trees. We reject parasite avoidance as an adaptive explanation for the pattern of sleeping site use. Our results and those from other studies suggest that predation avoidance is a predominant factor driving sleeping site preferences. The patterns of aggregation at night and the preference for trees with low probability of shedding branches suggest that social preferences and safety from falling during windy nights may also affect sleeping tree selection. The importance of other factors, such as seeking comfort and maintaining group cohesion, was not supported by our results. Other capuchin populations show different sleeping habits which can be explained by differences in forest structure and by demographic differences.

Animals↗

PubMed2005

Development and reproduction of Adalia bipunctata (Coleoptera: Coccinellidae) on eggs of Ephestia kuehniella (Lepidoptera: Phycitidae) and pollen.

Due to growing criticism over the use of non-indigenous coccinellids, the two-spot ladybird, Adalia bipunctata (L.), has enjoyed increasing attention for aphid biocontrol in Europe. In the current study, eggs of the Mediterranean flour moth, Ephestia kuehniella Zeller, whether or not supplemented with bee pollen, were evaluated as a factitious food for larvae and adults of A. bipunctata. The predator showed slower larval development and lower survival when reared on live pea aphids, Acyrthosiphon pisum (Harris), than on E. kuehniella eggs. Survival on gamma-irradiated eggs of E. kuehniella was superior to that on frozen flour moth eggs, but other developmental characteristics were similar. Adults of A. bipunctata reared on Ac. pisum were only half as fecund as those offered irradiated or frozen E. kuehniella eggs, but egg hatch was markedly better on live aphids than on flour moth eggs (61 versus 20-27%, respectively). However, when a diet of flour moth eggs was supplemented with frozen moist bee pollen, egg hatch of A. bipunctata was equally as good as on live aphids. Supplementing flour moth eggs with dry pollen did not yield satisfactory results. Only 10% of larvae reached adulthood on moist bee pollen alone and resulting adults weighed less than half as much as those obtained on flour moth eggs. Our findings indicate that A. bipunctata is able to compensate for a suboptimal diet of animal prey by supplementary feeding on flower pollen. It is concluded that pollinivory may be a crucial trait for both the rearing of this natural enemy and its use in biological control programmes.

Animals↗

PubMed2001

Wave of chaos: new mechanism of pattern formation in spatio-temporal population dynamics.

The dynamics of a simple prey-predator system is described by a system of two reaction- diffusion equations with biologically reasonable non-linearities (logistic growth of the prey, Holling type II functional response of the predator). We show that, when the local kinetics of the system is oscillatory, for a wide class of initial conditions the evolution of the system leads to the formation of a non-stationary irregular pattern corresponding to spatio-temporal chaos. The chaotic pattern first appears inside a sub-domain of the system. This sub-domain then steadily grows with time and, finally, the chaotic pattern invades the whole space, displacing the regular pattern.

Animals↗