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Karen L. Cheney - One of the best experts on this subject based on the ideXlab platform.
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Colour vision and response bias in a coral reef fish
The Journal of Experimental Biology, 2013Co-Authors: Karen L. Cheney, Cait Newport, Eva C. Mcclure, N. Justin MarshallAbstract:Animals use coloured Signals for a variety of communication purposes, including to attract potential mates, recognize individuals, defend territories and warn predators of secondary defences (aposematism). To understand the mechanisms that drive the evolution and design of such visual Signals, it is important to understand the visual systems and potential response biases of Signal Receivers. Here, we provide raw data on the spectral capabilities of a coral reef fish, Picasso triggerfish Rhinecanthus aculeatus , which are potentially trichromatic with three cone sensitivities of 413 nm (single cone), 480 nm (double cone, medium sensitivity), 528 nm (double cone, long sensitivity) and a rod sensitivity of 498 nm. The ocular media have a 50% transmission cut off at 405 nm. Behavioural experiments confirmed colour vision over their spectral range; triggerfish were significantly more likely to choose coloured stimuli over grey distractors, irrespective of luminance. We then examined whether response biases existed towards coloured and patterned stimuli to provide insights into how visual Signals - in particular, aposematic colouration - may evolve. Triggerfish showed a preferential foraging response bias to red and green stimuli, in contrast to blue and yellow, irrespective of pattern. There was no response bias to patterned over monochromatic non-patterned stimuli. A foraging response bias towards red in fish differs to that of avian predators, who often avoid red food items. Red is frequently associated with warning colouration in terrestrial environments (ladybirds, snakes, frogs), whilst blue is used in aquatic environments (blue-ringed octopus, nudibranchs); whether the design of warning (aposematic) displays is a cause or consequence of response biases is unclear.
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Cleaner wrasse mimics inflict higher costs on their models when they are more aggressive towards Signal Receivers
Biology Letters, 2011Co-Authors: Karen L. CheneyAbstract:Aggressive mimics are predatory species that resemble a ‘model’ species to gain access to food, mating opportunities or transportation at the expense of a Signal receiver. Costs to the model may be variable, depending on the strength of the interaction between mimics and Signal Receivers. In the Indopacific, the bluestriped fangblenny Plagiotremus rhinorhynchos mimics juvenile cleaner wrasse Labroides dimidiatus. Instead of removing ectoparasites from larger coral reef fish, fangblennies attack fish to feed on scales and body tissue. In this study, juvenile cleaner wrasse suffered significant costs when associated with P. rhinorhynchos mimics in terms of reduced cleaning activity. Furthermore, the costs incurred by the model increased with heightened aggression by mimics towards Signal Receivers. This was apparently because of behavioural changes in Signal Receivers, as cleaning stations with mimics that attacked frequently were visited less. Variation in the costs incurred by the model may influence mimicry accuracy and avoidance learning by the Signal receiver and thus affect the overall success and maintenance of the mimicry system.
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Conspicuousness is correlated with toxicity in marine opisthobranchs.
Journal of Evolutionary Biology, 2010Co-Authors: Fabio Cortesi, Karen L. CheneyAbstract:Aposematism is defined as the use of conspicuous colouration to warn predators that an individual is chemically or otherwise defended. Mechanisms that drive the evolution of aposematism are complex. Theoretical and empirical studies show that conspicuousness can be either positively or negatively correlated with toxicity as once aposematism is established, species can allocate resources into becoming more conspicuous and/or increase secondary defences. Here, we investigated the evolution of conspicuousness and toxicity in marine opisthobranchs. Conspicuousness of colour Signals was assessed using spectral reflectance measurements and theoretical vision models from the perspective of two reef fish Signal Receivers. The relative toxicity of chemicals extracted from each opisthobranch species was then determined using toxicity assays. Using a phylogenetic comparative analysis, we found a significant correlation between conspicuousness and toxicity, indicating that conspicuousness acts as an honest Signal when signifying level of defence and provides evidence for aposematism in opisthobranchs.
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Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?
Behavioral Ecology, 2009Co-Authors: Karen L. Cheney, N. Justin MarshallAbstract:Batesian and aggressive mimics are considered to be under selective pressure to resemble their models, whereas Signal Receivers are under selection to discriminate between mimics and models. However, the perceptual ability of Signal Receivers to discriminate between mimics and models is rarely studied. Here we examined 15 model--mimic coral reef fish pairs using nonsubjective methods to judge the accuracy of mimics in terms of color and luminance. We then investigated the potential ability of fish with various visual systems to discriminate between model and mimic colors using theoretical vision models. We found the majority of mimics closely resembled models in terms of color and luminance from a nonsubjective perspective. However, fish that have potentially trichromatic (3 distinct cone photoreceptors) visual systems with ultraviolet sensitivity had a much better capacity to discriminate between models and mimics compared with fish with midrange sensitivity or dichromatic (2 cone photoreceptors) fish. The spectral reflectance of color patches reflected by models and mimics became more similar with an increase in depth, indicating that Signal Receivers may be more likely to distinguish mimics from models in habitats located closer to the surface. There was no such change in luminance contrast with depth. The selection pressure on mimics to accurately resemble their model is therefore predicted to vary depending on the visual system of the Signal receiver and the light environment. Copyright 2009, Oxford University Press.
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Aggressive mimics profit from a model-Signal receiver mutualism.
Proceedings. Biological sciences, 2007Co-Authors: Karen L. Cheney, Isabelle M. CôtéAbstract:Mimetic species have evolved to resemble other species to avoid predation (protective mimicry) or gain access to food (aggressive mimicry). Mimicry systems are frequently tripartite interactions involving a mimic, model and ‘Signal receiver’. Changes in the strength of the relationship between model and Signal receiver, owing to shifting environmental conditions, for example, can affect the success of mimics in protective mimicry systems. Here, we show that an experimentally induced shift in the strength of the relationship between a model (bluestreak cleaner fish, Labroides dimidiatus) and a Signal receiver (staghorn damselfish, Amblyglyphidodon curacao) resulted in increased foraging success for an aggressive mimic (bluestriped fangblenny, Plagiotremus rhinorhynchos). When the parasite loads of staghorn damselfish clients were experimentally increased, the attack success of bluestriped fangblenny on damselfish also increased. Enhanced mimic success appeared to be due to relaxation of vigilance by parasitized clients, which sought cleaners more eagerly and had lower overall aggression levels. Signal Receivers may therefore be more tolerant of and/or more vulnerable to attacks from aggressive mimics when the net benefit of interacting with their models is high. Changes in environmental conditions that cause shifts in the net benefits accrued by models and Signal Receivers may have important implications for the persistence of aggressive mimicry systems.
N. Justin Marshall - One of the best experts on this subject based on the ideXlab platform.
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Colour vision and response bias in a coral reef fish
The Journal of Experimental Biology, 2013Co-Authors: Karen L. Cheney, Cait Newport, Eva C. Mcclure, N. Justin MarshallAbstract:Animals use coloured Signals for a variety of communication purposes, including to attract potential mates, recognize individuals, defend territories and warn predators of secondary defences (aposematism). To understand the mechanisms that drive the evolution and design of such visual Signals, it is important to understand the visual systems and potential response biases of Signal Receivers. Here, we provide raw data on the spectral capabilities of a coral reef fish, Picasso triggerfish Rhinecanthus aculeatus , which are potentially trichromatic with three cone sensitivities of 413 nm (single cone), 480 nm (double cone, medium sensitivity), 528 nm (double cone, long sensitivity) and a rod sensitivity of 498 nm. The ocular media have a 50% transmission cut off at 405 nm. Behavioural experiments confirmed colour vision over their spectral range; triggerfish were significantly more likely to choose coloured stimuli over grey distractors, irrespective of luminance. We then examined whether response biases existed towards coloured and patterned stimuli to provide insights into how visual Signals - in particular, aposematic colouration - may evolve. Triggerfish showed a preferential foraging response bias to red and green stimuli, in contrast to blue and yellow, irrespective of pattern. There was no response bias to patterned over monochromatic non-patterned stimuli. A foraging response bias towards red in fish differs to that of avian predators, who often avoid red food items. Red is frequently associated with warning colouration in terrestrial environments (ladybirds, snakes, frogs), whilst blue is used in aquatic environments (blue-ringed octopus, nudibranchs); whether the design of warning (aposematic) displays is a cause or consequence of response biases is unclear.
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Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?
Behavioral Ecology, 2009Co-Authors: Karen L. Cheney, N. Justin MarshallAbstract:Batesian and aggressive mimics are considered to be under selective pressure to resemble their models, whereas Signal Receivers are under selection to discriminate between mimics and models. However, the perceptual ability of Signal Receivers to discriminate between mimics and models is rarely studied. Here we examined 15 model--mimic coral reef fish pairs using nonsubjective methods to judge the accuracy of mimics in terms of color and luminance. We then investigated the potential ability of fish with various visual systems to discriminate between model and mimic colors using theoretical vision models. We found the majority of mimics closely resembled models in terms of color and luminance from a nonsubjective perspective. However, fish that have potentially trichromatic (3 distinct cone photoreceptors) visual systems with ultraviolet sensitivity had a much better capacity to discriminate between models and mimics compared with fish with midrange sensitivity or dichromatic (2 cone photoreceptors) fish. The spectral reflectance of color patches reflected by models and mimics became more similar with an increase in depth, indicating that Signal Receivers may be more likely to distinguish mimics from models in habitats located closer to the surface. There was no such change in luminance contrast with depth. The selection pressure on mimics to accurately resemble their model is therefore predicted to vary depending on the visual system of the Signal receiver and the light environment. Copyright 2009, Oxford University Press.
Younggie Kim - One of the best experts on this subject based on the ideXlab platform.
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IROS - Robot localization using ultrasonic sensors
2004 IEEE RSJ International Conference on Intelligent Robots and Systems (IROS) (IEEE Cat. No.04CH37566), 1Co-Authors: Sewan Kim, Younggie KimAbstract:In this paper, we explain the mobile robot localization system, which consists of ultrasonic emitters and receiving sensor array. Two or more ultrasonic emitters are installed on the beacon, which is also a charging station and ultrasonic Signal Receivers on the robot pick up the Signal from the beacon. Based on the time measurement of the traveled ultrasonic waves, the robot determines its distance and orientation relative to the beacon. This system is actually deployed in the commercial cleaning robot, Roboking, released in the market in late 2004.
Paul J. Weldon - One of the best experts on this subject based on the ideXlab platform.
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Receiver-error in deception, including mimicry: making the leap from inter- to intraspecific domains
Biological Journal of the Linnean Society, 2016Co-Authors: Paul J. WeldonAbstract:The present study examines the constructs of ‘deception’ and ‘mimicry’ and describes how they are related as errors committed by Signal Receivers, citing parallels in inter- and intraspecific interactions. Previous authors have suggested that deception embraces two types of receiver-error that can be likened to type I and type II errors encountered in statistical tests of the null hypothesis: responses to misinterpreted cues (type I error: embracing a non-existent effect) and failed responses to concealed traits of interest or undetected opportunities (type II error: failing to detect a real effect). The present study builds upon these suggestions, co-opting the terms ‘type I and type II receiver-errors’ to denote the aforementioned kinds of deception. Type I receiver-errors occur in many cases of Batesian mimicry, bluffing, and intersexual mimicry, where members of one sex mimic members of the opposite sex. Type II receiver-errors are illustrated by prey and predator crypsis and some covert (‘sneaky’) mating strategies. A third kind of receiver-error, designated type II–I, occurs when organisms are misidentified contingent upon the concealment of tell-tale features, such as with cephalopods that hide select arms in visual mimetic displays. The occurrence of advantages and disadvantages for Signallers and Signal Receivers in inter- and intraspecific deception, and in their evolutionary repercussions, is discussed. Advergence, where deceptive Signallers evolve increased resemblance to honest Signallers, and divergence, where honest Signallers become distinct from deceptive Signallers, may arise from the dynamical interactions between Signallers and Signal Receivers. Signal senders, by definition, benefit from deception. Deceived Signal Receivers also may benefit from some, perhaps many, interactions. Deception and evolutionary responses to deception are abundantly represented in both inter- and intraspecific domains.
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Evolving détente: the origin of warning Signals via concurrent reciprocal selection
Biological Journal of The Linnean Society, 2015Co-Authors: Paul J. Weldon, Gordon M. BurghardtAbstract:Casualties and impediments inflicted on consumers by defended prey, and vice versa, may be averted by vocalizations, postures, coloration, scents, and other warning, or so-called aposematic, displays. The existence of aposematic Signals has challenged biologists who have sought plausible mechanisms for their evolution. Here, we elaborate on the rationale for the hypothesis that aposematic Signals arise via concurrent reciprocal selection (CRS) enacted between inimical Signal Receivers and Signal emitters, where Signal emitters, e.g., defended prey, select against non-discriminating Signal Receivers, e.g., predators, and Signal Receivers select against unrecognized Signal emitters. It is postulated that this mutual selective interaction culminates in the survival of discriminating Signal Receivers that avoid Signal emitters, and recognized (distinctive) Signal emitters that are avoided by Signal Receivers. A CRS hypothesis for the evolution of aposematism, therefore, maintains that distinctive features of prey arise in response to selection imposed by consumers, and that avoidances of those features by consumers arise in response to selection imposed by defended prey. We discuss the plausible inception of aposematism via CRS in light of related hypotheses, and describe points of concordance with previous observations and suggestions on the origin of aposematism. Aposematism arising via CRS is not contingent upon the relatedness of Signallers, aversions acquired by learning, or other conditions postulated for some other evolutionary hypotheses. CRS is a credible alternative hypothesis for the evolution of warning Signals in diverse consumer-prey interactions.
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Chemical aposematism
Chemoecology, 2013Co-Authors: Paul J. WeldonAbstract:Discussions of aposematism traditionally have focused on the visual displays of prey that denote unpalatability or toxicity to predators. However, the construct of aposematism accommodates a spectrum of unprofitable traits Signaled through various sensory modalities, including contact and distance chemoreception. Aposematism, involving learned aversions by Signal Receivers or selection for their unlearned avoidances, arises in predator–prey or other interspecific interactions where a mutually beneficial avoidance of Signal emitters by Signal Receivers exists. Aposematism evolves by selection against Signal Receivers, e.g., predators, imposed by Signal emitters, e.g., unprofitable prey, and vice versa, where both nondiscriminating Signal Receivers and unrecognized Signal emitters are imperiled. Chemical aposematism entails concurrent reciprocal selection where Signal emitters select for chemosensory avoidance responses in Signal Receivers, and where Signal Receivers select for the emission of identifiable (distinctive) chemicals in Signal emitters.
Jinjun Chen - One of the best experts on this subject based on the ideXlab platform.
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Optimal placement of barrier coverage in heterogeneous bistatic radar sensor networks
World Wide Web, 2019Co-Authors: Xianghua Xu, Chengwei Zhao, Zichen Jiang, Zongmao Cheng, Jinjun ChenAbstract:Barrier Coverage is an important sensor deployment issue in many industrial, consumer and military applications.The barrier coverage in bistatic radar sensor networks has attracted many researchers recently. The Bistatic Radars (BR) consist of radar Signal transmitters and radar Signal Receivers. The effective detection area of bistatic radar is a Cassini oval area that determined by the distance between transmitter and receiver and the predefined detecting SNR threshold. Many existing works on bistatic radar barrier coverage mainly focus on homogeneous radar sensor networks. However, cooperation among different types or different physical parameters of sensors is necessary in many practical application scenarios. In this paper, we study the optimal deployment problem in heterogeneous bistatic radar networks.The object is how to maximize the detection ability of bistatic radar barrier with given numbers of radar sensors and barrier’s length. Firstly, we investigate the optimal placement strategy of single transmitter and multiple Receivers, and propose the patterns of aggregate deployment. Then we study the optimal deployment of heterogeneous transmitters and Receivers and introduce the optimal placement sequences of heterogeneous transmitters and Receivers. Finally, we design an efficient greedy algorithm, which realize optimal barrier deployment of M heterogeneous transmitters and N Receivers on a L length boundary, and maximizing the detection ability of the barrier. We theoretically proved that the placement sequence of the algorithm construction is optimal deployment solution in heterogeneous bistatic radar sensors barrier. And we validate the algorithm effectiveness through comprehensive simulation experiments.