Animal vision and colour change for camouflage

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Understanding why individuals of the same species differ among and within populations, includingthose found in different environments, and the mechanisms that lead to such variation is afundamental problem in biology. A major cause of individual variation is colour change. This ability iswidespread in nature, from insects and crustaceans, through to reptiles, fish, and amphibians. Itoccurs on a wide range of timescales (seconds, hours, days, weeks, and months), and usually involveschanges in special pigment-containing cells in the body. Colour change is vital in guiding thecamouflage of many species, and has received much attention in unusually rapid changing speciessuch as cephalopods and chameleons. However, a major gap in our knowledge exists - although colourchange is widely assumed to be based on animals visually inspecting the background, this has rarelybeen directly investigated. In fact, we know very little about how the visual systems of colour changinganimals enable them to match their visual environment.This project will study two common UK species that are highly diverse in appearance and known to beable to change colour for camouflage: shore crabs (Carcinus maenas) and chameleon prawns(Hippolyte varians). It will involve conducting experiments in marine tanks with crabs and prawns andputting them on different backgrounds to assess their ability to change colour. Using special imageanalysis techniques and models of predator vision, the effectiveness of colour change on eachbackground in providing camouflage will be assessed. Concurrently, advanced techniques todetermine what photoreceptors are present in each species vision, and the wavelengths of light theycan detect, will be used to characterise the visual ability of each species. Using this information,models of prawn and crab vision can be constructed and used to determine how their visual abilityguides and constrains colour change. Finally, experiments will be conducted using coloured light filtersand LED lights to change the light conditions and patterns in experiments to tease apart the role oflight intensity, direction, and composition in guiding colour change, versus other factors, such as diet.This project will be the first to combine advanced understanding of the visual abilities and perceptionof animals and how this allows and constrains them to change colour for concealment in a wide rangeof visual environments.