Animal vision and colour change for camouflage
Lead Research Organisation:
University of Exeter
Department Name: Biosciences
Abstract
Understanding why individuals of the same species differ among and within populations, including
those found in different environments, and the mechanisms that lead to such variation is a
fundamental problem in biology. A major cause of individual variation is colour change. This ability is
widespread in nature, from insects and crustaceans, through to reptiles, fish, and amphibians. It
occurs on a wide range of timescales (seconds, hours, days, weeks, and months), and usually involves
changes in special pigment-containing cells in the body. Colour change is vital in guiding the
camouflage of many species, and has received much attention in unusually rapid changing species
such as cephalopods and chameleons. However, a major gap in our knowledge exists - although colour
change is widely assumed to be based on animals visually inspecting the background, this has rarely
been directly investigated. In fact, we know very little about how the visual systems of colour changing
animals enable them to match their visual environment.
This project will study two common UK species that are highly diverse in appearance and known to be
able 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 and
putting them on different backgrounds to assess their ability to change colour. Using special image
analysis techniques and models of predator vision, the effectiveness of colour change on each
background in providing camouflage will be assessed. Concurrently, advanced techniques to
determine what photoreceptors are present in each species vision, and the wavelengths of light they
can 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 ability
guides and constrains colour change. Finally, experiments will be conducted using coloured light filters
and LED lights to change the light conditions and patterns in experiments to tease apart the role of
light 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 perception
of animals and how this allows and constrains them to change colour for concealment in a wide range
of visual environments.
those found in different environments, and the mechanisms that lead to such variation is a
fundamental problem in biology. A major cause of individual variation is colour change. This ability is
widespread in nature, from insects and crustaceans, through to reptiles, fish, and amphibians. It
occurs on a wide range of timescales (seconds, hours, days, weeks, and months), and usually involves
changes in special pigment-containing cells in the body. Colour change is vital in guiding the
camouflage of many species, and has received much attention in unusually rapid changing species
such as cephalopods and chameleons. However, a major gap in our knowledge exists - although colour
change is widely assumed to be based on animals visually inspecting the background, this has rarely
been directly investigated. In fact, we know very little about how the visual systems of colour changing
animals enable them to match their visual environment.
This project will study two common UK species that are highly diverse in appearance and known to be
able 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 and
putting them on different backgrounds to assess their ability to change colour. Using special image
analysis techniques and models of predator vision, the effectiveness of colour change on each
background in providing camouflage will be assessed. Concurrently, advanced techniques to
determine what photoreceptors are present in each species vision, and the wavelengths of light they
can 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 ability
guides and constrains colour change. Finally, experiments will be conducted using coloured light filters
and LED lights to change the light conditions and patterns in experiments to tease apart the role of
light 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 perception
of animals and how this allows and constrains them to change colour for concealment in a wide range
of visual environments.
