Colour change and behavioural choice facilitate chameleon prawn camouflage against different seaweed backgrounds

Abstract

Camouflage is driven by matching the visual environment, yet natural habitats are rarely uniform and comprise many backgrounds. Therefore, species often exhibit adaptive traits to maintain crypsis, including colour change and behavioural choice of substrates. However, previous work largely considered these solutions in isolation, whereas many species may use a combination of behaviour and appearance to facilitate concealment. Here we show that green and red chameleon prawns ( Hippolyte varians ) closely resemble their associated seaweed substrates to the vision of predatory fish, and that they can change colour to effectively match new backgrounds. Prawns also select colour-matching substrates when offered a choice. However, colour change occurs over weeks, consistent with seasonal changes in algal cover, whereas behavioural choice of matching substrates occurs in the short-term, facilitating matches within heterogeneous environments. We demonstrate how colour change and behaviour combine to facilitate camouflage against different substrates in environments varying spatially and temporally.

Experimental evidence that matching habitat choice drives local adaptation in a wild population

“…This is in agreement with the almost universally accepted-though often not strictly confirmed-assumption that improved background colour matching conceals prey from visual predators [43,44,[54][55][56][57] (see also electronic supplementary material, S2 for supporting data for the study species). Similar presumably adaptive phenotype-environment associations for colour have been reported in a range of taxa, from arachnids [58] and crustaceans [34,59,60] to amphibians [27] and birds [56]. However, in many cases, the mechanism causing this association is unknown due to the difficulty in ascribing spatial clustering of similar phenotypes to the effects of self-assessment of local performance.…”

Effects of the antidepressant fluoxetine on pigment dispersion in chromatophores of the common sand shrimp, Crangon crangon: repeated experiments paint an inconclusive picture

“…Many crustaceans have the capacity to change colour over time as a means of remaining cryptic from predators through morphological changes to their carapace and shorter-term physiological changes in the pigment dispersion/concentration of the chromatophores (Keeble and Gamble 1904 ). In some species the hormonally controlled process of colour change is relatively fast (less than 1 h) whereas others change colour diurnally or seasonally (Detto et al 2008 , Siegenthaler et al 2017 ; Green et al 2019 ). For example, some planktonic organisms are considered to balance the benefits of transparency with protection of UV damage in shallow depths (Bashevkin et al 2019 ).…”

“…This highlights that both the physiological and behavioural responses are important to avoiding predation. Chameleon prawns ( Hippolyte varians ) come in two distinct colour forms (green and red) and display distinct behavioural preference for red and green algae as well as a capacity to change colour between day and night and seasonally to match their algal cover (Green et al 2019 ). Failure by an organism to behaviourally or physiologically adapt to its environment as a result of pollution would conceivably result in an increased predation, increased metabolic costs and potential risks through UV radiation.…”

Colour variation of the intertidal hermit crabClibanarius virescensconsidering growth stage, geographic area in the Indo–West Pacific Ocean, and molecular phylogeny

“…The relationship between colouration and phylogeny/natural history in organisms is an attractive topic in evolutionary biology, especially considering natural selection, adaptation and systematics (Olendorf et al ., 2006; Stevens & Merilaita, 2009; Bowen et al ., 2013; Green et al ., 2019). In animals, body colouration has various functions, including camouflage (Stevens & Merilaita, 2009), social communication (Detto et al ., 2006, 2008), mimicry (Randall, 2005), and thermoregulation (Silbiger & Munguia, 2008; Kronstadt et al ., 2013).…”

“…Moreover, there are various selective pressures inducing colour morphs. In the context of pattern matching, body colouration sometimes varies considerably depending on the substrate colour, the condition of environments, and season, and function as camouflage from visual predators (Russell & Dierssen, 2018; Green et al ., 2019). In terms of mating success, conspicuous colouration increases the detectability and attractivity for the counter sex, because such colouration often is originally reflected by the nutritional and/or maturity condition of individuals (Kodric-Brown, 1989; Guilford & Dawkins, 1991; Hill, 1999).…”