Animals from many taxa, from snakes and crabs to caterpillars and lobsters, change appearance with age, but the reasons why this occurs are rarely tested. We show the importance that ontogenetic changes in coloration have on the camouflage of the green shore crabs ( Carcinus maenas ), known for their remarkable phenotypic variation and plasticity in colour and pattern. In controlled conditions, we reared juvenile crabs of two shades, pale or dark, on two background types simulating different habitats for 10 weeks. In contrast to expectations for reversible colour change, crabs did not tune their background match to specific microhabitats, but instead, and regardless of treatment, all developed a uniform dark green phenotype. This parallels changes in shore crab appearance with age observed in the field. Next, we undertook a citizen science experiment at the Natural History Museum London, where human subjects (“predators”) searched for crabs representing natural colour variation from different habitats, simulating predator vision. In concert, crabs were not hardest to find against their original habitat, but instead, the dark green phenotype was hardest to detect against all backgrounds. The evolution of camouflage can be better understood by acknowledging that the optimal phenotype to hide from predators may change over the life history of many animals, including the utilization of a generalist camouflage strategy. A plain language summary is available for this article.

There is substantial and unexplored potential for scientists to engage with the private sector for a sustainable ocean. The importance of such cooperation is a frequent emphasis of international dialogues and statements, it is embedded within the Sustainable Development Goals, and has been championed by prominent business leaders and scientists. But an uncritical embrace of science-industry collaboration is unhelpful, and candid reflections on the benefits and pitfalls that marine scientists can expect from actively engaging with the private sector are rare. In this Perspective, we draw on our collective experiences working with ocean industries in different parts of the world to reflect on how this has influenced our work, the effects these collaborations have generated, and the barriers to overcome for such partnerships to become more common. In doing so, we hope to help empower a new generation of marine scientists to explore collaboration with industry as a way to develop and scale up solutions for ocean sustainability.

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25Changes in coloration enable animals to refine their camouflage to match different 26 visual environments. Such plasticity provides ecological benefits and could 27 potentially be exploited to support conservation or stock enhancement efforts. One 28 application could be ensuring that hatchery-reared animals, reared to stock wild 29 populations, are appropriately matched to their environment on release. European 30 lobster (Homarus gammarus) hatcheries aim to restock or enhance local lobster 31 populations by rearing juveniles through their most vulnerable stages, then releasing 32 them into the wild. However, little consideration has been given to their camouflage 33 and the implications of matching individuals to their release site. This study assesses 34 to what extent juvenile lobsters can change coloration to match their background and 35 whether hatchery practices could be altered to enhance lobster camouflage . We test 36 this by switching individuals between black or white backgrounds in the laboratory 37 and monitoring their coloration over time. Our work demonstrates the capacity of 38 juvenile lobsters to change lightness in response to their surroundings. We show that 39 juvenile lobsters are capable of small changes in luminance (perceived lightness) to 40 better match their background over 2-3 weeks. These changes potentially 41 correspond to improved camouflage, based on a model of predator (European 42 pollack, Pollachius pollachius) vision. However, over a longer period (5 weeks), 43 lobsters maintained on either background converged on the same darker coloration, 44suggesting that lobsters also experience changes in appearance associated with 45 ontogeny. By refining the approaches used here, there is potential for hatcheries to 46 rear lobsters on backgrounds that better match their release site. However, such release timing (which varies between stocking programmes). This study highlights 49 the potential to use colour change in stocking and aquaculture, as well as gaps that 50 could be addressed through further research in this area. 51 52 53 54 Background matching is one of the most widely used anti-predator defence 55 strategies in nature (1), with many species using colours and patterns to match their 56 surroundings and avoid detection and predation. In a wide range of taxa, both 57 terrestrial and aquatic, camouflage can be achieved through plastic changes in 58 appearance (2,3). This enables animals to respond to either fast and unpredictable 59 changes in the visual environment through rapid (seconds and minutes) colour 60 change, or slower and more predictable environmental change with gradual (hours, 61 days, and weeks) appearance changes (4). One of the most widely studied groups, 62 particularly in terms of the mechanisms and functions of colour change, are the 63 crustaceans (3,5). Many crustacean species employ camouflage to conceal 64 themselves from predators and several have been shown to change colour to better 65match their background, including crabs (6-8), prawns (9,1...