Camouflage and Exploratory Avoidance of Newborn Cuttlefish under Warming and Acidification

SIMPLE SUMMARY: Sub-lethal effects of climate change on organisms have received little attention to date. For instance, little is known concerning the ability of cuttlefish to camouflage and to explore under ocean acidification and warming. This study aimed to evaluate the physiology, camouflage performance, and exploratory avoidance behavior of cuttlefish hatchlings exposed to these stressors during embryogenesis. Hatchlings were placed in arenas with either sand or white and black gravel covering the bottom. Photographs were taken remotely to extract camouflage latency and pixel values in the cuttlefish body and the background. Mobility and proximity to the arena walls were recorded. Despite survival being lower under acidification and warming combined, our results indicate that camouflage was strengthened under warming, whilst no effect was found on spatial exploration. This study shows that cuttlefish mobility and exploratory avoidance behaviors are unlikely to be impacted by changes in climate. Moreover, camouflage, an anti-predator strategy essential to the survival of cuttlefish newborns, is not impeded and might be enhanced by future levels of ocean acidification and warming. ABSTRACT: Ocean warming and acidification have been shown to elicit deleterious effects on cephalopod mollusks, especially during early ontogeny, albeit effects on behavior remain largely unexplored. This study aimed to evaluate, for the first time, the effect of end-of-the-century projected levels of ocean warming (W; + 3 °C) and acidification (A; 980 µatm pCO(2)) on Sepia officinalis hatchlings’ exploratory behavior and ability to camouflage in different substrate complexities (sand and black and white gravel). Cuttlefish were recorded in open field tests, from which mobility and exploratory avoidance behavior data were obtained. Latency to camouflage was registered remotely, and pixel intensity of body planes and background gravel were extracted from photographs. Hatching success was lowered under A and W combined (AW; 72.7%) compared to control conditions (C; 98.8%). Motion-related behaviors were not affected by the treatments. AW delayed camouflage response in the gravel substrate compared to W alone. Moreover, cuttlefish exhibited a higher contrast and consequently a stronger disruptive pattern under W, with no changes in background matching. These findings suggest that, although climate change may elicit relevant physiological challenges to cuttlefish, camouflage and mobility of these mollusks are not undermined under the ocean of tomorrow.