Visual perception and camouflage response to 3D backgrounds and cast shadows in the European cuttlefish, <i>Sepia officinalis</i>

ABSTRACT To conceal themselves on the seafloor, European cuttlefish, Sepia officinalis, express a large repertoire of body patterns. Scenes with 3D relief are especially challenging because it is not possible either to directly recover visual depth from 2D retinal image or for cuttlefish alter its shape resemble nearby objects. Here, we characterised camouflage responses relief, and cast shadows, which complementary cues. Animals were recorded in presence cylindrical objects fixed (15 mm) diameter, but varying height, greyscale strength corresponding pictorial images. With cylinders, expressed ‘3D’ pattern, distinct previously described Uniform, Mottle Disruptive This pattern was insensitive variation object contrast shadow, except when shadows most pronounced, case patterns resembled those used backgrounds. suggests that stationary as cues by rather than matching image, response two-stage process whereby animal first classifies physical environment then selects an appropriate pattern. Each type triggered specific may compete, allowing select suitable camouflage, so categorical continuously variable. These findings give unique insight into how invertebrate senses generate response.