Data from: You are what you eat: diet-induced chemical crypsis in a coral-feeding reef fish

The vast majority of research into the mechanisms of camouflage has focused on forms that confound visual perception. However, many organisms primarily interact with their surroundings using chemosensory systems and may have evolved mechanisms to ‘blend in’ with chemical components of their habitat. One potential mechanism is ‘chemical crypsis' via the sequestration of dietary elements, causing a consumer's odour to chemically match that of its prey. Here, we test the potential for chemical crypsis in the coral-feeding filefish, Oxymonacanthus longirostris, by examining olfactory discrimination in obligate coral-dwelling crabs and a predatory cod. The crabs, which inhabit the corals consumed by O. longirostris, were used as a bioassay to determine the effect of coral diet on fish odour. Crabs preferred the odour of filefish fed their preferred coral over the odour of filefish fed a non-preferred coral, suggesting coral-specific dietary elements that influence odour are sequestered. Crabs also exhibited a similar preference for the odour of filefish fed their preferred coral and odour directly from that coral, suggesting a close chemical match. In behavioural trials, predatory cod were less attracted to filefish odour when presented alongside the coral it had been fed on, suggesting diet can reduce detectability. This is, we believe, the first evidence of diet-induced chemical crypsis in a vertebrate.

绝大多数关于伪装机制的研究均聚焦于可干扰视觉感知的伪装类型。然而，诸多生物主要通过化学感应系统与周遭环境交互，或许已演化出可与栖息地化学组分相“融合”的策略。其中一种潜在机制便是通过摄取储存膳食组分实现化学隐蔽（chemical crypsis），令捕食者的气味在化学特征上与其猎物趋于一致。本研究以食珊瑚的尖吻单棘鲀（*Oxymonacanthus longirostris*）为对象，通过检测专性栖居珊瑚的螃蟹与掠食性鳕鱼的嗅觉辨别能力，验证其是否具备化学隐蔽潜力。这些栖息于尖吻单棘鲀所食用珊瑚之上的螃蟹被用作生物测定材料，以探究珊瑚膳食对鱼类气味特征的影响。实验结果显示，相较于以非偏好珊瑚为食的革鲀气味，螃蟹更青睐以自身偏好珊瑚为食的革鲀气味，这表明鱼类会摄取储存能够影响气味的珊瑚特异性膳食组分。此外，螃蟹对以自身偏好珊瑚为食的革鲀气味，与该偏好珊瑚的直接气味表现出相似的偏好性，提示二者的化学特征高度匹配。在行为试验中，当掠食性鳕鱼同时接收到革鲀气味与其所食用的珊瑚气味时，其对革鲀气味的吸引力显著降低，这表明膳食摄入能够降低猎物的可探测性。我们认为，本研究首次在脊椎动物中发现了由膳食诱导产生化学隐蔽的证据。