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能够干扰视觉感知的伪装形式。然而，诸多生物主要通过化学感应系统与周遭环境进行交互，并可能演化出可与栖息地化学组分相“融合”的机制。其中一种潜在机制便是化学隐蔽（chemical crypsis）：通过截留并积累膳食组分，使取食者的气味在化学特征上与其猎物的气味相匹配。本研究以专性栖居珊瑚的螃蟹及一种掠食性鳕鱼为对象，通过检测其嗅觉辨别能力，探究食珊瑚的尖吻单棘鲀（Oxymonacanthus longirostris）中化学隐蔽的可能性。这些螃蟹栖息于尖吻单棘鲀所取食的珊瑚之上，被用作生物测定（bioassay）手段，以明确珊瑚食性对鱼类气味的影响。实验结果显示，相较于以非偏好性珊瑚为食的革鲀气味，螃蟹更倾向于选择以自身偏好珊瑚为食的革鲀气味，这表明能够影响气味的珊瑚特异性膳食组分被截留积累。同时，螃蟹对以自身偏好珊瑚为食的革鲀气味，以及该偏好珊瑚本身的直接气味，表现出相似的偏好性，这提示二者的化学特征高度匹配。在行为试验中，当掠食性鳕鱼接触到以某类珊瑚为食的尖吻单棘鲀的气味时，其对该气味的趋性显著降低，这表明食性能够降低猎物的可检测性。我们认为，本研究首次在脊椎动物中发现了由食性诱导产生的化学隐蔽现象。