Active photolocation: A new frontier in active sensing

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Active sensory systems, which rely on self-generated energy to gather information about the environment, have been well studied in several animals. For example, bats emit high-pitched sounds and detect their reflection to locate prey items, avoid obstacles, and communicate with conspecifics. The main active sensory modalities, echolocation and electrolocation, have received much attention, and generated a tremendous amount of influential findings. However, active photolocation, the process of sensing the environment through light emission or redirection, is virtually unstudied. This is surprising since a large number of deep-sea fish species, and several nocturnal reef fish species possess light producing organs near their eyes. These `flashlights' are hypothetically used for prey/predator detection, luring prey, and intraspecific communication such as group cohesion and individual recognition. However, the proposed functions of these light organs are mostly speculative; only a single study has quantified photophore use in flashlight fishes. Furthermore, recent studies, by a group of colleagues and myself, demonstrated that many diurnal fish possess structures on their irises that redirect or change the quality of ambient light, allowing them to increase their probability of detecting potential prey and predators. Diurnal active photolocation could be widespread in fish, and work from our group has laid the foundation for studying this behaviour and associated ecological and evolutionary consequences. With my first Discovery Grant I will initiate a comprehensive research programme aimed at understanding the mechanisms and functions of active photolocation. In the first five years, I will establish a long-term experimental program on 1) nocturnal active photolocation using the flashlight fish Anomalops katoptron as a model, and 2) diurnal active photolocation using the three-spined stickleback Gasterosteus aculeatus. My studies will provide a novel framework for testing trade-offs constraining the evolution of active photolocation, but also have ramifications on our understanding of the co-evolution of fish eyes among species. Active photolocation is heavily neglected in the active sensing literature, consequently offering exciting opportunities for novel discoveries. This research program will be unique in Canada and therefore make a distinctive Canadian contribution to the international study of active sensing. My research program will provide a multidisciplinary training environment for the next generation of scientist. My students will gain broadly transferable skills through e.g., animal husbandry and care, scientific SCUBA diving and other field work, and train with state of the art techniques including spectroradiometry, multispectral imaging, and advanced visual modelling. All research results will be communicated to the scientific community and the general public through the publishing of pre-print or open-access articles.