Hawai'i Institute of Marine Biology, University of Hawai'i at Mānoa, Kāne'ohe, HI, 96744, USA.
Department of Biology, University of Hawai'i at Mānoa, Honolulu, HI, 96822, USA.
Sci Rep. 2017 Sep 8;7(1):11042. doi: 10.1038/s41598-017-11459-8.
Elasmobranch fishes are among a broad range of taxa believed to gain positional information and navigate using the earth's magnetic field, yet in sharks, much remains uncertain regarding the sensory receptors and pathways involved, or the exact nature of perceived stimuli. Captive sandbar sharks, Carcharhinus plumbeus were conditioned to respond to presentation of a magnetic stimulus by seeking out a target in anticipation of reward (food). Sharks in the study demonstrated strong responses to magnetic stimuli, making significantly more approaches to the target (p = < 0.01) during stimulus activation (S+) than before or after activation (S-). Sharks exposed to reversible magnetosensory impairment were less capable of discriminating changes to the local magnetic field, with no difference seen in approaches to the target under the S+ and S- conditions (p = 0.375). We provide quantified detection and discrimination thresholds of magnetic stimuli presented, and quantify associated transient electrical artefacts. We show that the likelihood of such artefacts serving as the stimulus for observed behavioural responses was low. These impairment experiments support hypotheses that magnetic field perception in sharks is not solely performed via the electrosensory system, and that putative magnetoreceptor structures may be located in the naso-olfactory capsules of sharks.
板鳃鱼类被认为是能够利用地球磁场来获取位置信息和进行导航的广泛生物类群之一，但在鲨鱼中，对于涉及的感觉受体和途径，或者所感知刺激的确切性质，仍然存在很多不确定性。我们对圈养的沙虎鲨（Carcharhinus plumbeus）进行了条件反射训练，使它们在感知到磁场刺激时，通过寻找目标来获得奖励（食物）。研究中的鲨鱼对磁场刺激表现出强烈的反应，在刺激激活期间（S+），它们比在激活之前或之后（S-）更频繁地接近目标（p = < 0.01）。暴露在可逆转的磁感觉损伤中的鲨鱼，对于局部磁场变化的辨别能力降低，在 S+和 S-条件下，它们接近目标的次数没有差异（p = 0.375）。我们提供了所呈现的磁场刺激的量化检测和辨别阈值，并量化了相关的瞬态电干扰。我们表明，这些电干扰不太可能成为观察到的行为反应的刺激。这些损伤实验支持了以下假说：鲨鱼对磁场的感知不仅仅是通过电感觉系统进行的，而且假定的磁受体结构可能位于鲨鱼的鼻-嗅觉囊中。
