Epidermal oxysterols function as alarm substances in zebrafish
Yaxi Li,
Zhi Yan,
Ainuo Lin,
Xiao Yang,
Xiaodong Li,
Xiuli Yin,
Weiming Li,
Ke Li
Affiliations
Yaxi Li
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
Zhi Yan
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; School of Ocean, Yantai University, Yantai 264005, China
Ainuo Lin
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
Xiao Yang
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
Xiaodong Li
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China
Xiuli Yin
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China
Weiming Li
Department of Fisheries & Wildlife, Michigan State University, Lansing, MI 48824, USA
Ke Li
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China; Corresponding author
Summary: Alarm substances signal imminent predation thread and enable anti-predation strategies. In shoaling fish, alarm cues diffuse from injured skins that induce intense fear and anti-predation behaviors in other members. While these “fear substances” are shown to be present in numerous fishes and thought to exist in roughly 8,000 Ostariophysan species, their chemical nature remains largely unknown. We posited that fish alarm cues comprise small compounds and induce specific behaviors characteristic of fish exposed to skin extracts. Using the behaviors as bioassays, we tracked the alarm function of zebrafish skin extract to two compounds, 24-methyl-5α-cholestane-3α,7α,12α,24,28-pentahydroxy 28-sulfate, an oxysterol sulfate, and 5α-cyprinol sulfate. At concentrations of less than one nanomolar, each compound induced anti-predator behaviors and increased cortisol levels in zebrafish. Their mixture, at the natural ratio, replicated the skin extract in eliciting the full suite of anti-predator behavior patterns. Our findings reveal a molecular mechanism whereby fish escape predation danger.
