Chemically mediated rheotaxis of endangered tri-spine horseshoe crab: potential dispersing mechanism to vegetated nursery habitats along the coast
Kit Yue Kwan,
Xin Yang,
Chun-Chieh Wang,
Yang Kuang,
Yulong Wen,
Kian Ann Tan,
Peng Xu,
Wenquan Zhen,
Xueping Wang,
Junhua Zhu,
Xing Huang
Affiliations
Kit Yue Kwan
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Xin Yang
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Chun-Chieh Wang
Guangxi Key Laboratory of Marine Environmental Science, Guangxi Beibu Gulf Marine Research Center, Guangxi Academy of Sciences, Nanning, China
Yang Kuang
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Yulong Wen
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Kian Ann Tan
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Peng Xu
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Wenquan Zhen
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Xueping Wang
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Junhua Zhu
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Xing Huang
College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University, Qinzhou, Guangxi, China
Background An enhanced understanding of larval ecology is fundamental to improve the management of locally depleted horseshoe crab populations in Asia. Recent studies in the northern Beibu Gulf, China demonstrated that nesting sites of Asian horseshoe crabs are typically close to their nursery beaches with high-density juveniles distributed around mangrove, seagrass and other structured habitats. Methods A laboratory Y-maze chamber was used to test whether the dispersal of early-stage juvenile tri-spine horseshoe crab Tachypleus tridentatus is facilitated by chemical cues to approach suitable nursery habitats. The juvenile orientation to either side of the chamber containing controlled seawater or another with various vegetation cues, as well as their movement time, the largest distance and displacement were recorded. Results The juveniles preferred to orient toward seagrass Halophila beccarii cues when the concentration reached 0.5 g l−1, but ceased at 2 g l−1. The results can be interpreted as a shelter-seeking process to get closer to the preferred settlement habitats. However, the juveniles exhibited avoidance behaviors in the presence of mangrove Avicennia marina and invasive saltmarsh cordgrass Spartina alterniflora at 2 g l−1. The juveniles also spent less time moving in the presence of the A. marina cue, as well as reduced displacement in water containing the S. alterniflora cue at 1 and 2 g l−1. These results may explain the absence of juvenile T. tridentatus within densely vegetated areas, which have generally higher organic matter and hydrogen sulfide. Conclusion Early-stage juvenile T. tridentatus are capable of detecting and responding to habitat chemical cues, which can help guide them to high-quality settlement habitats. Preserving and restoring seagrass beds in the intertidal areas should be prioritized when formulating habitat conservation and management initiatives for the declining horseshoe crab populations.
