Chemically mediated rheotaxis of endangered tri-spine horseshoe crab: potential dispersing mechanism to vegetated nursery habitats along the coast

PeerJ

article

Kit Yue Kwan¹  Xin Yang¹  Chun-Chieh Wang²  Yang Kuang¹  Yulong Wen¹  Kian Ann Tan¹  Peng Xu¹  Wenquan Zhen¹  Xueping Wang¹  Junhua Zhu¹  Xing Huang¹ 

[1] College of Marine Sciences, Beibu Gulf Ocean Development Research Centre, Guangxi Key Laboratory of Beibu Gulf Biodiversity Conservation, Beibu Gulf University;Guangxi Key Laboratory of Marine Environmental Science, Guangxi Beibu Gulf Marine Research Center, Guangxi Academy of Sciences

关键词: Dispersal;    Cordgrass;    Mangrove;    Seagrass;    Settlement;    Tachypleus tridentatus;   

DOI  :  10.7717/peerj.14465

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

BackgroundAn 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.MethodsA 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.ResultsThe 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.ConclusionEarly-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.

【 授权许可】

CC BY