Marine Futures Lab, School of Biological Sciences, University of Western Australia, Crawley, Western Australia, Australia.
Pristine Seas, National Geographic Society, Washington, DC, United States of America.
PLoS One. 2022 Oct 19;17(10):e0275458. doi: 10.1371/journal.pone.0275458. eCollection 2022.
Mutualistic and commensal interactions can have significant positive impacts on animal fitness and survival. However, behavioural interactions between pelagic animals living in offshore oceanic environments are little studied. Parasites can negatively effect the fitness of their hosts by draining resources and diverting energy from growth, reproduction, and other bodily functions. Pelagic fishes are hosts to a diverse array of parasites, however their environment provides few options for removal. Here we provide records of scraping behaviour of several pelagic teleost species, a behaviour that is likely used for parasite removal. These records span three ocean basins and, to the best of our knowledge, include the first records of scraping interactions involving tunas, blue sharks, and mako sharks as well as the first records of intraspecific scraping. We found that scrapers preferred scraping their head, eyes, gill cover, and lateral surfaces, areas where parasites are commonly found and where damage would likely have a substantial impact on fitness. Scraper species varied in their scraping preferences with tunas scraping mostly on the posterior caudal margins of sharks and occasionally conspecifics, while rainbow runner scraped in more varied locations on both sharks and conspecifics. Lengths of scrapers and scrapees were positively correlated and fish scraping on sharks were larger than those scraping on conspecifics, suggesting that risk of predation may be a limiting factor. We show that pelagic teleosts prefer to scrape on sharks rather than conspecifics or other teleosts and suggest that this behaviour may have a positive impact on teleost fitness by reducing parasite loads. The decline of shark populations in the global ocean and the reduction in mean size of many species may limit these interactions, eroding possible fitness benefits associated with this behaviour, and consequently placing more pressure on already highly targeted and vulnerable species.
互利共生和共栖相互作用对动物的适应度和生存有显著的积极影响。然而，生活在近海海洋环境中的浮游动物之间的行为相互作用却很少被研究。寄生虫通过消耗资源和将能量从生长、繁殖和其他身体功能中转移，对宿主的适应度产生负面影响。浮游鱼类是各种寄生虫的宿主，但它们所处的环境几乎没有可供寄生虫清除的选择。在这里，我们提供了几种远洋硬骨鱼类刮擦行为的记录，这种行为可能用于清除寄生虫。这些记录跨越了三个大洋，据我们所知，其中包括首次记录涉及金枪鱼、蓝鲨和灰鲭鲨的刮擦相互作用，以及首次记录同种内的刮擦行为。我们发现，刮擦者更喜欢刮擦头部、眼睛、鳃盖和侧表面，这些是寄生虫通常存在的地方，也是损伤可能对适应度产生重大影响的地方。刮擦者的物种偏好不同，金枪鱼主要在鲨鱼的后部尾鳍边缘刮擦，偶尔也会刮擦同种鱼，而彩虹鲷则在鲨鱼和同种鱼的更多不同部位刮擦。刮擦者和被刮擦者的长度呈正相关，而且在鲨鱼上刮擦的鱼比在同种鱼上刮擦的鱼更大，这表明被捕食的风险可能是一个限制因素。我们表明，远洋硬骨鱼类更喜欢在鲨鱼上刮擦，而不是在同种鱼或其他硬骨鱼类上刮擦，这表明这种行为可能通过减少寄生虫负担对硬骨鱼类的适应度产生积极影响。全球海洋中鲨鱼种群的减少和许多物种平均体型的缩小可能会限制这些相互作用，削弱与这种行为相关的适应度益处，并因此对已经高度受到关注和脆弱的物种施加更大的压力。
