Alves F, Towers J R, Baird R W, Bearzi G, Bonizzoni S, Ferreira R, Halicka Z, Alessandrini A, Kopelman A H, Yzoard C, Rasmussen M H, Bertulli C G, Jourdain E, Gullan A, Rocha D, Hupman K, Mrusczok M-T, Samarra F I P, Magalhães S, Weir C R, Ford J K B, Dinis A
CIIMAR/CIIMAR-Madeira, Interdisciplinary Centre of Marine and Environmental Research of Madeira, Funchal, Portugal.
Oceanic Observatory of Madeira, Funchal, Portugal.
J Anat. 2018 Feb;232(2):263-269. doi: 10.1111/joa.12729. Epub 2017 Nov 17.
Laterally bent dorsal fins are rarely observed in free-ranging populations of cetaceans, contrary to captivity, where most killer whale Orcinus orca adult males have laterally collapsed fins. This topic has been poorly explored, and data/information on its occurrence and possible causes are limited. The present study: (i) undertakes a review of the available information on bent dorsal fins in free-ranging cetaceans, and updates it with new records, (ii) reports on the proportion of bent fins in different study populations, and (iii) discusses possible causes. An empirical approach based on bibliographic research and compilation of 52 new records collected worldwide resulted in a total of 17 species of cetaceans displaying bent dorsal fins. The species with the highest number of records (64%) and from most locations was O. orca. On average, individuals with bent dorsal fins represent < 1% of their populations, with the exception of false killer whales Pseudorca crassidens and O. orca. While line injuries associated with fisheries interactions may be the main cause for P. crassidens, and the vulnerability to health issues caused by the evolutionary enlargement of the fin may be the cause for O. orca adult males, factors contributing to this abnormality for other species are still unclear. The occurrence of bent dorsals could be influenced by a set of variables rather than by a single factor but, irrespective of the cause, it is suggested that it does not directly affect the animals' survivorship. While still rare in nature, this incident is more common (at least 101 known cases) and widespread (geographically and in species diversity) than hypothesized, and is not confined only to animals in captive environments. Investigation into the occurrence of bent fins may be an interesting avenue of research.
在自由放养的鲸类种群中，很少观察到侧向弯曲的背鳍，这与圈养环境相反，在圈养环境中，大多数成年雄性虎鲸（逆戟鲸）的背鳍会侧向塌陷。这个话题的研究较少，关于其发生情况和可能原因的数据/信息有限。本研究：（i）对自由放养的鲸类中背鳍弯曲的现有信息进行综述，并用新记录进行更新；（ii）报告不同研究种群中背鳍弯曲的比例；（iii）讨论可能的原因。基于文献研究和全球收集的52条新记录进行的实证研究，共发现17种鲸类出现背鳍弯曲。记录数量最多（64%）且分布地点最多的物种是逆戟鲸。平均而言，背鳍弯曲的个体占其种群的比例不到1%，伪虎鲸和逆戟鲸除外。虽然与渔业互动相关的线状损伤可能是伪虎鲸背鳍弯曲的主要原因，而鳍的进化性增大导致的健康问题易感性可能是成年雄性逆戟鲸背鳍弯曲的原因，但其他物种背鳍弯曲的促成因素仍不清楚。背鳍弯曲的发生可能受一系列变量而非单一因素影响，但无论原因如何，表明它不会直接影响动物的生存。虽然在自然界中仍然罕见，但这种情况比假设的更为常见（至少有101个已知案例）且分布广泛（地理分布和物种多样性方面），并不局限于圈养环境中的动物。对背鳍弯曲现象的研究可能是一个有趣的研究方向。
