Jauniaux Thierry, Garigliany Mutien-Marie, Loos Pauline, Bourgain Jean-Luc, Bouveroux Thibaut, Coignoul Freddy, Haelters Jan, Karpouzopoulos Jacky, Pezeril Sylvain, Desmecht Daniel
Department of Veterinary Pathology, Fundamental and Applied Research for Animals & Health (FARAH), University of Liege, Sart Tilman B43, B-4000, Liege, Belgium.
Coordination Mammalogique du Nord de la France, 806 rue Haute, 62850, Alembon, France.
PLoS One. 2014 Dec 2;9(12):e108993. doi: 10.1371/journal.pone.0108993. eCollection 2014.
Bite-like skin lesions on harbour porpoises (Phocoena phocoena) have been suspected to be caused by grey seals (Halichoerus grypus), and a few field observations have been reported. Bite-like skin lesions observed on stranded animals were characterized by two main components: large flaps of loose or missing skin and blubber with frayed edges and puncture lesions. Definitive demonstration of predation by a grey seal was not reported so far in those stranded animals. In this study, five stranded porpoises with bite-like skin lesions were swabbed for genetic investigations. In addition, the head of a recently dead grey seal was used to mimic bite-like skin injuries on a porpoise carcass. Subsequently, the artificial skin injuries were swabbed, along with the gum of the seal used for inflicting them (positive controls). Total DNA was extracted from the swabs and was used to retrieve a fragment of mitochondrial DNA by PCR. Primers were designed to amplify a specific stretch of mitochondrial DNA known to differ between grey seals and porpoises. The amplicon targeted was successfully amplified from the positive control and from two of the stranded porpoises, and grey seal-specific mitochondrial DNA was retrieved from all those samples. We conclude that (1) it is possible to detect grey seal DNA from dead porpoises even after several days in seawater and (2) bite-like skin lesions found on dead porpoises definitively result from grey seals attacks. The attacks are most likely linked with predation although, in a number of cases, scavenging and aggressive behaviour cannot be excluded.
港湾鼠海豚（Phocoena phocoena）身上类似咬伤的皮肤损伤一直被怀疑是由灰海豹（Halichoerus grypus）造成的，并且已有一些实地观察报告。在搁浅动物身上观察到的类似咬伤的皮肤损伤有两个主要特征：大片松弛或缺失的皮肤和脂肪层皮瓣，边缘磨损并有穿刺伤。到目前为止，在那些搁浅动物中尚未有灰海豹捕食的确切证据。在本研究中，对五只带有类似咬伤皮肤损伤的搁浅鼠海豚进行了拭子采样用于基因调查。此外，还利用一只刚死亡的灰海豹的头部在一只鼠海豚尸体上模拟类似咬伤的皮肤损伤。随后，对人工造成的皮肤损伤以及用于造成损伤的海豹牙龈进行了拭子采样（阳性对照）。从拭子中提取了总DNA，并通过聚合酶链反应（PCR）用于检索线粒体DNA片段。设计的引物用于扩增一段已知在灰海豹和鼠海豚之间存在差异的线粒体DNA特定片段。从阳性对照和两只搁浅鼠海豚中成功扩增出了目标扩增子，并且从所有这些样本中都检索到了灰海豹特异性线粒体DNA。我们得出结论：（1）即使在海水中浸泡数天后，仍有可能从死亡的鼠海豚中检测到灰海豹的DNA；（2）在死亡鼠海豚身上发现的类似咬伤的皮肤损伤确实是由灰海豹攻击所致。这些攻击很可能与捕食有关，不过在一些情况下，也不能排除食腐和攻击行为。
