Kahle Patricia, Gallus Maren, Kierdorf Horst, Kierdorf Uwe
Department of Biology, University of Hildesheim, Hildesheim, Germany.
Anat Histol Embryol. 2023 Mar;52(2):300-311. doi: 10.1111/ahe.12884. Epub 2022 Nov 11.
Age estimation of individuals is an important tool for the management of marine mammals and is mostly done by microscopic analysis of growth layer groups (GLGs) in teeth (cementum and dentin) and bone. The present study evaluated the use of sutural and synchondrosal closure in the skull of the harbour seal (Phoca vitulina) as a potential non-destructive alternative for age estimation. For that, we scored the ectocranial closure of 12 selected sutures and synchondroses in a sample of 303 Eastern Atlantic harbour seals (P. v. vitulina; 138 males, 165 females), for which data on age at death were available, based on determined gross-morphological criteria in individuals younger than 1 year and cement layer analysis in canines in older individuals. A strong positive relationship between the sum of closure level scores (SCS) and age (males: r = 0.8797, females: r = 0.8825) was recorded, which was stronger than that for the relationship between age and condylobasal length (CBL, males: r = 0.7085, females: 0.7086) (all p-values <0.0001). In adult individuals (≥5 years), CBL was higher in males than females (p < 0.0001), while SCS did not significantly differ between the two sexes (p = 0.148). Our findings show that the analysis of sutural/synchondrosal closure is a valid alternative for age estimation in harbour seals, thereby confirming results of previous studies on other pinniped species.
个体年龄估计是管理海洋哺乳动物的一项重要工具，目前主要通过对牙齿（牙骨质和牙本质）和骨骼中的生长层组（GLGs）进行显微镜分析来完成。本研究评估了港湾海豹（Phoca vitulina）颅骨的缝线和软骨联合闭合情况，作为一种潜在的非侵入性年龄估计方法。为此，我们在303只东大西洋港湾海豹（P. v. vitulina；138只雄性，165只雌性）样本中，根据1岁以下个体确定的大体形态学标准以及成年个体犬齿的牙骨质层分析，对12条选定的颅外缝线和软骨联合的闭合情况进行了评分。记录到闭合水平得分总和（SCS）与年龄之间存在强正相关关系（雄性：r = 0.8797，雌性：r = 0.8825），这一关系比年龄与髁基长度（CBL，雄性：r = 0.7085，雌性：0.7086）之间的关系更强（所有p值<0.0001）。在成年个体（≥5岁）中，雄性的CBL高于雌性（p < 0.0001），而SCS在两性之间没有显著差异（p = 0.148）。我们的研究结果表明，缝线/软骨联合闭合分析是港湾海豹年龄估计的一种有效替代方法，从而证实了先前对其他鳍足类物种的研究结果。
