Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 321, 05508-900, São Paulo, SP, Brasil.
J Biosci. 2011 Mar;36(1):117-21. doi: 10.1007/s12038-011-9005-5.
Most techniques used for estimating the age of Sotalia guianensis (van Beneden, 1864) (Cetacea; Delphinidae) are very expensive, and require sophisticated equipment for preparing histological sections of teeth. The objective of this study was to test a more affordable and much simpler method, involving of the manual wear of teeth followed by decalcification and observation under a stereomicroscope. This technique has been employed successfully with larger species of Odontoceti. Twenty-six specimens were selected, and one tooth of each specimen was worn and demineralized for growth layers reading. Growth layers were evidenced in all specimens; however, in 4 of the 26 teeth, not all the layers could be clearly observed. In these teeth, there was a significant decrease of growth layer group thickness, thus hindering the layers count. The juxtaposition of layers hindered the reading of larger numbers of layers by the wear and decalcification technique. Analysis of more than 17 layers in a single tooth proved inconclusive. The method applied here proved to be efficient in estimating the age of Sotalia guianensis individuals younger than 18 years. This method could simplify the study of the age structure of the overall population, and allows the use of the more expensive methodologies to be confined to more specific studies of older specimens. It also enables the classification of the calf, young and adult classes, which is important for general population studies.
大多数用于估计宽吻海豚（Sotalia guianensis）（鲸目；海豚科）年龄的技术都非常昂贵，并且需要复杂的设备来制备牙齿的组织学切片。本研究的目的是测试一种更经济实惠且简单得多的方法，涉及手动磨损牙齿，然后进行脱钙和立体显微镜观察。这种技术已成功应用于较大的齿鲸物种。选择了 26 个标本，每个标本的一颗牙齿都进行了磨损和脱钙以读取生长层。所有标本中都有生长层的证据；然而，在 26 颗牙齿中的 4 颗中，并非所有层都能清晰观察到。在这些牙齿中，生长层组厚度明显减少，从而阻碍了层的计数。层的并置阻碍了通过磨损和脱钙技术读取更多层。在单个牙齿中分析超过 17 层的结果并不明确。这里应用的方法被证明可以有效地估计年龄小于 18 岁的宽吻海豚个体的年龄。这种方法可以简化对整个种群年龄结构的研究，并允许将更昂贵的方法仅限于对更老标本的更具体研究。它还可以对小牛、幼崽和成年类进行分类，这对于一般种群研究很重要。
