Babcock S K, Blais J L
Department of Biology, MSC 7801, James Madison University, Harrisonburg, Virginia 22807, USA.
J Morphol. 2001 Feb;247(2):142-59. doi: 10.1002/1097-4687(200102)247:2<142::AID-JMOR1009>3.0.CO;2-Y.
We describe caudosacral and caudal vertebral morphology across life history stages in three caudate amphibians: Ambystoma jeffersonianum (Ambystomatidae), Desmognathus ocoee (Plethodontidae: Desmognathinae), and Hemidactylium scutatum (Plethodontidae: Plethodontinae). All three species have aquatic larvae, but adults differ in habitat and predator defense strategy. Predator defense includes tail autotomy in D. ocoee and H. scutatum but not A. jeffersonianum. Of the species that autotomize, H. scutatum has a specialized constriction site at the tail base. We investigated whether aquatic larvae exhibit vertebral features similar to those previously described for aquatic adults and examined the effect of metamorphosis, if any, on vertebral morphology and the ontogeny of specialized vertebral features associated with tail autotomy. Interspecific comparisons of cleared-and-stained specimens indicate that vertebral morphology differs dramatically at hatching and that caudosacral and caudal vertebrae undergo continuous ontogenetic change throughout larval, metamorphic, and juvenile periods. Larvae and juveniles of H. scutatum do not exhibit adult vertebral features associated with constricted-base tail autotomy. The pond-type larvae of A. jeffersonianum and H. scutatum have tapering centrum lengths posterior to the sacrum. This pattern is functionally associated with aquatic locomotion. The stream-type larvae of D. ocoee undergo enhanced regional growth in the anterior tail such that the anterior caudal centra become longer than the preceding caudosacral centra. With the exception of the first two caudal vertebrae, a similar growth pattern occurs in H. scutatum adults. We hypothesize that enhanced growth of the anterior caudal segments is associated with tail elongation and autotomy.
杰斐逊钝口螈（钝口螈科）、奥科伊肋突螈（隐鳃鲵科：肋突螈亚科）和四线小鲵（隐鳃鲵科：小鲵亚科）。这三个物种都有水生幼体，但成体在栖息地和捕食者防御策略方面存在差异。捕食者防御包括奥科伊肋突螈和四线小鲵的尾部自切，但杰斐逊钝口螈没有。在进行尾部自切的物种中，四线小鲵在尾基部有一个特殊的收缩部位。我们研究了水生幼体是否表现出与先前描述的水生成体相似的椎骨特征，并研究了变态（如果有）对椎骨形态以及与尾部自切相关的特殊椎骨特征个体发育的影响。对透明和染色标本的种间比较表明，孵化时椎骨形态差异很大，并且尾骶部和尾椎在整个幼体、变态和幼年时期经历持续的个体发育变化。四线小鲵的幼体和幼体不表现出与基部收缩尾部自切相关的成体椎骨特征。杰斐逊钝口螈和四线小鲵的池塘型幼体在骶骨后方的椎体长度逐渐变细。这种模式在功能上与水生运动相关。奥科伊肋突螈的溪流型幼体在前尾区域生长增强，使得前尾椎体比前面的尾骶椎体更长。除了前两个尾椎外，四线小鲵成体也出现类似的生长模式。我们推测前尾节段的生长增强与尾部伸长和自切有关。
