Bonine K E, Gleeson T T, Garland T
Department of Zoology, University of Wisconsin, 430 Lincoln Drive, Madison, WI 53706, USA.
J Morphol. 2001 Dec;250(3):265-80. doi: 10.1002/jmor.1069.
The lizard family Phrynosomatidae comprises three subclades: the closely related sand and horned lizards, and their relatives the Sceloporus group. This family exhibits great variation in ecology, behavior, and general body plan. Previous studies also show that this family exhibits great diversity in locomotor performance abilities; as measured on a high-speed treadmill, sand lizards are exceptionally fast sprinters, members of the Sceloporus group are intermediate, and horned lizards are slowest. These differences are paralleled by differences in relative hindlimb span. To determine if muscle fiber-type composition also varies among the three subclades, we examined the iliofibularis (IF), a hindlimb muscle used in lizard locomotion, in 11 species of phrynosomatid lizards. Using histochemical assays for myosin ATPase, an indicator of fast-twitch capacity, and succinic dehydrogenase, denoting oxidative capacity, we classified fiber types into three categories based on existing nomenclature: fast-twitch glycolytic (FG), fast-twitch oxidative-glycolytic (FOG), and slow-twitch oxidative (SO). Sand lizards have a high proportion of FG fibers (64-70%) and a low proportion of FOG fibers (25-33%), horned lizards are the converse (FG fibers 25-31%, FOG fibers 56-66%), and members of the Sceloporus group are intermediate for both FG (41-48%) and FOG (42-45%) content. Hence, across all 11 species %FOG and %FG are strongly negatively correlated. Analysis with phylogenetically independent contrasts indicate that this negative relationship is entirely attributable to the divergence between sand and horned lizards. The %SO also varies among the three subclades. Results from conventional nested ANCOVA (with log body mass as a covariate) indicate that the log mean cross-sectional area of individual muscle fibers differs among species and is positively correlated with body mass across species, but does not differ significantly among subclades. The log cross-sectional area of the IF varies among species, but does not vary among subclades. Conversely, the total thigh muscle cross-sectional area does not vary among species, but does vary among subclades; horned lizards have slimmer thighs. Muscle fiber-type composition appears to form part of a coadapted suite of traits, along with relative limb and muscle sizes, that affect the locomotor abilities of phrynosomatid lizards.
亲缘关系较近的沙蜥和角蜥，以及它们的近亲斯氏蜥蜴类群。这个科在生态、行为和总体身体结构方面表现出很大的差异。先前的研究还表明，这个科在运动表现能力方面也具有很大的多样性；在高速跑步机上测量时，沙蜥是异常快速的短跑者，斯氏蜥蜴类群的成员处于中等水平，而角蜥是最慢的。这些差异与相对后肢跨度的差异相对应。为了确定肌肉纤维类型组成在这三个亚分支中是否也有所不同，我们检查了11种鬣蜥科蜥蜴的髂腓肌（IF），这是一种用于蜥蜴运动的后肢肌肉。使用针对肌球蛋白ATP酶（快速收缩能力的指标）和琥珀酸脱氢酶（表示氧化能力）的组织化学分析方法，我们根据现有的命名法将纤维类型分为三类：快速收缩糖酵解型（FG）、快速收缩氧化糖酵解型（FOG）和慢速收缩氧化型（SO）。沙蜥的FG纤维比例较高（64 - 70%），FOG纤维比例较低（25 - 33%），角蜥则相反（FG纤维25 - 31%，FOG纤维56 - 66%），斯氏蜥蜴类群的成员在FG（41 - 48%）和FOG（42 - 45%）含量方面都处于中间水平。因此，在所有11个物种中，FOG%和FG%呈强烈的负相关。系统发育独立对比分析表明，这种负相关完全归因于沙蜥和角蜥之间的分化。SO%在这三个亚分支中也有所不同。传统的嵌套协方差分析（以对数体重作为协变量）结果表明，单个肌肉纤维的对数平均横截面积在物种间存在差异，并且在物种间与体重呈正相关，但在亚分支间没有显著差异。IF的对数横截面积在物种间有所不同，但在亚分支间没有变化。相反，大腿肌肉的总横截面积在物种间没有变化，但在亚分支间有所不同；角蜥的大腿更细。肌肉纤维类型组成似乎是一套协同适应的性状的一部分，与相对肢体和肌肉大小一起，影响着鬣蜥科蜥蜴的运动能力。
