The locomotor muscle morphology of diving mammals yields insights into how they utilize their environment and partition resources. This study examined a primary locomotor muscle, the longissimus, in three closely related, similarly sized pelagic delphinids (n = 7–9 adults of each species) that exhibit different habitat and depth preferences. The Atlantic spotted dolphin (Stenella frontalis) is a relatively shallow diver, inhabiting continental shelf waters; the striped (Stenella coeruleoalba) and short‐beaked common (Delphinus delphis) dolphins are sympatric, deep‐water species that dive to different depths. Based upon comparative data from other divers, it was hypothesized that the locomotor muscle of the deepest‐diving S. coeruleoalba would exhibit a higher percentage of slow oxidative fibers, larger fiber diameters, a higher myoglobin concentration [Mb], and a lower mitochondrial density than that of the shallow‐diving S. frontalis, and that the muscle of D. delphis would display intermediate values for these features. As expected, the locomotor muscle of S. coeruleoalba exhibited a significantly higher proportion of slow (57.3 ± 3.9%), oxidative (51.7 ± 2.5%) fibers and higher [Mb] (8.2 ± 0.7 g/100 g muscle) than that of S. frontalis (41.3 ± 3.9%, 31.0 ± 3.2%, 4.7 ± 0.05 g/100 g muscle, respectively). There were no differences in fiber size or mitochondrial density among these species. Like other deep divers, S. coeruleoalba displayed locomotor muscle features that enhance oxygen storage capacity and metabolic efficiency but did not display features that limit aerobic capacity. These results suggest a previously undescribed muscle design for an active, small‐bodied, deep‐diving cetacean.

中文翻译：

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三种远洋海豚的运动肌肉形态

潜水哺乳动物的运动肌肉形态有助于深入了解它们如何利用环境和分配资源。这项研究检查了三个密切相关、大小相似的远洋海豚科动物（每个物种的 n = 7-9 只成虫）的主要运动肌肉最长肌，它们表现出不同的栖息地和深度偏好。大西洋斑点海豚（Stenella frontalis）是一种相对较浅的潜水员，栖息在大陆架水域；条纹海豚 (Stenella coeruleoalba) 和短喙普通海豚 (Delphinus delphis) 是同域的深水物种，可以潜入不同的深度。根据其他潜水员的比较数据，假设潜入最深的蓝蓝白斑鱼的运动肌肉会表现出更高百分比的慢氧化纤维、更大的纤维直径、与浅潜水的 S. frontalis 相比，肌红蛋白浓度 [Mb] 更高，线粒体密度更低，并且 D. delphis 的肌肉将显示这些特征的中间值。正如预期的那样，S. coeruleoalba 的运动肌肉表现出明显更高比例的慢 (57.3 ± 3.9%)、氧化 (51.7 ± 2.5%) 纤维和更高的 [Mb] (8.2 ± 0.7 g/100 g 肌肉) S. 额肌（分别为 41.3 ± 3.9%、31.0 ± 3.2%、4.7 ± 0.05 g/100 g 肌肉）。这些物种之间的纤维大小或线粒体密度没有差异。与其他深海潜水员一样，蓝蓝白斑鱼显示出增强氧气储存能力和代谢效率的运动肌肉特征，但没有显示出限制有氧能力的特征。这些结果表明了一个以前未描述的肌肉设计，用于活跃的，