García-Esponda César M, Candela Adriana M
Cátedra Zoología III Vertebrados, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Avenida 122 y 60, La Plata, 1900, Argentina.
CONICET, División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque, La Plata, 1900, Argentina.
J Morphol. 2016 Mar;277(3):286-305. doi: 10.1002/jmor.20495. Epub 2015 Dec 2.
The caviomorph species Hydrochoerus hydrochaeris (Cavioidea), or capybara, is the largest living rodent. This species is widely distributed, from northern South America to Uruguay and eastern Argentina, inhabiting in a wide variety of densely vegetated lowlands habitats in the proximity of water. Hydrochoerus hydrochaeris not only runs with agility, like other members of the Cavioidea, but it can also swim and dive easily. For these reasons, it has been classified as a cursorial as well as semiaquatic species. However, comprehensive anatomical descriptions of the osteology and myology of the capybara are not available in the literature and analyses on its swimming abilities are still required. We hypothesize that some of the characters of the hindlimb of H. hydrochaeris could reveal a unique morphological arrangement associated with swimming abilities. In this study, an anatomical description of the hindlimb musculature of H. hydrochaeris, and a discussion of the possible functional significance of the main muscles is provided. In addition, we explore the evolution of some myological and osteological characters of the capybara in the context of the cavioids. We concluded that most of the muscular and osteological features of the hindlimb of H. hydrochaeris are neither adaptations to a specialized cursoriality, nor major modifications for an aquatic mode of life. Hydrochoerus hydrochaeris share several features with other cavioids, being a generalized cursorial species in the context of this clade. However, it shows some adaptations of the hindlimb for enhancing propulsion through water, of which the most notable seems to be the shortening of the leg, short tendons of most muscles of the leg, and a well-developed soleus muscle. These adaptations to a semiaquatic mode of life could have been acquired during the most recent evolutionary history of the hydrochoerids.
豚鼠型亚目物种水豚（Hydrochoerus hydrochaeris，豚鼠科）是现存最大的啮齿动物。该物种分布广泛，从南美洲北部到乌拉圭和阿根廷东部，栖息于靠近水源的各种植被茂密的低地栖息地。水豚不仅像豚鼠科的其他成员一样行动敏捷，还能轻松游泳和潜水。基于这些原因，它被归类为奔跑型和半水栖型物种。然而，文献中尚无关于水豚骨骼学和肌肉学的全面解剖描述，对其游泳能力的分析仍有待进行。我们推测，水豚后肢的某些特征可能揭示出与游泳能力相关的独特形态结构。在本研究中，我们对水豚后肢肌肉组织进行了解剖描述，并讨论了主要肌肉可能的功能意义。此外，我们在豚鼠型亚目的背景下探讨了水豚一些肌肉学和骨骼学特征的演化。我们得出的结论是，水豚后肢的大多数肌肉和骨骼特征既不是对特殊奔跑习性的适应，也不是对水生生活方式的重大改变。水豚与其他豚鼠型亚目动物有一些共同特征，在这个分类群中是一种广义的奔跑型物种。然而，它的后肢显示出一些为增强水中推进力而做出的适应，其中最显著的似乎是腿部缩短、腿部大多数肌肉的肌腱较短以及比目鱼肌发达。这些对半水栖生活方式的适应可能是在水豚科动物最近的进化历史中获得的。
