Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA 01730, USA
Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA 01730, USA.
J Exp Biol. 2020 Aug 17;223(Pt 16):jeb223743. doi: 10.1242/jeb.223743.
Mallard ducks are capable of performing a wide range of behaviors including nearly vertical takeoffs from both terrestrial and aquatic habitats. The hindlimb plays a key role during takeoffs from both media. However, because force generation differs in water versus on land, hindlimb kinematics and muscle function are likely modulated between these environments. Specifically, we hypothesize that hindlimb joint motion and muscle shortening are faster during aquatic takeoffs, but greater hindlimb muscle forces are generated during terrestrial takeoffs. In this study, we examined the hindlimb kinematics and contractile function of the lateral gastrocnemius (LG), a major ankle extensor and knee flexor, during takeoffs from water versus land in mallard ducks. In contrast to our hypothesis, we observed no change in ankle angular velocity between media. However, the hip and metatarsophalangeal joints underwent large excursions during terrestrial takeoffs but exhibited almost no motion during aquatic takeoffs. The knee extended during terrestrial takeoffs but flexed during aquatic takeoffs. Correspondingly, LG fascicle shortening strain, shortening velocity and pennation angle change were greater during aquatic takeoffs than during terrestrial takeoffs because of the differences in knee motion. Nevertheless, we observed no significant differences in LG stress or work, but did see an increase in muscle power output during aquatic takeoffs. Because differences in the physical properties of aquatic and terrestrial media require differing hindlimb kinematics and muscle function, animals such as mallards may be challenged to tune their muscle properties for movement across differing environments.
野鸭能够进行多种行为，包括从陆地和水生栖息地进行近乎垂直的起飞。后肢在两种介质的起飞中都起着关键作用。然而，由于水与陆地的力生成方式不同，后肢运动学和肌肉功能可能在这两种环境之间进行调节。具体来说，我们假设在水生起飞时，后肢关节运动和肌肉缩短速度更快，但在陆地起飞时产生更大的后肢肌肉力量。在这项研究中，我们研究了野鸭从水到陆地起飞时后肢的运动学和外侧比目鱼肌（LG）的收缩功能，LG 是主要的踝关节伸肌和膝关节屈肌。与我们的假设相反，我们观察到两种介质之间的踝关节角速度没有变化。然而，髋关节和跖趾关节在陆地起飞时进行了大幅度的运动，但在水生起飞时几乎没有运动。膝关节在陆地起飞时伸展，但在水生起飞时弯曲。相应地，由于膝关节运动的差异，LG 肌纤维缩短应变、缩短速度和羽状角变化在水生起飞时大于陆地起飞时。尽管如此，我们没有观察到 LG 应力或功的显著差异，但确实看到了在水生起飞时肌肉功率输出的增加。由于水和陆地介质的物理特性不同，需要不同的后肢运动学和肌肉功能，因此像野鸭这样的动物可能会面临调整肌肉特性以适应不同环境的挑战。
