Like most ray-finned fishes (Actinopterygii), pipefishes (Syngnathoidei) feed by suction. Most pipefishes reach their prey by a rapid dorso-rotation of the head. In the present study, we analysed the feeding kinematics of the razor fish,Centriscus scutatus, and of the greater pipefish,Syngnathus acusin detail. We found capture times of as little as 4–6 ms forC. scutatusand 6–8 ms forS. acus. We then hypothesized that the long snout of pipefishes is optimal for such fast feeding. To test this, we implemented in a mathematical model the following considerations. To reach the prey as fast as possible, a low moment of inertia increases the head's angular speed, whereas a long snout decreases the angle over which the head must be turned. The model accurately predicted the snout lengths of a number of pipefishes. We found that the optimal snout length, with which a prey will be reached fastest, is inversely related to its cross-section. In spite of the small cross-section, the development of a long snout can be an evolutionary advantage because this reduces the time to approach the prey.

A considerable body of work has examined the dynamics of different dog gaits, but there are no studies that focused on limb dynamics in jumping. Jumping is an essential part of dog agility, a dog sport in which handlers direct their dogs through an obstacle course in a limited time. We hypothesized that limb parameters like limb length and stiffness indicate the skill level of dogs. We analyzed global limb parameters in jumping for 10 advanced and 10 beginner dogs. In experiments, we collected 3D kinematics and ground reaction forces during dog jumping at high forward speeds. Our results revealed general strategies of limb control in jumping and highlighted differences between advanced and beginner dogs. In take-off, the spatially leading forelimb was 75% (p<0.001) stiffer than the trailing forelimb. In landing, the trailing forelimb was 14% stiffer (p<0.001) than the leading forelimb. This indicates a strut-like action of the forelimbs to achieve jumping height in take-off and to transfer vertical velocity into horizontal velocity in landing (with switching roles of the forelimbs). During landing, the more (24%) compliant forelimbs of beginner dogs (p=0.005), resulted in 17% (p=0.017) higher limb compression during the stance phase. This is associated with a larger amount of eccentric muscle contraction, which might in turn explain the soft tissue injuries that frequently occur in the shoulder region of beginner dogs. For all limbs, length at toe-off was greater for advanced dogs. Hence, limb length and stiffness might be used as objective measures of skill.