Movement in Vertebrates
Vertebrates belong to the phylum Chordata and possess a cranium and column of vertebrae that enclose the central nervous system i.e. the brain and spinal cord. Comprising fishes, amphibians, reptiles, birds and mammals, vertebrates make up less then 50% of Kingdom Animalia.
All types of vertebrate locomotion rely on some kind of rhythmic activity to move forward; be it undulations of the body, oscillations of the legs, or oscillations of the wings. Animal movement is based on the contraction of muscles against a skeleton. Without a skeleton, you would sag from your own weight. Chordates have endoskeletons consisting of hard supporting elements such as bones, buried within the soft tissues of an animal.
In this section, we will study vertebrate locomotion in three different mediums: water, air and land.
Locomotion in Fish
Fish are vertebrates having a skeleton made of either bone or cartilage. A typical fish moves via undulatory swimming. To picture this, imagine trying to row a boat using only one oar. By moving the oar side to side, the boat is pushed forward as the water is forced backwards. This is similar, but much less complex, than the undulatory movements of a fish.
Long, fiexible fishes such as eels swim by undulating their entire bodies in a series of wavws passing from head to tail. This is called anguilliform locomotion. Several waves pass down the body in simultaneous fashion,moving faster as they approach the animal’s tail. Anguilliform locomotion,named for the eel genus Auguilla,occurs only in fishes with a similar body from whereby the surface area of the head end is the same as that of the tail end. They move by undulating most or all their bodies through the water as shown in Figure 7.10 and 7.11