 |
The elegant fish in the photograph is the Gymnarchus niloticus, a native of Africa found in the Nile River.
Gymnarchus has some interesting traits. It swims gracefully with equal facility either forward or backward. Instead of propelling itself by lashing its tail sideways, as most fish do, it keeps its spine straight--not only when swimming straight ahead, but even when turning. Its propulsion is accomplished by means of the undulations of the fin along its back. Gymnarchus navigates with great precision, darting after its prey and evading obstacles in its path. What is surprising is that it does so just as precisely when swimming backward. Furthermore, Gymnarchus is nearly blind; its eyes respond only to extremely bright light. How then, is it able to locate its prey in the dim light of a muddy river? |