How to Dissect by William Berman

Author:William Berman
Language: eng
Format: epub
Publisher: A Fireside Book

9

A Member of the Master Class of Fishes

THE PERCH

STAND ON THE FOREFRONT ROCKS OF A BREAKWATER AND WATCH the surging schools of minnows contesting the tidal currents, or observe the violent swirling and tearing of the ocean’s surface as schools of bluefish slaughter their prey, and you can have no doubt about which animals are dominant in the seas. They are the bony fishes, the Osteichthyes, many of which you may have known or eaten most of your life—herring, cod, flounder, tuna, salmon, and others.

The bony fishes are the only fishes that have successfully invaded the fresh waters of the world and established themselves in great populations as prime inhabitants of rivers, lakes, ponds, and streams. The mighty sharks and their close relatives, the rays and skates, have been unable to colonize the freshwater world. The other main group of fishes, the Crossoptyerigians (lobe-finned fishes) the lungfishes, represent a small group but a tremendously successful venture from the oceans toward a terrestrial existence.

Most scientists in the field of evolution believe that the first land-living, four-footed creatures, the Amphibia, arose from this group some time between 400 million and 450 million years ago, in the Devonian geological period of history. Thus, from this ancient period to the present time the bony fishes have remained the dominant vertebrates in the waters of the world.

While most fishes represent an ancient, vital, and pervasive group of animals, one group, the lungfishes, contributed most directly to the origin of a higher vertebrate group, the Amphibia.

An examination of Fig. 100 (p. 156), the Evolutionary Tree of Life, and Taxonomy of the Chordates ( p. 157 ) will reveal the position of the superclass Pisces (the Fishes) in relation to the vertebrates in the animal kingdom. The emergence and development of the Tetrapoda, four-footed vertebrates, will be seen as associated with the Dipnoi, the lungfishes. Before beginning the dissection of the perch (Perca flavescens) it would be helpful to review the chapter on the shark ( Chapter 8 ). The anatomy and physiology of the shark is similar to that of the perch.

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