Chapter 4 - The Perch

Abstract

This chapter considers the anatomy of the perch. The yellow perch—Perca flavescens—is an actinopterygian. These bony fishes are a huge success story, both in terms of diversity and numbers, with about 30,000 species known. The fins of actinopterygians are supported by slender, rod-like rays, or lepidotrichia, radiating from the base of the fin; the musculature controlling the fin is largely within the body wall. The perch belongs to Perciformes, a member of Acanthopterygii, the spiny-finned fishes. Another interesting group is Ostariophysi, which includes catfishes, characins, and minnows. These fish share a unique sound detection system—the Weberian apparatus—which involves the swim bladder and modified elements of the first few trunk vertebrae. The vertebrae act as a conduction system between the swim bladder and the inner ear at the back of the skull. Vibrations of the swim bladder caused by sound waves are transmitted by the bony elements to a posterior extension of the ear's membranous labyrinth, stimulating the auditory center of the brain. Many female specimens possess a very large ovary that fills most of the pleuroperitoneal cavity.