Anatomy of finfish and shellfish

Unit 10 - Skeletal system

10.3. Appendicular Skeleton and Fins
Using the preserved perch and the skeleton, locate the following structures:
Median Fins
The dorsal fins of the perch have fin rays for support. The anterior dorsal fin has ossified fin rays which provide stiff support, while the fin rays of the posterior dorsal fin are not ossified and are flexible. Only the first two fin rays of the anal fin are ossified. The caudal fin is composed entirely of soft, unossified fin rays.
Pectoral Girdle and Fins
The pectoral fins are attached to a bony girdle, the pectoral girdle. The pectoral girdle is composed of a number of fused elements. The girdle is also fused to the skull (the head and trunk of the perch move as a unit). The fins are supported by soft fin rays.
Pelvic Girdle and Fins
The pelvic fins are attached to the pelvic girdle, which is composed of two bony pelvic plates. The plates may be fused along the midline. The pelvic girdle is not attached to the vertebral column nor to the pectoral girdle, but is free-floating (embedded in muscle only). Only the medial fin rays are bony, the rest are the typical soft unossified type.