Median fins and scales

Median fins

unpaired fins of a fish located on the median plane, or midline, of the body

Dorsal fin modification

modifications:

-sucking disk (remoras)

-angling apparatus (anglerfishes)

Anal fin modification

modifications:

-Gonopodium (guppies, internal fertilization)

-Andropodium (for holding mate in place)

placoid scales

small, tooth-like spines that make up a shark's skin

-"dermal denticles"

-do not increase with size only new ones added

-reduces drag

cosmoid scales

rhombic scales

-present in coelacanths

-scales grow with fish and new bone is added to basal layers

Ganoid scales

diamond shaped scales

-found in bichirs, bowfin, gars

-modified cosmoid scale

-Ganoine covering scales (enamel like)

-armor like plates (heavy)

Modified ganoid scales

sturgeon scales are modified into large plates (scutes)

-rest of body bare

cycloid scales

thin, overlapping scales with a smooth posterior edge that are found in some of the more primitive bony fishes

ctenoid scales

thin flexible and overlapping scales in bony fish that have tiny spines

-have ctenii (teeth) on posterior region of scale that breaks up turbulence at high speeds