LEC.165 Lecture 7

Fish Structure

Chondrichthyes

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Cartilaginous fish

Examples of Chondrichthyes

Sharks, Rays

Benefits of cartilage

Enables tighter turning, flexibility, and aids in buoyancy

Negatives of cartilage

Less structural differentiation and adaptability between species.

What is the oldest scale types, what properties does it have.

Placoid. In cartilaginous fish, heavy, inflexible, rough.

Properties of cycloid scales

Teleost fishes. Round, contains rings which can be used for aging fish and finding growth rates. Lighter

What is the most modern scale type

Ctenoid scales

What type of fin allows increased speed

Symmetrical, homocercal caudal fin.

What type of fins do shark, lungfish, and perch have (respectively)

Heterocercal, diphycercal, homocercal.

How has the pectoral fin changed over time

Moved from almost horizontal, to a vertical angle

Name these fins

A. Dorsal

B. Caudal

C. Anal

D. Pelvic

E. Pectoral

Why might teleost fins diversify? Give 5 reasons

•Camouflage

•Communication

•Lures

•Complex movements

•Hydrodynamics

•Predator evasion

•Attachment to habitat (ramora)

What is fusiform. Why is it used?

Typical elongated teardrop fish shape. More efficient for hydrodynamics and reducing drag.

How is drag reduced?

Fusiform shape, overlapping scales, mucus coating.

How do sharks maintain buoyancy?

Pectoral fin has a positive attack angle, constantly moving forwards means this provides uplift.

Myomeres

Muscle blocks attatched to collegenous septa, binds them to bone.

What can the caudal fin tell us?

The deeper the fork, the more frequent sustained swimming is for that species.

What does less caudal fin wake indicate?

More efficient fin design.

Where is the pelvic fin

Varies between species, more recent the fish, the closer to the head.

What is the pelvic fin for

Steering, by operating antagonistically. Breaking by flaring out.