Musculature in Fishes. A lecture for B.Sc Students.pptx

Musculature in fishes

1.   Musculature in Fishes – Structure, Function and Adaptations Dr. Showkat Ahmad Wani

2. 1. Introduction Brief overview of the importance of musculature in fish: Enables locomotion, feeding, respiration, and other movements. Highly adapted to aquatic life. Types of muscles in general: Skeletal (striated) – for locomotion. Smooth – in internal organs. Cardiac – in the heart.

3. 2. Types of Muscles in Fishes A. Skeletal (Striated) Muscles Main component for locomotion . Segmented into myomeres . Myosepta : connective tissue separating myomeres. Zigzag or W-shaped in cross-section. B. Smooth Muscles Found in walls of digestive tract, urinary system, blood vessels. Involuntary control. C. Cardiac Muscles Found only in the heart . Involuntary and striated.

4. 3. Arrangement of Skeletal Muscles A. Trunk Muscles Most prominent muscle mass in fish. Divided by horizontal septum into: Epaxial muscles (upper) Hypaxial muscles (lower) Composed of myomeres for rhythmic contractions. Function: undulatory swimming movements. B. Cranial Muscles Associated with: Jaw movements (e.g. feeding). Eye movements. Gill arch and opercular movements. C. Fin Muscles Control movement of paired and unpaired fins. Finer motor control for steering and balance.

5. 4. Muscle Fiber Types A. Red Muscle (Slow Twitch) Rich in myoglobin and mitochondria. Aerobic metabolism. Located as a thin lateral band. Supports sustained swimming (e.g., tuna). B. White Muscle (Fast Twitch) Poor in myoglobin. Anaerobic metabolism. Bulk of body musculature. Used for short bursts of speed (e.g., ambush predators like pike).

6. 5. Special Adaptations Eel-like fish (anguilliform swimmers) have long, flexible muscles for whole-body undulations. Tuna and sharks : high proportion of red muscle for continuous swimming. Electric fishes (e.g., Electrophorus ): modified muscle cells (electrocytes) for electric discharge.

7. 6. Function of Musculature in Locomotion Movement generated by wave-like contractions of myomeres. Coordinated contraction leads to thrust against water. Fins modify direction and help in stabilization.

8. 7. Evolutionary Perspective Comparison with tetrapods : Myomere segmentation is retained in early tetrapods . Muscle specialization increased with evolution. 8. Summary Fish musculature is highly specialized and efficient for aquatic locomotion. Two main types: red (endurance) and white (burst). Myomere arrangement allows efficient undulatory motion. Muscle adaptations reflect ecological niche and behavior .

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