Shark Dissection
Materials: ★★★ Requires materials not commonly found in school laboratories
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely
Categories: Body Systems, Dissections
Alternative titles: Dogfish Shark Dissection (Squalus acanthias)
Summary
Students dissect a preserved dogfish shark to examine external features, muscular organization, and the major systems of a cartilaginous fish. The investigation includes identifying fins and sensory structures, exposing trunk and head muscles, opening the body cavity to trace digestive and circulatory organs, locating urogenital features, and optionally revealing the brain.
Procedure
Links
Variations
Compare male and female specimens, documenting claspers and reproductive tract differences.
Examine injected specimens (arterial, venous, portal) to map circulatory pathways.
Dissect a bony fish for comparison and create a table contrasting cartilage vs. bone, tail form, scales, and swim bladder presence.
Open and rinse the spiral intestine to visualize the internal valve and estimate surface area increase.
Prepare a nervous system focus lab that only exposes brain regions and cranial nerves.
Safety Precautions
Wear gloves and a lab coat; work in a well-ventilated area or fume hood when possible.
Use scissors for most cuts; if a scalpel is needed, make shallow, controlled strokes on the tray and cut away from hands.
Beware of sharp dorsal fin spines; remove or pad as directed by your instructor.
Handle preserved tissues and fluids as potential irritants; avoid skin and eye contact and keep food and drink out of the lab.
Do not remove organs with force; use a blunt probe to free connective tissue to avoid accidental cuts.
Dispose of tissues as biological waste and blades in approved sharps containers; disinfect tools and benches after use.
Brain exposure should be instructor demonstration only due to risk of damaging underlying structures.
Questions to Consider
What advantages does a heterocercal tail provide for a shark’s swimming and buoyancy? (It generates lift and thrust to counteract negative buoyancy.)
How are placoid scales related to shark teeth in structure and origin? (Teeth are modified placoid scales derived from similar dermal tissues.)
What is the functional difference between epaxial and hypaxial muscles during swimming? (Epaxial control dorsal flexion and stabilization; hypaxial contribute to ventral flexion and lateral undulation.)
Why does the spiral valve increase efficiency in the shark intestine? (It lengthens the absorptive path and increases surface area for nutrient uptake.)
Trace the path of blood through the shark heart chambers you identified. (Sinus venosus → atrium → ventricle → conus arteriosus → gill capillaries.)
How does the rectal gland help maintain internal salt balance? (It actively secretes excess NaCl into the gut for elimination.)
What osmoregulatory role does urea play in sharks? (High blood urea elevates osmotic pressure to approximate seawater, reducing water loss and salt gain.)
Which external features help the shark sense its environment? (Lateral line detects water movement; nostrils and olfactory lobes detect dissolved chemicals; eyes and spiracles aid feeding and respiration.)