🦈8.6 Shoals Marine Lab: Shark Dissection

During my dissection of a spiny dogfish shark, I observed how its fusiform body shape is highly adapted for efficient movement through the water, providing hydrodynamic advantages. The shark’s streamlined form is ideal for a demersal lifestyle, with a reduced anal fin and lower lobe of the caudal fin, a common feature in benthic species. The integumentary system was also notable, with placoid scales covering its skin, providing both protection and aiding in the smooth flow of water around the body. As I examined the digestive system, I noted the sequential process of food processing, beginning in the oral cavity where the shark's teeth—designed for catching both soft and hard prey—play a key role in ingestion and mechanical digestion. The spiral valve intestine, specialized for digestion and nutrient absorption, stood out as a critical feature of the shark’s alimentary canal. The respiratory system was another striking aspect, with the gills arranged to allow for efficient oxygen exchange through countercurrent flow, essential for life in oxygen-deprived waters. I also observed the shark’s ability to expel waste through its cloaca and regulate salt balance using its kidneys and rectal glands, a vital function for survival in saltwater. Additionally, I discovered a fish still inside the shark’s stomach. It was really fun dissecting sharks!