Lab 10: Amphioxus and Dogfish Shark

Amphioxus Classification

• Belongs to Kingdom Animalia, Phylum Chordata, Subphylum Cephalochordate
• Commonly known as the Common Lancelet

Amphioxus Anatomy

• Dorsal fin extends along the body, broadens, and becomes the ventral fin
• Caudal fin is responsible for propulsion and steering at the posterior end
• Rostrum serves as a distinctive feature, aiding in movement
• Oral hood is a funnel-shaped membrane at the anterior end for food intake and storage
• Atriopore is the opening of the atrium located in front of the ventral fin, allowing water exit
• Myotomes are segmented muscle blocks that enable motor control
• Gill bars and slits act as a filter feeding device
• Notochord provides body support and shape, serving as a muscle attachment site
• Anus is the site for waste excretion
• Gonads are involved in reproduction

Dogfish Shark Classification

• Classified under Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata, Order Squaliformes

Dogfish Shark Anatomy

• Pectoral fins help control swimming direction
• Pelvic fins also aid in directional control and are termed claspers in males for sperm transfer
• Dorsal fin assists in swimming direction
• Caudal fin is the primary propulsion structure
• Rostrum features a pointed snout to reduce water resistance during swimming
• Spiracles enable water intake when the mouth is occupied
• Gill slits allow for water discharge after passing over the gills
• Lateral line detects movement and vibrations in the water
• Cloacal opening serves multiple systems for excretion and reproductive functions

Shark Physiology

• Placoid scales, also known as dermal denticles, are modified teeth that provide protection
• Peritoneum lines the body cavity and covers internal organs
• Mesenteries are tissues that attach organs to the body wall
• Liver stores oil for buoyancy, nutrients, and assists in digestion
• Hepatic veins transport blood from the liver to the sinus venosus
• Hepatic portal vein carries blood from abdominal organs to the liver
• Gallbladder stores bile, while bile duct connects the gallbladder and liver
• Esophagus links the mouth to the stomach
• Stomach is J-shaped with cardiac and pyloric regions for digestion
• Rugae are folds in the stomach that increase surface area for absorption
• Duodenum is the small intestine section where digestive secretions are added
• Pancreas produces digestive enzymes essential for food breakdown
• Spleen acts as a blood reservoir, involved in immune responses and blood filtration
• Ileum is the largest section of the intestine involved in digestion and absorption processes