Shark Anatomy, History and Attacks

• Study notes based on the provided questions and terms.

Shark Classification

• Sharks are in the Kingdom Animalia.
• Sharks are in the Phylum Chordata, meaning they possess a notochord.
• Sharks are in the Class Chondrichthyes, meaning they have a cartilaginous skeleton.

Shark History and Diversity

• Sharks have been around for approximately 400-450 million years.
• The ancestors of sharks are placoderms.
• Most of the 350-450 species of sharks are relatively small.

Shark Diet and Predation

• Most sharks eat other fish.
• The largest predatory fish in the ocean is the Great White Shark.
• The biggest shark is the whale shark.
• Sharks that attack humans include great white, tiger and bull sharks.

Shark Attacks

• Shark Attack Office in Florida lists shark attacks.
• The exact number of attacks is difficult to determine due to underreporting.
• Worldwide, shark attacks occur each year; with a smaller number of deaths in the U.S. (1)
• Most Great White Shark attacks are "hit and run" attacks.
• Most Great White attacks occur in South Africa, Australia, and California.
• Great white sharks likely attack humans because they mistake them for seals.
• Great white sharks normally eat seals, sea lions, and other marine mammals.
• The biggest killer of seals each year are sharks, specifically Great White Sharks.

Shark Anatomy and Physiology

• Sharks sink when they stop moving because they lack a swim bladder and have a dense cartilaginous skeleton.
• Sharks may also suffocate if they stop swimming if they need ram ventilation.
• Some sharks can stop swimming because they can pump water over their gills.
• Sharks get few diseases.
• A feeding frenzy occurs when sharks are stimulated by blood.
• Feeding frenzies often occur when chumming, which is attracting sharks using bait and blood.
• Sharks get their buoyancy from their large, oily liver.
• The liver produces oil which is less dense than seawater, helping the shark to be more buoyant

Shark Senses

• Sharks find their food using several senses in order:
  • Smell: Can detect tiny amounts of blood in water.
  • Mechanical Reception: Can sense vibrations over distance
  • Vision: Good eyesight, especially in low light conditions.
  • Electroreception: Ampullae of Lorenzini detect electrical fields.
  • Taste: Taste stimuli and decide whether to consume prey
• The lateral line detects vibrations and pressure changes in the water.
• Ampullary organs of Lorenzini are pores filled with a jelly-like substance that can detect electrical fields generated by other organisms.

Shark Behavior

• The threat display of sharks involves exaggerated swimming, pectoral fin depression, and jaw gaping.
• Sharks are generally not territorial.

The Red Triangle

• The Red Triangle is an area known for frequent Great White Shark attacks.
  • Location is in California
• Corners of the Red Triangle:
  • Bodega Bay
  • Big Sur
  • Farallon Islands

Biological Classification

• Classification is not consistent because:
  • New discoveries and data can change relationships
  • Different scientists may interpret data differently
  • Evolutionary relationships are complex and not always clear
• Seven major classification groups (in order):
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

Spiny Dogfish

• Spines are used to protect the spiny dogfish shark by deterring predators.
• Spines are located in front of each dorsal fin and can inject venom.

Shark Teeth

• Shark teeth are constantly replaced, growing on a conveyer belt system.
• Shark teeth are homologous to scales (placoid scales).

Shark Circulatory System

• Sharks have a closed circulatory system.
• Fish hearts have two chambers.

Great White Sharks

• Great White sharks are partially warm-blooded (regional endothermy).

Phylum Chordata

• Characteristics of the phylum Chordata:
  • Notochord
  • Dorsal hollow nerve cord
  • Pharyngeal slits
  • Post-anal tail

Anatomical Terms

• Cranial: Toward the head
• Caudal: Toward the tail
• Pectoral fins: Located on the sides of the body near the head (used for steering and lift)
• Pelvic fins: Located on the underside of the body near the tail (used for stabilization)
• Caudal fin: Tail fin (used for propulsion)
• Dorsal fin: Located on the back (used for stabilization)
• Spine: Sharp, pointed structure, sometimes venomous.
• Claspers: Found on male sharks, used for reproduction.
• Nostrils: Used for smelling (not breathing).
• Liver: Large organ that stores energy and aids in buoyancy.
• Lateral line: Detects vibrations and pressure changes in the water.
• Ampullary organs of Lorenzini: Detect electrical fields.
• Placoid scales: Small, tooth-like scales that cover the skin.
• Myotomes: Segmented muscle bundles.
• Stomach: Stores food and begins digestion.
• Rugae: Folds in the stomach lining that increase surface area.
• Pyloric sphincter: Regulates the passage of food from the stomach to the intestine.
• Duodenum: First part of the small intestine.
• Spiral intestine: Increases surface area for nutrient absorption (two functions: increase surface area and slow down passage of food).
• Pancreas: Produces digestive enzymes and hormones (two functions are to produce insulin and digestive enzymes)
• Bile: Emulsifies fats and aids in digestion (two functions are to aid digestion and emulsify fats).
• Gall bladder: Stores bile.

Digestion

• Mechanical digestion: Physical breakdown of food (e.g., chewing).
• Chemical digestion: Chemical breakdown of food using enzymes and acids.

Bony Fish Classification

• Bony fish are in the Phylum Chordata, named for their notochord.
• Bony fish are in the Class Osteichthyes, named for their bony skeleton.

Types of Bony Fish

• Primitive ray-finned fishes include:
  • Sturgeons
  • Paddlefish
  • Gars
• Sturgeon is responsible for caviar.
• Most species of ray-finned fishes are teleosts.
• Common fleshy-finned fishes include:
  • Coelacanths: Thought to have been extinct.
  • Lungfish

Bony Fish Buoyancy and Osmoregulation

• Most bony fish get their buoyancy from a swim bladder.
• Hyperosmotic solutions: Higher solute concentration than the surrounding environment; fish tend to gain water.
• Hypoosmotic solutions: Lower solute concentration than the surrounding environment; fish tend to lose water.
• Diffusion: Movement of molecules from an area of high concentration to an area of low concentration.
• Osmosis: Movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

Empty Oceans and Overfishing

• Technology contributing to overfishing:
  • Sonar
  • GPS
  • Large nets and long lines
• Environmental factors contributing to fish decline:
  • Pollution
  • Habitat destruction
  • Climate change
• Large fish endangered of becoming extinct include:
  • Swordfish
  • Marlin
  • Blue Fin Tuna
• Bycatch accounts for 25% of the total weight of fish caught by the US fishing fleet.
• Shrimp fishing has the most bycatch per weight caught. Ratio is 5:1 (5 pounds of bycatch for every 1 pound of shrimp).
• Long lining: Using a long line with thousands of baited hooks.
• Bottom trawling nets: Dragging a large net along the ocean floor, destroying habitats.
• Average size of swordfish caught has decreased since the early 1960s.
  • Sexually mature swordfish size = 150 pounds.
• US, Japan, and European fishermen are now fishing in more distant and previously unexploited waters.
• Alaska has very good fishery management plans.
• Consumers can make a difference by:
  • Choosing sustainably caught seafood
  • Supporting responsible fishing practices
• Most of the ocean is biologically a desert.

PPT Phylum Chordata

• Four principle features of chordates:
  • Notochord: Flexible rod providing support.
  • Dorsal hollow nerve cord: Develops into the brain and spinal cord.
  • Pharyngeal slits: Used for filter feeding or gas exchange.
  • Post-anal tail: Tail that extends beyond the anus.
• General characteristics of chordates:
  • Bilateral symmetry
  • Segmentation
  • Coelom
• Fish found in the group Agnatha:
  • Hagfish
  • Lampreys
• Caviar refers to sturgeon eggs.
• Caviar is traditionally made by salting and curing sturgeon eggs.
• Dolphin fish: Also known as Mahi-Mahi, a type of ray-finned fish.
• Puffer fish poison (tetrodotoxin) is produced by bacteria in the fish's body.
• Eels, sea horses, and sea dragons are classified as ray-finned fishes (teleosts).