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The Fishes. Chapter 12 - Marine Biology. Nurse shark in Key Largo 2007. The Barracuda waits for its next meal in the shadows of a coral reef and then suddenly…. The fish are an ancient group of animals. They date back to more than 500 million years
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The Fishes Chapter 12 - Marine Biology Nurse shark in Key Largo 2007
The Barracuda waits for its next meal in the shadows of a coral reef and then suddenly…
The fish are an ancient group of animals • They date back to more than 500 million years • There are more than 15,000 to 20,000 different species • They are incredibly diverse Sharptail eel, Bonaire 2007
The Phylum Chordata • Some members of this phylum do not have a backbone! • They have a notochord, dorsal nerve cord and pharyngeal slits, but no vertebrate.
Protochordates - chordates with no vertebrate • Tunicates are members of this phylum. • They are also known as sea squirts. • They look like blobs of jelly that grow in clumps, yet they are in the same phylum as we are.
Lancelets (Amphioxus) • Another primitive chordate. • They live in the sand and filter plankton from the water.
The Jawless Fish • These fish are considered vertebrates, but do not have jaws and do not have a true backbone. • They include the sea lamprey and the hagfish. • They live as parasites and scavengers. • The lamprey does not have true scales.
Lampreys use their teeth and rasping tongues to make holes in their prey and suck out the blood and tissues.
Hagfish - often are found burrowing into the bodies of dead or dying fish
Cartilaginous fishes • Cartilage is the flexible connective tissue composed of cells and protein. • It is found in our outer ear, our nose and at the ends of bones where movable joints are found. • These fish are in the Class Chondricthyes.
Cartilaginous fish include the sharks, skates and rays…600 different species.
Cartilaginous fish have placoid scales (tiny teeth embedded in skin) Dogfish placoid scales - very different from the mucus covered scales that come off easily in bony fish. It feels like Sandpaper if you rubbed the shark back to front.
Cartilaginous fish have visible gill slits for breathing - they are not covered like bony fish.
Cartilaginous fish have spiracles - where water passes through and flows to the gills. They are very useful for bottom-dwelling species.
The fins of cartilaginous fish are more rigid and provide lift to prevent sinking
Fins in skates and rays are highly developed and enable them to fly underwater
Stingrays can inflict a painful stab wound..that can be fatal
Sawfish: An unusual cartilaginous fish - it uses the saw to stun and kill small fish.
The Sharks • There are over 250 different species of sharks. • The smallest shark is the pigmy shark at 25 cm long. The largest shark is the whale shark at over 45 feet long.
Whale sharks are harmless to humans and other vertebrates. • They are filter feeders that consume enormous amounts of plankton as they swim near the surface with their mouths open. Basking sharks are also filter feeders.
Nurse sharks and leopard sharks are bottom dwelling sharks that feed on mollusks mostly.
Leopard and nurse sharks • Generally docile and hang out under reef ledges.
Dangerous sharks include the great white, tiger shark, and hammerheads.
Eyesight in sharks • Sharks are slightly farsighted and see in color. • Their eyes can function in light ten times dimmer than that of the human eye because of a shiny reflective pigment called tapetum lucidum that is also found in cat’s eyes. • Some sharks posses a nictitating membrane which closes to protect the eye as the shark attacks prey. • In sharks, such as the great white, the eye rolls upward for protection just before the shark bites.
Do sharks have a favorite color? http://videos.howstuffworks.com/discovery/6816-shark-week-if-a-shark-had-a-favorite-color-video.htm Nictitating membrane in a Blue shark
Hearing and Vibrations • Sharks are attracted to low frequency, pulsing sounds such as the sounds made by injured or dying fish. • Lateral Lines are a series of fluid-filled canals containing hair-like receptors (similar to the cochlea of the human ear) which extend along the sides of the head and body. These sense vibration, change in pressure, movement and sound.
Hammerheads sense of hearing and smell are highly evolved • http://videos.howstuffworks.com/animal-planet/29054-whats-to-love-hammerhead-sharks-senses-video.htm • Just under the snout are two nares, or nasal cavities. Each nare has two openings, one for water to enter and one for water to exit. The nasal sacs are filled with sensory cells, which send signals to the shark's brain. • The olfactory lobes in the shark's brain analyze the smells, looking for those that match the scent of their prey or the pheromones of potential mates.
Shark’s sense of smell • The sharks nostril can sense blood in the water as little as one part per million from a mile away. • Lemon sharks can sense fish oil in water one part per 25 million or the equivalent of just ten drops in an average home swimming pool. • Caribbean reef sharks can sense grouper flesh concentrations as low as one part per 10 billion or the equivalent of one drop in a quarter acre pond. • Two thirds of their brain is devoted to smell.
Sharks can detect electrical fields • Ampullae of Lorenzini are receptor cells located at the base of canals on the shark’s snout, lower jaw and around the eyes. • The Ampullae of Lorenzini detect electrical fields, their direction, and strength. Every living creature gives off an electrical field which provides a stimulus or homing device for the shark. • It is believed that sharks use this sense to detect changes in the earth’s magnetic field and for navigation.
A shark’s super sixth sense! • http://videos.howstuffworks.com/animal-planet/29022-fooled-by-nature-senses-of-a-scalloped-hammerhead-video.htm Ampullae of Lorenzini
Shark’s have incredible teeth for catching prey • http://videos.howstuffworks.com/animal-planet/28415-fooled-by-nature-sharks-teeth-video.htm • They have several rows of razor sharp teeth that constantly move forward to replace teeth that are lost. • They can have 100s of teeth at any one time.
Do sharks always have to swim? • If they do not want to sink, then they have to keep swimming. • Swimming provides a constant stream of oxygenated water to move over their gills. • Their large pectoral fins and very large, oily livers help keep the sharks buoyant.
Shark liver - large and oily to give the shark buoyancy. People use it for various medicinal purposes.
Shark Reproduction • Cartilaginous fish have internal reproduction, which is very different from most bony fish. • Male sharks have claspers, located between the pelvic fins, that transfer sperm to the female’s reproductive tract.
Different modes of embryonic development • The sharks can develop internally and the mom will live-bear the young. Dogfish develop for 2 years inside the mother and often cannibalize siblings for nutrition. • The shark can have external development where the embryo develops in a black, leathery pouch, called a mermaid’s purse.
The Bony Fish - Osteichthyes • Unlike sharks, these fish have a skeleton that is made up of bone. They have a bony vertebrate that protects their spinal cord. • They are found in every type of aquatic habitat on earth. Smooth trunk fish, Key Largo
Protective scales cover bony fish • The scales are loosely attached and rub off in your hands. • Bony fish feel slimy to the touch because of the mucus which acts as a barrier to infection and allows them to move easily through the water.
The scales can indicate the age of the fish - they have growth rings called circuli.
How do fish breathe? • They use gills - like many marine animals. • The gills are covered with an operculum. • When the fish breathes the gills and operculum open and close together. • The gills get rid of carbon dioxide and get oxygen from the water. • The gills have gill rakers that channel food away from the delicate gills and send it down the esophagus.
