Presentation on theme: "Marine Fishes Chapter 8 Page 154. Vertebrates Subphylum Vertebrata Four fundamental characteristics: – Have a backbone (Vertebral Column or spine with."— Presentation transcript:
Vertebrates Subphylum Vertebrata Four fundamental characteristics: – Have a backbone (Vertebral Column or spine with vertebrae – Nerve Cord (Spinal Cord) which is protected by vertebrae. – Bilaterally symmetical body – Endoskeleton
Fishes Oldest, simplest vertebrates Total of 30,000 species 24,000 known to science (15,300 are marine). Make up half of the vertebrates on earth. Three groups: – Jawless (Agnatha) – Hagfish and Lampreys – Cartilagenous (Chondricythes) – Sharks, Rays, Skates, Ratfishes (Chimaeras). – Bony Fishes (Osteichthyes)
Agnatha Considered Jawless fishes, as they feed by suction with no jaws. Round mouth with rows of teeth. Body like an eel Do not have true vertebrae.
Hagfishes (Myxine) Also called Slime Eels (as produce slime against predators. Feed on dead or dying fish Live in burrows in cold waters 20 species known Skin used to manufacture leather goods Will attack bait lines
Lampreys (Petomyzon) Freshwater fishes Breed in freshwater, move to the sea as adults Parasitic – attach to other fish and suck their blood or feed on invertebrates. 30 species
Cartilagenous Fishes (Chondricthyes) Cartilage – lighter and more flexible than bone. Moveable jaws with well-developed teeth Mouth ventral, or underneath head Paired lateral (side) fins for efficient swimming Placoid skin scales – sandpaper like with a tip pointed backwards (can cause bleeding)
Sharks Similar to species from 100 million yrs ago. Very agile Tail (Caudal fin) is well developed,powerful. Tail is heterocercal (upper lobe longer) Two dorsal (upper) fins – first triangular Paired pectoral (chest or breast) fins – large and pointed Five to seven gill slits (behind the head and on each side of the body). Numerous rows of teeth that shift forward like a conveyor belt
Body plan Hammerhead head serves as a rudder (directional) with eyes on edges Sawsharks – mouth is under a blade with teeth on the edge. Thresher sharks – large tail kills fish to eat
Size variations Spined pygmy shark – Only 10 inches long Whale shark – largest fish of all – filter feeder – feeds on plankton – 60 feet long Basking shark – filter feeder – 30-40 feet long Great White – Up to 20 feet in length
Locations Throughout all oceans Mostly in tropical coastal waters (Florida) – definitely during breeding Bull shark can travel up rivers and lakes in the tropics (salt and fresh water) Larger sharks found in deep water.
Reproduction Are being overfished in many areas of the world, so reproduction numbers are very reduced. Whitetip sharks are only at 1% of population in 1950 (60 years). Killed for shark oil and skin (used to make shagreen (leather) and sandpaper. Finning is common for shark fin soup – animal caught, fins cut off while alive, animal dumped back into water to attract other sharks. People believe that the cartilage can help with arthritis Fishing of sharks is now managed in most countries, and certain species are illegal to fish.
Attacks 25 species of shark have attacked humans Most dangerous: Great White, Tiger, Bull Sharks Average of 61 attacks, with 2/3 in U.S. Portrayed as hideous creatures, but just looking for food. Most sharks inflict bites, then leave and wait for prey to weaken before eating. No known shark repellent What attacts them? – Garbage, seals, sea lions, blood, urine, feces. – More active at night – Attracted to splashing, as think it is fish or mammals in distress. **They eat most of the dead biomass in the oceans, so they are a vital predator for the oceans.**
Rays and Skates Approximately 500 species Flattened bodies Live on ocean floor (Demersal) Some look like sharks, but are not classified that way. Five pairs of gills slits on underside (ventral) of body. Pectoral fins expanded to look like wings. Eyes on top of the head Rays are Vivaprous – give birth to live young.
Stingrays Also Eagle ray, Bat ray, and Cow Nosed Ray Whip-like tail with stinging spine at base Wounds caused by the venom (injected) by whip- like action or stepping on them. Most wounds caused by mishandling or accidental encounters, as under the sand. Eat clams, crabs, small fish and invertebrates. Teeth are grinding plates that crush their prey
Electric Rays (Torpedo) Special organs that produce electricity on each side of the head. Deliver shocks of up to 200 volts to stun fish and discourage predators (Electrical outlets produce 110 – 120 volts – Appliances take 220-240 volts). Considered the original shock treatment used by the Greeks and Romans to cure headaches.
Skates (Raja) Similar to rays in appearance and feeling Lack a whip-like tail and stinging apparatus. Some do give an electric shock They lay egg cases (oviparous) in which their young mature before being born. Are fished for food in some parts of the world.
Ratfishes (Chimaeras) 30 species One pair of gill slits (Operculum) Some have a tail Feel on bottom dwelling crustaceans and molluscs.
Bony Fishes (Osteichthyes) Skeleton made partially of bone 23,000 species – 96% of fishes More than half live in the ocean. Cycloid (ctenoid) scales – can be smooth or have tiny spines. Covered by a thin layer of skin and mucus. Operculum – A gill cover that is a flap of tissue and plates to protect the gills.
Bony Fish (Con’t) Caudal Fin (tail) lobes are Homocercal (same size) Fins have fin rays or bony spines in them for support The finds can protect, steer, maneuver, or move them forward. Mouth terminal (located at one end) Teeth attached to jawbone and are replaced, but not like a conveyor belt.
Bony Fish (Con’t) ** Swim Bladder** - This is a gas filled sac just above the stomach and intestines that helps the fish to adjust their buoyancy. Helps to compensate for a heavy bony skeleton. How they seem to float in the water. Helps them also stay deeper if they need to.
Body Shape Directly related to lifestyle Streamlined – Open water fish Laterally compressed – Inshore fish (snapper, damselfishes, etc..) Demersal – Flattened – Rays and Skates Flatfishes – Live on bottom – Flounder, Halibut - **Body is actually laterally (on one side) compressed – Both eyes on top (Eye migrates from the side to the top during their lifetime)!! Distinctly Elongated – Narrow spaces – Eels and Pipefishes. Useful for camouflage.
Coloration Can be used for camouflage (cryptic coloration), breeding, mood, warnings of venom, break up outline (Disruptive coloration), Disguise in open water (Countershading – sharks have). Color found in chromatophores (special cells in the skin that can contract and expand to change the fishes color). Structural colors – Are constructed of crystals that reflect light called Iridophores – Why some fish are so shiny.
Locomotion Used to get food, escape from predation, breeding, and oxygenation. See Page 162 – Mostly swim in an S-pattern (like snakes). Move forward using muscle contractions with bands muscle called Myomeres. Most bony fish are mostly muscle. Sharks have to keep swimming constantly, as they do not have a swim bladder. The oil in the liver, the fins, and the tail compensate. Most bony fish can maneuver, as have swim bladder. Some can hover or move backwards, as fins not needed for bouyancy. Tails and pelvic fins mostly used for rudder control. Some fish now “walk” on their fins on the bottom of the ocean. Remoras get around by attaching to other fish.
Feeding Most sharks are carnivorous – A tiger shark caught off South Africa had eaten the front half of a crocodile, find leg of a sheep, three seagulls, and two cans of peas. Cookie cutter sharks cut out chunks of flesh from still living organisms (they have even attacked submarines). Filter feeders – Whale shark, basking shark, manta ray, megamouth shark. They filter the water through their gill arches, and the spaces in between the arches determines how much they catch.
Feeding (Con’t) Most bony fish are carnivorous – can catch prey in sediment, on rocks, or on the bottom. Some chase prey, others lie in wait. Usually have well-developed teeth to hold prey or a very large mouth to hold, chew, then swallow. Some eat only sponges, some eat only coral, some eat sea cucumbers, some eat dead material only. Grazers – fish that eat seaweed and plants only. (algae off of coral). Some fish eat only plankton (herring, sardines and anchovies).
Digestion Digestion begins for fish in their actual stomach. The stomach may be curved into a J-shape, may be a grinding structure, or there may not be one. Then, in the intestine, there are Pyloric Caeca which secrete digestive enzymes. The pancreas also secretes enzymes and the liver secretes bile to break down the fats. If the fish is a grazer, their intestines are coiled, or there may be a Spiral Valve, which increases surface area to help fully digest meals. Any digestible nutrients get passed into the blood. All other waste passes out the Cloaca (handles all waste and reproductive systems).
Circulatory System Two Chambered heart (below the gills) Blood flows from body (de-oxygenated) into first chamber. Then pumped backwards to second chamber, then pumped to gills for oxygenation, then out to rest of body.
Respiratory System Paired gills are where fish obtain oxygen and release carbon dioxide – the gills lie in the pharynx (chamber behind the mouth). Gills have to be constantly irrigated or ventilated with water flow for fish to get oxygen. Irrigation occurs through swimming and opening and closing of the mouth (some sharks). When fish are caught in a net, they drown, as they cannot swim to force water over the gills (that is why they open and close their mouths continuously).
Respiratory System (Con’t) For sharks, there is expansion and contraction of the pharynx walls and gill slits. Each gill has its own chamber and separate gill slit. The first pair of gills behind the eye is modified into spiracles (round openings that help cartilaginous fishes take in water no matter the circumstances).