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22 Cards in this Set

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What are the two main groups from class Agnatha?
-Hagfish (marine)
-Lampreys (marine & freshwater)
-Extinct one: Class Agnatha, Subclass Ostracodermi
-Living one: Subclass Cyclostomata (lampreys, hagfishes)
What are the general details of class Agnatha?
-Oldest and most primitive vertebrate group
-Greatly modified, degenerate descendents of armored agnathans
-Body eel-like with no scales
-No paired fins
-Fibrous and cartilaginous skeleton
-Notochord remains throughout life (degenerate—ostracoderms had bony skeletons)
-Well-developed teeth
-Oral disc in lampreys
-Eversible (stick-out-able) rows of teeth on “tongue” in hagfishes—this can be stuck out of the mouth, and this is their main way of actually getting food. They just file stuff loose from the source.
-Gills – pore-like openings
-7 pairs of gills in lamprey
-5-15 pairs of gills in hagfish, but only one opening.
-Both hagfishes and lampreys have a mesonephric kidney (the hagfish also has a pronephric kidney)
-No stomach!
What are the general details of the Lamprey?
-Many are parasitic on other fishes
-Attach to a fish with the oral sucker, rasp hole in fish, and feed on the blood
-Kill many fish (if the fish is too small, or if infection sets in)
-Sea Lamprey destroyed many Great Lakes fisheries (especially lake trout) after invading from the Atlantic Ocean
-Life cycle
-Breed in streams
-External fertilization
-Ammocoete larvae
-3-7 year larval stage
-Parasitic forms feed for 1 year or more before spawning
-Non-parasitic forms just spawn and die.
-The American Brook Lamprey is NOT parasitic!
What are the general details of the Hagfishes?
-Marine scavengers
-Rasp-like tongue tears flesh off of things (eat little chunks of stuff)
-Sensory mouth tentacles
-Very different from lampreys in many respects
-Often placed in a separate class from the lampreys
-Spend most time hiding on ocean bottom with snoutt, barbles exposed
-Only vertebrate that is isotonic to seawater – much like marine invertebrates
-Adult has two sets of kidneys, pronephric and nephric (only the nephric set is functional).
-4 sets of hearts located at various points in the circulatory systems to boost blood flow
-Mucous from slime glands – can turn a pail of water into slime in a matter of minutes! EEEEEW!
-Monoecious (only one sex!) – only produce one type of gamete at a time!
-Cannot self fertilize, because the gamete types do not function simultaneously, but it makes it easy to survive because everyone you meet is potentially a reproductive mate.
-Spawning year-round, NO LARVAL STAGE.
What is class Placodermi?
-Ancient jawed fishes – all extinct
-Likely ancestral to Chondrichthyes
Describe class Chondrichthyes.
-Sharks, rays, skates, chimaeras
-Lots of body form diversity thanks to variable living environments
-Most distinctive feature: the cartilaginous skeleton
-AGAIN, this is more than likely a degenerate condition, derived from bony ancestors
-Mostly marine, but SOME freshwater forms (like in large river systems that connect to the oceans!)
-Body very streamlined
-Paired fins – pectoral and pelvic
-Mouth ventrally located, some distance from the end
-Usually 5-7 pairs of gill openings (like in the lamprey!) – varying numbers for different species, but all members of a given species will have the same number of gill openings.
-Skin contains placoid scales.
-No other class of fish has these!
-Structurally similar to teeth!
-Dentine-like core surrounded by an enamel-like covering
What is the subclass Elasmobranchii of class Condrichthyes?
The sharks, skates, and rays
-No swim bladder to help maintain hydrostatic equilibrium within the water column.
-They swim continually to stay at a particular level of the water column (fat deposits may help maintain buoyancy).
-Sexes completely separate and the fertilization is internal
-Males have pelvic claspers for orienting the genital pores to one another
What are some general details of the subclass Elasmobranchii?
-Different ways of developing the young in this class:
-Oviparous: egg-laying
-Ovoviviparous: Egg internal development, but have egg nutrients. No direct link to mother.
-Viviparous: inside the body completely, direct umbilical/placental link to mother!
-Mesonephric kidney functional in adults (intermediate kind of kidney)
-Generally predaceous, with well-developed nervous system.
-Eyes good, can see well in dim light, can see colors
-Excellent sense of smell
-Used to locate potential prey (blood)
-Large olfactory bulb reflects the importance of smell
Some sharks may deposit eggs in horned egg cases
-Hooks onto vegetation, other objects
What is special about sharks' electrical sensing?
-Sharks can detect electricity, which is emitted in small amounts by every living animal!
-May be more sensitive to electric fields than any other animal
-Have special network of jelly-filled canals in the head called ampullae of Lorenzini to detect electric fields
-Can pick up weak electrical stimuli from muscle contractions of animals
-May also serve to detect magnetic fields, which some sharks may use in navigation!
What is the lateral line system?
-Canal system extending along sides and over head
-There are openings to the surface, with special sensory cells inside
-Basically the fish equivalent of our ears!
-Sensitive to vibrations, currents
-Helps them to detect objects, moving animals
What is special about the shark digestive system?
-Spiral valve in intestine
-Down center of intestine
-Decreases the rate of food movement through the intestine, increases absorption, because food has to spiral its way through this helical tube.
What are some general details of skates and rays?
-Skate: each pelvic fin has 2 lobes, tail stout with no stinging spine
-Ray: each pelvic fin has a single lobe, tail whip-like with a spine midway along the length
-In both, the pectoral fins are greatly expanded. They swim with undulations.
-Many rays have specialized electric organs
-High voltage discharges (up to 220 V!)
Describe subclass Holocephali in the class Chondrichthyes.
-Ratfish (have a rat-like tail)
-Structurally between sharks and bony fish
-Evolutionarily on their way out – peaked 50 to 100 million years ago
-Poor swimmers (use their broad, undulating pectorals), not good predators (not very fast, etc.)
-Males have extra claspers (on the pelvic fins and the forehead [gross]) for courtship, internalization
-Lays egg case after elaborate courtship rituals
-18-30 hours to extrude
-This gets dragged around for 4-6 days by tendrils until it falls off or gets buried in the sand!!!
-Oil from liver has commercial value for medicinal purposes
What are the general details of class Osteichthyes?
-“bone fish”
-Skeleton more or less bony
-Primitive characteristics retained
-Skull more complete, fused
-Pectoral girdle fused to skull, pelvic free
What are the different forms the post-anal tail can take?
-Homocercal – teleost fish (superorder Teleostei). most advanced fish tail!
-Heterocercal – primitive fish like sturgeons, paddlefish (superorder Chondrostei). most primitive fish tail!
-Modified heterocercal – bowfin and gars (superorder Holostei, the bony ganoids). intermediate fish tail!
-Peculiar ones:
-Diphycercal – lungfish and crossopterygians
Describe scales and the three main types.
-Skin of most bony fishes is covered with mucous glands and embedded dermal scales
-Major types:
-Ganoid or rhomboid scales (made up of ganoin) primitive
-Heavy, diamond-shaped, non-overlapping
-On primitive fishes like the gars
-Cycloid scales intermediate
-Roughly circular, thin, flexible, overlapping
-On more modern bony fishes such as minnows, suckers, and trout
-Ctenoid scales (pronounced: “ten-oid”) most advanced
-Have minute “ctenae,” or teeth
-Roughly rectanglar
-Modern bony fishes such as sunfishes, perches
-Fish growth is reflected in scale growth
-Larger fish have larger scales
-Scales are continually growing, and the rate at which they grow is largely temperature dependent!
-We are able to determine the age of fish in areas with winter, because there is greatly reduced growth during that period!
-“Rings” get closer together and form bands
Describe the fins of Osteichthyes.
-Unpaired fins with fin rays of bone or cartilage
-Dorsal (one or more), Caudal, and Anal
-Some have adipose fins (no rays) – the weird little thing between the dorsal and caudal fins (Salmonidae, Ictaluridae, Rainbow Smelt).
-Paired fins
-Pectoral fins: homologous to front legs
-Pelvic fins: homologous to hind legs
-Abdominal = more primitive
-Thoracic = more advanced
Describe locomotion in Osteichthyes.
-Most locomotion accomplished through the use of the caudal fin (propelling force through the water)
-The fastest fish (maintaining a speed, not in short bursts) is the Barracuda (27 mph!!! Holy crap!)
-Propulsive muscles along side of fish are W-shaped myomeres (myotomes)
-Creates sinusoidal movement of the body by alternating contractions on one side of the body, then the other
Describe circulation in Osteichthyes.
-2-chambered heart: one chamber receives blood, other pumps it out
-Arteries, veins
-Blood: nucleated red cells (unlike ours, which do not have nuclei!)
Describe respiration in Osteichthyes.
-Via 4 pairs of gills
-No individual openings to the outside
-Gills on each side covered by single, flap-like operculum
-Single, moveable operculum has allowed a pumping mechanism to develop (the fish can actually move it away from the body and toward the body)
-Continually forces water across the gills, even when the fish is stationary
-With mouth open, opercula flare outward but remain in contact with the body (having the opercula open at the same time as the mouth creates a sort of “suction” motion back into the opercular region). Then, the opercula get pulled back in, which forces the water over the gills and out the opercular openings.
Describe the gill structure of Osteichthyes.
-Gill filaments are finely divided into small lamellae to increase the surface area.
-Blood flows through the lamellae in a direction opposite that of water flow (countercurrent exchange mechanism)
-Countercurrent flow makes it more efficient for these two fluids to exchange gaseous components.
-Active fish like tuna must keep moving continually to move water across the gills (if you held a tuna still in an aquarium, it would suffocate!)
-Lack the pumping mechanism
-Some fish use lungs to breathe!
-Lungs = pouches branching off of the esophagus
-Breathe air at surface, or remain out of water for a period of time
Describe the swim bladder of Osteichthyes.
-Many fish possess a swim bladder (Actinopterygii: ray-finned fishes)
-Creates neutral buoyancy so the fish can remain motionless in the water column
-Not in sharks (remember, they have an oily liver and special airplane-like fins to help them stay lifted).
-Swim bladder probably arose from paired lungs of primitive fish
-Lungs were present before the swim bladder
-Paired lungs were probably necessary in primitive times because of alternating wet and dry periods (pools drying up, needed to cross into other ponds, etc.)