-Aquatic vertebrates (they havebackbones)
-Most have paired fins, scales onsome parts of the body, and gills.
-Fins are for movement
-Scales provide protection fromenvironment and predators
-Gills aid in gas exchange with theenvironment (O2, CO2,etc.)
-Lateral line system: can help fish tosense the motion of other organisms
-air bladder prevents fish fromsinking in the water
-Heart and closed circulatorysystem (blood stays inarteries and veins)
-2-chambered heart pumpsblood in single loop: heart togills, gills to rest of body, thenback to heart
-Nervous system: includesbrain, cerebrum, cerebellum,medulla oblongata
-cerebrum primarily regulatessense of smell in fishes-cerebellum regulates bodymovements-medulla oblongata controlsmost internal organs
Reproduction: can be
internal or external (3 types)
-oviparous (egg-laying– released into water- egg yolk for nourishment)
-ovoviparous (embryos remain inside female, but feed on egg yolk)
-viviparous (parasites– nourishment from female instead of egg yolk)
Most oviparous fishes do
not care for their young, but
there are exceptions:
Bettas and bubble nest Male seahorse and young
Stickleback male guarding nest Female cichlid mouth-brooding
Jawless fishes: lampreys and hagfish
-Fibrous skeletons, no true jawsor teeth-Parasitic as adults-Most of lamprey’s head is asucking disc with a roundmouth in the center -Attaches to other fish, bores a hole and sucks out host’stissues and fluids-Hagfish: no eyes, 4-6 tentacleson mouth, thick slime layer toprotect against predators-Eats dead or dying fish, can also absorb nutrients through skin and gills like invertebrates-Could be transitional species-Lampreys decimated GreatLakes fish populations
Cartilaginous fishes: sharks, rays and skates-skeleton is cartilage; most sharks have toothlike scales on skin, rough as sandpaper
-sharks have streamlined bodies, a large,curved tail, a pointed snout, and thousands ofteeth in rows. -New teeth replace the old– up to 20,000 teeth in a lifetime!
-Sharks eat fishes, including other sharks,marine mammals, birds, and invertebrates.
-A few are filter feeders, like most rays andskates.
-Most sharks, rays and skates areoviparous (egg cases laid– enough food for 2months in yolk sac)
-Some sharks bear live young– sandtigershark pups survive by eating their siblingsand even unfertilized eggs inside the mother!
Bony fishes
-Skeleton of true bone
-Incredible diversity, from flying fish toflounders, some can breathe air(e.g.,lungfish, tarpon)
-Some are vegetarians, some omnivores and some are strictly carnivorous
-Most live in either fresh water or theocean
-However, some species, likesalmon, can move from freshwaterto saltwater ecosystems and viceversa.
Granddad
Salmon begin life infreshwater rivers andstreams, but eventuallymigrate to the oceans.
-1-4 years later, they returnto their birthplace to breed
-Trip can take severalmonths and almost 2,000miles!
-Salmon recognize theirhome streams using theirsense of smell