Fishes Lesson 4

-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

Hagfish slime!

Dr. Gene S. Helfman

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

Of course, not all make it back home, and not all the eggs hatch, but salmon, like other fishes, are an important part of the food web