Download Fishes and Marine Mammals Lesson 4

Fishes
Lesson 4
-Aquatic vertebrates (they have
backbones)
-Most have paired fins, scales on
some parts of the body, and gills.
-Fins are for movement
-Scales provide protection from
environment and predators
-Gills aid in gas exchange with the
environment (O2, CO2,etc.)
-Lateral line system: can help fish to
sense the motion of other organisms
-air bladder prevents fish from
sinking in the water
Heart and closed circulatory
system (blood stays in
arteries and veins)
-
-2-chambered heart pumps
blood in single loop: heart to
gills, gills to rest of body, then
back to heart
-Nervous system: includes
brain, cerebrum, cerebellum,
medulla oblongata
-cerebrum primarily regulates
sense of smell in fishes
-cerebellum regulates body
movements
-medulla oblongata controls
most 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
Stickleback male guarding nest
Male seahorse and young
Female cichlid mouth-brooding
Jawless fishes: lampreys and hagfish
-Fibrous skeletons, no true jaws
or teeth
-Parasitic as adults
-Most of lamprey’s head is a
sucking disc with a round
mouth in the center
-Attaches to other fish, bores
a hole and sucks out host’s
tissues and fluids
-Hagfish: no eyes, 4-6 tentacles
on mouth, thick slime layer to
protect against predators
-Eats dead or dying fish, can also
absorb nutrients through skin and
gills like invertebrates
-Could be transitional species
-Lampreys decimated Great
Lakes fish populations
Hagfish slime!
Dr. Gene S. Helfman
Cartilaginous fishes: sharks, rays and skates
skeleton is cartilage; most sharks have tooth
like scales on skin, rough as sandpaper
-
-sharks have streamlined bodies, a large,
curved tail, a pointed snout, and thousands of
teeth 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 and
skates.
-Most sharks, rays and skates are
oviparous (egg cases laid– enough food for 2
months in yolk sac)
-Some sharks bear live young– sandtiger
shark pups survive by eating their siblings
and even unfertilized eggs inside the mother!
Bony fishes
Granddad
-Skeleton of true bone
-Incredible diversity, from flying fish to
flounders, 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 the
ocean
-However, some species, like
salmon, can move from freshwater
to saltwater ecosystems and vice
versa.
Salmon begin life in
freshwater rivers and
streams, but eventually
migrate to the oceans.
-1-4 years later, they return
to their birthplace to breed
-Trip can take several
months and almost 2,000
miles!
-Salmon recognize their
home streams using their
sense 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