Marine Invertebrates
for Educators
The Group … Higher Vertebrates
Learning about Intertidal
Invertebrates
Zonation: Rocky Intertidal Zones
Presentation Purpose
■
Provide an overview of
zonation in the rocky
intertidal zone
■
Identify some types of
invertebrates we observed
in the rocky intertidal zone
■
Provide a foundation for a
possible poster for display
at the lab … a start!
Splash Zone and High Intertidal
■
Zone 1 – The splash
zone
is almost always
exposed to air, and has
relatively few species. It
is above the normal
reach of tides, but is
occasionally washed by
sea spray.
■
Zone 2 – The high
intertidal
zone is
Periwinkle Sea Snails
■
Found in high and
mid-intertidal on rock and
algae from Alaska to
Puget Sound
■
Many colors and up to 1
inch long
■
Graze on diatoms, algae,
Limpets
■
Marine snails that live in
a single conical shell
■
Scrape algae from rocks
and seaweed while
submerged, but clamp
down tight when
exposed to air
■
Birds, fish and crabs prey
Acorn Barnacles
■ Look like little volcanoes and
grow in distinct bands in the high and mid intertidal
■ Open when covered with
water, and close tightly when exposed to air
■ Barnacles begin life as free
swimming larvae but then settle on rocks
■ They glue their head to the
Blue Mussels
■ Small bivalves that occur in
mid to subtidal zone
■ Mussels attach firmly to
rocks with proteinaceous threads called byssal threads
■ Sea stars, whelks, crabs,
ducks, sea otters, and other animals eat mussels
■ Mussels sometimes
immobilize an attacking
Tube Worms
■ Calcareous Tube Worms are
related to earthworms, but live in the ocean
■ They build hard, white, coiled
tubes on rocks equipped with a door
■ When they are feeding, they
stick their feathery plumes out of the tube and wave
Zone 3 – Mid-Intertidal
Zone 4 – Low Intertidal
Mid-Intertidal
■ This zone is exposed to air
briefly once or twice a day, and has many common organisms
■ Organisms include sea
anemones, tube worms, urchins, red algae, and mussels
Low Intertidal
■ The low intertidal zone is
exposed only during the lowest tides. Organisms in this zone generally are not well adapted to periods of dryness and
temperature extremes.
■ Organisms include anemones,
Anemones
■ Sea Anemones exist as
polyps only, having lost the free swimming medusa stage
■ They look like beautiful
flowers which are really a ring of feeding tentacles armed with stinging cells
■ They maintain their shape
Hydroids
■ Hydroids, also called Sea Firs,
Sea Plumes, or Sea Ferns, are common but small, and easily overlooked
■ Though they may look like
small stiff brown ferns, they are actually a colony of tiny
animals, armed with stinging cells that paralyze their even tinier prey
■ In one part of their life cycle,
Bryozoans
■ Bryozoans, “Moss Animals,”
are tiny colonial animals that live on rocks and algae in the mid and low intertidal zones
■ They can be a tan or gray,
lacy crust, look like leaves, or even antlers
■ An entire colony composed
of thousands of individuals might be only an inch across
■ Bryozoans capture
Chitons
■ Chitons, also called “sea cradles”
are related to limpets, snails, clams, and octopi
■ 8 overlapping shell plates shaped
like little white butterflies are
hidden under a leathery covering.
■ They curl into a ball when
disturbed, or crawl into cracks in the rocks
■ Armor plates protect them from
pounding waves Move very slowly, creeping along on their muscular foot, scraping algae and animal life from rocks with their tongue
■ Gumboot Chiton is the largest
Tunicates
■ They are named for the outer
layer of tissue, their body wall, which is called a tunic
■ They resemble small blobs of
jelly in protected locations on the sides of boulders or rock crevices
■ The tunic can enclose one or
Sea Stars
■ Sea Stars are composed of
a central disk with several to many arms
■ They have thousands of
tiny tube feet. Sea stars are generally carnivorous and prey on clams, mussels, and sea urchins
■ They live in the low and
Sea Cucumbers
■ Looks like a vegetable but is
a type of mollusk with five rows of tube feet running its length
■ Feeds through a plume of
tentacles on its oral end
which captures microscopic organisms and detritus
■ If roughly handled, it can
eject some its internal organisms which it can regenerate
■ Burrow in rocks and mud in
