Hello marine biology students.
In this video we're going to talk about lophophorate
and echinoderms.
[Intro Music]
So this next group of animals we're going
to talk about actually encompass three phyla
but what unites them is they're feeding structure.
A lophophore 
is a distinctive ciliated feeding structure
and often it is horseshoe-shaped.
There are three animal phyla which all have
this feature.
Now, these phyla were far more common in the
geologic past in that they make up a disproportionately
large portion of the fossil record compared
to their modern-day abundances.
The first of these lophophorates are the bryozoans,
phylum Bryozoa.
Their name literally translates into “moss
animals” because these colonies look very
moss-like.
All bryozoans are colonial, form small colonies.
Some are encrusting, others form small fan-shape
or tree-shaped colonies.
They are found in certain marine environments
nowadays, but in the past there are entire
fossil beds that are simply Bryozoan fossils
and they can be key indicator species for
identifying which time period a fossil bed
came from.
They are suspension feeders and there are
about 6,000 species, again, most of them in
the oceans.
The two other phyla for lophophorates include
the Phoronids, phylum Phoronida.
And 
the phronids they are tube worms with this
specialized lophophore feeding appendage.
So they're very worm-like and they're tube
is usually made out of sand grains.
They have a circular or horseshoe shaped lophophore.
There are 32 recognized species, all marine
and in shallow water.
In the last group of lophophorates are the
brachiopod or lamp shells.
Brachiopods have two shells that enclosed
their body and so you might think that they
are molluscs or bivalves, but because of this
lophophore, we know that they are different.
They're similar in appearance to bivalves,
but their external anatomy is very different.
While there are 400 living species of brachiopods
there are thousands of different fossil species
that are known.
Again, they used to make up a very significant
portion of the marine invertebrates in the
areas they were found in.
The next phylum we're going to discuss is
phylum Echinodermata.
Their name literally means spiny skin.
One interesting aspect of echinoderms is that
they have pentamerous radial symmetry
meaning they are often star-shaped or they
have five units of symmetry around their center
in adults but bilaterally symmetrical larva.
All echinoderms have a water vascular system,
which is a series of tubes that they can use
to send water from one area to another, and
they control tube feet which the Echinoderms
use for moving and feeding.
The Echinoderms use their skin for respiration.
And unlike some of the organisms that we've
talked about recently, their nervous system
is decentralized, their brain is absent.
Even though echinoderms have spiny skin, they
have an endoskeleton, meaning that their skeleton
is going to be surrounded by skin and soft-tissue.
The Echinoderms have amazing regenerative
ability and they can easily replace lost body
parts and sometimes the lost body parts replace
the missing portion of the organism.
All 7,000 species of echinoderms are exclusively
marine.
So let's talk about these different groups
of echinoderms.
The first are the sea stars, class Asteroidea.
Sea stars move around using their tube feet.
They have a central disc in the center of
their body surrounded by five arms or multiples
of five and the internal organs of the sea
star will spread not only through the central
disc but also into their arms.
Their skeleton is usually composed of calcium
carbonate plates
which are loosely embedded in the spiny skin,
making them slightly flexible.
Sea Stars have a structure on their surface
that prevents other organisms from attempting
to grow on top of them, they are little pinchers
called pedicellariae
and they help keep the surface of the organism
clean.
Maybe surprisingly, sea stars are carnivores.
They feed on a diversity of invertebrates
in the environments they're found in.
Here we see a diagram of a typical sea star.
It has an oral and aboral surface or the surface
that contains the mouth and the surface that
is opposite the mouth, and we can see that
the internal structures are continuous within
the legs of the individuals.
Our next type of echinoderms are the brittle
stars, the ophuroids, class Ophuroidea.
What distinguishes brittle stars from the
other sea stars is that they have very thin
flexible legs.
Their internal organs are all restricted to
the central disc and do not extend into the
legs themselves.
Brittle stars also have tube feet without
suckers which they use for feeding on detritus
and small animals.
Brittle stars are not the predators that their
seastar brethren are.
Surprisingly, even though sea stars have a
complete digestive system, brittle stars do
not they instead have a gastrovascular cavity
which has a single opening that serves as
both the mouth and an anus.
Our next group of echinoderms are from class
Echinoidea, which are the clearest examples
of how echinoderms got their name.
These are the sea urchins with long conspicuous
movable spines.
For the sea urchins and sand dollars, their
calcium carbonate plates fuse into a solid
test or shell.
They move using their tube feet with their
mouth oriented on the bottom of the organism
and the anus on the surface or aboral topside.
Urchins have a specialized mouth called Aristotle's
lantern.
It is a feeding structure composed of jaws
and muscles that allow these urchins to feed
on seaweeds, detritus and encrusting organisms
that they scrape off of surfaces.
So here we can see both a sea urchin and a
sand dollar, which is simply a modified flattened
urchin with less obvious spines.
Here we can see the feeding structure known
as Aristotle's lantern and a few different
types of urchin body shapes.
Our next group of echinoderms are the sea
cucumbers, class Holothuroidea.
They appear worm-like, with the mouth and
an anus on opposite ends and five rows of
tube feet restricted to one side.
However they do still have their pentamerous
radial symmetry, even if superficially they
appear to have bilateral symmetry.
Their skin can be embedded with calcareous
spicules, but they do not have spines and
for the most part they feel soft to the touch.
They are deposit feeders with most species
obtaining their organic matter from ingested
sediment.
Sea cucumbers are known for a unique defense
mechanism known as evisceration
in which, when threatened, they expel their
internal respiratory organs, often ensnaring
and definitely confusing the predator.
These internal organs can end up being regenerated
and replaced.
The last class of echinoderms we'll talk about
are the crinoids class Crinoidea.
Crinoids usually have five or more arms that
branch out for suspension feeding.
Some crinoids are stationary as adults and
they are attached to a stalk settled on the
bottom.
This is true for most deep-water crinoid species,
however there are some free living and swimming
crinoids as well that inhabit coral reefs.
So sea lilies live attached 
in deep water, yet feather stars crawl on
the bottom and live mostly in shallow water
coral reefs.
Crinoids are another example of an organism
that was far more abundant in the past, based
on our fossil record, than their modern-day
counterparts would lead you to believe.
Some crinoids use of a mucous net to aid in
food capture.
So that completes our introduction to lophophorates
and echinoderms.
Now if you ever have been really close to
achieving a goal only to fall short?
Our next group of organisms understands that
all too.
Well, I'll see you in the next video.
