Invertebrates

Echinoderms & Mollusks

VI. Phylum Echinoderma (Spiny Skinned Animals)Starfish, sea urchins, sea cucumbers, and sand dollars belong to a group or phylum of animals called echinoderms. This means "spiny skinned" in Latin. Echinoderms live in salt water only. There are around 6000 species of echinoderms.

Most living echinoderms are pentameral; that is, they have fivefold radial symmetry, with rays or arms in fives or multiples of five.

Echinoderms have a system of internal water-filled (hydraulic) canals, which in many echinoderms form suckered "tube feet", with which the animal may move or grip objects.

A Echinoderm has a mouth and stomach area. Some have a mouth on the bottom and an anus on the top. Starfish can actually turn their stomachs outside of their body and insert it into its prey's such as a clam.

A Echinoderm is either a male or female. The males and females discharge their eggs and sperm into the water where they are fertilized. A female can release one hundred million eggs at once. If a piece of certain echinoderms is chopped off, a new piece or even a new echinoderm can regrow.

http://www.youtube.com/watch?v=dvrQr0PeTBA

http://www.youtube.com/watch?v=ihvKwVDw8PcAttack of the Sea Urchin

A testThis is called a “spiny sea urchin.” Well, excuse me for asking, but aren’t all sea urchins spiny?

In many parts of the world, the roe or egg clusters are a delicacy.

http://www.youtube.com/watch?v=wXf_YodWw40World’s Weirdest….

VII. Phylum Mollusca

Mollusks are members of a large and very diverse phylum of “soft-body” animals that include snails and slugs, clams, and octopuses.

After arthropods (which we will talk about next), mollusks make up the second largest phylum of invertebrates with an estimated 50,000-100,000 species.

Mollusks differ greatly from each other. Some have shells, others do not. Some have internal shells. Some live on land, others in water. Some are marine, others live in fresh water. Some are filter feeders, others predators. Some are algae grazers. Some have gills while other have lungs.

Each mollusk has a special fold of skin known as a mantle.

A. Gastropods

The first class of mollusks includes snails and slugs.

• Snails have single shells while slugs do not.

• Most slugs are terrestrial. Snails can be terrestrial, aquatic, or marine.

• Slugs and snails both have antennae like structures that really have eyes on top and a special feeding feature known as a radula that the creature uses to scrape algae off hard surfaces.

• Both have a muscular foot that aids in mobility.

Slugs

http://www.youtube.com/watch?v=sHg536CII2M

Whelks are common along the Georgia coast. In fact…

It’s the state seashell!

And yes, people eat these too.

These strange looking things are whelk eggs.

Whelk eggs look a little different than these snail eggs.

Conch are a popular gastropod in parts of Florida and the tropics.

You can try fried coconut conch…

Or just plain fried conch.

If conch is too big and chewy for you, there are always the smaller snails to eat.

Or perhaps some snail and plantain soup is more to your liking.

I wouldn’t recommend trying to gather these cone shells to eat though. They have a long thread-like stinger that ejects a deadly venom---deadly enough to kill a person in a matter of minutes.

Like we discussed before, gastropods can be pretty confusing. For example, most snails live in water, but some like these giant land snails are terrestrial.

But we also said that most slugs live on land, however, some slugs live…

…some slugs live in the ocean! They look a little like marine flatworms, but they are much more advanced.

We know snails can carry parasites, but they can also be attacked by them.

http://www.youtube.com/watch?v=Go_LIz7kTok

B. Bivalves

The next class of mollusks is also very common and includes species that are a source of food for millions of people around the world.

Bivalves are mollusks with 2 shells such as clams, scallops, mussels, and oysters.

All bivalves are filter feeders.

They have special muscles (adductors) that open and close the shell.

1. Clams bury themselves in the mud and extend a long “neck” or siphon through a hole. The clam filters bits of food from the seawater through the siphon.

Hard shell clams

Soft shell clams

Razor clam

Giant Clam

2. Oysters and mussels are sessile bivalves that attach themselves to hard surfaces with a powerful glue.

Freshwater Mussels are not edible.

Zebra mussels are an invasive species that is causing a lot of problems in many U.S. lakes and rivers. They spread very rapidly.

3. Scallops are bivalves that live on the seabed. They can jet through the water by opening and closing their shells rapidly. Scallops have light sensing “eyes” that appear as a ring of small dots.

C. CephalopodsCephalopods are the largest and most complex of all invertebrates. They have highly developed body systems including brains, complete digestive systems, muscles, and eyes.

Like other gastropods, most cephalopods have shells, but they are actually on the inside of the animal rather than the outside.

The bodies of cephalopods are covered by a covering or flap of skin called the mantle.

Cephalopods include octopuses, squid, nautiluses, and cuttlefish.

Cephalopods move through the water by inhaling water through a special siphon then jetting it out of the body to propel them forward. The octopus can also walk on its tentacles.

As a protective measure, squid and octopuses can squirt a cloud of ink into the water.

Squid, cuttlefish, and octopuses have the ability to change their skin color to match their surroundings. They are the masters of camouflage.

All cephalopods are predators.

Cephalopods have powerful suckers on their tentacles that allow them to grip.

Scientific studies have shown that cuttlefish and especially octopuses have a high level of intelligence. Octopuses have even demonstrated the ability to problem solve

1. Squid

Squid have 8 “arms” and 2 tentacles. They swim through the entire depth of the water column, but do not generally live on the bottom like octopuses do.

The largest of all invertebrates, the giant squid, is thought to live in the deep ocean, below the reaches of the sun’s rays. No giant squid has ever been observed in its natural environment, but several have showed up in the nets of some very surprised fishermen.

Holy calamari!!!

Summon the Kraken!

Summon….

The KROKEN!

2. Cuttlefish are most similar to squid. They have 8 arms and 2 tentacles like the squid. They also have an internal shell. Cuttlefish tend to be more bottom dwelling than squid, and have shorter, stubbier arms.

http://www.youtube.com/watch?v=E-zodF-XrSE

3. Nautilus

The nautilus is one of the strangest species of animals on earth, and one of the oldest species. The nautilus of today is relatively unchanged from the nautiluses of millions of years ago, prompting some scientists to call them “living fossils.”

Nautiluses have up to 90 tentacles, but they do not have suckers on them. The nautilus also has an external chambered shell. The nautilus pumps water into and out of its shell to change its buoyancy (the degree to which it floats or sinks). The nautilus can also withdraw its tentacles completely into its shell for protection.

http://www.youtube.com/watch?v=QMFqV4SJLWg

http://www.youtube.com/watch?v=QMFqV4SJLWg

4. Octopus

Octopuses are not only the smartest invertebrates, but one of the smartest aquatic animals.

Octopuses have 8 strong tentacles, a beaked mouth, and a highly developed brain. In scientific studies, octopuses have shown that they are able to solve problems like how to get a small crab out of bottle that has a stopper in it---even though they had never done it before.

https://www.youtube.com/watch?v=IvvjcQIJnLg

https://www.youtube.com/watch?v=PmDTtkZlMwM

They are also able to squeeze their bodies through the tiniest of holes to hide from predators or hunt for prey. Most octopuses are very “shy”, but when it comes to feeding---they are voracious predators.

http://www.youtube.com/watch?v=PmDTtkZlMwM

Octopi are masters of camouflage…

http://www.youtube.com/watch?v=8CLKyMFHSfg

The blue ring octopus is only the size of a man’s hand, but it is highly venomous.

This Caribbean octopus looks like it has a Cinderella dress on and is headed for the ball.

Gee, I wonder where they got the name “Dumbo Octopus” from?

Here are some gastropod delicacies:

Cuttlefish surprise…

Octopus appetizers…Calamari (squid)

Chopped herbed octopus sauté Cuttlefish cooked in its ink