Echinoderms

Echinoderm means spiny skin. Echinoderms include sea urchins, sea stars, sand dollars, sea cucumbers and some other odd organisms like feather stars and basket stars. All echinoderms have radial symmetry, spiny skin, and an endoskeleton called a test.

Most people are familiar with an orange sea star because on the east coast, that's all we've got. On the west coast and in other places around the world, it is easier to find a variety of sea stars in other colors and with different amounts of legs.

Sea stars have powerful tube feet that use water suction to open molluscs. When they eat molluscs, they actually stick their stomach into the shells of the mollusc, digest it, and then put their stomach.

Feather stars and basket stars both have crazy looking legs that they wave around to filter feed. Sea urchins and sand dollars are both covered with protective spines and eat with a scraping mouth called Aristotle's Lantern.

Sea cucumbers have lost most of their exoskeleton and are a bit squishier than other echinoderms. Sea cucumbers are important detritus eaters on the sea floor. When attacked by predators they will expel their guts as a meal for the predator as they make a get away. Sea cucumbers are able to regenerate these guts over time.

Barnacles

BARNACLES
If you look at a diagram, barnacles are like little shrimp glued on their backs with a white fence around them. They stick their feathery legs out to filter feed plankton. They are plankton for a while and once settled and glues onto a hard substrate never move again. This makes mating difficult, but the hermaphroditic barnacles have special talents. Gooseneck barnacles have a stalk that they attach to substrates with.

Shrimp

SHRIMP - miniature lobsters... use their swimmerettes to keep themselves moving - most Americans have never seen one with its head and legs still attached!

• Gulf shrimp are the ones people most people are familiar with because these are the ones we eat!
• Shore shrimp live in sea grasses, are fairly small and clear, and are not commercially harvested because no one would make any money.
• Snapping shrimp (or pistol shrimp) have slightly larger claws and can use them to make sonic waves to stun their prey with sound. 
• Mantis shrimp whack their prey with arms that can unfold and strike lightning quick. 
• Cleaner shrimp make their living eating parasites off of fish and other sea creatures. 

One cool crustacean we have been learning about is the mantis shrimp. Mantis shrimp have folded claws like a praying mantis. They have lightning quick reflexes and shoot their arms out to smack their prey. It is said that they have enough power to break aquarium glass. If you want to see an interesting video of a mantis shrimp attacking and eating different prey - check here.

Crabs

CRABS - In general, you can tell the difference between boy crabs and girl crabs by looking at the shape of the plate on the abdomen. Boys have a thinner more pointy plate, girls have a wider more rounded plate because it is used to hold the egg mass. The mothers carry the eggs because not many predators will mess with them to get to the eggs.

• Blue Crabs are found in the Chesapeake Bay. They are very agressive, like to pinch, but are good to eat. They have a pointy-ended shell and swim fins. (you can kind of see the swim fins on the last leg of the crabs on the right)
• Spider Crabs have a rounder body shape, often a bumpy shell that will grow algae for camouflage, and longer more spindly legs. Spider Crabs include snow crabs and king crabs like the ones seen on Deadliest Catch. A decorator crab is a kind of spider crab that attaches stuff to its bumpy shell to blend in.
• Fiddler Crab males have one claw that is a lot bigger than the other. This is for impressing the ladies, and used to show dominance over other males. 
• Hermit Crabs have a weak exoskeleton and thus protect it with a stolen mollusc shell. They have adapted to this lifestyle and have modified back legs that hook on the inside to hold the shell on and one claw that is slightly larger to use as an operculum.

Crustacean Basics

Crustaceans have bilateral symmetry and a hard crunchy exoskeleton. Because the crustacean grows and the exoskeleton does not, crustaceans have to molt or shed their hard outercovering, exposing a new softer bigger covering that will harden in a few days.

LOBSTERS

There are two basic lobsters to be familiar with - the clawed lobster and the spiny lobster. Both are primarily scavengers. The clawed lobster has two different claws - a lighter faster shredder and a heavier more powerful crusher. The clawed lobster is more solitary because it is more aggressive. The spiny lobster does not have big claws, but can defend itself with its long whip like antennae. This lobster likes to congregate in groups and is not as aggressive. Both lobsters carry their eggs on the swimmerettes protecting them from potential predators. 

Unit 6 Invertebrate Overview

Invertebrates do not have backbones and make up 95% of the animals living on earth (us vertebrates are actually way way way in the minority).

We have covered molluscs, crustaceans, and echinoderms in larger units, but there are lots of other invertebrate phyla including three types of worms, sponges, and cnidarians.

Cnidarians include coral, jellies, and sea anemones and will be covered in Unit 10. They have radial symmetry and stinging tentacles surrounding their mouth.

Sponges in phyla Porifera have asymmetry because of their irregular shapes. Water flows in through many small pores and out large centralized openings called osculum. This is how sponges get their food and how they get rid of waste. Sponges have two types of structural support - spicules that are spiny or pointy and made of calcium carbonate and springy spongin. Sponges we use around the house used to be made of sponges harvested from the ocean that were pounded to remove the spicules. Now, plastic sponges are commonly used.

There are three types of worms - Flatworms (Platyhelminthes), R0undworms (Nematodes), and Segmented Worms (Annelids).

Flatworms (Platy-hel- minthes) are flat and ribbon like, have bilateral symmetry and include things like tapeworms, planarians, flukes, and brightly colored marine flatworms. Marine flatworms have similar adaptations to nudibranchs (molluscs), but are flat and have no tufts. They are simple animals and are often parasites.

Roundworms (Nematodes) are ubiquitous and found commonly worldwide in every biome... but they are poorly understood because they are very very small. Less than 5cm. They have radial symmetry and often are parasites. Roundworms have scary looking mouths with teeth for attaching - often used in scary movies.

Segmented Worms (Annelids) include earth-worms, leeches, bristle-worms, and christmas tree worms. They are more advanced than the other worms with segments and body organs. They have radial symmetry and tunnel through their food.

For those of you studying invertebrates, you can use these matching cards to help!

Giant Squid

Students read a historical narrative about sea monsters and how those stories of the Kraken were based on squid sightings. We have known about the giant squid for several hundred years because of dead specimens and pieces found, but the first live one was not observed until 2005. Sailors used to think that the giant squid was much bigger because of a measurement error. Sucker marks on sperm whales were used to estimate size until they relaized that those marks and scars grew bigger as the whale grew.

Students then read a fictional account about a squid attacking the Jersey Shore (article pictured at left) and had to identify what parts of the stories were accurately portraying the squid and which parts were inaccurate.

http://animals.nationalgeographic.com/animals/invertebrates/giant-squid/