Marine lifeGreen Sea Urchins

&Dungeness Crab

Green Sea Urchin

Common name: Green Sea Urchin

Scientific name: Strongylocentrotus droebachiensis

Description Usually this urchin is greenish with reddish brown tones The skeletal structure of the sea urchin is a rigid test or

theca that is made up of plates encircling the mouth in the center of the oral side, encompassing the urchin’s inner organs

Pores in the five ambulacral plates allow the tube feet access to the external environment

It has spines that are crowded, short and rather fine

The test may be 8.3 cm wide with the spines reaching around 2.5 cm

urchins are radically symmetrical and its diameter is not more than twice its thickness

•The ridges on the spines have rounded surfaces and periodic sculpturing (these somewhat fan-shaped)

Food and eating habits

The green sea urchin primarily grazes on seaweeds (kelp being its preferred food source), but will also consume a wide variety of organisms including mussels, sand dollars, barnacles, whelks, periwinkles, sponges, bryozoans, dead fish.

They use their teeth to pluck algae, seaweed, parts of other plants, and even parts of animals off to digest.

Reproduction

Green sea urchins release their gametes into the water column where the eggs are fertilized

The sexes are separate. The resulting larva undergoes development planktonically for a period of one to several months before settling on the sea floor and metamorphosing into the adult form

Reproduction occurs on an annual cycle with spawning occurring in the spring, generally between February and May, but sometimes as late as June

Habitat Sea urchins live only in the

ocean and cannot survive in fresh water. They are found from the intertidal to the deep ocean.

In the intertidal, sea urchins often wear away at the rock, over generations, to produce hollows in which they are partially protected from predators.

These "Urchin Beds" can extend for acres in the intertidal and house tens of thousands of sea urchins and many other life forms.

There are over 800 types of sea urchin found today

The shell of the urchin (after the animal and spines have been removed) displays a beautiful symmetrical design

Green sea urchins are more abundant than other sea urchins

Dungeness Crab While crabs measuring 10 inches

across the back have been taken off the coast of Washington, the crab seldom exceeds 8 inches and averages just under 7 inches of shell width. The Dungeness Crab has white-tipped claws and a brownish shell.

The carapace width of mature Dungeness crabs may reach 25 centimeters (9.8 in) in

Dungeness crabs have a wide, long, hard shell, which they must periodically molt to grow

They have five pairs of legs, which are similarly armored, the foremost pair of which ends in claws that the crab uses both as defense and to tear apart large food items.

Its scientific name is: Cancer Magister

Food and Eating habits The crab uses its smaller appendages to

pass the food particles into its mouth. Once inside the crab's stomach, food is further digested by the "gastric mill", a collection of tooth-like structures. Caner magister prefers to eat clams, other crustaceans and small fish, but is also an effective scavenger.

Reproduction Mating occurs between hard-shelled males and

recently molted, soft-shelled females, generally in the late spring and summer.

Male crabs are polygamous- they mate with more than one female crab. Females store the fertilized eggs for several months under their abdomen until the eggs hatch

Habitat The Cancer magister occurs along the west coast

of North America.  It ranges from the Aleutian Islands to central California.  The crab plays a key role in these areas being vital to the commercial fishing industry and the local economies associated with them.

The Cancer magister tends to reside in three main habitat types in intertidal zones: shells, eelgrass, and muddy areas. 

Many Dungeness crabs find the shells of bi-valves and reside in them. The eelgrass provides a safe habitat along with a wide variety of prey organisms for the Cancer magister to consume, making it a quite popular habitat.

While some smaller crabs will hide in the mud, this habitat it mostly utilized by larger crabs which do not need as much cover to find preferred food items or other smaller crabs.

Interesting facts Crabs do not hibernate; rather they lie

dormant for the long winter Crabs’ teeth are in their stomachs If a crab loses a limb, it will grow back.