Marine life Green 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.