Exploring the Intertidal

Check out the intertidal zone and its biodiversity!

Echinodermata

Echinoderms are an exclusively marine group! They include such organisms as: seastars, sea urchins, sea cucumbers and sand dollars. "Echino" means "spiny", and "derm" means "skin" - so these are the spiny-skinned animals. If you pick up a sea urchin, the reason for this name quickly becomes apparent! All echinoderms have a 5-point radial symmetry. The skeleton is composed of spiny, calcareous ossicles, and is found under the skin - so echinoderms have an "endoskeleton" just like us! A special water vascular system circulates throughout the animal. This system is important for many body functions, such as respiration, digestion, circulation and locomotion. Echinoderms all have "tube feet" which are used for attachment and motion. The feet do not have any muscles, and instead are controlled by hydraulics. Seastars have the amazing ability to shed arms to escape from predators and then to regenerate them later on. Seastars also have small claws called pedicellaria that cover their surface and prevent settlement of other organisms. Sea cucumbers will spit out their guts and then re-grow them in order to distract a predator! These are pretty amazing animals

Class Asteroidea

Dermasterias imbricata (Leather Star)
Description: Red-brown to orange. Covered in a slippery secretion.
Range:  Prince William Sound, Alaska to southern California.
Habitat:Rocky shores. Low intertidal to 91m deep.
Cool Fact:  Often smells like garlic or sulphur!

Henricia leviuscula (Pacific Blood Star)
Description: Blood red to purple. Four to six thin arms.
Range: Aleutian Islands, Alaska to Baja, California.
Habitat:  Protected, rocky shores, under rocks. Low intertidal to 435m deep.
Cool Fact:  Young, small females brood their eggs but large females release eggs directly into the water.

Pisaster ochraceous (Ochre Star)
Description: Purple or orange. Stiff, white ossicles visible on surface.
Range: Alaska to Baja, California.
Habitat: Exposed and shelter rocky shores. Mid to low intertidal. Most common intertidal star in B.C.
Cool Fact: A keystone predator. It's predation on mussels prevents the bivalves from taking over the entire intertidal!

Pycnopodia helianthoides (Sunflower Star)
Description: Yellow to purple. 24 arms!
Range: Prince William Sound, Alaska to southern California.
Habitat: Sandy and rocky shores. Low intertidal to 437m deep.
Cool Fact: Voracious predator! Put this star together with a sea cucumber, and the cuke will start "galloping" away!

Class Echinoidea

Strongylocentrotus franciscanus (Red Sea Urchin)
Description: Red to purple test. Spine half the length of the test (relatively longer than in purple or green urchins) Spines up to 7.6cm long!
Range: Alaska to Baja, California.
Habitat: Exposed rocky shores. Low intertidal to 91m deep.
Cool Fact: Gonads eaten as a delicacy in Japan! Juveniles often found under the spines of adults.

Class Holothuroidea

Parastichopus californicus (California Sea Cucumber)
Description: Red-brown with soft spines in five rows along body.
Range: Gulf of Alaska to Baja, California.
Habitat: Exposed and sheltered shores. Low intertidal to 90m deep.
Cool Fact: After the cucumber ejects its guts out of the anus to distract a predator, it regrows them in 6-8 weeks.

see also Sea Stars and Sea Cucumber pages!

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