Starfish, Pacific Northwest
The Starfish is made up of over 6000 marine species of sea urchins, feather stars, sea stars, brittle stars, sand dollars, and sea cucumbers. There are around 180 species of these animals that live in the waters along the Pacific Northwest. Look in any tidal pool and you will see many types of these fascinating creatures.
Although they come in many forms and body shapes, they all have radial symmetry and a five-part symmetry and they all have tube feet or tubular appendages.
A brittle stars arms are supported plates made from calcium carbonate. These plates work together like ball and socket joints to give the brittle star’s arms flexibility. This gives these stars very flexible arms that can have a graceful movement that allows them to move quite quickly.
They don’t move using their feet like sea stars and urchins do, but move by wriggling their arms. When they move, one arm points the way forward, while the arms on either side coordinate the rest of the brittle star’s movements in a “rowing” motion so that the star moves forward.
If you ever get the chance to see them move, you will be quite surprised at how fast they can go, they look a lot like spiders, sea spiders.
Most Spawn to reproduce. Male and female brittle stars release sperm and eggs, respectively, into the water. After fertilization, they first become a 4 armed larvae. These tiny larvae feed on plankton for a few weeks and go through a metamorphosis to become 5 armed tiny juvenile brittle stars. In what is known as their settling stage, at this point, they sink to the ocean floor and begin life as brittle stars.
Some species brood their eggs in a chamber inside the female’s body until they reach the juvenile stage. The juveniles leave the brood pouch when they are about 2 mm in size, it seems that the smaller species of brittle stars brood more often than the bigger ones.
They can also reproduce asexually. When one or more arms and a portion of the central body break off, both pieces of the brittle star will grow new bodies and arms to form two animals.
They can be seen from sandy beaches to rocky areas, hiding under kelp and other plants, waiting to pounce on an unsuspecting meal.
They are of a red to orange color normally but can be yellow, purple or purple-grey. they are in the form of a broad disc with up to 24 rays (arms) but are usually born with five rays. They are covered in a network of spines on the top side and have pincers and gills on the underside.
These starfish are the fastest in our area and can travel at about 110 meters an hour.
They can be seen right at the shoreline and show up in great numbers there but they also are seen up to depths of 450 meters. They like to dig up and feed on butter clams.
They can be found in the Pacific Northwest from Alaska to southern California, they are common along the coast of British Columbia and can be seen on all of Vancouver Island. Leather starfish can be found from the intertidal zone to depths of over 90 meters.
The diet of these sea stars varies from sea anemones and sea squirts to sea cucumbers, sea pens, and sponges. Some of them scavenge on the bottom of the ocean. They have sensors at the end of each of their arms which detect prey. However, some anemones are adapted to sense a chemical produced by the leather starfish and are able to detach and float away before being eaten. When a leather starfish encounters food which is sedentary, it will protrude its stomach out through its mouth and use enzymes from its stomach to breakdown the food into a liquefied form. After digesting its prey, the leather starfish pulls its stomach back into its body.
They have adapted to reproduce asexually. They have the ability to regenerate. If a limb is lost, they just grow a new one. One sea star can be cut in half and each side will regenerate a new half becoming 2 starfish.
Leather starfish are preyed upon by seagulls and sea otters. Sea otters tend to only eat a part of the Leather star, which allows the remainder of the sea star the chance to regenerate. Gulls will tear off and eat the arms.
Echinoderms like sea urchins and sea stars play a very important role in the ecology of the ocean shore by controlling the quantity and quality of seashore plants and creatures with their ferocious appetites.
Some of them will only eat live animals while some will eat both live and dead creatures, helping to keep the shores clean and some others only eat plant life.
The predator most feared by echinoderms are the sea stars themselves, but birds, otters, and humans all feed to a lesser degree on them.
They can reproduce in more than one way. Starfish can either spawn together, or they can asexually reproduce, though this isn’t the ideal way to produce new starfish because it doesn’t promote genetic diversity within the species. While sexual reproduction is a naturally occurring process, asexual reproduction for starfish is usually only the result of dismemberment that results in the formation of two new starfish whom both have the same DNA.
They usually reproduce sexually by spawning. Spawning means that the sex cells are released into the water. They will gather in groups to reproduce, which increases the likelihood the sperm and eggs will find each other. They have sexual organs in each arm. During a breeding season, the male’s organs fill with sperm and the females fill with eggs. When starfish spawn, the male’s release sperm, and the females release eggs in great numbers. Female starfish may release millions of tiny eggs into the water during a spawning session.