Common Name: Sunflower Sea Star

Scientific Name: Pycnopodia helianthoides

Kingdom: Animalia

Phylum: Echinodermata

Class: Stelleroidea

Order: Forcipulatida

Family: Asteriidea

Genus: Pycnopodia

Species: P. helianthoides

 

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This animal is known to many people as the “starfish,” but what some don’t know, is that it is not at all. In Fact, research shows that this amazing creature has been renamed as the “sea star.” Did you also know, sea stars, have been living on this Earth for more than 500 million years, and currently over 1500 have been discovered, and one of those species is called the Sunflower Sea Star? The Pycnopodia helianthoides, meaning “dense feet,” is the largest and fastest of the sea stars. They can travel up to 9 ft per minute and weigh in about 5kg. Their rays are around 40cm long and have over 15,000 suction cups on the bottom of their feet, which are so strong that if you try to pull a sea star off a rock, the suction cups may break loose from the sea star and continue to stick to the rock. The Sunflower Star’s overall description is very unique, but to the human eye it appears quite plain. Its general body coloration is commonly orange, yellow, red to brown and sometimes even purple or slightly pinkish. A Sunflower Sea Star’s torso is also covered in a velvety texture. Their size is usually 65 cm give or take a little, but some of the larger specimens can reach around 3 ft! That’s nearly the size of a small child.

 

This sea star has many adaptations to help it survive and thrive in the ocean. There 26 soft flexible arms allowing it to anchor itself under rocks for protection, and also making it capable of moving swiftly around on the tips of their numerous rays. They are found living in marine environments, ranging from the shallow waters of the Aleutian Islands to Alaska, and San Diego, California. Sunflower Sea Stars are usually found on various substrates like mud, sand, gravel, boulders, and rocks, and often on dock pilings. They make themselves at home in the subtidal area, no more than 435 m deep, but mostly staying around the 120 m mark. Urban runoff and sewage spills harm sea stars, so it’s best not to disturb them when you see them. Some people actually have the heart to kill such innocent creatures, just to try and protect oyster and clam beds, from being eaten. This is part of what is contributing to the change in their population.

 

Sunflower Sea Stars feed upon a large variety of organisms which include sea urchins, sand dollars, bivalves, sea cucumbers, mussels, crabs, barnacles, clams, gastropods, and rarely algae and sponges. But occasionally they will scavenge dead fish. Actually, it's mere presence causes many animals to show a dramatic escape response. Then, there are the animals that include them as part of their diet, which is the Alaska King Crab, sea otters every now and then and other aggressive sea stars. Birds such as seagulls also have been known to prey upon Sunflower Sea Stars. Predators mainly eat the sea stars during their larval and juvenile stages, usually around 9-10 weeks. But if a predator does attack, then the sea star can let its arm drop off and send a chemical that causes an alarm response to other Sunflower Stars in the area. If its arm is irritated or disturbed by a predator, it will drop it off or automize the arm. The autonomy is triggered by a chemical that is released by injured tissues. This allows Sunflower Stars to escape from the predator holding onto its arm.

 

What allows the Pycnopodia helianthoides to compete for food is their strong sense of smell and very sensitive indicators of light and dark to find their prey. They can move at a quick rate of 10 cm per second or 18 ft per minute. While moving, it puts its eight leading arms in front and when it comes in contact with the prey, it throws its rays down on top of the prey. Then the sea star protrudes its stomach, envelops the entire prey and digests it. The arms and greatly expandable tube feet are the basic tools of prey capture. What stands out about the Sunflower Sea Star is that they don’t have a brain or a heart. Organs at the tip of each ray allow them to smell and sense between light and dark, but they can’t see images. A sea stars lifespan commonly averages between 3-5 years. Their breeding season is between May and June. What happens is the female will lay her eggs and they'll float on the surface of the water for 2-10 weeks. Soon they will drift to the bottom and remain there until they have formed into a mature sea star. But the real interesting part is that as babies, the Sunflower Star starts out with only 5 arms!

 

Author: Megan S

Published: 02/2008

 

Sources:

http://www.montereybayaquarium.org/efc/living_species/default.asp?hOri=1&inhab=497 http://www.nwmarinelife.com/htmlswimmers/p_helianthoides.html http://www.ptmsc.org/images/crittercare/SunflowerStar.pdf http://en.wikipedia.org/wiki/Sunflower_sea_star

 

Photo Credit: BC Marine life/ www.elasmodiver.com