Sunflower

sea star

11/29/20

Image by Robin Riggs

images-uploads-24_Sunflower_Sea_Star_-_R

Sunflower Sea Star

The sunflower sea star, or Pycnopodia helianthoides, is the largest sea star(up to 3 feet long and up to 13 pounds), has the most arms(15-24), and may also be the fastest sea star(10 feet per minute)! On their arms, they have 15,000 tube feet that help them move and attach to rocks. They can live about 3-5 years. The sunflower sea star originally could be found from the waters of Alaska to Mexico, where they are found from 394 feet in the intertidal zone to 1,427 feet. Sunflower sea stars may be pink, yellow, brown, or purple, with white spines. They have suction cups that help them move and cling to rocks in the waters. Sunflower sea stars are carnivorous and eat sea urchins, fish, mussels and crustaceans, clams, sea cucumbers, gastropods, sand dollars, and occasionally sponges and algae; most of their diet is usually sea urchins. To hunt, sunflower sea stars use their strong sense of smell and light receptors to find prey, which they then chase, using their forwardmost 8 arms to grab the prey. This is made harder by some species of prey, like abalone, who have adapted to swim fast and whip back and forth to break the sea star’s hold. Once prey is caught, the sea star will eat it by enlarging it’s stomach, found on its underside, and swallowing prey. While most sea stars have a one piece skeleton, sunflower star’s have a skeleton made of disjointed pieces. Thus, when attacked by predators or handled too much, arms may detach and can be regenerated. If part of the central part of the star was also detached, that may also be regenerated. Another fascinating feature of the sunflower sea star is that they are broadcast spawners; they release gametes into water and leave fertilization to chance. Then, for 10 weeks, sunflower sea star eggs hatch into larvae and live as plankton. Then it changes into a young sea star with 5 arms, growing more arms as it matures. 

Why Are They Endangered?

Until as recently as 2013, the sunflower sea star was as common as a robin. However, recently a terrible disease has devastated their population and the population of many other sea stars. This disease annihilated populations in all the sunflower sea stars habitat. This continues to reoccur on and off to this day. A disease that affects sea stars, called SSWD, or sea star wasting disease, was found in about 20% of the sea stars who died. However the rest were not susceptible to SSWD, meaning that there is some other overlying disease affecting sea stars. Sunflower sea stars have almost completely disappeared because of this disease. Any hope that the sea stars had just gone into deeper water to wait out the epidemic was destroyed by surveys taken by divers. In 2016 700 searches for sea stars did not find a single one. In 2018 one was found. While other sea stars have been less susceptible to whatever disease this is, the sunflower sea star is extremely threatened by this disease. Other creatures who are more tolerant of  this disease can also pass it to sunflower sea stars. The overall rising of ocean temperatures, caused by climate change, also stresses sunflower sea stars out, making them more vulnerable to the disease. The ochre sea star is another sea star that was badly affected by this disease, however they are recovering, and their genome has even been modified because of it. Hopefully, the sunflower sea star will too be able to recover with help from humans. Other problems affecting the sunflower sea star, in addition to this widespread disease, include pollution and climate change.

SUNFLOWERSTAR-500x666.jpg

Image by Ed Gullekson

sunflower_sea_stars.jpg

Image by Smithsonian Magazine

Effects

The sunflower sea star is a keystone predator because it keeps sea urchins and mussels, some of its main sources of prey, from taking over the intertidal zone. Without them sea urchins will eat too much kelp and muscles will clog the coast. Thus because of this disease, 90% of kelp forests in California have been lost. Kelp forests are a very important ecosystem for many creatures. Creatures affected by this devastation of kelp forests include red abalone, whales, sea otters, seals, and many birds. Without the sunflower sea star, biodiverse ecosystems of kelp are turned into barren stretches of ocean where only sea urchins live. Because the red abalone’s population has declined so dramatically, fishing of it has been suspended, impacting fisherpeople as well.  Because of global warming, the sort of widespread epidemic like this will become much more common. 

What Can You Do?

You can advocate for the sunflower sea star to be protected by government programs like the Endangered Species Act, which are supposed to help all animals, not just the ones humans think are cute. When saving animals we have to also save the ecosystems, which also helps many other animals and plants as well. You can also tell people about this amazing, many-legged sea star and the disease that is devastating it. 

sources cited

Daley, J. (2019, January 31). Why Almost All of the West Coast’s Sunflower Sea Stars Have Wilted Away. Retrieved October 09, 2020, from https://www.smithsonianmag.com/smart-news/why-almost-all-west-coasts-sunflower-sea-stars-have-wilted-away-180971387/

Harvell, D., & Gaydos, J. K. (2019, October 03). As sunflower stars go, so goes the health of our seas. Retrieved October 09, 2020, from http://www.eeb.cornell.edu/harvellcom/2019/02/18/as-sunflower-stars-go-so-goes-the-health-of-our-seas/

Pacific, A. (n.d.). Sunflower Sea Star. Retrieved October 09, 2020, from https://www.aquariumofpacific.org/onlinelearningcenter/species/sunflower_sea_star