Sunflower sea star

Sunflower sea stars can reach an arm span of . They are the heaviest known sea star, weighing about 5 kg. They are the second-biggest sea star in the world, second only to the little known deep water Midgardia xandaros, whose arm span is and whose body is 2.6 cm (roughly 1 inch) wide. Growth begins rapidly, but slows as the animal ages. Researchers estimate a growth rate of 8 cm (3.1 in)/year in the first several years of life, and a rate of 2.5 cm (0.98 in)/year later. Most sea star species have a mesh-like skeleton that protects their internal organs. ==Distribution and habitat==

Sunflower sea stars were once common in the northeast Pacific from Alaska to southern California, Between 2013 and 2015, the population declined rapidly due to sea star wasting disease The species disappeared from its habitats in the waters off the coast of California and Oregon, and saw its population reduced by 99.2% in the waters near Washington. In 2020, the species was declared critically endangered by the International Union for Conservation of Nature. , Alaska, 2022 Sunflower sea stars generally inhabit low subtidal and intertidal areas up to 435m deep that are rich in seaweed, kelp, sand, mud, shells, gravel, or rocky bottoms. ==Diet and behavior==

Sunflower sea stars are efficient hunters, moving at a speed of using 15,000 tube feet that lie on their undersides. Easily stressed by predators such as large fish and other sea stars, they can shed arms to escape, which regrow within a few weeks. They are preyed upon by the king crab. ==Reproduction==

Sunflower sea stars can reproduce sexually through broadcast spawning. They have separate sexes. The lifespan of most sunflower sea stars is three to five years. == Conservation efforts ==

Since 2013, sunflower sea star populations have been in a rapid decline due to disease and changes in climate. In 2020, the IUCN first assessed that the sunflower sea star was critically endangered. Captive breeding efforts include seasonal production, larval development, and growth and feeding experiments. On August 18, 2021, the Center for Biological Diversity created a petition asking that the sunflower sea star be protected under the Endangered Species Act. In March 2023, the National Marine Fisheries Service proposed listing the sunflower sea star as threatened under the act. Sea star wasting disease spreads throughout the whole body. The limbs become affected and eventually fall off, ultimately causing death from degradation. The disease creates behavioral changes and lesions. This disease is known to be more prevalent and harmful in warmer water. The warming waters in California, Washington, and Oregon have coincided with the increased risk of sea star wasting disease. Sunflower sea stars are one of sea urchins' main predators. Sea stars control their population and help maintain the health of kelp forests. Due to the decrease in sea star population, sea urchin populations are increasing and posing a threat to biodiversity, particularly in kelp forests. ==References==