Sunflower sea star explained

Pycnopodia helianthoides, commonly known as the sunflower sea star, is a large sea star found in the northeastern Pacific Ocean. The only species of its genus, it is among the largest sea stars in the world, with a maximum arm span of . Adult sunflower sea stars usually have 16 to 24 limbs. They vary in color. A carnivorous animal, Sunflower sea stars eat many different kinds of dead and alive prey to fill their diets. [1] They are predatory, feeding mostly on sea urchins, clams, sea snails, and other small invertebrates.[2] Although the species was widely distributed throughout the northeast Pacific, its population rapidly declined from 2013.[3] The sunflower sea star is classified as Critically Endangered on the IUCN Red List.

Description

Sunflower sea stars can reach an arm span of 1m (03feet). They are the heaviest known sea star, weighing about 5 kg.[4] 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.[5] 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.

Their color ranges from bright orange, yellow-red to brown, and sometimes purple, with soft, velvet-textured bodies and 5–24 arms with powerful suckers.[5] [6] 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,[5] and were dominant in Puget Sound, British Columbia, northern California, and southern Alaska.[7] Between 2013 and 2015, the population declined rapidly due to sea star wasting disease and warmer water temperatures[8] caused by global climate change.[9] 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.[3] Ecologists using shallow-water observations and deep offshore trawl surveys found that, in their study period (2004–2017), mean biomass of sunflower sea stars declined 80–100%.[10] In 2020, the species was declared critically endangered by the International Union for Conservation of Nature.[11] There are suggestions that sea star wasting disease was caused by bacterial pathogens or parasites and was contagious, due to its tendency to spread to multiple locations.[12]

Sunflower sea stars generally inhabit low subtidal and intertidal areas up to 435m deep[13] that are rich in seaweed,[14] kelp,[15] sand, mud, shells, gravel, or rocky bottoms.[16] They do not venture into high- and mid-tide areas because their body structure is heavy, and requires water to support it.[17] [7]

Diet and behavior

Sunflower sea stars are efficient hunters, moving at a speed of 1m/min using 15,000 tube feet that lie on their undersides.[5] [6] They are commonly found around urchin barrens, as the sea urchin is a favorite food. They also eat clams, snails, abalone, sea cucumbers and other sea stars.[5] In Monterey Bay, California, they may feed on dead or dying squid. Sea star appetites and food can depend on environmental factors in their habitats, such as climate, amount of prey in the area, and latitude.[16] Although the sunflower sea star can extend its mouth for larger prey, the stomach can extend outside the mouth to digest prey, such as abalone.[18]

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.[19] They have separate sexes.[18] Sunflower sea stars breed from May through June. In preparing to spawn, they arch up using about a dozen arms to hoist their fleshy central mass above the seafloor and release gametes into the water for external fertilization.[18] The larvae float and feed near the surface for two to ten weeks. After the planktonic larval period, the larvae settle to the bottom and mature into juveniles.[7] Juvenile sunflower sea stars begin life with five arms, and grow the rest as they mature.[20] The lifespan of most sunflower sea stars is three to five years.[21]

Conservation efforts

Since 2013, sunflower sea star populations have been in a rapid decline due to disease and changes in climate.[22] In 2020, the IUCN first assessed that the sunflower sea star was critically endangered.[23] The Nature Conservancy and its partner institutions, along with the University of Washington are working to initiate captive breeding.[24] Captive breeding efforts include seasonal production, larval development, and growth and feeding experiments.[25] 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.[26] In March 2023, the National Marine Fisheries Service proposed listing the sunflower sea star as threatened under the act.[27]

Sea star wasting disease spreads throughout the whole body. The limbs become affected and eventually fall off, ultimately causing death from degradation. Sea star wasting disease appears to be a Sea Star-associated Densovirus (SSaDV).[28] The disease creates behavioral changes and lesions.[29] 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.[30] Sea stars control their population and help maintain the health of kelp forests.[31] Due to the decrease in sea star population, sea urchin populations are increasing and posing a threat to biodiversity, particularly in kelp forests.

External links

Notes and References

  1. Web site: Sunflower Sea Stars Facts . 2023-09-21 . SeaDoc Society . en-US.
  2. McGaw . Iain J. . Twitchit . Tabitha A. . 2012-03-01 . Specific dynamic action in the sunflower star, Pycnopodia helianthoides . Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology . 161 . 3 . 287–295 . 10.1016/j.cbpa.2011.11.010 . 22127024 . 1095-6433.
  3. Yong . Ed . 30 January 2019 . A starfish-killing disease is remaking the oceans . The Atlantic . 30 January 2019.
  4. Web site: Yagoda . Shayna . Pycnopodia helianthoides . 2023-09-18 . Animal Diversity Web . en.
  5. Web site: Sunflower sea star . Species ID . Fisheries . . dead . 2021-08-04 . 2 February 2018 . https://web.archive.org/web/20180202023425/http://www.nmfs.noaa.gov/speciesid/fish_page/fish6a.html .
  6. Book: Telnack, Jennifer . Intertidal Marine Invertebrates of the South Puget Sound . NW Marine Life.
  7. Scott . Boyd . Sunflowerstar . article & LD photos . Emerald Sea Photography . 2021-03-31.
  8. Harvell . C. D. . Montecino-Latorre . D. . Caldwell . J. M. . Burt . J. M. . Bosley . K. . Keller . A. . Heron . S. F. . Salomon . A. K. . Lee . L. . Pontier . O. . Pattengill-Semmens . C. . 2019 . Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides) . Science Advances . 5 . 1 . eaau7042 . 2019SciA....5.7042H . 10.1126/sciadv.aau7042 . 6353623 . 30729157.
  9. Caballes . Ciemon F. . Byrne . Maria . 2021-12-01 . Demography, Ecology, and Management of Sea Star Populations: Introduction to a Special Issue in The Biological Bulletin . The Biological Bulletin . en . 241 . 3 . 217–218 . 10.1086/718198 . 35015623 . 245051292 . 0006-3185.
  10. Harvell, C.D. . Montecino-Latorre, D. . Caldwell, J.M. . Burt, J.M. . Bosley, K. . Keller, A. . Heron, S.F. . Salomon, A.K. . Lee, L. . Pontier, O. . Pattengill-Semmens, C. . Gaydos, J.K. . 6 . 30 January 2019 . Disease epidemic and a marine heat wave are associated with the continental-scale collapse of a pivotal predator (Pycnopodia helianthoides) . Science Advances . 5 . 1 . eaau7042 . 10.1126/sciadv.aau7042 . 30729157 . 6353623 . 2019SciA....5.7042H .
  11. Gravem, S.A. . Heady, W.N. . Saccomanno, V.R. . Alvstad, K.F. . Gehman, A.L.M. . Frierson, T.N. . Hamilton, S.L. . 2020-08-26 . Pycnopodia helianthoides . IUCN Red List of Threatened Species . 10.2305/iucn.uk.2020-3.rlts.t178290276a178341498.en . free .
  12. Hewson . Ian . Button . Jason B. . Gudenkauf . Brent M. . Miner . Benjamin . Newton . Alisa L. . Gaydos . Joseph K. . Wynne . Janna . Groves . Cathy L. . Hendler . Gordon . Murray . Michael . Fradkin . Steven . Breitbart . Mya . Fahsbender . Elizabeth . Lafferty . Kevin D. . Kilpatrick . A. Marm . 2014-12-02 . Densovirus associated with sea-star wasting disease and mass mortality . Proceedings of the National Academy of Sciences . en . 111 . 48 . 17278–17283 . 10.1073/pnas.1416625111 . 0027-8424 . 4260605 . 25404293 . 2014PNAS..11117278H . free .
  13. Web site: Fisheries . NOAA . 2023-08-24 . Sunflower Sea Star NOAA Fisheries . 2023-09-23 . NOAA . en.
  14. Book: North Coast Intertidal Guide . Seastars & Urchins . Humboldt State University . Arcata, CA.
  15. Web site: Sunflower Star . Channel Islands National Park . National Park Service .
  16. 2020-08-26. Pycnopodia helianthoides: Gravem, S.A., Heady, W. N., Saccomanno, V. R., Alvstad, K. F., Gehman, A. L. M., Frierson, T. N. & Hamilton, S.L.. 10.2305/iucn.uk.2021-1.rlts.t178290276a197818455.en . free.
  17. Web site: Sunflower Star . North Island Explorer.
  18. Web site: Sea Stars and Relatives . City of Edmonds, Washington.
  19. Web site: Shepard, Aaron . Pycnopodia helianthoides, the Sunflower Star . Evergreen State College . Invertebrate Zoology . 28 February 2012.
  20. Book: Sunflower star: Pycnopodia helianthoides . Online . Field Guide . Monterey Bay Aquarium . mbayaq.org . dead . https://web.archive.org/web/20030724144140/http://www.mbayaq.org/efc/living_species/print.asp?inhab=497 . 2003-07-24.
  21. Web site: Yagoda . Shayna . Pycnopodia helianthoides . 2023-09-22 . Animal Diversity Web . en.
  22. Montecino-Latorre . Diego . Eisenlord . Morgan E. . Turner . Margaret . Yoshioka . Reyn . Harvell . C. Drew . Pattengill-Semmens . Christy V. . Nichols . Janna D. . Gaydos . Joseph K. . 2016-10-26 . Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids . PLOS ONE . en . 11 . 10 . e0163190 . 10.1371/journal.pone.0163190 . 1932-6203 . 5082671 . 27783620 . 2016PLoSO..1163190M . free .
  23. Gravem, S.A. . Heady, W. N. . Saccomanno, V. R. . Alvstad, K. F. . Gehman, A. L. M. . Frierson, T. N. . Hamilton, S.L. . 2021 . Pycnopodia helianthoides . 2021 . e.T178290276A197818455 . 10.2305/IUCN.UK.2021-1.RLTS.T178290276A197818455.en . 19 November 2021.
  24. Web site: Critically endangered sea star not recovering in the wild, scientists point to the need for restoration efforts.. 2021-11-05. The Nature Conservancy. en-US.
  25. Hodin. Jason. Pearson-Lund. Alexi. Anteau. Fluer P.. Kitaeff. Pema. Cefalu. Shannon. Shannon. Troy. Yannou. Bernard. Leroy. Yann. Cluzel. François. 2021. Dataset for the manuscript: "Progress towards complete life-cycle culturing of the endangered sunflower star Pycnopodia helianthoides". The Biological Bulletin. 241. 3. 243–258. 10.1086/716552. 35015622 . 1773/46681 . 244446037 .
  26. Web site: Petition Seeks Protection for Sunflower Sea Star After 90% Population Decline. 2021-11-05. Center for Biological Diversity. en.
  27. Web site: Sunflower sea star, once a common sight off Oregon Coast, proposed for federal protection . 2023-03-16 . The Register-Guard . en-US.
  28. News: Scigliano . Eric . 23 January 2015 . Signs of hope, and a prime suspect, in sea star wasting disease . . Washington Sea Grant . 2021-08-04.
  29. Hewson. Ian. Button. Jason B.. Gudenkauf. Brent M.. Miner. Benjamin. Newton. Alisa L.. Gaydos. Joseph K.. Wynne. Janna. Groves. Cathy L.. Hendler. Gordon. Murray. Michael. Fradkin. Steven. 2014-11-17. Densovirus associated with sea-star wasting disease and mass mortality. Proceedings of the National Academy of Sciences. 111. 48. 17278–17283. 10.1073/pnas.1416625111 . 25404293 . 4260605. 2014PNAS..11117278H . 0027-8424. free .
  30. Web site: Sean . Fleming . 2021-05-20 . This sea star was almost killed off. Now scientists are breeding it to help fight climate change . 2022-01-01 . World Economic Forum . en.
  31. Web site: Simon Fraser University . 2018-08-13 . Sea stars critical to kelp forest resilience . 2021-11-24 . phys.org . en.

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