Overview

Key Features:

Large body diameter (40-65 cm) soft flexible body, many arms/rays (up to 26), and usually gray or orange.

Similar Species:

Morning sun star sea star (Solaster dawsoni)

Primary Common Name:

Sunflower star

General Grouping:

Sea stars, urchins, cucumbers, sand dollars, brittle stars

Geographic Range:

Unalaska (Aleutian Islands) Alaska to Baja California; uncommon south of Carmel Bay.

Northern range limit of the sunflower star is Alaska, southern range limit is Baja California, but typically are uncommon south of Carmel Bay. Unalaska (Aleutian Islands) Alaska to Baja California; uncommon south of Carmel Bay. Sunflower stars are occasionally found in the San Diego/Baja California area, at their southern range limit.  These warmer ocean temperatures to the south likely are a limiting factor for sunflower distribution, as they prefer temperate waters. Sunflower stars can be found as far north as Alaska, and the Aleutian Islands, where they are limited by colder waters. Sunflower stars can be found on sand, mud, and rocky substrates.

Intertidal Height:

0 to 0 feet (0 to 0 meters)

Notes:

Within central California, Pycnopodia helianthoides is occasionally found in the low intertidal and in large, deep tidepools. In the northern part of the range, they are more common in the lower intertidal.

Subtidal Depth Range:

Minimum Depth: 0 meters or 0 feet
Maximum Depth: 435 meters or 1400 feet

Notes:

Can occur at depths of about 435 m.

Habitats:

continental slope, kelp forest

Notes:

Sunflower stars prefer relatively cold (temperate) waters, in areas with algae and the herbivores that consume the algae, which in turn are often prey of the stars. In the recent past, sunflower stars in MBNMS were commonly seen beneath the canopies of Giant Kelp Macrocystis pyrifera. Prior to 2014, Pycnopodia helianthoides was abundant from the low intertidal zone, to the subtidal zone (435 m).

Abundance:

Relative Abundance:

Prior to 2014, this species was frequent from the very low intertidal zone to 435 m deep.  They can occur on sand, mud, and rock, especially in areas with an abundance of prey.  In late 2013, sunflower stars and about 20 other sea star species were devastated by sea star wasting disease.  Sunflower stars were particularly hard hit, and since 2015 very few have been seen along the central coast of California, and no adults.

 

A study in 2019 indicated that losses observed in the shallow subtidal areas surveyed by SCUBA divers were paralleled by absences in deepwater trawl surveys.

Species Description:

General:

The sunflower star, Pycnopodia helianthoides, has from 15-24 rays (arms) in adults, while juveniles have as few as 5. Pycnopodia means "dense feet," and helianthoides means "sunflower." Pycnopodia has the largest body diameter of any sea star (40-65 cm). Numerous arms gives it tremendous predatory advantages over other sea stars, in both dexterity and speed. They can move very rapidly and actively, at a rate of up to 1 meter per minute, greater than any other observed sea star. This species displays a variety of colors including purple, pink, orange, brown, yellow, and red. Like other sea stars, Pycnopodia has large numbers of tiny tube feet, as well as digestive glands and gonads on its underside, which is a lighter yellowish color. Sunflower stars have eyespots on some of their rays that help them respond to light, currents, and touch. They also have tiny spines and pincer-like structures (pedicellariae) along their dermal gills that can be used to catch prey, ward off predators, and deter larvae from settling on their aboral surface.

Distinctive Features:

The Sunflower star has many rays (up to 26 or as few as 15 in adults, and usually 5 in smaller juveniles). They have a broad disk size, flexible and soft, various aboral coloring (purple, pink, red, brown, yellow, and orange). They are the largest and heaviest of all sea stars, with a maximum recorded diameter of 90cm (35.4 in.). They are also the fastest of all Pacific coast sea stars.

Size:

Diameter: 40 to 65 cm (15.7 to 25.6 in.).  Record lengths >90cm (35.4 in.).  Weight: average adult ~ (5-11 lbs).

Natural History:

General:

Pycnopodia helianthoides have tube feet that uses a hydrostatic system, drawing in water through the madreporite (visible on the aboral surface as small disc), and using muscles to squeeze on the water, thereby extending and retracting hundreds of tube feet that allow the star to grip the seafloor and to move. They also have tiny soft tissue patches of dermal gills that contract when touched. The sunflower stars endoskeleton consists of disconnected ossicles (bone-like discs), but remains flexible while other species are much more rigid.  When under attack, Pycnopodia helianthoides can detach their arms (autotomy), and later regenerate them. Pycnopodia helianthoides has an average life span of 3 to 5 years, and their spawning season is typically from March through July.  Sunflower stars can react to chemical cues given off by injured animals and will readily scavenge.  Many invertebrates can detect the approach of these sea stars, and have developed various escape responses. For example, shelled prey will twist their shells violently, attempting to break free from the numerous tube feet.  Sea urchins use tiny pincers (pedicellariae) to damage the tube feet of the stars, which may lead to the sea star retreating.

Predator(s):

The King Crab Paralithodes camtschatica can consume sunflower stars and is its main predator, found primarily in Alaska. Other sea stars (Solaster dawsoni), and rarely sea otters and seagulls, will also attack sunflower stars.

Prey:

The preferred diet of the sunflower star consists mainly of snails, small sea urchins and bivalves. In MBNMS sunflower stars also feed on dead or dying squid, which are available seasonally. The squid's pen is indigestible, and the sunflower star is unable to excrete it, so the pens can sometimes be seen extruding through their soft upper body. They also feed on a variety of chitons and snails, polychaetes, small fishes, sea cucumbers, hermit and grapsoid crabs.

Feeding Behavior:

Carnivore, Scavenger

Notes:

Sunflower stars can be a voracious predator. They feed seasonally on squid that die and sink to the bottom shortly after the squid's reproduce. Sunflower stars typically ingest their prey, but may sometimes partially evert their stomachs in order to envelop small prey. A hunting strategy that is commonly employed by sunflower stars is to locate clams under the sand and then dig around the clams. This practice leaves large pits in the sand that are a common site for divers. The main factors for the sunflower stars success in competition for space and food are its large size, combined with its ability to use over 15,000 tube feet against its competitors and prey.

Seasonal Behavior

Reproduction:

Pycnopodia helianthoides do not exhibit sexual dimorphism. It uses external broadcast fertilization, and is polygynandrous. Sunflower stars typically breed from March through July, and the peak of their breeding season is in May and June, although fertilizable eggs have been obtained from Sunflower stars from December to June. The separate sexes shed their respective sperm or eggs, where fertilization takes place by ran-dom occurrence. Sunflower stars do not provide parental care; instead their eggs develop into swimming, pelagic, plankton feeding larvae. After no more than 10 weeks, the plankton settles on the sea floor, where it metamorphoses into its juvenile (5 armed) form.

Issues

Monterey Bay National Marine Sanctuary:

Sewage spills, and urban runoff are harmful to sunflower stars, and the entire marine eco-system. Collection by humans and other anthropogenic disturbances from visitors, pose another threat to the general wellbeing of Sunflower stars. They play a role of secondary importance to the sea otter, in keeping sea urchin populations in check, allowing for higher levels of plant diversity and primary productivity, in turn helping their own larvae gain greater access to food. The population of Sunflower stars as a whole is generally considered healthy and occurs over a fairly broad range. When handled roughly, adult Sunflower stars have been known to shed their arms, and it is common to see them in the field with arms that are being regenerated. It is currently not listed by the IUCN.

Monitoring Trends:

This star has been severely depleted along the west coast of the US.  Washington, Oregon and California have lost 99% of all sunflower stars since 2015.  A sea star wasting disease is the presumed culprit.

References

• Brewer Reid, Konar Brenda, 2005 Chemosensory Responses and Foraging Behavior of the Seastar Pycnopodia helianthoides Marine Biology (2005) 147: 789-795
• Duggins David, 1983 Starfish Predation and the Creation of Mosaic Patterns in a Kelp-Dominated Community Friday Harbor Laboratories, Friday Harbor Washington Ecology, 64(6), 1983, pp. 1610-1619. The Ecological Society of America
• Mladenov et al, 1989 Purification and Partial Characterization of an Autonomy-Promoting Factor from the Sea
  Star Pycnopodia helianthoides Department of Biology, Mount Allison University, New Brunswick Canada Biological Bulletin. 176-169-175. (April, 1989)
• Morris, R.H., D.P Abbott, and E.C. Haderlie. 1980. Intertidal Invertebrates of California. Stanford University Press, Stanford, California. 690 p.
• WWW
  Animal Diversity Web http://animaldiversity.ummz.umich.edu/site/accounts/information/Anthopleura_xanthogrammica.html
  Accessed 8/19/09 for Giant green anemone
  Accesed 3/31/09 for Pycnopodia helianthoides
  Accessed 8/1/09 for purple sea urchin
  Accessed 11/11/09 for American Avocet
  Accessed 12/15/2009 for Black-crowned Night Heron
  Accessed 07/07/2009 for Pied-billed Grebe
  
• WWW
  Crowles, Dave 2005. Walla Walla University
  http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Echinodermata/Class%20Asteroidea/Pycnopodia_helianthoides.html
  Accessed 3/31/09 for Pycnopodia helianthoides
  Accessed 9/12/09 for Stalked tunicate
  Accessed 8/29/09 for Blueband hermit crab
  
• WWW
  Monterey Bay Aquarium. Online Field Guide, 2008.
  http://www.mbayaq.org/efc/living_species/
  Accessed [04/27/06]
  Accessed 01/30/2009 for Pelagic Cormorant
  Accessed 8/19/09 for Bryozoan
  Accessed 7/31/09 for Spiny brittle star
  Accessed 3/31/09 for Sunflower star
  Accessed 8/9/09 for red octopus
  Accessed 8/19/09 for Decorator crab
  Accessed 7/31/09 for warty sea cucumber
  
• WWW
  Zipcodezoo. The Bay Science Foundation 2009
  http://zipcodezoo.com/Animals/P/Pycnopodia_helianthoides
  Accessed 03/31/2009 for Pycnopodia helianthoides
  Accessed 08/19/2009 for Stalked tunicate
  Accessed 08/19/2009 for Blueband hermit crab
  Accessed 01/26/2010 for Pigeon Guillemot
  

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