Asterias amurensis

Geographic Range

Northern Pacific sea stars are found throughout parts of the Pacific Ocean near Japan, Russia, Northern China, and Korea as a native species. However, this species has also been introduced to oceanic habitats near parts of the southern Australian coast (especially Tasmania), Alaska and the Aleutian Islands, Europe, and the state of Maine.

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
• palearctic palearctic
  • native native
• australian australian
  • introduced introduced
• atlantic ocean atlantic ocean
  • introduced introduced
• pacific ocean pacific ocean
  • native native

Habitat

Northern Pacific sea stars live in estuarine, intertidal, and coastal zones and prey on other marine inhabitants in or on the substrate. They are found near protected areas of coasts, far away from areas of the ocean with high wave action, at depths up to 220 meters. They prefer a slightly cold environment of about 7-10ºC; however, this species has adapted to the warmer waters of the Australian coast, which average about 22ºC. It can survive in a temperature range of 0–25ºC. Due to their presence in estuarine habitats, these sea stars are able to tolerate a large range of salinities, from 18.7-41.0 ppt.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• benthic benthic
• coastal coastal
• brackish water brackish water

• Other Habitat Features
• estuarine estuarine
• intertidal or littoral intertidal or littoral

Physical Description

Northern Pacific sea stars have five arms, all ending in small, upward-turned tips. Each of these arms joins in the center of the organism to form a central disc. This species shows a wide range of colors, from orange to yellow, and sometimes purple on their dorsal side. Irregularly arranged spines run down the length of each arm. A row of spines from each arm come together near the mouth area, creating a fan-like appearance. Spines also line the ventral groove of each arm, where the tube feet are found. This species can grow to be up to 50 cm in diameter.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry
• radial symmetry radial symmetry

• Sexual Dimorphism
• sexes alike

Development

Male and female sea stars release their respective gametes in to the aquatic environment. The gametes come together to form a fertilized egg, which undergoes holoblastic and radial cleavage followed by gastrulation, completing the beginning stages of larval development. The larva begins to feed once the gastrovascular canals are formed, and at this stage is called a bipinnaria. This stage later develops brachiolar arms, with three of them combining with a central adhesive disk to form the brachiolar complex. This marks the transition of the larva into the brachiolaria state. A brachiolarian larva can remain in the water column for about 120 days before it finally settles and undergoes metamorphosis into the adult sea star. Metamorphosis is induced by the detection of metamorphic inducing factors by the adhesive papillae on the brachiolar arms, such as chemical cues from adult sea stars in the environment. It takes a larva as little as 41 days to about 120 days, from the time of fertilization, to develop into an adult sea star. This process is all dependent upon the temperature of the water in which the sea star is developing; the warmer the water, the faster the rate of development.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Female Northern Pacific sea stars release their eggs into the surrounding marine environment; they are then externally fertilized by sperm released by male sea stars. This species reproduces seasonally and spawns during the months of January to April in Japan and during the months of June to October in Russia and Australia.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Sexual maturity occurs in both males and females when they are 3.6-5.5 cm in length. Females can be identified for 5-6 months of the year due to the presence of their maturing ovaries. Mature ovaries are characterized by the constant release of eggs as well as their orange color. Females are capable of carrying about 10-25 million eggs. Males are also reproductively mature for about 6 months of the year, with maturity being characterized by the yellowish-brown color of the testes. These sea stars have ectosomatic organs, meaning that the pores for gamete expulsion are in direct contact with the marine environment. As gametes are released, they are replaced by constantly ongoing gametogenesis within the gonads. Spawning usually occurs in the late winter and early spring months, continuing into the summer.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• asexual asexual
• fertilization fertilization
  • external external
• broadcast (group) spawning
• oviparous oviparous

Gametes are released freely into the environment, and offspring develop independently of the parents.

• Parental Investment
• no parental involvement

Lifespan/Longevity

The average lifespan of a sea star is around 10 years, although many sea star species are able to live to about the age of 50. There is no specific information available regarding the lifespan of Northern Pacific sea stars.

Behavior

These sea stars exhibit positive phototactic behavior, moving toward light. In situations where part of the organism is shaded and part is illuminated, it has been seen that the animal moves towards the illuminated area. As they move, the animals exhibit what is known as a “typical advancing posture". This means that the sea star moves with a particular ray of its body in a certain direction and the rest of the organism slowly follows. The adult and juvenile forms of these sea stars both have limited motility. When they do move, they step using their tube feet. However, larval stages are free-swimming and are known to travel using water currents.

• Key Behaviors
• motile motile
• sedentary sedentary

Home Range

There is no home range information available for Northern Pacific sea stars.

Communication and Perception

Northern Pacific sea stars are able to perceive light stimuli and are positively phototactic. As previously mentioned, when four of five arms are shaded, a sea star will move with its illuminated ray forward. All other documented information about the communication and perception abilities of these sea stars regards sensory interactions between larval and adult forms. Larvae are capable of sensing metamorphosis inducing factors expelled by adults via use of neural cells that are held within the adhesive papillae on the external surface of the brachiolar arms.

• Communication Channels
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Northern Pacific sea stars are known to be voracious predators with a varied diet, essentially eating any type of animal that they encounter. Bivalves, such as mussels, scallops and clams compromise the largest part of this species' diet. They are known to pull apart the shell of these organisms with their arms, and then evert their stomachs into the shell cavity to digest their prey. This species also preys on gastropods, crabs, and barnacles. Occasionally, they have been seen exhibiting cannibalistic behavior when food sources are particularly low. This species has also been observed digging out buried prey from under the substrate, and feeding on algae.

• Primary Diet
• carnivore carnivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• mollusks
• aquatic crustaceans
• echinoderms

• Plant Foods
• algae

Predation

Northern Pacific sea stars are not generally preyed upon by other organisms. However, they may occasionally be eaten by Japanese sun stars ( Solaster paxillatus ). In Alaska, king crabs are known to feed on this species, and in laboratory settings, snails in the genus Charonia (tritons) have shown a preference for this species, as opposed to feeding on other marine life.

Ecosystem Roles

Northern Pacific sea stars are an invasive species in some areas and an obligate predator whose presence has a great impact on benthic infauna, including mollusks, crustaceans, echinoderms, and other organisms that are preyed upon by this sea star. This species is known to host the bacterium Colwellia asteriadis , although negative effects on the sea star due to the presence of this microbe have not been described.

Economic Importance for Humans: Positive

There are no known positive economic effects of Asterias amurensis on humans.

Economic Importance for Humans: Negative

The negative economic effects of Northern Pacific sea stars are extensive. In their native Japan, they have devastated the shellfish industry. In Australia, the economic effects of the species are still being fully evaluated, but it is thought that if their spread continues, the soft sediment communities along the coast of Australia may be compromised. It is evident that several fisheries have been negatively impacted – there has been an estimated one billion dollar loss in the industry in Tasmania. Because these fishing industries are important to the economy of the region, several “sea star hunting days” have been organized in which several thousand sea stars have been removed from the coasts. Northern Pacific sea stars are also on the Global Invasive Species Database's list of the 100 Worst Invasive Species.

Conservation Status

This species hs no special conservation status.

Additional Links

Encyclopedia of Life

Contributors

Foram Shah (author), The College of New Jersey, Shikha Surati (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

Byrne, M., M. Morrice, B. Wolf. 1997. Introduction of the Northern Pacific asteroid Asterias amurensis to Tasmania: reproduction and current distribution. Marine Biology , 127(4): 673-685.

Choi, E., H. Kwon, H. Koh, Y. Kim, H. Yang. 2010. Colwellia asteriadis sp. nov., a marine bacterium isolated from the starfish Asterias amurensis. International Journal of Systematic and Evolutionary Microbiology , 60/8: 1952-1957.

McEdward, L., K. Morgan. 2001. Interspecific relationships between egg size and the level of parental investment per offspring in echinoderms. The Biological Bulletin , 200(1): 33-50.

Murabe, N., H. Hatoyama, K. Mieko, H. Kaneko, Y. Nakajima. 2007. Adhesive papillae on the brachiolar arms of brachiolaria larvae in two starfishes, Asterina pectinifera and Asterias amurensis , are sensors for metamorphic inducing factors(s). Development, Growth, and Differentiation , 49(8): 647-656.

Paik, S., H. Park, S. Yi, S. Yun. 2005. Developmental duration and morphology of the sea star Asterias amurensis in Tongyeong, Korea. Ocean Science Journal , 40(3): 65-70.

Ross, D., C. Johnson, C. Hewitt. 2002. Impact of introduced seastars Asterias amurensis on survivorship of juvenile commercial bivalves Fulvia tenuicostata . Marine Ecology Progress Series , 241: 99-112.

Stevens, C. 2012. "ISSG Database: Ecology of Asterias amurensis " (On-line). Global Invasive Species Database. Accessed March 18, 2012 at http://www.issg.org/database/species/ecology.asp?si=82&fr=1&sts=&lang=EN .

Uscian, J. 2006. Alaska SeaLife Center Guide to Marine Life For Visitors, Staff, and all Marine Life Enthusiasts . Seward, Alaska: The Alaska SeaLife Center. Accessed November 26, 2012 at http://ir.library.oregonstate.edu/xmlui/handle/1957/19568 .

Yoshida, M., H. Ohtsuki. 1968. The phototactic behavior of the starfish, Asterias amurensis . The Biological Bulletin , 134: 516-532.

2012. " Asterias amurensis (Japanese seastar)" (On-line). The National Introduced Marine Pest Information System- NIMPIS. Accessed March 18, 2012 at http://adl.brs.gov.au/marinepests/index.cfm?fa=main.spDetailsDB&sp=6000005721#generalInfo .

2012. " Asterias amurensis Feeding and Predators" (On-line). The National Introduced Marine Pest Information System. Accessed March 20, 2012 at http://adl.brs.gov.au/marinepests/index.cfm?fa=main.spDetailsDB&sp=6000005721#feedingPredators .

2012. "Introduced Marine Aquatic Invaders - A Feld Guide" (On-line). Department of Fisheries, Western Australia. Accessed March 20, 2012 at http://www.fish.wa.gov.au/docs/pub/IMPMarine/IMPMarinePage06a.php#03 .

The National System for the Prevention and Management of Marine Pest Incursions. National Control Plan for the Northern Pacific Seastar Asterias amurensis . Australia: Commonwealth of Australia. 2008. Accessed March 20, 2012 at http://www.marinepests.gov.au/__data/assets/pdf_file/0010/952489/Asterias-ncp-08.pdf .

2012. "Ocean Biogeographic Information System" (On-line). OBIS. Accessed March 20, 2012 at http://www.iobis.org/ .