Northern pacific seastar, Japanese common starfish
Asterias amurensis, also known as the Northern Pacific seastar and Japanese common starfish, is a seastar found in shallow seas and estuaries, native to the coasts of northern China, Korea, far eastern Russia, Japan, Alaska, the Aleutian Islands and British Columbia in Canada. Two forms are recognised: the nominate and forma robusta from the Strait of Tartary. It mostly preys on large bivalve molluscs, and it is mostly preyed on by other species of starfish. Population booms in Japan can affect the harvest of mariculture operations and are costly to combat.
This species has been introduced to oceanic areas of southern Australia, and is an invasive species there causing damage to native species, especially in Tasmania.
It is known in English vernacular as the northern Pacific seastar, flatbottom seastar, Japanese seastar, Japanese starfish, north Pacific seastar, purple-orange seastar and Japanese common starfish.
Ca
CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
Mo
MolluscivoreA molluscivore is a carnivorous animal that specializes in feeding on molluscs such as gastropods, bivalves, brachiopods, and cephalopods. Known mo...
Cr
CrawlingOv
OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
Po
PolygynandryPolygynandry is a mating system in which both males and females have multiple mating partners during a breeding season.
No
Not a migrantAnimals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
A
starts withIt can grow up to 50 cm in diameter, although this is exceptional and the arms usually grow to 16.1 cm, with the ratio between the length of the arm and the radius of its disc ranging from 3.6:1 to 5.9:1. It has five arms and a small central disk. It can be distinguished from similar species by the distinctive upturned tips of its arms. The underside is completely yellow. It shows a wide range of colours on its dorsal side: orange to yellow, sometimes red and purple. The arms are unevenly covered with small, jagged-edged spines, which line the groove in which the tube feet lie, and join up at the mouth in a fan-like shape.
They prefer a slightly cold environment of about 7–10 °C. The optimum temperature is also said to be 9–13 °C. It has a temperature tolerance of 0–25 °C according to one source, or 5–20 °C according to another. It is able to tolerate a large range of salinities, from 18.7–41.0 ppt., and can survive in estuaries. It has been found at a maximum depth of 220m.
It prefers shallow, sheltered areas. Adults are found on a wide range of substrates, including kelp forests, mud, sand, pebbles, rock, flotsam, nets and artificial substrates. It is not found in areas of high wave action or on reefs.
These seastars move towards light. The adults are mobile with a top speed of 20 cm/minute. Tagged seastars in Tokyo Bay, Japan, logged maximum travel distances 2.5 km in 32 days (78m/day) in the west of the bay, and 8.1 km in 129 days (62.8m/day) at the east. The population goes through boom-and-bust cycles in Japan, where it can swarm on occasions; during swarms the adults can float on the sea surface due to air retained within the body cavity. The population is mixed, with different age groups found intermingled. The animals can survive at least four years in the wild in Japan, but it is estimated that most live to two to three years. If the seastar is ripped apart, each arm can grow into a new animal (fissiparity) if a part of the main disk is attached. This is not entirely uncommon.
The population has not been assessed by the IUCN.
