''Solaster dawsoni'', the morning sun star, is a
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of
starfish in the family
Solasteridae
The Solasteridae are a family of sea stars.
Genera
The following genera are listed in the World Register of Marine Species:
* '' Crossaster'' Müller and Troschel, 1840
* '' Heterozonias'' Fisher, 1910
* '' Laetmaster'' Fisher, 1908
* '' Lop ...
. It is found on either side of the northern Pacific Ocean. It has two subspecies:
*''S. d. arcticus'' Verrill, 1914
*''S. d. dawsoni'' Verrill, 1880
Description
The morning sun star has a wide disc and 8 to 13 (usually 11 or 12) long, tapering arms, often with turned-up tips. The upper or aboral surface is smooth, and its colour is usually red, orange, grey, or pale brown, sometimes with paler patches. It grows to a width of about .
Distribution
The morning sun star occurs in the northern Pacific Ocean at depths to about . Its range extends from Japan, China, and Siberia to the coasts of North America as far south as California.
[ It is often found in rocky habitats, but can also inhabit other types of seabed.][
]
Behaviour
The morning sun star is a predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
, feeding mostly on other starfish. It is feared by other stars which move away as fast as they can if touched by a morning sun star. In British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
, about half of its diet consists of leather stars (''Dermasterias imbricata''), which move too slowly to evade it. Other sea stars such as the velcro star (''Stylasterias forreri'') and the rainbow star (''Orthasterias koehleri'') fight back at their attacker. They have numerous tiny pincer-like organs called pedicellaria
A pedicellaria (plural: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echi ...
e and coil their arms around the morning sun star, nipping it with these. It recoils and its prey often manages to escape. Another sometimes successful defence strategy is used by the slime star (''Pteraster tesselatus'') which inflates its aboral surface making it difficult for the attacker to get a grip on it and at the same time exudes copious amounts of noxious mucus
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
.[ Even the often larger sunflower seastar (''Pycnopodia helianthoides'') retreats when touched by a morning sun star.][ If grabbed, the sunflower star may leave one of its arms behind, a process called ]autotomy
Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude ...
, sacrificing this limb to make its escape. The morning sun is also a cannibal
Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, bo ...
, feeding on other individuals of its own species, and also feeds on sea cucumbers and diamondback nudibranchs.[
The morning sun star breeds between March and June. The gonads release eggs and sperm which rise to the surface where the eggs are fertilised. They have large yolks and the developing larvae rely on this and do not feed. They can swim and they drift with the currents as part of the ]zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
. They later sink to the seabed and undergo metamorphosis into juvenile starfish.[
This species has been subject to the Sea star wasting disease since 2013.]
References
{{Taxonbar, from=Q2008443
dawsoni
Fauna of the Pacific Ocean
Animals described in 1880
Taxa named by Addison Emery Verrill