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''Leptasterias hexactis'' is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...
in the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Asteriidae The Asteriidae are a diverse family of Asteroidea (sea stars) in the order Forcipulatida. It is one of three families in the order Forcipulatida. The oldest unambiguous fossils of the family date to the Late Cretaceous. Genera The World Regi ...
, commonly known as the six-rayed star. It is found in the intertidal zone of the western seaboard of the United States. It is a
predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
and is unusual among starfish in that it
broods Broods are a musical duo from Nelson, New Zealand, composed of Georgia Josiena Nott on lead vocals, with older brother and multi-instrumentalist Caleb Allan Joseph Nott on production and backing vocals. They released the single "Bridges (Broo ...
its eggs and young.


Taxonomy

''Leptasterias hexactis'' forms part of a
species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
. Over the years, various authorities have discussed the phylogenetic relationships of ''L. epichlora'', ''L. aequalis'' and ''L. hexactis'', all species of ''Leptasterias'' found in the north west Pacific Ocean. The authorities were Bush (1918), Fisher (1930), Chia (1966), Kwast (1990) and Stickle (1992). More recent morphological and behavioural studies have resulted, according to the World Register of Marine Species (WoRMS) in the retention of a single species, ''L. hexactis'', with the other two being considered synonyms. WoRMS now recognizes three subspecies, ''L. hexactis hexactis'' (Stimpson, 1862) ''L. hexactis occidentalis'' Djakonov, 1938 and ''L. hexactis vancouveri'' (Perrier, 1875).


Description

''Leptasterias hexactis'' is a rather squat starfish growing to a diameter of about with 6 short, broad arms. These are about as long as the disc is wide. The colour of the aboral (upper) surface varies, usually being a plain or mottled dark grey, brown or olive green colour or occasionally brick red. It is densely clad with short,
mushroom A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the n ...
-shaped spines, interspersed among which are
pedicellaria A pedicellaria (: 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 Echinoidea). ...
e (small, two-jawed pincers). The central row of spines on each arm is distinctive. The oral (under) surface is a pale colour with parallel rows of
tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...
with suckers extending along the arms.''Leptasterias hexactis''
Race Rocks. Retrieved 2012-02-04.

Walla Walla University. Retrieved 2012-02-04.
In California ''Leptasterias hexactis'' might be confused with '' Leptasterias pusilla'' but that species is smaller, is usually a pale grey-brown or reddish colour and has elongated, thinner arms and sharp spines.


Distribution and habitat

''Leptasterias hexactis'' occurs in the
intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...
of the north east Pacific Ocean with a range extending from the
San Juan Islands The San Juan Islands is an archipelago in the Pacific Northwest of the United States between the U.S. state of Washington and Vancouver Island, British Columbia, Canada. The San Juan Islands are part of Washington state, and form the core of ...
in Washington to the
Channel Islands of California The Channel Islands () are an eight-island archipelago located within the Southern California Bight in the Pacific Ocean, off the coast of California. They define the Santa Barbara Channel between the islands and the California mainland. The ...
. It favours exposed locations battered by surf and may be found at low tide under boulders and hiding among seaweed on the lower shore. Its tube feet are very adhesive and it clings securely to rocks.


Biology and ecology

''Leptasterias hexactis'' is a carnivore and is able to attack and capture surprisingly large
prey Predation is a biological interaction in which 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 ki ...
items with high nutritional content. The diet includes
sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...
s,
snails A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...
,
limpet Limpets are a group of aquatic snails with a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. This general category of conical shell is known as "patelliform" (dish-shaped). Existing within the class Gastropoda, ...
s,
mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...
s,
chiton Chitons () are marine molluscs of varying size in the class Polyplacophora ( ), formerly known as Amphineura. About 940 extant and 430 fossil species are recognized. They are also sometimes known as sea cradles or coat-of-mail shells or suck ...
s and
barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...
s as well as
carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...
. Over much of its range it competes with the larger ''
Pisaster ochraceus ''Pisaster ochraceus'', generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, ''P. ochraceus'' is considered an important ind ...
'' (ochre starfish) for food. ''Leptasterias hexactis'' is
dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...
with individuals being either male or female. In
Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...
, reproduction takes place between November and April. The eggs have yolks and between 50 and 1500 are laid, depending on the size of the female. They are fertilized by sperm that has been discharged into the
water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...
by males. The female then holds the eggs with her tube feet in a mass near her mouth, arching her body up as she broods them. She is unable to eat at this time and clings to the rock as best she can with the remaining tube feet though it may only be the tips of the arms that are available to hold her in place. While the eggs are being brooded, she tends to them and keeps them clean. They are lecithotrophic and consume the yolks of their eggs as they develop. After about 40 days the eggs begin to hatch into juveniles, miniature starfish with truncated limbs. These continue to be brooded by the mother for a few weeks before setting off independently on their own. If breeding has taken place in an
aquarium An aquarium (: aquariums or aquaria) is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...
, they can be seen crawling over the glass, and sometimes floating on the surface of the water as
neuston Neuston, also called pleuston, are organisms that live at the surface of a body of water, such as an ocean, estuary, lake, river, wetland or pond. Neuston can live on top of the water surface or submersed just below the water surface. In additio ...
. They will become mature in about 2 years.


References

{{Taxonbar, from=Q2326273 hexactis Echinoderms described in 1862