Geographic Range
Red sea stars are found in the Antarctic region, most prevalently in the waters surrounding
the Antarctic continent and islands.
- Biogeographic Regions
- antarctica
Habitat
Red sea stars are unique amongst sea stars in their ability to withstand the cold
environment of the Antarctic region (averaging -1.8 degrees Celsius). They live at
depths of 0-914 meters and are found most often in shallower waters (14 m).
- Habitat Regions
- polar
- saltwater or marine
- Other Habitat Features
- intertidal or littoral
Physical Description
Like most other sea stars, red sea stars have a central disk with five arms radiating
outward. These sea stars are typically a dark shade of red dorsally and a light shade
of pink ventrally. Red sea stars have a rather large lightly-colored, pink madreporite
dorsal plate which is an opening to its water vascular system. Red sea stars grow
1-2 grams per year and range from 2-11 centimeters in diameter (average 6-8 centimeters).
There are no externally visible physical features distinguishing males and females
of this species.
- Other Physical Features
- ectothermic
- radial symmetry
- Sexual Dimorphism
- sexes alike
Development
Fertilized eggs develop into planktotrophic larvae, allowing members of the species
to disperse. Red sea stars have a rather slow rate of growth, typically gaining 1-2
grams per year.
Reproduction
As with most echinoderms, red sea stars reproduce via broadcast spawning and external
fertilization.
- Mating System
- polygynandrous (promiscuous)
This species reaches sexual maturity at 3-6 years. Reproduction occurs once a year
during the winter season, between the months of April and June, with peak spawning
occurring during June. Scientists are able to determine when the sea stars are spawning
by a decrease in the size of their gonads (sexual organs). Fertilization occurs from
June to September. This sea star is known for releasing a large number of oocytes
that, once fertilized, then mature into larva. The ova of this sea star typically
take 18 months to mature.
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- broadcast (group) spawning
There is currently no evidence that red sea stars exhibit any parental investment.
- Parental Investment
- no parental involvement
Lifespan/Longevity
The lifespan of this sea star is not currently known, although there is evidence that
they can live up to 100 years.
Behavior
This sea star is typically sedentary and often found attached to rocks in the water.
They move significant distances only in times of extreme starvation or distress. Red
sea stars exhibit "arm fencing," a behavior in which they compete for dominance and
eating rights.
Home Range
These sea stars are found at an average density of 2.7 per m^2.
Communication and Perception
Red sea stars detect their environments with using chemoreceptors, which they rely
on to recognize potential prey. These chemoreceptors also have the ability to elicit
an alarm response which tells the sea star to move away from the stimulus quickly.
There is both interspecific and intraspecific communication using chemoreceptors.
- Communication Channels
- chemical
- Perception Channels
- chemical
Food Habits
Red sea stars are omnivorous, feeding on a variety of species such as bivalves (e.g.
Limatula hodgsoni
and
Laternula elliptica
), sponges (e.g.
Rossella racovitzae
,
Rossella nuda
,
Scolymastra joubini
,
Tetilla leptoderma
, and
Homaxinella balfourensis
), hydroids (e.g.
Halecium arboreum
), other echinoderms (e.g.
Acodontaster conspicuus
and
Sterechinus neumayeri
), and isopods (
Glyptonotus antarcticus
), as well as red algae, diatoms and seal feces. Due to the harsh environment of the
Antarctic, red sea stars must be capable of surviving for long periods (potentially
an entire winter) with no food. This sea star does not exhibit cannibalism; however,
it is quite common for it to prey on other sea stars, particularly
Acodontaster conspicuus
. It is not yet known if red sea stars are more likely to search for food in groups
or individually.
- Primary Diet
-
carnivore
- eats non-insect arthropods
- molluscivore
- eats other marine invertebrates
- scavenger
-
herbivore
- algivore
- omnivore
- Animal Foods
- carrion
- mollusks
- aquatic crustaceans
- echinoderms
- cnidarians
- Plant Foods
- algae
- phytoplankton
- Other Foods
- detritus
- dung
Predation
Red sea starts tend to form larger clusters when a potential predator is sensed, as
if to ward off any predators by seeming to be one large entity. This is unique because
echinoderms are otherwise only known to form groups or clusters in order to better
capture food or to increase the likelihood of fertilization. Known predators of red
sea stars include sea anemones, sea stars, and jellyfish.
Ecosystem Roles
Red sea stars eat the larvae of several sympatric sea stars that prey on various sponge
communities, sometimes so heavily as to negatively impact the sponges' populations.
Therefore, these sea stars may help maintain sponge populations.
- Ecosystem Impact
- keystone species
Economic Importance for Humans: Positive
The Antarctic conditions required by red sea stars mean that they are usually not
kept in captivity and so they have little economic importance for humans.
Economic Importance for Humans: Negative
There are no known negative economic impacts of this species.
Conservation Status
Despite the harsh conditions within the Antarctic, red sea star populations appear
to be thriving and the species has no special conservation status.
Additional Links
Contributors
Natalie Ramirez (author), Sierra College, Jeremy Wright (editor), University of Michigan-Ann Arbor.
- Antarctica
-
lives on Antarctica, the southernmost continent which sits astride the southern pole.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- polar
-
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- benthic
-
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- intertidal or littoral
-
the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- radial symmetry
-
a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- external fertilization
-
fertilization takes place outside the female's body
- sedentary
-
remains in the same area
- social
-
associates with others of its species; forms social groups.
- chemical
-
uses smells or other chemicals to communicate
- chemical
-
uses smells or other chemicals to communicate
- carrion
-
flesh of dead animals.
- phytoplankton
-
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
- detritus
-
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
- keystone species
-
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
- carnivore
-
an animal that mainly eats meat
- molluscivore
-
eats mollusks, members of Phylum Mollusca
- scavenger
-
an animal that mainly eats dead animals
- herbivore
-
An animal that eats mainly plants or parts of plants.
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
References
Brueggeman, P. 1998. "Cnidaria – Scyphozoa: jellyfish UNDERWATER FIELD GUIDE TO ROSS ISLAND & MCMURDO SOUND, ANTARCTICA" (On-line pdf). Accessed August 31, 2012 at http://www.peterbrueggeman.com/nsf/fguide/cnidaria--scyphozoa.pdf .
Janosik, A., K. Halanych. 2010. Unrecognized Antarctic Biodiversity: A Case Study of the Genus Odontaster (Odontasteridae; Asteroidea). Integrative & Comparative Biology , 50/6: 981-992. Accessed March 11, 2012 at http://icb.oxfordjournals.org/content/50/6/981.full .
Kidawa, A. 2009. Food Selection of the Antarctic Sea Star Odontaster validus : Laboratory Experiments With Food Quality And Size. Polish Journal of Ecology , 57/1: 139-147. Accessed March 11, 2012 at http://www.pol.j.ecol.cbe-pan.pl/article/ar57_1_11.pdf .
McClintock, J., R. Angus, C. Ho, C. Amsler, B. Baker. 2008. A laboratory study of behavioral interactions of the Antarctic keystone sea star Odontaster validus with three sympatric predatory sea stars. Marine Biology Journals , 154: 1077-1084. Accessed March 20, 2012 at http://www.springerlink.com/content/jj25k262m1647w86/ .
Pearse, J. 1963. The Reproductive Cycle of the Antarctic Asteroid, Odontaster validus Koehler. XVI International Congress of Zoology, 1: 111. Accessed March 28, 2012 at http://books.google.co.uk/books?id=o0IrAAAAYAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false .
Stanwell-Smith, D., A. Clarke. 1998. Seasonality of reproduction in the cushion star Odontaster validus at Signy Island, Antarctica. Marine Biology Journals , 131/3: 479-487. Accessed March 20, 2012 at http://www.springerlink.com/content/b06nal3juljp73eu/ .
2012. "Encyclopedia of Life" (On-line). Odontaster validus. Accessed August 31, 2012 at http://eol.org/pages/4704670/details .
Belgian Biodiversity platform. 2012. "Odontaster validus Koehler, 1906" (On-line). SCAR Antarctic Field Guides. Accessed March 11, 2012 at http://afg.biodiversity.aq/species/21-odontaster-validus .