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
Despite the harsh conditions within the Antarctic, red sea star populations appear to be thriving and the species has no special conservation status.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
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.
There are no known negative economic impacts of this species.
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.
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
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, Craniella 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.
Animal Foods: carrion ; mollusks; aquatic crustaceans; echinoderms; cnidarians
Plant Foods: algae; phytoplankton
Other Foods: detritus ; dung
Primary Diet: carnivore (Eats non-insect arthropods, Molluscivore , Eats other marine invertebrates, Scavenger ); herbivore (Algivore); omnivore
Red sea stars are found in the Antarctic region, most prevalently in the waters surrounding the Antarctic continent and islands.
Biogeographic Regions: antarctica (Native )
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).
Range depth: 0 to 914 m.
Habitat Regions: polar ; saltwater or marine
Aquatic Biomes: benthic ; coastal
Other Habitat Features: intertidal or littoral
The lifespan of this sea star is not currently known, although there is evidence that they can live up to 100 years.
Range lifespan
Status: wild: 100 (high) hours.
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.
Range length: 2 to 11 cm.
Average length: 7 cm.
Other Physical Features: ectothermic ; radial symmetry
Sexual Dimorphism: sexes alike
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.
Known Predators:
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.
Breeding interval: Red sea stars breed once yearly.
Breeding season: April to June
Range age at sexual or reproductive maturity (female): 3 to 6 years.
Range age at sexual or reproductive maturity (male): 3 to 6 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning
There is currently no evidence that red sea stars exhibit any parental investment.
Parental Investment: no parental involvement
Odontaster validus is a species of sea star in the family Odontasteridae. Its range includes the Southern Ocean and the seas around the mainland and islands of Antarctica.
Odontaster validus can grow to about 10 cm (4 in) in diameter. The disc is broad, thick and cushion-like, creased by interambulacral grooves. There is a large madreporite near the centre and the surface is covered in small granulations organised in radial rows. The five short arms are wide at the base tapering sharply and the tip is often raised off the substrate showing the pale coloured tube feet beneath. The colour of the upper or aboral surface is plain red while the underside is pink.[1]
Odontaster validus is the most common sea star found in Antarctica. Its range includes the Antarctic Peninsula, the South Shetland Islands, the South Orkney Islands, South Georgia and the South Sandwich Islands, the Shag Rocks, the Prince Edward Islands and Bouvet Island. It is found at depths down to 900 metres.[2]
Odontaster validus is an omnivorous scavenger and consumes anything it finds including carrion, detritus, the faeces of seals, red algae, bivalve shells, sponges, hydroids, other sea star, sea urchins, isopods, bryozoans, amphipods, crustacean larvae, ostracods, shrimps and diatoms.[2] They have been observed aggregating on banks of mussels that have been exposed and damaged and on injured sea star, Acodontaster conspicuus.[3] In turn, they are preyed upon by sea anemones and other species of sea star.[2] It is an ecologically important species because of its consumption of benthic larvae and the control it exerts on the sea star Acodontaster conspicuus and the nudibranch Doris spp. which themselves tend to limit the growth of sponges that tend to dominate the seabed.[4]
Odontaster validus takes 3 to 6 years to reach maturity but may live for 100 years.[2] This is a consequence of the animal being cold-blooded, the harsh environmental conditions in which it lives and the low metabolic rate that ensues.[2] In McMurdo Sound, where it has been extensively studied, the water temperature is about −1.8 °C (28.8 °F).[5] The initiation of oogenesis occurs from August to February and the eggs take about 18 months to mature. Spawning takes place between May and September and may be linked to seasonal changes in light levels, sunrise taking place in McMurdo Sound in August.[5] The larval development is also slow with the first, bipinnaria, stage lasting 2 months. The larvae remain near the seabed during this time but become pelagic for up to 6 months as brachiolaria larvae which allows them to disperse widely. They then return to the seabed, undergo metamorphosis and develop into juvenile sea star.[2]
Odontaster validus does not attack members of its own species but can attack sea star of other species. This seems to be due to chemoreceptors which can identify conspecifics by their odour.[6] Sea star often converge on food sources and a study was undertaken to examine how they do this. It was found that food-deprived individual Odontaster validus could distinguish between the odours emitted by satiated and by starved sea star of the same species. They were strongly attracted to the former and took little notice of the latter.[6]
Odontaster validus is much less sensitive to higher water temperatures than the other Antarctic marine species on which it feeds which mostly find temperatures above 3 °C lethal. Even when not killed at higher temperatures, many organisms cease to feed, may remain immobile or fail to reproduce and others started metabolising anaerobically.[7] A study was undertaken to examine the implications of this for the Antarctic marine environment if water temperatures rise as a result of global warming.[7]
Another research study examined the parameters required for successful fertilisation of the eggs of Odontaster validus compared to similar temperate water sea stars. It was found that a density of sperm of 105 sperm per millilitre was sufficient to cause a high proportion of eggs to be fertilised and that this was at least ten times the density required by comparable species in less harsh environments. The sperm still retained a minimal fertilisation ability after 24 hours but had a narrow tolerance to variations in water temperature.[8]
Odontaster validus is a species of sea star in the family Odontasteridae. Its range includes the Southern Ocean and the seas around the mainland and islands of Antarctica.