seastar Acodontaster conspicuus

Acodontaster conspicuus is found throughout Antarctica and the Antarctic Peninsula, South Shetland Islands, South Orkney Islands, South Sandwich Islands, and South Georgia Island between 0 and 761+ meters depth [3,5,6,7]. A. conspicuus has been collected at sizes up to fourteen centimeters in radius from its center to the tip of an arm [4,6].

The color of Acodontaster conspicuus (shown on the right compared to A. hodgsoni on the left) has been recorded as pink, orange, pale orange, brown, and brownish yellow and it may be yellowish towards the edges [4,6]. A. conspicuus has a flattened disc with arms wide at their base and narrowing quickly with a thin edge [6].

One way to distinguish Acodontaster conspicuus from the other Ross Sea Acodontaster species is by the presence of pincer-like pedicellariae on the underside of A. conspicuus [4].


A preserved specimen of Acodontaster conspicuus shows the pincer-like pedicellariae with greater clarity [4].

Pedicellaria keep the seastar's body surface clear of encrusting organisms by pinching or cutting their settling larvae.

Showing an Acodontaster sp. here, A. conspicuus is a predator of the sponges Homaxinella balfourensis, Rossella racovitzae, Anoxycalyx (Scolymastra) joubini (shown here), Tetilla leptoderma, Haliclona dancoi, Mycale (Oxymycale) acerata, and Kirkpatrickia variolosa [1,2]. Observations suggest that a single A. conspicuus does not stay long on the sponge Anoxycalyx (Scolymastra) joubini but several accumulate, do not leave, and consume enough of the sponge to kill it [2]. In this image, see the isopod standing alongside Acodontaster sp. Some isopods shelter in sponges so it's possible that this isopod is inspecting a predatory visitor dining on its home.

At left is a gang attack on an Acodontaster sp. by the predatory seastar Odontaster validus. Predators of A. conspicuus include the seastar O. validus (shown here), the nemertean proboscis worm Parborlasia corrugatus (in foreground), and the anemone Urticinopsis antarcticus [2,3]. A. conspicuus would reach population densities destroying the sponge community if not kept in check by O. validus which preys upon the larvae, young and adult A. conspicuus [2]. A single O. validus climbs up onto an A. conspicuus armray, everts its stomach, and digests a hole into it. An attack by a single O. validus isn't fatal but nearby O. validus probably respond to the release of A. conspicuus coelomic fluid and join the attack [2].

Showing an Acodontaster sp. here, a gang attack eventually slows the larger Acodontaster conspicuus seastar's movement, more Odontaster validus join the attack, and the large nemertean proboscis worm Parborlasia corrugatus joins in as well. A. conspicuus seastars can become completely buried under high piles of attacking O. validus seastars and P. corrugatus worms [2].

1: Science 245:1484-1486, 1989; 2: Ecological Monographs 44(1):105-128, 1974; 3: Adaptations within Antarctic Ecosystems : Proceedings of the Third SCAR Symposium on Antarctic Biology. George A. Llano, ed. Washington : Smithsonian Institution ; Houston, Tex. : distributed by Gulf Pub. Co., 1977. pp.293-326; 4: The Fauna of the Ross Sea, Part 3, Asteroidea. HES Clark. New Zealand Department of Scientific and Industrial Research Bulletin 151, New Zealand Oceanographic Institute Memoir 21, 1963; 5: Polar Biology 20(4):229-247, 1998; 6: Equinodermos Antarticos. II. Asteroideos. 5. Asteroideos de la Extremidad Norte de la Peninsula Antartica. I Bernasconi. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" e Instituto Nacional de Investigacion de las Ciencias Naturales. Zoologia (aka Ciencias Zoologicas) 9(10):211-281 and plates, 1970; 7: U.S. National Museum of Natural History, Dept of Zoology, Invertebrate Zoology, Invertebrate Zoology Collections database http://goode.si.edu/webnew/pages/nmnh/iz/Query.php

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