Ciliated grooves (cribriform organs) between the marginals, which continue across the oral surface as grooves between transverse rows of plates edged with spinelets. The aboral surface has paxillae, and its marginals are moderately solid. Pointed tube feet. No intestine.
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Ctenodiscus crispatus is a small sea star, with a soft, slightly inflated aboral surface bearing a characteristic elevated cone in the centre (epiproctal cone). Five short triangular arms (exceptionally four or six) extend up to 5.4 cm long. The aboral side is grey to yellow-white, and the oral side is lighter with tinges of pale orange. The ratio of arm to disc is from 1.7 to 2.7. The paxillae of the aboral surface are low, with few to many short skin-covered spinelets. Each arm has a definite vertical side formed by 11 to 20 marginals. There is a single conical spine at the upper ends of the superomarginals and inferomarginals. Deep grooves between the marginals and across the oral intermediates are bordered on both sides by flat spinelets that extend over the furrow. The adambulacrals have an oblique series of 3 to 5 sharp furrow spines. The tube feet are large and pointed. The mouth plates are prominent, with 7 marginal spines; the apical spine is the largest.
No other species has an elevated cone in the centre of the disc.
Ctenodiscus crispatus is a non-selective deposit feeder. Tube feet around the mouth shovel sediment into the stomach, which digests the organic material, much of it bacteria on the surface of sand grains. Fragments of bivalves, small crustaceans and worm tubes have been found in the stomachs of collected specimens. C. crispatus regularly extrudes indigestible material. It establishes a temporary burrow in soft sediment and uses its extensible epiproctal cone to maintain a connection with the water above. Currents created by ciliated grooves called cribriform organs draw sea water into the burrow for respiration. Any incidental food particles are trapped by a cleansing mucus and ingested. Cells lining these grooves have complex surfaces (microvilli) that can absorb amino acids directly from sea water. This type of nutrition may be important for surface cells that are not supplied by an internal blood system.
In the Gulf of Maine, there is no seasonal variation in gonad size, suggesting continuous reproduction. The full range of eggs can be found in the gonad at anyone time, but large mature eggs are most numerous in late autumn and mid winter in a Norwegian fiord. As with some other invertebrates, spawning seems to be related to phytoplankton production. The large, yolky egg implies direct development, but this is not known for certain. The Mud Star attains full size in three years. The species is extremely variable genetically.
Circumpolar to New England on the Atlantic coast, and to Panama and Japan in the Pacific, at depths of 10 to 1890 metres. Found on soft mud and rock, and in the Arctic, on rock or sand. Common in this region (the area from Glacier Bay to Puget Sound to a depth to 200 metres).
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
18/11/2019 6:51:52 AM]
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