Flat shield-shaped hedgehog [1] ( lat. Echinarachnius parma ) is the largest of the flat sea urchins . The diameter of its shell reaches 8-10 cm. The edges of the disc are thin; a distinctive figure with five rays (or petals) formed by rows of ambulacral canals is easily distinguishable on the back. Branching grooves converging in the center of the carapace at the mouth opening are noticeable on the ventral side. The needle cover looks velvety; does not serve for protection. Pedicellaria are one of the smallest in sea urchins. The color of the shell is brown to lilac, the needles are greenish.
| Flat shield-shaped hedgehog |
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| Scientific classification |
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| No rank : | Bilateral symmetrical |
| Overclass : | Cryptosyringida |
| Subclass : | Real sea urchins |
| Infraclass : | Wrong sea urchins |
| View: | Flat shield-shaped hedgehog |
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| International scientific name |
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Echinarachnius parma Lamarck , 1816 |
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Echinarachnius parma is widely distributed in the waters of the northern hemisphere. It is found in the Pacific Ocean from the Bering Sea to Japan and from Alaska to British Columbia ; in the Atlantic Ocean it is common along the east coast of North America to New Jersey .
It lives everywhere from the coastal zone to a depth of 150 m, although it most often occurs at a depth of 6-12 m. It prefers sandy soils, into which it is completely buried with needles in about 10 minutes. In places of cohabitation with other flat hedgehogs, Echinarachnius parma buries most deeply, up to 150 mm. The number of flat hedgehogs in the coastal waters of the Far Eastern seas is so great that in some areas they literally cover the sandy bottom of a continuous "bridge".
It feeds on detritus contained in the bottom layers of water. Detritus settling on the surface of the hedgehog with the help of currents created by cilia on needles is transmitted from the dorsal side to the abdominal side and further along the grooves to the mouth opening. Unicellular algae , small copepods, and rhizopods can also be used as food.
Form spawning clusters. Spawn from late July - early August to the first half of September. Having a high abundance, flat hedgehogs (mainly 1-3 cm in diameter) are an important food item for many species of flounders and Kamchatka crab . [2]
Echinarachnius parma eggs were used to study the mitosis process.
