Ophiuroidea Brittle Stars

Despite the relatively common occurrence of luminous echino-derms, only two species of ophiuroid, Ophiopsila califomica and Amphiura filiformis, have been biochemically investigated. It is surprising that the former species luminesces with a photoprotein system, whereas the latter emits light with a luciferin-luciferase system. 

The brittle star Ophiopsila califomica (Fig. 10.1.1) is abundant around Catalina Island, off the coast of Los Angeles. An average-sized specimen weighs about 3-4 g, and has five arms of about 10 cm long, which emit greenish light upon stimulation (Xmax 510 nm). 

Extraction and purification of photoprotein (Shimomura, 1986b). The live animals are chilled to 5°C, and the five arms of each specimen are cut off and dropped into cold 3.5% magnesium acetate solution. After 10 min, the arms are drained from the solution, and stored at 

Step 1. Frozen arms are ground with cold water, and centrifuged. The pellets are further ground with water and centrifuged. The supernatants are combined, saturated with ammonium sulfate, and the precipitate formed is collected by centrifugation. 

Step 2. The pellets are extracted with 10 mM sodium phosphate buffer, pH 6.7, containing 2mM EDTA and 0.2 M NaCl, and chromatographed on a gel-filtration column (Ultragel AcA 54 LKB) using the same pH 6.7 buffer. The photoprotein is eluted slightly before a brownish substance. 

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Class Asteroidea, sea stars, is one of the most widely recognized groups of marine organisms due to their prevalence upon the shoreline and their characteristic shape. Asteroids are top predators in benthic ecosystems, often preying upon bivalves from the phylum Mollusca. The isoprenoid compound mytiloxanthin, for example, has been isolated from both the sea star Asterias rubens and the bivalve Mytilus edulis,119 The class Concentricycloidea was first identified in 1986 and consists of two species in the genus Xyloplax. Class Ophiuroidea, brittle stars, contains the greatest number... 

In addition to Asteroidea and Holothuroidea, the phylum Echinodermata (Greek echinos, spiny derma, skin) comprises the classes Ophiuroidea (brittle stars), Crinoidea (sea lilies and feather stars) and Echinoidea (sea urchins). There is no report of occurrence of steroid or triterpenoid glycosides in sea lilies, feather stars or sea urchins. Brittle stars contain sulfated polyhydroxylated steroids [10-12] and only two sulfated steroidal monoglycosides have been isolated from the brittle star Ophioderma longicaudum [13]. 

The phylum Echinodermaia, which comprises about 6000 living species, is divided into five classes Crinoidea (sea lilies and feather stars), Holoturoidea (sea cucumbers or holothurians), Eebinoidea (sea urchins), Asteroidea (sea stars or starfishes) and Ophiuroidea (brittle stars). 

Sato, D. and Ando, Y. (2002) Distribution of novel nonmethylene-interrupted fatty acids over neutral and polar lipids of ophiuroidea (brittle star)./. Oieo.Sci., 51, 563-567. 

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