Brittle stars

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). 

Fig. 10.1.2 Absorption spectra of the photoprotein of the brittle star Ophiopsila calif omica (solid line) and the spent product of the photoprotein after H2O2-triggered luminescence (dashed line). From Shimomura, 1986b, with permission from the American Society for Photobiology.

This luminous brittle star has been briefly studied recently (Mallefet and Shimomura, 2004, unpublished). The animal contained a high level of coelenterazine luciferase activity (4 x 1012 photons s-1g 1), which is comparable to those in the luminous antho-zoans such as the sea pansy Renilla and sea pen Ptilosarcus (Shimomura and Johnson, 1979b). There is no evidence for the presence of a photoprotein in this brittle star. Thus, the luminescence system of Amphiura filiformis is considered to be a coelenterazine-luciferase system, differing from that of Ophiopsila californica. The luciferase has a molecular weight of 23,000 on the basis of gel filtration on Superdex 200 Prep, and catalyzes the luminescence reaction of coelenterazine in the presence of oxygen the light emission (A.max 475 nm) is optimum at pH 7.2. 

Shimomura, O. (1986b). Bioluminescence of the brittle star Ophiopsila californica. Photochem. Photobiol. 44 671-674. 

Renilla, 147-151 scaleworms, 242-246 Symplectoteutbis, 204-215 Watasenia, 200-205 Bivalvia (Clams), 180, 181 Bolinopsis, 334 Borophryne, 339 Brisinga, 337 Brittle star, 163 Brosnticulus, 339 BSA, 11, 39,164,178... 

Hutchins DA, Teyssie J-L, Boisson F, et al. 1996b. Temperature effects on uptake and retention of contaminant radionuclides and trace metals by the brittle star Ophiothrix fragilis. Mar Environ Res 41(4) 363-378. 

Figure 32.5 Plutonium-239+240 in environmental samples at Thule, Greenland, between 1970 and 1984, after a military accident in 1968. (Modified from Aarkrog, A. 1990. Environmental radiation and radiation releases. Inter. Jour. Radiation Biol. 57 619-631.) Within the contaminated area of 3.2 x 10 m , the fresh weight biomass of shrimps was 0.11 x 10 kg of brittle star echinoderms 0.06 x 10 kg and of clam (Macoma balthica) soft parts 0.32 x 10 kg. The seawater mass was 3 x 10 kg, and the dry weight of the upper 15-cm sediment layer was 3 x 10" kg. 

No sterols with sulfate groups in the sidechain have been isolated from sponges to date. This contrasts with echinoderms. Many of the sterol sulfates isolated from echinoderms, especially from ophiuroids (brittle stars) contain sulfate groups in the sidechain [2]. 

The phylum Echinodermata comprises about 7000 living species [177]. Echinoderm means spiny-skinned and these organisms are characterised by the tube feet, which they use to move about. These have suction discs on the ends, which operate by an internal bulb pumping water in and out of the foot, causing expansion and contraction. The phylum is sub-divided into five classes the asteroids (sea stars), the holothurians (sea cucumbers), the crinoids (sea lilies), the echinoids (sea urchins) and the ophiuroids (brittle stars) [178]. As stated in the introduction to this review, sulfated sterols and saponins, which comprise the majority of echinoderm metabolites containing sulfur, are not included here. 

There is a lesson to be learned here if a fish species responds in a certain way to a feature of the environment, the range of its response may be limited according to the environment where it spent its early life. The food of cod on the Faroe Bank consists of organisms that live on or near the sea bottom, such as crustaceans, brittle stars and other echinoderms, and small fish. It is not known how the food supply varies through a whole year, but in our limited experience (Love et al., 1974) we found that the ranges of water contents were almost identical in fish caught on 6 June 1966 and on 13 September 1968. The dates of similar voyages in other years lay between these two extremes. 

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]. 

Starfish (sea stars), sea cucumbers, brittle stars, sand dollars, and sea urchins are members of a group of spiny-skinned animals known as echinoderms. All echinoderms are radially symmetrical, and most have five or more arms extending from a central disk, as shown in Figure 4.5. Their bodies are supported by internal skeletons which are solid in some species and jointed in others. Most echinoderms are designed so that their mouths are located on the ventral sides and their anuses on the dorsal surface. Depending on the species, the nutritional strategies of echinoderms vary from carnivores to detritivores or herbivores. 

Ascidians and other soft-bodied organisms (e.g., alcyonaceans, anemones, annelids, some brittle stars) are more difficult to preserve. These organisms are... 

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). 

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