Sea cucumbers

Other Lethal Agents. There are a number of substances, many found in nature, which are known to be more toxic than nerve agents (6). None has been weaponized. Examples of these toxic natural products include shellfish poison, isolated from toxic clams puffer fish poison, isolated from the viscera of the puffer fish the active principle of curare "heart poisons" of the digitaUs type the active principle of the sea cucumber active principles of snake venom and the protein ricin, obtained from castor beans (See Castor oil). 

Phylum Echinodermata Sea lilies, seastars, sea urchins, sand dollars, sea cucumbers... 

Coelenterates and Echinoderms. In the phylla Coelenterata and Echinodermata approximately 90 species have been investigated for toxicity (see Tables II and IH). Only 20 or so have been extensively studied (e.g., sea anemones, sea cucumber, and jellyfish). Even so, while relatively complete studies have been made on isolation, characterization, and elucidation of mechanisms of action, in no one species have all of the toxins present been identified. Thousands of species have not been subjected to even the most cursory examination. 

Sea cucumbers (Holothurioidea) contain highly toxic saponins which presumably play a role in protection since the relatively unprotected bodies of these species make them particularly vulnerable to predation. When "attacked", a sea cucumber expels Cuverian glands whose projections elongate and enmesh an assailant while, at the same time, exuding ichthyotoxic saponins to discourage further attacks. Some 30 species of sea cucumbers contain saponins which are highly toxic to other marine creatures as well as fish. 

Goad (40) and others have extensively reviewed coelenterate and echinoderm sterols including the saponins found in starfish and sea cucumbers. Cholesterol is a common sterol in most families, except for gorgonians and zoanthids some soft corals contain polyhydroxylated sterols. The amount of variation associated with phylogeny is illustrate in the echinoderms by the fact that crinoids, ophuiroids, and echinoids contain A 5 sterols while holothuriodeans and asteroids contain A 7 sterols. Some classes contain uniquely structured sterols. 

There has been considerable discussion regarding the mode of action of the sea cucumber and starfish saponins. Both the triterpene and steroidal glycosides inhibit both Na/K ATPase and Ca/Mg ATPase 06) possibly as a result of their aglycone structures. However, their detergent properties cause membrane disruption which will influence the activity of membrane-bound enzymes such as the ATPases. In investigating the actions of saponins on multilamellar liposomes, it was found that cholesterol serves as the binding site for such saponins and that cholesterol-free lip-somes are not lysed by saponins 107). 

Many of the toxins obtained from coelenterates and echinoderms, because of their hemolytic or cytotoxic actions, are assumed to have a general disruptive action on cell membranes. However, since many of these toxins are capable of forming pores or channels in the plasma membrane of cells, their cytolytic actions may be a result of this highly selective action. On the other hand, the saponins from starfish and sea cucumbers have a direct lytic action as a result of their detergent action on the integrity of cells. 

Tsushima, M., Fujiwara, Y., and Matsuno, T., Novel marine di-Z-carotenoids cucu-mariaxanthins A, B and C from the sea cucumber Cucumaria japonica, J. Nat. Prod., 59, 30, 1996. 

Sea cucumbers (Holothuroidea, Echinodermata) appear to be unique in their mode of squalene oxide (37) cyclization. Tritium-labeled lanosterol (33), cycloartenol (32) and parkeol (38) were individually administered to the sea cucumber Holothuria arenicola. While the former two triterpenes were not metabolized [22], parkeol was efficiently transformed into 14x-methyl-5a-cho-lest-9(l l)-en-3/ -ol (39) (Scheme 3). Other A1 sterols present in H. arenicola were not found to be radioactive and were thus assumed to be of dietary origin. The intermediacy of parkeol was confirmed by the feeding of labeled mevalonate (23) and squalene (26) to the sea cucumber Stichopus californicus [15]. Both precursors were transformed into parkeol, but not lanosterol nor cycloartenol, aqd to 4,14a-dimethyl-5a-cholest-9(ll)-en-3/J-ol (40) and 14a-methyl-5a-cholest-9(ll)-en-3/ -ol. Thus, while all other eukaryotes produce either cycloartenol or lanosterol, parkeol is the intermediate between triterpenes and the 14-methyl sterols in sea cucumbers. 

Korotchenko and coworkers detected PGs by TLC and bioassay in three sea cucumbers (Holothuroidea) Stichopus japonicus, Cucumaria fraudatrix, and C. japonica [189]. 

In echinoderms, zinc concentrations are usually higher in detrital feeders than in carnivores, higher in surface feeders than in sediment feeders, and higher in specimens collected inshore than those collected offshore in deeper waters (Eisler 1980). Sea cucumbers, Stichopus tremulus, accumulate radiozinc-65 from seawater by a factor of 1400 however, radiozinc accumulation data should be viewed with caution because addition of stable zinc can reduce zinc-65 accumulations in echinoderm viscera up to tenfold (Eisler 1981). Zinc inhibits the formation of the fertilization membrane in sea urchin eggs, possibly by interfering with cortical granule-derived proteases and proteins (Nakamura et al. 1989). 

Threatened or wounded sea cucumber Holothuraided) will contract its body exposing the small skeletal bones that make up the body wall, which can act as hooks to the mouths of predators. For most species, the connective tissue that makes up the greater part of the body wall is the primary deterrent to predators.The contracted body not only makes a more compact body to bite, but increases the stiffness of the body wall. The sea cucumber also has a very unusual defense mechanism. Many species use the Cuvierian tubules, which are located in the digestive system of the animal to confuse... 

Similarly to the latter two examples, there are many other defense toxins isolated from a variety of invertebrates, sponges, tunicates, sea urchins, sea cucumbers, and others. Many of the latter compounds are bioactive. ... 

Echinoderms. Sea cucumbers are commonly eaten throughout the Orient... 

Hydrolysis of thelothurins A and B, the defensive saponins of the Indo-Pacific sea cucumber Thelonota ananas, with aqueous acetic acid yields the genuine aglycones (51) and (52) whose structures were proved chemically by interrelation... 

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