Seaweed diet

Predators ignore sea hares because, like other mollusks without shells, they have chemicals that afford them the protection once given by a shell. (We saw earlier that a compound from a tropical sea hare is now a promising anticancer drug.) Many sea hares have an acrid or fetid odor that is distinctly unpleasant to humans. Their egg masses and their skin must be distasteful, because one exploratory bite is enough to convince a would-be assailant to look elsewhere for food. For some species, the deterrents responsible for these properties may come directly from their seaweed diet, but other species seem to synthesize these defenses for themselves. The evidence is mixed and confusing. 

Hawaiian name limu mane ono o) (4b,47). In their diet alone the Hawaiians may be getting all of the necessary agents for the initiation and promotion of gastrointestinal cancer. Epidemiological studies, however, are needed to evaluate the actual role of seaweed diet in the incidence of stomach cancer in Hawaii ( ). 

Iodine occurs to a minute extent (less than 0.001 %) in sea water, but is found in greater concentration, combined in organic form, in certain seaweeds, in oysters and in cod livers. Crude Chile saltpetre, or caliche contains small amounts of sodium iodate, NalOj. from which iodine can be obtained (see below). Some insoluble iodides, for example liiose of silver and mercury(II), occur in Mexico. Iodine is found in the human body in the compound thyroxin in the thyroid gland deficiency of iodine in diet causes enlargement of this gland (goitre). 

Most carbohydrates exist in the form of polysaccharides. Polysaccharides give stmcture to the cell walls of land plants (cellulose), seaweeds, and some microorganisms and store energy (starch in plants and glycogen in animals). They are important in the human diet and in many commercial apphcations. 

Bolser RC, Hay ME (1996) Are tropical plants better defended Palatability and defenses of temperate versus tropical seaweeds. Ecology 77 2269-2286 Boudouresque CF, Lemme R, Mari X, Meinesz A (1996) The invasive alga Caulerpa taxifolia is not a suitable diet for the sea urchin Paracentrotus lividus. Aq Bot 53 245-250 Briggs JC (1974) Marine zoogeography. McGraw-Hill, New York... 

Fig. 10.2 The host ranges of species that utilize hosts that produce ( Present ) or do not produce ( Absent ) lipophilic chemistry (Poore et al., unpublished data). The more generalized amphipods and fishes have a broader host range when incorporating chemically rich seaweeds in their diet, while the host range of the more specialized slugs does not display any effect of secondary metabolites...

A The animals are adapted to this (staple) diet by virtue of their specialized runen biota. B CR depressed by astringent seaweeds, the most astringent types (Ascophyllum nodosum, Fucus vesiculosus) not being consumed Vihen others were available. Phlorotannins are the presumed cause of astringency. 

Brominated compounds widely occur in marine organisms, particularly seaweeds and invertebrates. Many of them play a defensive role against parasites and predators, and are incorporated by opisthobranch mollusks to this scope from the diet. Bromine is uptaken by seaweeds and invertebrates from bromide dissolved at sparingly 1 mM concentration in seawater. The process is catalyzed by haloperoxidases, which have been characterized both as structure and function (Butler 1997). 

The culture of edible seaweeds has a long tradition in the East. Particularly the red Porphyra tenera Kjelliman is the object of a large trade owing to a larger content of proteins, with a better balance of amino acids relevant to the human diet, than most other seaweeds. Certain marine... 

Asian-style sauces are high in salt and should be avoided by people on low-sodium diets. Seaweed... 

Seaweed has been shown to be of value in the control of parasites. Jensen (1972) reported that inclusion of seaweed in the diet markedly reduced the incidence of liver condemnations from ascarid damage in pigs at slaughter. This aspect of seaweed inclusion is of interest to organic farmers but does not appear to have been investigated in poultry. 

Explain why observation of deaths of organisms and resultant declines in populations, though straightforward and unequivocal, are often insufficient to fully explain the effects of toxic substances on ecosystems. Why is it important to have the capability to study sublethal effects Certain sheep that have been raised for centuries in coastal areas of Scotland exist on a diet of seaweed that is high enough in arsenic to kill other kinds of sheep. Does this observation illustrate pollution-induced community tolerance Explain. 

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