Marine elasmobranchs

Marine vertebrates, including fishes and elasmobranchs, have low zinc concentrations in tissues (i.e., 6 to 400 mg/kg DW) when compared to marine plants and invertebrates (Eisler 1980, 1981, 1984). Highest concentrations in muscle of marine fishes (20.1 to 25.0 mg/kg FW) were recorded in northern anchovy (Engraulis mordax) and Atlantic menhaden (Brevoortia tyrannus NAS 1979). 

Foureman GL, Hernandez O, Bhatia A, et al. The stereoselectivity of four hepatic glutathione S-transferases purified from a marine elasmobranch (Raja erinacea) with several K-region polycyclic arene oxide substrates. Biochim Biophys Acta 1987 914(2) 127-135. 

Hepatic microsomal and solubilized mixed-function oxidase systems from the little skate, Baja erinacea, a marine elasmobranch. In Ullrich, V., Hildebrandt, A., Roots, I., Eastabrook, R.W. (Eds.) Microsomes and Drug Oxidations (1976). Pergamon Press, Oxford, pp 16O-I69. 

In general, our studies with cytochrome P-450-dependent metabolism have emphasized the similarity of the hepatic MFO system in marine fish to that found in mammals. Thus, in the little skate (Raja erinaoea), a marine elasmobranch, enzyme activity is localized in the microsomal fraction, requires NADPH and molecular oxygen for maximum activity, and can be inhibited with CO (1, 2). Moreover, when hepatic microsomes from the little skate were solubilized and separated into cytochrome P-450, NADPH-cytochrome P-450 reductase, and lipid fractions, all three fractions were required for maximal MFO activity in the reconstituted system (3). We have also found, as have others, that the administration of polycyclic hydrocarbons (3-methylcholanthrene, 1,2,3,4-dibenzanthracene [DBA]), 2,3,7,8-tetrachlorodibenzo-p-dioxin... 

It is an ideal compound for regulation of osmotic pressure, since it has a low molecular mass, is highly soluble and has no net charge. It serves this function in some of the tissues of elasmobranch fish such as the skate and shark, and in marine invertebrates. Any damage to these tissues releases taurine, which is used as a chemoattractant for predators such as the shrimp, which wiU attack small fish. 

MARINE FISHES AND ELASMOBRANCHS Whitetip shark, Carcharhinus longimanus Muscle 3.1 FW 21... 

Beach, D. H., Sherman, I. W. Holz, G. G., Jr (1973). Incorporation of docosahexaenoic fatty acid into the lipids of a cestode of marine elasmobranchs. Journal of Parasitology, 59 655-66. 

Artemia embryos Insects—freezing Insects—salinity Marine elasmobranchs T eleosts—freezing Amphibia—freezing Mammals—kidney Mammals—brain... 

Marine elasmobranchs TMAO, glycine betaine, sarcosine... 

Gastropods—estivating Marine elasmobranchs with methylamines... 

Pentreath, R.J. The roles of food and water in the accumulation of radionuclides by marine teleost and elasmobranch fish, p. 421-436, Symp. Interaction of Radioactive Contaminants with the Constituents of the Marine Environment, Seattle, Washington, July 10-14, 1972. IAEA, Vienna, 1973. 

Urea Ureotelia Urea cycle Amphibians, mammals, marine elasmobranchs... 

The organisms living in the sea, like the elasmobranchs (sharks, skates, rays) and some-others have developed another method for their osmoregulation. They maintain isosmosity with their environment by retaining inert solutes like urea and trimethylamine oxide (TMAO). These compounds are relatively inert, non-toxic and readily diffusible. Also, retention of these can be accomplished even upto a concentration of 0.5 M. Many species can also biosynthesize them and therefore these two compounds and specially urea, find favour with most marine vertebrates. 

The organs and blood of the Elasmobranchii contain considerable quantities of urea. In the blood of marine Elasmobranchii, urea may attain a concentration of 26g/l and is never less than 18g/l. Here we are dealing with a case of selective retention of urea since the other nitrogenous compounds in Elasmobranch blood are no more concentrated than in the blood of other Vertebrates. 

Zinc.— Zn, a.n. 30 a.w. 65-37. A universal micro-constituent. Among plants, values range from less than 1 mg. Zn per kg. fresh tissue in fruit pulp, up to 10 mg. per kgm. in leaves rich in chlorophyll, such as lettuce, cress, spinach, dandelion. Marine animals show values ranging from 3-5 mg. per kg. in elasmobranchs up to 188-5-341 mg. in oysters. About half of the total zinc in oysters can be removed as a simple solute, by dialysis. The 70 kg. human body contains on an average 2-2 gm. of zinc, most of which is in bone and hair. The ordinary mixed diet supplies about 12 mg. Zn daily. 

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