Life in the Open Ocean. Joseph J. Torres
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Название: Life in the Open Ocean
Автор: Joseph J. Torres
Издательство: John Wiley & Sons Limited
Жанр: Биология
isbn: 9781119840312
isbn:
Because small swimming species that are the focus of this book are ectotherms, temperature is the environmental variable with the most potential to influence survival, zoogeographic distributions, and biological rate processes such as metabolism and growth. Upper and lower lethal limits of open‐ocean species, like those of all ectotherms, are dictated by their physiological and biochemical characteristics. Limited live animal experimentation on species from a variety of open‐ocean systems as well as more extensive work with enzymes and membranes strongly suggest that open‐ocean pelagic species show the basic responses to temperature described here in detail. That is, we see no exotic or unusual adaptations to temperature. Rate measurements show Q10s in the range of 2–3 and temperature adaptation is observed when ecological analogues in polar and temperate systems are compared.
The increased pressure associated with mesopelagic depths has the potential to influence biochemical and physiological processes ranging from the ion transport necessary for nerve and muscle function to enzyme function in the anaerobic and aerobic pathways of intermediary metabolism. Animals that live at modest pressures (<100 atm) are either insensitive to it, as are the vertically migrating euphausiids, or show a slight acceleratory response as in the deeper‐living mesopelagic migrators. In contrast, surface‐dwelling species exposed to pressures outside those of their normal environment show excitement at low (50 atm) pressures, moribundity at higher pressures (150 atm), and death due to tetany at high pressures (200 atm). Adaptations to pressure include increases in the fluidity of biological membranes as well as slight changes in the structure of enzymes to confer pressure insensitivity.
Zones of minimum oxygen are present at intermediate depths throughout the world ocean, but in a few locations oxygen reaches levels low enough to limit animal life. Three such locations are coastal California, the eastern tropical Pacific, and the Arabian Sea. When there is oxygen present in sufficient quantities to enable extraction, such as off California, pelagic species have evolved mechanisms to live aerobically despite the vanishingly low oxygen. Such adaptations include a high gill surface area to allow for efficient extraction of oxygen, a well developed circulatory system, and an efficient means of ventilating the gills. Animals that migrate into regions of zero oxygen, such as in the Arabian Sea, use a strategy of minimizing accumulation of toxic end products by changing the end point of their anaerobic metabolism from lactate to ethanol.
Depth itself exerts a profound influence on the metabolic characteristics of pelagic species. In swimming species that are either visual predators or are preyed upon by visual predators, i.e. the crustaceans, squids, and fishes, metabolism declines profoundly with increasing depth of occurrence. A fish living at the surface has a metabolism about 50 times that of a species living at 1000 m. Weaker swimmers where vision plays less of a role, such as jellyfishes and chaetognaths, do not show an equivalent decline in metabolic rate with depth of occurrence. Benthic and benthopelagic fishes show a similar decline with depth of occurrence, but benthic crustaceans do not.
References
1 Baldwin, J. (1971). Adaptation of enzymes to temperature: acetylcholinesterases in the central nervous systems of fishes. Comparative Biochemistry and Physiology 40: 181–187.
2 Baldwin, J. and Hochachka, P.W. (1970). Functional significance of isoenzymes in thermal acclimatization: acetylcholinesterase from trout brain. Biochemical Journal 116: 883–887.
3 Belman, B.W. and Childress, J.J. (1976). Circulatory adaptations to the oxygen minimum layer in the bathypelagic mysid Gnathophausia ingens. Biological Bulletin 150: 15–37.
4 Brett, J.R. (1952). Temperature tolerance in young Pacific salmon, genus Oncorhynchus. Journal of the Fisheries Research Board of Canada 9: 265–323.
5 Brett, J.R. and Groves, T.D.D. (1979). Physiological energetics. In: Fish Physiology, vol. 8 (eds. W.S. Hoar, D.J. Randall and J.R. Brett). New York: Academic Press.
6 Bridges, C.R. (1994). Bohr and root effects in cephalopod hemocyanins – paradox or pressure in Sepia oficinalis? In: Physiology of Cephalopod Molluscs: Lifestyle and Performance Adaptations (eds. H.O. Portner, R.K. O’dor and D.L. Macmillan). New York: Gordon and Breach.
7 Brix, O., Bardgard, A., Cau, A. et al. (1989). Oxygen binding properties of cephalopod blood with special reference to environmental temperatures and ecological distribution. Journal of Experimental Zoology 252: 34–42.
8 Campenot, R.B. (1975). The effects of high hydrostatic pressure on transmission at the crustacean neuromuscular junction. Comparative Biochemistry and Physiology 52B: 133–140.
9 Childress, J.J. (1968). Oxygen minimum layer: vertical distribution and respiration of the mysid Gnathophausia ingens. Science 160: 1242–1243.
10 Childress, J.J. (1971). Respiratory adaptations to the oxygen minimum layer in the bathypelagic mysid Gnathophausia ingens. Biological Bulletin 141: 109–121.
11 Childress, J.J. (1975). The respiratory rates of midwater crustaceans as a function of depth of occurrence and relation to the oxygen minimum layer off Southern California. Comparative Biochemistry and Physiology 50A: 787–799.
12 Childress, J.J. and Mickel, T.J. (1985). Metabolic rates of animals from the hydrothermal vents and other deep‐sea habitats. Biological Society of Washington 6: 249–260.
13 Childress, J.J. and Nygaard, M.H. (1973). The chemical composition of midwater fishes as a function of depth of occurrence off southern California. Deep‐Sea Research 20: 1093–1109.
14 Childress, J.J. and Seibel, B.A. (1998). Life at stable low oxygen levels: adaptations of animals to oceanic oxygen minimum layers. Journal of Experimental Biology 201: 1223–1232.
15 Childress, J.J. and Somero, G.N. (1979). Depth‐related enzymic activities in muscle, brain, and heart of deep‐living pelagic marine teleosts. Marine Biology 52: 273–283.
16 Childress, J.J. and Thuesen, E.V. (1995). Metabolic potentials of deep‐sea fishes: a comparative approach. In: Biochemistry and Molecular Biology of Fishes (eds. P.W. Hochachka and T.P. Mommsen). Berlin: Elsevier Science.
17 Childress, J.J., Cowles, D.L., Favuzzi, J.A., and Mickel, T.J. (1990). Metabolic rates of benthic deep‐sea decapod crustaceans decline with increasing depth primarily due to the decline in temperature. Deep‐Sea Research 37: 929–949.
18 Cossins, A.R. and Bowler, K. (1987). Temperature Biology of Animals. London: Chapman and Hall.
19 Cossins, A.R. and MacDonald, A.G. (1984). Homeoviscous theory under pressure. 2. The molecular order of membranes from deep‐sea fish. Biochimica et Biophysica Acta 776: 144–150.
20 Cowles, D.L., Childress, J.J., and Wells, M.E. (1991). Metabolic rates of midwater crustaceans as a function of depth of occurrence off the Hawaiian Islands: food availability as a selective factor? Marine Biology 110: 75–83.
21 Diaz, R.J. and Rosenberg, R. (1995). Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna. Oceanography and Marine Biology: An Annual Review 33: 245–303.
22 Donnelly, J. and Torres, J.J. (1988). Oxygen consumption of midwater fishes and crustaceans from the eastern Gulf of Mexico. Marine Biology 97: 483–494.
23 Drazen, J.C. and Seibel, B.A. (2007). СКАЧАТЬ