138 



ANALYSIS OF THE ENVIRONMENT 



Amoeba proteiis, for example. The pseudo- 

 podia remain extended until about 450 at- 

 mospheres, at which point amebae round 

 up and are Ukely to die if kept under pres- 

 sure of this magnitude for an hour. Ameba 

 gives evidence of increased fluidity under 

 pressure. Some, though not all, of the indi- 

 vidual protozoans, of such genera as 

 Chlamijdomonas, Paramecium, Vorticella, 

 and Euplotes, survive pressures of 500 at- 

 mospheres for twenty-four to forty-eight 

 hours. 



Many invertebrate metazoans are inacti- 

 vated by exposure to from 400 to 600 at- 

 mospheres. This group includes the mollusk, 

 Cardium,; the annelid, Nereis; the crusta- 

 cean, Gammarus; and others. Some echino- 

 derms {Asterias) and coelenterates {Alcy- 

 onium and Actinia) are more resistant and 

 have survived pressures of 1000 atmos- 

 pheres for an hour. 



Surface fishes without swim bladders, or 

 with emptied swim bladders, are not af- 

 fected by 100 atmospheres, but lose mo- 

 bility at double that pressure and are killed 

 at 300 atmospheres. Small flatfish (Pleiiro- 

 nectes) consume oxygen at a decidedly in- 

 creased rate up to pressures of 125 kg/cm^. 

 Fish eggs (Salmonidae) from surface 

 waters will develop and hatch at the normal 

 time up to 200 atmospheres. Eggs in 300 

 atmospheres are retarded about 10 per cent 

 in time to hatching. Higher pressures kill 

 the developing embryos, more rapidly, the 

 higher the pressure; 650 atmospheres 

 brought death in two days' exposure. Early 

 cleavages of eggs of the common minnow, 

 Fundidtis, are retarded by 100 to 130 at- 

 mospheres when applied for from 0.5 to 3.0 

 hours. Such pressures produce abnormalities 

 in developed embryos even though no sig- 

 nificant changes can be observed during or 

 immediately after the onset of treatment 

 (Draper and Edwards, 1932). 



The statement is common that the tissues 

 of many deep-sea fishes have a loose texture 

 when examined at the surface, and the as- 

 sumption has been that the enormous pres- 

 sure under which they normally live would 

 make their flesh firmer. Such assumptions 

 have not been confirmed. Pressure acts on 

 fish tissues as it does on water, which (p. 

 136) shows a reduction of less than 2 per 

 cent at 4000 meters' depth; fish tissues 

 under similar stress should increase in firm- 

 ness by about that amount (Krogh, 1934). 



Pressures, such as obtain in the ocean. 



tend to increase the hydration of colloidal 

 systems. Gels in water take up more water 

 when compressed. "According to the the- 

 orem of Le Chatelier, pressure, which 

 causes a decrease in volume, should pro- 

 mote the imbibition of water" (Cattell, 

 1936). Bayliss (1931) states Le Chatelier's 

 theorem as follows: "When any tendency or 

 factor capable of changing the equilibrium 

 of a system is altered, the system tends to 

 change in such a way as to oppose and an- 

 nul the alteration of this factor." If a re- 

 versible reaction involves a change in vol- 

 ume, the application of pressure will shift 

 the position of equilibrium to the side of 

 lesser volume, and if the number of mole- 

 cules differs in two aspects of a reacting 

 system, increased pressure will shift equilib- 

 rium towards the side with fewer molecules. 

 This principle is widely exhibited among 

 animals experimentally exposed to pressures 

 such as obtain in oceanic mid-depths; char- 

 acteristically, such animals show great 

 swelling. Animals accustomed to such pres- 

 sures must acclimate to this as well as to 

 the other peculiarities of their deep-sea 

 environment. 



Fishes with air bladders, diving mam- 

 mals, and diving birds introduce a compli- 

 cation. The increasing pressures produce 

 important changes in the tension of the 

 gases dissolved in blood and other proto- 

 plasm. A sudden release of pressure often 

 permits gas bubbles to form in the blood 

 (gas embolism) with hannful or fatal re- 

 sults. The invasion rate of nitrogen is an 

 important determining factor in gas embo- 

 lism. Men can stand exposure to about 9 

 atmospheres if unaided by a rigid suit and 

 if compression and decompression are 

 slow. Small mammals have successfully 

 withstood pressures up to 25 atmospheres, 

 again if decompression comes slowly. 

 Whales dive into higher pressures than 

 these and may go below the level of alve- 

 olar collapse, after which nitrogen invasion 

 of the blood must be slow. Gas embolism 

 occurred in a seal after an experimental 

 dive to a pressure of 30 atmospheres; it 

 probably occurs exceptionally in whales, 

 which, when harpooned, may dive to 800 

 meters. Sperm whales must be able to 

 withstand large changes in pressure, since 

 they feed mainly on giant squid that live 

 pelagically at depths of 500 mm. (Krogh. 

 1934; Scholander, 1940; Sverdrup, John- 

 son, and Fleming, 1942). 



