Respiration and Metabolism 



253 



abode, in the absence of oxygen, and comes to the surface for air ("aeropercep- 

 tiver Sinn ").■'* L^imhricus also is claimed to react tropistically to oxygen defi- 

 ciency.^-^ Likewise the need for oxygen converts the usually sessile protozoan, 

 Vorticella, into a temporary free-swimmer, which takes up its stationary post 

 again in water with adequate oxygen. -""^ Some teleost fish characteristically 

 "surface" in oxygen-deficient water to gulp air, as for example the catfish and 

 Leucisciis.^^- •"•' Similar behavior patterns may be concerned in \ertical migra- 

 tions of earthworms and other burrowing forms. The sipunculid worm, Phas- 

 colosoma liirco, from the region of the Malay Archipelago, has migrated from 

 its marine beginnings to take up residence in the intertidal zone among the 

 mangrove roots— driven shoreward by the need for oxygen, presumably, but 

 tethered to the sea by osmotic and structural limitations. 



TABLE 45. OXYGEN WITHDRAWAL BY THE PUFFER FISH FROM 

 SEA WATER OF VARYING OXYGEN TENSIONS"'' 



(Temp. 20° C.) 



Two species of Paramecium, the chlorophyll-containing P. hiirsaria and the 

 colorless P. candatiim, react differently to oxygen stress in the presence of light 

 and darkness. ^"^ Although both avoid regions of oxygen deficiency in the light 

 and seem unaffected by dark when oxygen is plentiful, their behavior is 

 decidedly different when they move from a region of light to one of darkness 

 during exposure to low oxygen tensions. The green infusorian, being able to 

 produce small amounts of oxygen in the light region, is immediately aflFected 

 by the darkness, which interrupts the photosynthetic production of oxygen; 

 it therefore turns away from the dark region. P. caudatiini, on the other hand, 

 being unable to produce oxygen, does not respond to the change from light 

 to dark under comparable anaerobic conditions. 



Certain insects resort to a biological supply and obtain oxygen from the 

 underwater stems of aquatic plants. The syrphid fly larvae, Chrysogaster, 

 which lives in oxygen-deficient waters, pierces the roots of aquatic grasses 

 and obtains vital oxygen.^'^" 



Along with these structural and behavioristic adaptations, many types of 

 physiological accommodation have developed to facilitate oxygen uptake at 

 low tensions. Certainly the relative increase in rate of oxygen consumption 

 itself, by way of oxyregulation, as well as hyperventilation, reduction of un- 

 loading tension by carbon dioxide (see Chapter 9), and oxygen secretion, 

 may be considered significant adaptations which become increasingly im- 

 portant at low oxygen pressures. Moreover, in the near or complete absence of 

 oxygen, most animals have found a way of getting along anaerobically, either 



