PELAGIC AND BENTHIC FISHES, SWIMBLADDER, ECONOMY OF DEEP-SEA LIFE 97 



hydrostatic equilibrium at a depth of 4000 m., could swim upwards for 800 m. without the need to 

 lose gas. When it descended there would be no extra gas to find. 



These abyssal fishes have not retained their swimbladders simply to solve problems in the second 

 law of thermodynamics. A fish with a swimbladder is able to remain poised off the bottom without 

 undue effort and it can thus devote a greater part of its energy to seeking its food. If a near-bottom 



rm 



gg 



rm 



gg 



Text-fig. 41 . Swimbladders of (a) Bassozetus taenia ; (b) B. compressus ; (c) Antimora rostratus ; (d) Lionurus filicauda ; (e) Argy- 

 ropelecus aculeatus. In the two species of Bassozetus and Lionurus filicauda, note the extremely long retia mirabilia, which may 

 be compared with the rete of Argyropelecus. Note also the capillary loops in the gas gland of Bassozetus compressus. gg, gas- 

 gland ; rm, rete mirabile. (a, x 3-6 ; B, x 3 ; c, x 0-7 ; D, x 3 ; E, x 3.) 



13 DM 



