. Text-fig. 39. Venous part of the circulation to the oval in Myctophum punctatum ( x 15). Note the size of the oval veins relative to the retial vein, ov, oval; ra, retial artery; rv, retial vein; rm, rete mirabile; vov, veins to oval. lumen of swimbladder Text-fig. 40. Part of the resorbent capillary network of the swimbladder of Argyropelecus aculeatus. Note the very thin layer of tissue separating the capillaries from the lumen of the swimbladder. Partial migrators Gas secretion During their vertical migrations, fishes that do not penetrate beyond the upper thermocline will be subjected to
. Text-fig. 39. Venous part of the circulation to the oval in Myctophum punctatum ( x 15). Note the size of the oval veins relative to the retial vein, ov, oval; ra, retial artery; rv, retial vein; rm, rete mirabile; vov, veins to oval. lumen of swimbladder Text-fig. 40. Part of the resorbent capillary network of the swimbladder of Argyropelecus aculeatus. Note the very thin layer of tissue separating the capillaries from the lumen of the swimbladder. Partial migrators Gas secretion During their vertical migrations, fishes that do not penetrate beyond the upper thermocline will be subjected to lesser physical stress than those that go on to the surface mixed layer. A hatchet fish migrating from a depth of 150 to 400 m. is not faced with providing as much oxygen for the swim- bladder as a lantern fish moving from 20 to 400 m. However, as we have seen (pp. 74-75) the rete and gas-gland of a hatchet fish swimbladder are highly developed, seemingly as well as those of a lantern fish. In view of the earlier discussion concerning gas-production in thermocline-crossers, this aspect need not be pursued at greater length.
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Keywords: ., bookcentury1900, booksubjectocean, booksubjectscientificexpediti
