Changes in swimbladder retial morphology in Anguilla rostrata during premigration metamorphosis

During metamorphosis from the yellow to the silver phase in Anguilla rostrata , the length of the swimbladder retial capillaries increases by a factor of 2.5, the mean retial capillary lumen diameter and total retial cros‐sectional area increase by 1.5 and the calculated counter current exchange efficiency increases by 3.4. Metamorphosis of the retia begins before changes in integument pigmentation become apparent. These changes in retial morphology are part of a complex of transformations that permit. The maintenance to swimbladder function at greater depths during the spawning migration.