Structural and functional features of gill epithelium and the brood pouch of pipefish <Emphasis Type="Italic">Sygnathus acusimilis</Emphasis> (Syngnathidae,Gasterosteiformes) during adaptation to dilute sea water

Study of the dilate sea-water tolerance of the pipefish Syngnathus acusimilis indicated that it successfully acclimatized to an abrupt change in water salinity from 5 to 32‰. Larvae in the brood pouch also successfully acclimatized to salinity change, and, after several days, juveniles left the brood pouch and continued to live. In freshwater, adult and fry perished during several minutes. In the gill epithelium of S. acusimilis, chloride cells of only a marine type were found. A comparison of the ultrastructure of chloride cells of gill epithelium and mitochondrion-rich cells of the brood pouch of S. acusimilis demonstrated their high similarity. The ultrastructure of cells of the brood pouch indisputably attests to their involvement in maintaining an osmotic and ionic homeostasis in the cavity of the brood pouch.