Meeting Abstract
S3-1.6 Saturday, Jan. 5 Metabolic and osmoregulatory challenges of emersion in fishes. WILSON, JM*; CHEW, SF; IP, YK; CIMAR, Porto, Portugal; Nanyang Tech. Univ., Singapore; National Univ. Singapore, Singapore wilson.jm.cimar@gmail.com
The climbing perch (Anabas testudineus), combtooth blenny Lipophrys pholis, and weatherloach Misgurnus anguillicaudatus are three examples of teleost fishes that have adapted to terrestrial conditions. The gill in fishes, which is generally the main organ for aquatic respiration, is also the site of ion-regulation and excretion of metabolic (nitrogenous) waste primarily as ammonia. However, the typical teleost fish gill is designed to function in water and collapses in air and with the loss of ventilatory water flow to maintain favorable diffusion gradients combine to challenge metabolic waste elimination and osmoregulation. The climbing perch is a euryhaline, freshwater fish that is capable of surviving days out of water. It has a specialized labyrinth organ in the suprabranchial chamber that facilitates aerial gas exchange. The climbing perch is capable of maintaining aquatic rates of ammonia excretion while emersed in contrast to most other fishes, although we have made a similar observation in the intertidal blenny. As an indicator of iono regulatory status, plasma Na+ and Cl– levels fell 10 and 5%, respectively, after 5d emersion. The expression levels of two key branchial ion pumps, Na++/K+-ATPase (NKA) and H+-ATPase, were found not to be modulated under these conditions. This can be contrasted with the intertidal L. pholis in which branchial NKA activity increased during emersion. The facultative intestinal air-breathing weather loach has adapted to long periods of emersion during the dry season by volatilizing ammonia through its intestine using facilitated NH4+ excretion while in the gill NH3 excretion by a different Rhcg-H+-ATPase coupled mechanism is up regulated. This work was partially supported by FCT grant POCTI/BSE/47585.
