Journal article

Publication year: 1986

Pages: 406-418

Journal: Physiological Zoology

Volume number: 59

Issue number: 4

ISSN: 0031-935X

DOI Link: https://doi.org/10.1086/physzool.59.4.30158594

Publisher: University of Chicago Press

Abstract: 
The gills of Synbranchus marmoratus become isolated from water for long periods of time while this fish breaths air or resides in moist burrows. In order to evaluate how interruptions in gill/water contact affect ionic regulation, we have undertaken urine collections and measurements of net and unidirectional sodium fluxes on intact, conscious fish. Comparative ionic flux measurements were made on the lungfishes Lepidosiren paradoxa and Protopterus spp. All three species demonstrated Na+ influx rates that are low for fish and freshwater vertebrates in general. Synbranchus marmoratus has an affinity (Km) of 0.45 mM and a capacity (Jmax) of 41.1 .mu.Eq/kg h-1, suggesting a relatively low-affinity, low capacity ion transport system. The transepithelial potential difference measured between the bath and extracellular fluid was -7 mV (inside reference); thus the fluxes could not be accounted for by passive transport mechanisms (Ussing criterion). Synbranchus marmoratus has both a low urine flow (1.8 ml/kg h-1) and a low urinary Na+ excretion rate (17.9 .mu.Eq/kg h-1), which, when combined with the extrarenal Na+ loss (3.9 .mu.Eq/kg h-1), indicate that it has a very low rate of turnover of Na+. Interruptions of branchial/water contact during air breathing do not affect influx or efflux of sodium. Experiments that partitioned Na+ fluxes in the head (gill and skin) from those in the body (skin and urinary) showed that 75% of the influx occurred across the body surface. We therefore conclude that S. marmoratus utilizes its skin as an ion-transporting organ. Histologic studies of this fish reveal structural characteristics common to other ion-transporting epithelia, such as junctional complexes, apical microridges, and mitochondria-rich cells.

Harvard Citation style: STIFFLER, D., GRAHAM, J., DICKSON, K. and STOCKMANN, W. (1986) CUTANEOUS ION-TRANSPORT IN THE FRESH-WATER TELEOST SYNBRANCHUS-MARMORATUS, Physiological Zoology, 59(4), pp. 406-418. https://doi.org/10.1086/physzool.59.4.30158594

APA Citation style: STIFFLER, D., GRAHAM, J., DICKSON, K., & STOCKMANN, W. (1986). CUTANEOUS ION-TRANSPORT IN THE FRESH-WATER TELEOST SYNBRANCHUS-MARMORATUS. Physiological Zoology. 59(4), 406-418. https://doi.org/10.1086/physzool.59.4.30158594