Direct current electric field in some teleost species: Effect of medium salinity

Abstract

A direct current electric field up to 3 mV/ cm was recorded in 33‰ sea water around the fishMyoxocephalus brandti, Hexogrammos octogrammos, Enophrys diceraus, Pleuronectes stellatus, Bathimaste r derjugini, Sebastes scorpaeniformis. The body surface potentials were positive in relation to the external and internal media; they attained 10 mV and slowly varied near the mean value at every point. The potentials at the surface points of individual skin sections adjoining the oral and branchial cavities, the anal orifice and peripheral fin sections were normally characterized by polarities opposite to those of body surface potentials (in sea water they were negative in relation to the external medium). When placed in sea water during their fresh water cycle, the salmonOncorhynchus keta and the fresh water fishSalvelinus alpinus andMisgurnus fossilis had no d.c. field. In fresh water containing less than 0.03‰ salt, a d.c. field up to 25 mV/cm was recorded around all the above mentioned species. The potentials had an opposite polarity to that recorded in sea water. The distribution of potentials over the fish surface depends on the species. The potentials at some points of the body surfaces were found to vary when other fish or metal objects were placed in the aquarium. The parameters of the direct current electric field generated by a whole fish and by isolated skin pieces were identical and varied by the same law with changed medium salinity. Thus it may be assumed that the d.c. electric field around the fish is produced by active electrogenic ion transport mechanisms localized in the skin.