Distribution of ionocytes in the saccular epithelium of the inner ear of two teleosts (Oncorhynchus mykiss and Scophthalmus maximus).

The saccular membranes of trout (Oncorhynchus mykiss) and turbot (Scophthalmus maximus) were examined to characterize specialized epithelial cells that might be responsible for ion exchange. The approach for localizing cell types was new for this tissue, as observations were made with a stereomicroscope and a light microscope in order to have a general view of the epithelium. No important differences between the two species were seen. The saccular tissue is a monolayer epithelium (except for the macula neural zone) surrounded by a layer of connective tissue invaded by many blood vessels. The use of the fluorescent probe DAPSMI and zinc iodide/osmium fixation-coloration defined two areas in which ionocytes were present. In the first, large ionocytes were grouped into a nearly complete, crowned meshwork around, but separated from, the macula. In the second area, opposite the macula, the ionocytes were smaller, cubical, and grouped in patches. Cells rich in Na+, K+-ATPase and carbonic anhydrase II were present in both areas. Contrary to previous studies in mammals and fish, ionocytes were also found in the epithelium of the saccule.

Ionic composition of endolymph in teleosts: origin and importance of endolymph alkalinity.

Ionic (Na+, K+, Cl-, PO4(3-), pH), total CO2, total calcium and protein concentrations in the plasma and endolymph of the inner ear were compared in trout Oncorhynchus mykiss and turbot Scophthalmus maximus. In both species, saccular endolymph was characterized by high levels of K+ and total CO2 and in trout by an alkaline pH. The kinetic characteristics of proton secretion across the saccular epithelium of trout were investigation using a titration technique in which isolated saccules were mounted as closed sacs. The rate of proton secretion depends strongly on the pH of the Ringer's solution and secretion stops at a pH below 7.2. Proton secretion is driven by an energy-dependent mechanism involving basolateral ouabain-sensitive Na+/K+ exchangers. Proton secretion was partially inhibited by acetazolamide and completely inhibited in Na(+)-free Ringer or in the presence of 1 mmol l-1 amiloride. A cellular model stressing the importance of proton exchange through the saccular epithelium is proposed to explain the regulation of endolymph pH, a crucial factor for the deposition of otolith calcium.

[Studies on genetic variability of intermuscular bones in the carp]. / Untersuchungen über die genetische Varianz der Zwischenmuskelgräten des Karpfens.

The number of intermuscular bones was determined in several sibships of carp by x-ray photographs. Differences between groups were found to be highly significant and specific characteristic frequencies were found for different populations in different ponds and for progeny of crosses between populations. Comparisons of the numbers of intermuscular bones in different body segments also showed highly significant differences between populations. The number of intermuscular bones between two neural spines was determined with an x-ray television camera. Correlation coefficients for number of total intramuscular bones to number of bones between two neural spines ranged fromr = 0.1 tor = 0.6, while the correlation coefficients for the number of intermuscular spines in the terminal 8 caudal vertebrae to total number of spines ranged, with one exception, fromr = 0.6 tor = 0.9.