Kidney morphology in sturgeons: a microdissectional and ultrastructural study

Abstract

The anatomy and ultrastructure of nephrons were studied in various euryhaline and freshwater sturgeons. Microdisscction failed to reveal marked differences in the ncphron structure between freshwater and euryhaline fishes which might be considered as specific adaptations to the salinity of the environment. Some adaptive changes in the nephron structure were revealed by electron microscopic examination. The glomerular basal membrane is thicker in euryhaline sturgeons than in the freshwater sterlet. The processes of mesangial cells penetrating the basal membrane are much more numerous in fishes caught in the sea than in those from fresh water. Euryhaline sturgeons exhibit a great variability in the ultrastructure of epithelial cells of proximal and distal tubules. The numher of mitochondria-rich cells possessing well-developed basolaterdl foldings is significantly higher in fishes caught in the sea. In the freshwater sterlet the ultrastructure of the epithelium of proximal and distal tubules resembles that in freshwater teleosts.Comparison was made of the kidney morphology and ultrastructure in sturgeons, elasmobranchs and bony fishes. It is speculated that in sturgeons the adaptation to varying salinity is achieved by changes in the ultrastructure ofglomeruli and differentiation of thecells of the tubular epithelium.

Acclimation trials of juvenile Italian sturgeon to different salinities: morpho‐physiological descriptors

“…A decrease in glomerular size was observed in many euryhaline teleosts acclimated experimentally to higher salinities (Wendelaar Bonga, 1973;Oliverau & Oliverau, 1977;Colville et al, 1983;Cataldi et al, 1991;Cataudella et al, 1991). A decrease in nephron size was observed in BW-adapted A. naccarii, in agreement with observations on wild A. gueldenstaedti Brandt from sea and from inland waters (Gambaryan, 1988). However, in 60 day-SW-acclimated sturgeons the degenerative features observed in the whole nephron were similar to those observed in Oreochromis niloticus L. and O. mossambicus, which displayed a low degree of salt tolerance .…”

Renal corpuscle of the sturgeon kidney: An ultrastructural, chemical dissection, and lectin‐binding study

“…The tubular microfibrils embedded in the subendothelial lamina have been found in the GBM of several fish groups (Bargmann and Hehn, 1971;Tsujii et al, 1984a, b) and appear to be produced by the mesangial cells (Sakai and Kriz, 1987). The wide electron-lucent space that appears beneath the basal surface of the endothelial cells has previously been described in the sturgeon kidney (Gambaryan, 1988) and is unlikely to be an artifact. We suggest that it is due to the lack of production of the endothelial component of the GBM.…”

“…The presence of numerous mesangial cells with long processes extending into the GBM has been described in other sturgeon species (Gambaryan, 1988). The mesangial cells represent an obstacle to the free passage of molecules through the filtration barrier.…”

“…The presence of an NS has been observed in the renal corpuscle of several fish species (Hentschel and Elger, 1989), including the sturgeon (Gambaryan, 1988). However, ultrastructural data have not previously been reported.…”

“…The GBM in A. naccarii is about three times as thick as that of the freshwater and marine teleosts (Hickman and Trump, 1969;Zuasti et al, 1983), and about 15% thicker than that of the freshwater sturgeon A. ruthenus (Gambaryan, 1988). In mammals, the mature GBM forms by fusion of three initially independent BMs: the podocyte BM, the mesangial BM, and the capillary BM (Abrahamson, 1987).…”