Histological and Stereological Characterization of Brown Trout (Salmo truttaf.fario) Trunk Kidney

Abstract

The large variability in kidney morphology among fish makes it difficult to build a "universal" model on its function and structure. Therefore, a morphological study of brown trout trunk kidney was performed, considering potential seasonal and sex effects. Three-year-old specimens of both sexes were collected at four stages of their reproductive cycle. Kidney was processed for light and electron microscopy. The relative volumes of renal components, such as renal corpuscles and different nephron tubules, were estimated by stereological methods. Qualitatively, the general nephron structure of brown trout was similar to that described for other glomerular teleost species. Quantitatively, however, differences in the relative volume of some renal components were detected between sexes and among seasons. Particularly, highest values of vacuolized tubules and new growing tubules were observed after spawning, being more relevant in females. Despite seasonal changes, more linear correlations were found between those parameters and the reno-somatic index than the gonado-somatic index. Thus, we verified that some brown trout renal components undergo sex dependent seasonal variations, suggesting a morphological adaptation of the components to accomplish physiological needs. These findings constitute a baseline for launching studies to know which factors govern the morphological variations and their functional consequences.

Kidney anatomy, histology and histometric traits associated to renosomatic index in Gymnotus inaequilabiatus (Gymnotiformes: Gymnotidae)

“…To date, there are no anatomical, histological or histopathological descriptions of the kidney in G. inaequilabiatus, which prevent a comparative analysis within the Gymnotiformes Genus. However, the values found of the relative volumetric density from the proximal tubules are similar to the sum of the proximal tubules I and II values reported in the Salmo trutta (Resende et al, 2010), in accordance to the low percentage of renal corpuscles. Both tubular segments were not estimated separately once the distinct morphological features are more clearly recognized by transmission microscopy (Takashima, Hibiya, 1995;Elger et al, 2000).…”

“…However, the renosomatic index has been poorly reported in association with useful histological biomarkers. This index tracks metabolic variations in response to parasite infections, heavy metal contamination, involvement in physiological adjustment to environmental conditions or seasonality (Resende et al, 2010;Jordanova et al, 2017;Strepparava et al, 2018). On the other hand, the quantification of morphometric measurement allows detection of minimal differences in cells and tissues, favoring the qualitative analysis in addition to responding to the functional and pathological changes in an organ (Oberholzer et al, 1996;Nyengaard, 1999;Hamilton et al, 2014).…”

“…suggest that they adapted to low oxygen rates or have a wide capacity for survival in extreme hypoxic environments, probably by an outstanding physiological adaptive process (Crampton, 1998;Moraes et al, 2002). On this point, renal histomorphometry assessment can play a key role owing to the functional plasticity of this organ (Sakai, 1985;Resende et al, 2010;Hassan et al, 2017;Pelster et al, 2018).…”

Ion Transporters and Osmoregulation in the Kidney of Teleost Fishes as a Function of Salinity

“…In euryhaline species, glomeruli and tubular segments are tangled and in close connection with hematopoietic tissue, especially in the anterior part of the kidney, while urine producing nephrons are more numerous toward the posterior part ( Anderson and Loewen, 1975;Resende et al, 2010). Afferent arterioles enter into a network of capillaries at the vascular pole of the glomerulus.…”

The Role of Aquaporins in the Kidney of Euryhaline Teleosts

“…Vasculature, glomeruli, and tubular segments are interwoven and interspersed with hematopoietic tissue especially in the anterior part (Anderson and Loewen, 1975; Resende et al, 2010). The number and size of glomeruli as well as the differentiation of functional segments of teleost nephrons are reduced compared to the mammalian type, and vary according to evolutionary origin and habitat.…”