Ultrastructure and osmoregulatory function of the kidney in larvae of the Persian sturgeon Acipenser persicus

The effects of the water-soluble fractions of crude oil on liver and kidney tissues of Caspian Kutum juveniles, Rutilus frisii

The lethal and histopathological impacts of crude oil's Water-Soluble Fraction (WSF) on the liver and kidney tissues of juvenile Rutilus frisii were investigated. The LC₅₀ 96 h of WSF was calculated at 33.95 ppm. Fish exposed to two concentrations (0.1 LC₅₀ and LC₅₀) of WSF and control for 24 and 96 h were used for histopathological studies. Tissues in the control group and 0.1 LC₅₀-24 h were healthy, and no specific damages were observed. With increasing exposure time (96 h) and concentration (LC₅₀), damages' type, frequency, and intensity gradually increased. Cloudy swelling, loss of cell boundary, nuclei deformation, and congestion of blood vessels were found in the liver, enlarged glomeruli, reduced Bowman's space, and occlusion of the tubular lumen, were found in the kidney. It is demonstrated that the WSF of crude oil can cause severe damage to the tissues of juvenile Kutum, depending on the exposure concentration.

New Data on Nephron Microanatomy and Ultrastructure of Senegal Bichir (Polypterus senegalus)

Simple Summary

Transitional forms of animals between Pisces and Amphibia are interesting to study, as they are the first to begin the development of a new environment - terrestrial. Such a transitional form are amphibious fish. The study of the structure of the nephron, the main structure that performs an osmoregulatory function, makes it possible to build evolutionary series that describe the processes of transition from the aquatic environment to the terrestrial one. Bichirs is a monophyletic group that arose in the Devonian and formed a species complex only in the Neogene. They share features with lungfish and amphibians, which formed convergently in the early stages of evolution. Therefore Bichirs are of great interest as a transitional form of animals. This study presents new data on the nephron age of Polypterus senegalus. Two groups of features are described. The first group consists of ancestral traits that have been preserved in the modern population of P. senegalus and are associated with habitat conditions in the aquatic environment. The second group is a complex of characters associated with the adaptation of P. senegalus to air breathing and periodic ground migrations.

Abstract

This study presents new data on the microanatomy and ultrastructure of Polypterus senegalus nephrons. It was shown that the diameter and ultrastructure of renal corpuscles, a well-developed neck segment, and ultrastructure of two types of epithelial cells of the proximal tubule are ancestral signs of the modern population of P. senegalus associated with habitat conditions in the aquatic environment. The outer diameter of the tubules, the height of the epitheliocytes, the presence of two types of epithelial cells of the intermediate and distal tubules of the corresponding ultrastructure, and a large area of nephrogenic tissue are progressive features of the modern population of P. senegalus, associated with adaptation to air respiration and periodic terrestrial migrations, which were formed at the early stages of evolution of P. senegalus convergently with lungfish and amphibians.

An update on the evolutionary origin of aglomerular kidney with structural and ultrastructural descriptions of the kidney in three fish species

The kidney of fish contains numerous nephrons, each of which is divided into the renal corpuscle and renal tubules. This glomerular structure is the filtration unit of the nephron and is important for the kidney function, but it has been reported that the renal corpuscle was lost in at least four independent linages of fish (i.e., aglomerular kidney). In this study, the authors newly described renal structures for three species by histological and ultrastructural observations: two aglomerular kidneys from a seahorse Hippocampus barbouri and a toadfish Allenbatrachus grunniens and a glomerular kidney from a snake eel Pisodonophis boro. The renal development of H. barbouri was also described during 1-35 days after birth. In all species tested, the anterior kidney was comprised of haematopoietic tissues and a few renal tubules, whereas the posterior kidney contained more renal tubules. Although the glomerular structure was present in P. boro, light microscopic observations identified no glomeruli in the kidney of H. barbouri and A. grunniens. Ultrastructurally, abundant deep basal infoldings with mitochondria in the renal tubules were observed in A. grunniens compared to H. barbouri and P. boro, suggesting the possible role of basal infoldings in maintaining the osmotic balance. By integrating the results from the three species and comprehensive literature search, the authors further showed that 56 species have been reported to be aglomerular, and that the aglomerular kidney has evolved at least eight times in bony fishes.

Ontogeny and osmoregulatory function of the urinary system in the Persian sturgeon, Acipenser persicus (Borodin, 1897)

The structure of the kidney and the localization of Na(+), K(+)-ATPase (NKA) immunopositive cells were examined throughout the postembryonic development of the Persian sturgeon, Acipenser persicus, from newly hatched prelarvae (10mm) to 20 days post hatch (20 DPH) larvae (31mm). Investigations were conducted through histology and immunohistochemistry by using the light and immunofluorescence microscopy. The pronephros was observed in newly hatched prelarvae. The cells lining the distal pronephric tubules and their collecting ducts showed laterally expressed NKA immunofluorescence that later extended throughout the whole cytoplasm. Mesonephrogenous placodes and pre-glomeruli were distinguished at 2 DPH along the collecting ducts posteriorly. Their tubules were formed and present in kidney mesenchyma, differentiated into neck, proximal, distal and collecting segments at 7 DPH when NKA immunopositive cells were observed. Their distal and collecting tubules showed an increasing immunofluorescence throughout their cytoplasm while the glomeruli remained unstained. From D 9 to D 17, the epithelial layer of pronephric collecting duct changed along the mesonephros to form ureters. Ureters, possessing isolated strong NKA immunopositive cells, appeared as two sac-like structures hanging under the trunk kidney. Since NKA immunopositive cells were not observed on the tegument or along the digestive tract of newly hatched prelarva, and also the gills are not formed yet, the pronephros is the only osmoregulatory organ until 4 DPH. At the larval stage, the pronephros and mesonephros are functional osmoregulatory organs and actively reabsorb necessary ions from the filtrate.