A study of the morphology of the gills of an extreme alkalinity and hyperosmotic adapted teleost Oreochromis alcalicus grahami (boulenger) with particular emphasis on the ultrastructure of the chloride cells and their modifications with water dilution

Abstract

The general gill morphology of Oreochromis alcalicus grahami, a teleost adapted to high salinity and hyperosmosis, is basically similar to that of other teleostean fish. The species has four pairs of gill arches, all of which have well developed filaments. Each of the arches (holobranchs) has two rows of filaments (hemibranchs). Bilaterally situated secondary lamellae branch from the central axis of the filaments. The lamellae reach their maximum size at the middle of the filament, gradually decrease in size and eventually disappear towards the tip of the filament, which is bare. The leading edge of the gill filament and the immediate interlamellar space is covered by a stratified epithelium consisting of pavement cells, mucous cells, chloride cells and undifferentiated cells. The surface of these cells is made up of concentric microridges. The chloride cells were found only on the primary epithelium (filamental epithelium) and very rarely on the secondary epithelium (lamellar epithelium). Two types of chloride cells were observed in the gills of Oreochromis. The superficial chloride cells have fewer mitochondria concentrated towards the basal aspect of the cell, and a network of tubules towards the apical surface and are less electron dense. These cells intercommunicate with the water through an apical pore. The deep chloride cells have numerous diffuse mitochondria intercalated between a fine profuse tubular network and are more electron dense. These cells are covered by one or more layers of pavement cells and thus do not have access to the external surface. After gradual dilution of the lake water in which the fish were kept, both types of chloride cells remained topographically and ultrastructurally distinct. However, in both kinds of cell the mitochondria decreased in number and size. Initially there was an increase in the diameter and the degree of interdigitation of the tubules followed by a gradual decrease. An increase in the quantity of rough endoplasmic reticulum, particularly at the perinuclear region of the cell, was noted. The morphometric analysis of the branchial system indicated that the gills of Oreochromis are well adapted for gas exchange by having numerous and relatively long gill filaments with a high lamellar density. These features provide a large surface for gas exchange which, when coupled with the notably thin water-blood barrier of an average thickness of only 0.83 micro, would facilitate efficient absorption of oxygen by the gills. Oreochromis alcalicus was observed to be incapable of adapting to freshwater. This may have been due to the progressive degeneration of the chloride cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Fine structure of the branchial epithelium in the teleost Oreochromis niloticus

“…Our observations confirm the presence of two functionally and structurally distinct MRC populations, with pale cells being in close contact to lamellar vessels and dark cells appearing in the interlamellar region (Laurent, 1984;Pisam et al, 1989Pisam et al, , 1995Maina, 1990Maina, , 1991Cioni et al, 1991;Pisam and Rambourg, 1991;Goss et al, 1992;Avella et al, 1993). The presence of a crypt in pale MRC also supports previous findings that this structure is not a distinctive feature of marine teleosts or a structural change displayed when a euryhaline species is transferred from freshwater to seawater (Laurent, 1984;Hossler et al, 1985;Wendelaar Bonga and Van der Meij, 1989;Maina, 1990). In contrast to previous descriptions (Maina, 1990(Maina, , 1991Cioni et al, 1991;Avella et al, 1993), we here confirm that pale MRC exhibited a lateral-apical projection beneath lamellar PVC and a depressed apical crypt, with microvilli, a submembrane terminal web and horizontally orientated small rod-like dense vesicles that exocytosed their contents into the crypt lumen (Pisam et al, 1995).…”

“…Although their role in NaCl excretion in seawater species is clearly established, in freshwater fishes this role is still under investigation, with some suggesting the uptake of both Na 1 and Cl 2 , and others that they are the site of Cl 2 uptake whereas the uptake of Na 1 occurs through PVC (Pisam and Rambourg, 1991;Goss et al, 1992;Evans et al, 2005). Our observations confirm the presence of two functionally and structurally distinct MRC populations, with pale cells being in close contact to lamellar vessels and dark cells appearing in the interlamellar region (Laurent, 1984;Pisam et al, 1989Pisam et al, , 1995Maina, 1990Maina, , 1991Cioni et al, 1991;Pisam and Rambourg, 1991;Goss et al, 1992;Avella et al, 1993). The presence of a crypt in pale MRC also supports previous findings that this structure is not a distinctive feature of marine teleosts or a structural change displayed when a euryhaline species is transferred from freshwater to seawater (Laurent, 1984;Hossler et al, 1985;Wendelaar Bonga and Van der Meij, 1989;Maina, 1990).…”

Bioaccumulation and ultrastructural alterations of gill and liver in Asian sea bass,Lates calcarifer(Bloch) in sublethal copper exposure

“…The transmission microscopic structure of the gill in the fish exposed to various chemicals has been reported in earlier works (Maina 1990;Pfeiffer et al 1997;Zahra khoshnood et al 2011;Ba-Omar et al 2011). The teleost liver has been shown to be very sensitive to pollutant exposure (Pinkney et al 2004;Blazer et al 2007).…”

Thin and Strong! The Bioengineering Dilemma in the Structural and Functional Design of the Blood-Gas Barrier

“…Gas exchange largely occurs across the simple, thin secondary epithelium that covers the secondary lamellae ( Fig. 7, B, D, and E), while metabolic functions, e.g., osmoregulation and ammonia/urea excretion, occur in the more elaborate primary epithelium that lines the gill filaments (121,136). Chloride (mitochondria-rich) and mucus cells occur in the primary epithelium (Fig.…”