Faculty of Veterinary Medicine University of Zagreb
Abstract
Effects of air exposure on the respiratory organs of Channa striata possessing bimodal respiration for exploitation of water (via gills and skin) as well as air (through air - breathing organs – suprabranchial chamber, ABOs) have been investigated. On air exposure the fish survived for 8 h. Following air exposure the fine, thin-walled blood capillaries (BLCs) at the surface of the ABO swelled and bulged out due to congestion when the blood came very close to air in the lumen. In the initial periods, mucous cells (MCs) of all three respiratory organs showed periodic fluctuations in their density and staining properties and stain for sulphated moieties known to hold an additional quantity of water. The sub-epithelial connective tissues of the ABO and skin also contained a large quantity of sulphated mucopolysaccharides. Subsequently, severe wear and tear and sloughing leading to haemorrhage took place from the skin. The outer cellular layers of the epidermis sloughed off. The density of sacciform-granulated cells (SGCs) increased and stained strongly with PAS technique (almost negative in controls). Air exposure also caused extensive damage in the gills. In the initial periods the BLCs showed severe congestion, causing extensive bulging and protrusion onto the surface. Later, the epithelial linings of gill filaments (PL) as well as respiratory lamellae (SL) were detached and lifted up. Subsequently, the neighbouring SL fused, causing decreased surface area, thereby reducing the efficiency of gills. The ladder-like arrangements of the pillar cells - blood capillaries (PLCs-BLCs) also collapsed. PAS-positive materials appeared within these PLCs. Subsequently, the BLCs dilated and showed congestion. The RBCs of gills also showed PAS staining. A thin layer of sulphated slime often covered the respiratory epithelia. Prior to death of the fish, the cells of the gills degenerated extensively. Thus, air exposure also prevented normal branchial respiration and the fish died due to anoxia and other physiological disorders.Istraženi su učinci izlaganja zraku dišnih organa ribe dvodihalice Channa striata koja za disanje koristi vodu (putem škrga i kože) ili zrak (putem organa zračnog disanja odnosno suprabranhijalne komore). Izložene zraku ribe su preživjele 8 sati. Nakon izloženosti zraku, nježne krvne kapilare tankih stijenki na površini organa zračnog disanja, odebljale su i izbočile se zbog kongestije kad je krv došla vrlo blizu zraku u lumenu organa. Sluznične stanice svih triju dišnih organa pokazivale su u početnim razdobljima povremeno kolebanje u gustoći i sposobnosti bojanja sulfatnih dijelova poznatih po zadržavanju dodatne količine vode. Subepitelno vezivno tkivo organa za zračno disanje i kože također je sadržavalo veliku količinu sulfatnih mukopolisaharida. Kao posljedica velike istrošenosti i ljuštenja javilo se krvarenje na koži. Vanjski slojevi stanica epidermisa su se ljuštili. Gustoća vrećastih zrnatih stanica se povećala i stanice su se snažno obojale PAS metodom (kontrola gotovo negativna). Izloženost zraku uzrokovala je i opsežna oštećenja škrga. Krvne kapilare su u početnom razdoblju bile zadebljane, nabubrene s izbočinama na površini. Kasnije su se bazalni epitel škržnih listića i dišni nabori odvojili i otkinuli. Potom su se susjedni dišni listići spojili dovodeći do smanjene površine, a time i do smanjene učinkovitosti škrga. Palisadni poredak stupčastih stanica krvnih kapilara također je propao. PAS pozitivni materijal pojavio se u stanicama škržnih listića. Nakon toga su se tanke stijenke krvnih kapilara proširile i zadebljale. Dišne stanice su se također obojale PAS metodom.Tanak sloj sulfatne sluzi često je prekrivao dišni epitel. Neposredno prije uginuća škržne stanice su degenerirale. Tako je izloženost zraku također spriječila normalno branhijalno disanje i ribe su uginule zbog nedostatka kisika i drugih fizioloških poremećaja
