Faculty of Veterinary Medicine University of Zagreb
Abstract
Histopathological alterations caused by desiccation stress in the aerial (accessory) respiratory organs (ARO) of Heteropneustes fossilis which has a developed bimodal respiratory mechanism for exploitation of water (through its gills) as well as air (through its ARO) have been described. The ARO assist the fish in surviving extreme drought conditions. When out of water, even though the fish survive for about 16 h, their air sacs suffer extensive damage. In the initial stages the fish very frequently open their mouths to gulp in more air. The blood channels of secondary lamellae of the ARO, engorged with ridged blood channels, exhibit extensive protrusion into the lumen where they form a network of very thin-walled tube-like structures. Prolonged desiccation causes wear and tear to these greatly extended blood channels, leading to haemorrhaging into the lumen. Simultaneously, from the blind ends of the ARO, many of the ridges approach very close to each other and finally meet, leaving no free respiratory surface in the lumen to breathe aerially, ultimately resulting in failure of aerial respiration and the demise of the fish.Opisane su histopatološke promjene, izazvane stresom isušivanja, zračnih (pomoćnih) dišnih organa u dvodihalice Heteropneustes fossilis koja je razvila dvostruki dišni mehanizam, i to iz vode (putem škrga) i iz zraka (putem zračnih dišnih organa). Ribe s zračnim dišnim organima preživljavaju ekstremne sušne uvjete. Kada su izvan vode preživljavaju oko 16 sati i tada njihove zračne vrečice trpe opsežna oštećenja. U početnoj fazi, riba često otvara usta kako bi uzela više zraka. Zračni kanali sekundarnih listića zračnih dišnih organa obuhvaćeni s grebenastim krvnim kanalima pokazuju znatnu protruziju u lumen gdje tvore mrežu cjevolikih struktura vrlo tankih stijenki. Produljeno isušivanje uzrokuje trošenje i kidanje tih jako izduženih krvnih kanalića i posljedično krvarenje u lumen. Istovremeno u slijepim krajevima zračnih dišnih organa mnogi se grebeni međusobno približavaju i spajaju, te tako više ne ostavljaju slobodnu zračnu dišnu površinu s konačnim zakazivanjem zračnog disanja i ugibanjem ribe
