| Abstract: | The respiratory organs of Amphipnous cuchia comprise a pair of aicsacs, vestigial gill filaments borne on second gill arch and vascular folds of the third gill arch. The volume of each air-sac, its surface area and its reltionship with the body weight of the fish have been determined. The air-sac is lined by a respiratory mucosa which is composed of vascular and non-vascular areas. Each vascular area, called here the ‘respiratory islet,’ studded with hundreds of vascular rosettes, which are formed of collagenous material and supported by endothelial cells. Pilaster cells are absent. The ‘islets’ are covered over by a single layer of squamous type of epithelial cells. The non-vascular areas (lanes') are the stratified part of the respiratory epithelium and contain a large number of mucous glands which secrete mainly acid mucopolysaccharides. The vascularisation of the gills have been studied by India ink injection methods. The secondary gill lamellae are absent, their place being taken up by coiled vascular loops. A quantitative estimation of haemoglobin in blood of ‘cuchia’ and other air- and water-breathing fishes have been made by colorimetric method and the results have been discussed in relation to their habit and habitats. The cranial muscles which are involved in respiration of ‘cuchia’ and the mechanics of muscle action in breathing have been described. |
