Development of dependence on aerial respiration in Polypterus senegalus (Cuvier)

Abstract

The respiratory behaviour and partitioning of O 2 uptake between air and water were investigated in Polypterus genegalus using continuous-flow and two-phase respirometers and lung gas replacement techniques. P. senegalus rarely resorts to aerial respiration under normal conditions. Partitioning of O 2 consumption depends on the activity and age offish and the availability of aquatic oxygen. Immature fish (12-22 g) cannot utilize aerial O 2 but older fish exhibit age-dependent reliance on aerial respiration in hypoxic and hypercarbic waters. Pulmonary respiration accounts for 50% of the total requirement at aquatic O 2 concentrations of about 3.5 mg . 1-' (or CO 2 of about 5%) and fish rely exclusively on aerial respiration at O 2 concentrations of less than 2.5 mg . I'. Branchial respiration is initially stimulated by hypercarbia (C0 2 : 0.5-0.8%) but increased hypercarbia (C02 -I %) greatly depresses (by over 90%) brancial respiration and initiates (C02: 0.5%) and sustains pulmonary respiration.

Development of cranial muscles in the actinopterygian fish Senegal bichir,Polypterus senegalusCuvier, 1829

“…The external gills are observed from embryonic to juvenile period in P. senegalus (Bartsch et al, 1997). It is considered that the skin and the internal gills are used for gas exchange in these stages (Babiker, 1984;Bartsch et al, 1997). Multiciliated epidermal cells are present from neurula stage in P. senegalus (Bartsch et al, 1997).…”

“…In P. senegalus, paired simple sac-like lungs are formed in early ontogeny. Until juvenile stage P. senegalus is unable to utilize aerial oxygen and is entirely dependent on aquatic respiration (Babiker, 1984). However, the formation of the internal gills remains unclear.…”

Effects of environmental hypercapnia on pulmonary ventilation of the South American lungfish

“….  ventilation in response to very light degrees of hypercapnia (equilibration of the water with 1% CO 2 ), while aerial as well as branchial ventilation were depressed by higher levels (Babiker, 1984). When exposed to anoxic water, both Lepidosiren and the bichir Polypterus sp., avoid losses of O 2 to the water via the gills (Lomholt & Glass, 1987), but this topic has not been studied extensively.…”

“…The order Polypteriformes retain many primitive characteristics, including a swim bladder in the form of paired, ventrally located lungs used for accessory respiration of air (Babiker, 1984) which is probably an ancestral condition (Carroll, 1988). The ventilatory control of the bichir Polypterus senegalis Cuvier has been evaluated (Babiker, 1984).…”

“…The ventilatory control of the bichir Polypterus senegalis Cuvier has been evaluated (Babiker, 1984). This African species increased pulmonary 1184 .…”