Fig. 1 in Scientific note The air-breathing cycle of Hoplosternum littorale (Hancock, 1828) (Siluriformes: Callichthyidae)

Fig. 1. Air-breathing cycle of Hoplosternum littorale: 1) ascent to the water surface; 2) in contact with the surface the fish expands its oral cavity, inspiring air; 3) turning head down, with compression of the oral cavity pushing air into the intestine and causing the expiration of old air from the anus (circle, continuous line); 4) return to bottom and release of small air bubbles through the opercula (circle, dotted line). Arrows indicate the action of the buccal pump.