Topics: Oxygen, Gill, Respiration Pages: 9 (2226 words) Published: February 26, 2014

Title: Factors affecting Bimodal respiration in the catfish Corydoras aeneus

Abstract: The catfish, Corydoras aeneus is an organism that respires bimodally , that it is being capable of drawing oxygen from both water and air. It carries out aerial respiration through it’s adapted posterior intestine.This experiment was done in order to determine the disadvantages of aerial respiration by manipulation of oxygen content and depth. The effect of dissolved oxygen, when the fish was placed into a cylinder of water and the oxygen concentration was determined while the number of breaths in a 10 minutes period was counted and recorded. Within the 10 minute period, three 15 seconds reps were used to observe the number of opercula beats. The results obtained were that the initial ambient level in the experiment was 5.7; the breaths taken and the operculum beats were observed and recorded. The number of operculum beats decreased, possibly due to experimental errors. The number of breaths per hour showed an increase. The oxygen content was decreased by bubbling nitrogen until about4 mg/L. This was repeated 5 times at different oxygen content levels and opercula beats and breaths recorded. At ambient level 1.23 was maintained through manipulation of depth. From the results obtained the number of operculum beats per minute increased and the number of beats per hour increased with increasing depth. The effect of depth was also determined this was done by simply filling a 1L measuring cylinder with a depth of 10cm of low oxygenated water. The fish was then placed into these conditions where the number of surface breaths/hr and opercular beats/min were recorded at various depths of 15, 20, 25 and 35cm.

1) To determine the effect of the dissolved oxygen concentration on the types of the respiration (aerial or aquatic) being used by the Corydoras aeneus, a bimodal respirator. 2) To determine the effect of depth on the types of respiration (aerial or aquatic) being used by Coryderas aeneus. These objectives seek to find insight on the disadvantages and advantages of aerial respiration in aquatic organisms

Introduction: All living organisms require oxygen to live and carry out daily functions. The oxygen needed is obtained through various mediums namely; air and aquatic sources that contain dissolved oxygen. These media are then passed over a respiratory surface such as lungs or gills. The action of extracting oxygen from the surrounding atmospheric air is aerial respiration, mostly utilized by terrestrial organisms. However, oxygen extracted from the water surrounding the organism is called aquatic respiration (Horn etal, 1999). Aquatic organisms mostly possess the ability to derive oxygen from both air and water this is referred to as bimodial respiration (Graham 1997). Corydoras aeneus is a bimodial respiration. The main respiratory surfaces in are gills; these adaptations can be found internally or externally. Gills greatly increase the diffusion surface area enabling great extraction of oxygen from water than would be possible with their body surface alone. Bimodial organisms are highly adaptable to environmental stresses, notably to where the oxygen levels are low; this is known as hypoxia (Utsch 1996). When environmental factors are not ideal some fishes can switch to aerial respiration, showing that they can become resistant to these conditions. It is done by reducing gill ventilation, which reduces contact with the undesirable substances or conditions present. Corydoras aeneus does this mechanism via the posterior intestine to support aerial respiration. Air is firstly inspired through the mouth, while expiration occurs through the anus of the fish during diving motion (Kramer, D.L, and M.McClure 1980). Corydoras aeneus although having the ability to carry out aerial respiration, they mostly use aquatic respiration. It does this because it requires a substantial amount of energy to swim to the surface to...

References: “Respiration." Accessed January 30th, 2014. "Aquatic Respiration." Accessed January 30th, 2014. (2006).
Kramer and McClure, 1980. “Aerial respiration in the catfish Corydoras aeneus”. Can. J. Zool.
Accessesd Feburary 1st, 2014. . "Fish Gills, Respiration and Ventilation Help”. Accessed February 1st, 2014.
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