A Histological Evaluation of the Development of Respiratory Structures in Channel Catfish (Ictalurus punctatus) and Tra (Pangasianodon hypophthalmus)

Abstract

In the realm of finfish production, Siluriformes is one of the most dominant orders on an international scale. Within the United States the family Ictiluridae is most common, while Pangasiids and Clariids are cultured in Africa, Asia, and parts of Europe. In more tropical climates the capacity for production is exponentially greater than in the U.S. due to the ability for higher stocking densities per unit of area. Representative species from these families have distinct morphologies resulting in the presence or absence of an accessory respiratory organ. Ictalurids such as Channel Catfish (Ictalurus punctatus) do not have an accessory respiratory organ however tra (Pangasianodon hypophthalmus) possess the advantage to utilize atmospheric oxygen to supplement in periods of low dissolved oxygen. Using histological analysis, we identified critical stages of development in Channel Catfish and Tra at which gill, and accessory respiratory structures develop and become functional. Future investigation of these species utilizing RNA sequencing to determine the levels of expression for genes that are active in gill, swimbladder, and air breathing organs.