Physiology of Finfish and Shellfish

2.1.1. Introduction

The physical and chemical process by which an organism supplies oxygen to its tissue’s and remove carbondioxide out of tissues. In aquatic organism, the gill (a thin –walled finely divided structures containing extensive capillary beds) is used for external respiration, ie carrying on gas exchange with the water. Then the dissolved oxygen is circulated through pigments and internal exchange, (ie transporting gases to and from the cells and tissues) are taken place inside the body.

The movement of oxygen from the external media to the cells is by way of diffusion, a substance moves from a higher to a lower concentration. In opposite direction CO₂ moves the same way.