ABSTRACT

Gastrointestinal tract (GIT) is a fertile arena for the absorption, biotransformation, elimination, and toxicity of xenobiotics. This chapter describes the fish GIT in terms of its contribution and complexity by briefly describing its anatomy and physiology. Relatively short and extremely distensible in most teleosts, the esophagus facilitates movement of food from the pharyngeal region to the stomach. The proximal intestine closest to the stomach or esophagus generally is larger and has a larger lumen than either the middle or distal intestine. In most teleost fish, the celiacomesenteric artery supplies the majority of blood to the GIT. One of the characteristic features of the GIT is the large variance seen in blood flow to the region. pH has been characterized throughout the GIT in relatively few teleost species. The chapter also describes how toxicants may interact with the GIT through the processes of absorption, biotransformation, and elimination. Finally, it reviews what is known regarding chemical toxicity to the fish GIT.