GLOSSARY 471 



Ammonium The ionized form of ammonia, NH4 . 



Anabolism Constructive metabolic processes in living organisms: tissue 

 building and growth. 



Anadromous Fish Fish that leave the sea and migrate up freshwater 

 rivers to spawn. 



Anaerobic Referring to a process or organism not requiring oxygen. 



Anal Pertaining to the anus or vent. 



Anal Fin The fin on the ventral median line behind the anus. 



Anal Papilla A protuberance in front of the genital pore and behind 

 the vent in certain groups of fishes. 



Anchor Ice Ice that forms from the bottom up in moving water. 



Anemia A condition characterized by a deficiency of hemoglobin, 

 packed cell volume, or erythrocytes. The more important anemias in 

 fish are (l) normocytic anemia caused by acute hemorrhaging, bac- 

 terial and viral infection, or metabolic disease; (2) microcytic anemia 

 due to chronic hemorrhaging, iron deficiency, or deficiency of certain 

 hematopoietic factors; (S) macrocytic anemia resulting from an 

 increase in hematopoietic activity in the spleen and kidney. 



Anesthetics Chemicals used to relax fish and facilitate the handling and 

 spawning of fish. Commonly used agents include tricane methane sul- 

 fonate (MS-222), benzocain, quinaldine, and carbon dioxide. 



Annulus A yearly mark formed on fish scales when rapid growth 

 resumes after a period (usually in winter) of slow or no growth. 



Anoxia Reduction of oxygen in the body to levels that can result in tis- 

 sue damage. 



Anterior In front of; toward the head end. 



Anthelmintic An agent that destroys or expels worm parasites. 



Antibiotic A chemical produced by living organisms, usually molds or 

 bacteria, capable of inhibiting other organisms. 



Antibody A specific protein produced by an organism in response to a 

 foreign chemical (antigen) with which it reacts. 



Antigen A large protein or complex sugar that stimulates the formation 

 of an antibody. Generally, pathogens produce antigens and the host 

 protects itself by producing antibodies. 



Antimicrobial Chemical that inhibits microorganisms. 



Antioxidant A substance that chemically protects other compounds 

 against oxidation; for example, vitamin E prevents oxidation and ran- 

 cidity of fats. 



Antiseptic A compound that kills or inhibits microorganisms, especially 

 those infecting living tissues. 



Antivitamin Substance chemically similar to a vitamin that can replace 

 the vitamin or an essential compound, but cannot perform its role. 



Anus The external posterior opening of the alimentary tract; the vent. 



Aquaculture Culture or husbandry of aquatic organisms. 



Artery A blood vessel carrying blood away from the heart. 



