GLOSSARY 489 



Mucking (Egg) The addition of an inert substance such as clay or starch 

 to adhesive eggs to prevent them from sticking together during spawn 

 taking. Most commonly used with esocid and walleye eggs. 



Mucus A viscid or slimy substance secreted by the mucous glands offish. 



Mutation A sudden heritable variation in a gene or in a chromosome 

 structure. 



Mycology The study of fungi. 



Mycosis Any disease caused by an infectious fungus. 



Myomere An embryonic muscular segment that later becomes a section 

 of the side muscle of a fish. 



Myotome Muscle segment. 



Myxobacteriosis A disease caused by any member of the Myxobacteria 

 group of bacteria. See Peduncle Disease, Cold Water Disease, Fin Rot 

 Disease, Columnaris Disease. 



Nares The openings of the nasal cavity. 



Necropsy A medical examination of the body after death to ascertain 

 the cause of death. Synonym for humans: autopsy. 



Necrosis Dying of cells or tissues within the living body. 



Nematoda A diverse phylum of roundworms, many of which are plant 

 or animal parasites. 



Nephrocalcinosis A condition of renal insufficiency due to the precipi- 

 tation of calcium phosphate (CaP04) in the tubules of the kidney. 

 Observed frequently in fish. 



Niacin One of the water-soluble B-complex vitamins, essential for 

 maintenance of the health of skin and other epithelial tissues in fishes. 



Nicotinic Acid See Niacin. 



Nitrification A method through which ammonia is biologically oxi- 

 dized to nitrite and then nitrate. 



Nitrite The NO7 ion. 



Nitrogen An odorless, gaseous element that makes up 78% of the earth's 

 atmosphere and is a constituent of all living tissue. It is almost inert in 

 its gaseous form. 



Nitrogenous Wastes Simple nitrogen compounds produced by the 

 metabolism of proteins, such as urea and uric acid. 



Nonpathogenic Refers to an organism that may infect but causes no 

 disease. 



Nostril See Nares. 



Nutrient A chemical used for growth and maintenance of an organism. 



Nutrition The sum of the processes in which an animal (or plant) takes 

 in and utilizes food. 



Nutritional Gill Disease Gill hyperplasia caused by deficiency of pan- 

 tothenic acid in the diet. 



