GLOSSARY 479 



Ectoderm The outer layer of cells in an embryo that gives rise to vari- 

 ous organs. 



Ectoparasite Parasite that lives on the surface of the host. 



Edema Excessive accumulation of fluid in tissue spaces. 



Efficacy Ability to produce effects or intended results. 



Effluent The discharge from a rearing facility, treatment plant, or 

 industry. 



Egg The mature female germ cell, ovum. 



Egtved Disease See Viral Hemorrhagic Septicemia. 



Emaciation Wasting of the body. 



Emarginate Fin Fin with the margin containing a shallow notch, as in 

 the caudal fin of the rock bass. 



Emboli Abnormal materials carried by the blood stream, such as blood 

 clots, air bubbles, cancers or other tissue cells, fat, clumps of bacteria, 

 or foreign bodies, until they lodge in a blood vessel and obstruct it. 



Embryo Developing organism before it is hatched or born. 



Endocrine A ductless gland or the hormone produced therein. 



Endoparasite A parasite that lives in the host. 



Endoskeleton The skeleton proper; the inner bony and cartilaginous 

 framework. 



Energy Capacity to do work. 



Enteric Redmouth Disease (ERM) A disease, primarily of salmonids, 

 characterized by general bacteremia. Caused by an enteric bacterium, 

 Yersinia ruckeri. Synonym: Hagerman redmouth disease. 



Enteritis Any inflammation of the intestinal tract. 



Environment The sum total of the external conditions that affect 

 growth and development of an organism. 



Environmental Gill Disease Hyperplasia of gill tissue caused by pres- 

 ence of a pollutant in the water that is a gill irritant. See Bacterial Gill 

 Disease. 



Enzootic A disease that is present in an animal population at all times 

 but occurs in few individuals at any given time. 



Enzyme A protein that catalyzes biochemical reactions in living organ- 

 isms. 



Epidermis The outer layer of the skin. 



Epizootic A disease attacking many animals in a population at the same 

 time; widely diffused and rapidly spreading. 



Epizootiology The study of epizootics; the field of science dealing with 

 relationships of various factors that determine the frequencies and dis- 

 tributions of diseases among animals. 



Eradication Removal of all recognizable units of an infecting agent 

 from the environment. 



ERM See Enteric Redmouth Disease. 



