GLOSSARY 473 



Bacteriocidal Having the ability to kill bacteria. 



Bacteriostatic Having the ability to inhibit or retard the growth or 



reproduction of bacteria. 

 Bacterium (plural: bacteria) One of a large, widely distributed group of 



typically one-celled microorganisms, often parasitic or pathogenic. 

 Balanced Diet (feed) A diet that provides adequate nutrients for normal 



growth and reproduction. 

 Bar Marks Vertical color marks on fishes. 

 Barbel An elongated fleshy projection, usually of the lips. 

 Basal Metabolic Rate The oxygen consumed by a completely resting 



animal per unit weight and time. 

 Basal Metabolism Minimum energy requirements to maintain vital 



body processes. 

 Bath A solution of therapeutic or prophylactic chemicals in which fish 



are immersed. See Dip; Short Bath; Flush; Long Bath; Constant-Flow 



Treatment. 

 Benign Not endangering life or health. 

 Bioassay Any test in which organisms are used to detect or measure the 



presence or effect of a chemical or condition. 

 Biochemical Oxygen Demand (BOD) The quantity of dissolved oxy- 

 gen taken up by nonliving organic matter in the water. 

 Biological Control Control of undesirable animals or plants by means 



of predators, parasites, pathogens, or genetic diseases (including sterili- 

 zation). 

 Biological Oxidation Oxidation of organic matter by organisms in the 



presence of oxygen. 

 Biotin Vitamin H, one of the B-complex vitamins. 

 Black Grub Black spots in the skin of fishes caused by metacercaria 



(larval stages) of the trematodes Uvilifer ambloplitis, Cryptocotyle lingua, 



and others. Synonym: black-spot disease. 

 Black Spot Usually refers to black cysts of intermediate stages of trema- 

 todes in fish. See Black Grub. 

 Black-Spot Disease See Black Grub. 

 Black-Tail Disease See Whirling Disease. 

 Blank Egg An unfertilized egg. 

 Blastopore Channel leading into a cavity in the egg where fertilization 



takes place and early cell division begins. 

 Blastula A hollow ball of cells, one of the early stages in embryological 



development. 

 Blood Flagellates Flagellated protozoan parasites of the blood. 

 Blue-Sac Disease A disease of sac fry characterized by opalescence and 



distension of the yolk sac with fluid and caused by previous partial 



asphyxia. 



