488 FISH HATCHERY MANAGEMENT 



Meristic Characters Body parts that can be counted (scales, gill rakers, 

 vertebrae, etc.); useful in species identifications. 



Merthiolate, Sodium (Thimerosal) o-Carboxyphenyl-thioethylmercury, 

 sodium salt; used as an external disinfectant, especially for living fish 

 eggs. 



Metabolic Rate The amount of oxygen used for total metabolism per 

 unit of time per unit of body weight. 



Metabolism Vital processes involved in the release of body energy, the 

 building and repair of body tissue, and the excretion of waste materi- 

 als; combination of anabolism and catabolism. 



Methylene Blue 3, 7-A/>Dimethylamino-phenazathionium chloride; a 

 quinoneimine dye effective against external protozoans and superficial 

 bacterial infections. 



Microbe Microorganism, such as a virus, bacterium, fungus, or proto- 

 zoan. 



Micropyle Opening in egg that allows entrance of the sperm. 



Migration Movement of fish populations. 



Milt Sperm-bearing fluid. 



Mitosis The process by which the nucleus is divided into two daughter 

 nuclei with equivalent chromosome complements. 



MJB Coffee can; essential measuring device used by some fish culturists 

 in lieu of a graduated cylinder. 



Monthly Temperature Unit (MTU) Equal to one degree Fahrenheit 

 above freezing (32° F) based on the average monthly water tempera- 

 ture (30 days). 



Morbid Caused by disease; unhealthy; diseased. 



Morbidity The condition of being diseased. 



Morbidity Rate The proportion of individuals with a specific disease 

 during a given time in a population. 



Moribund Obviously progressing towards death, nearly dead. 



Morphology The science of the form and structure of animals and 

 plants. 



Mortality The ratio of dead to living individuals in a population. 



Mortality Rate The number of deaths per unit of population during a 

 specified period. Synonyms: death rate; crude mortality rate; fatality 

 rate. 



Motile Aeromonas Septicemia (MAS) An acute to chronic infectious 

 disease caused by any motile bacteria belonging to the genus Aeromo- 

 nas, primarily Aeromonas hydrophila or Aeromonas punctate (= Aeromonas 

 liquifaciens) . Synonyms: bacterial hemorrhagic septicemia; pike pest. 



Mottled Blotched; color spots running together. 



Mouth Fungus See Columnaris Disease. 



