FISH DISEASES 353 



7. Metabolic waste products: Water in which fish have lived for a time is known as 

 "conditioned water" and presumably such water is better for that particular 

 species than for others, due, it is thought, to the concentration of certain species 

 specific beneficial metabolites. 



8. Diet : Many fish diseases are due to vitamin deficiency, particularly when fish 

 are kept in captivity and fed artificial diets. Liver and renal damage are prob- 

 ably the major ailments encountered. 



9. Handling: Directly or indirectly handling may be the cause of the majority of 

 deaths. Abrasions are sites for infections. Even with the greatest care, moving 

 established pairs or colonies from one tank to another usually means the loss of 

 some specimens. New fish, regardless of size, are often attacked by the per- 

 manent residents of a particular aquarium. 



10. Parasitism: Many ecto-parasites show no host specificity, hence there is great 

 virulence (see Nigrelli & Atz, 1943: Zoologica 27:1). 



REFERENCES 



""The Aquarium Journal" - San Francisco Aquarium Society. Golden Gate Park, San Francisco 13, Calif. ($3.00 per year). 

 "The Aquarium" - Aquarium Publishing Co. P. O. Box 832, Norristown, J.]. {$3. 00 per year). 

 "Tropical Fish Hobbyist" - 245 Cornelison Ave. Jersey City, N. J. {$3. 25 per year). 



"Duriiig the past several years the investigations in this 

 field (Developmental Physiology) have centered to a tremendous 

 degree upon the cellular complex arising during development 

 with a many-faceted study of the individual cell parts. While in 

 many ways the attacks on this single element have been more 

 definitely focused than previously , the degree of complexity of 

 the major problems of differentiation has not lessened for in 

 many cases we have moved only in descriptive vocabulary , cfiang- 

 ing from the physiomorphological to the chemical and sometimes 

 to physical terminology. It is true that in realizing the relative 

 complexity of specific cell components as functional entities we 

 have advanced considerably in this half century. We need a con- 

 solidation of our present position combined with a more vigorous 

 attack on the physical principles involved before we can really 

 synthesize the facts and factors which we, at present, intuitively 

 place in a perspective of greater prominence than the future may 

 show to be warranted. " 



J. S. Nicholas 1960: Ann. Rev. Physio. 22:95 



