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AILMENTS AND DISEASES 
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sporangium. ‘They subsist on the juices of their host. Other forms are 
parasitic upon either growing or dead and decaying plants. 
Parasitic Func. The aquatic forms of this order, the Phyco- 
mycetes, found on animals and plants, consist of densely interwoven 
masses of cellular filaments, which terminate in or constitute the rootlike 
mycelium, from which hyphe and spore capsules are developed. With 
some species there is but a single hypha with reproductive bodies at the 
ends, this being the case with the more ordinary forms which affect the 
freshwater fauna. As fungi contain no chlorophyll they must take up and 
assimulate nutritive substances from other organisms and are therefore 
either saprophytic or parasitic. . 
The Phycomycetes are separated into five groups or sub-orders: 1, the 
Clytridiacee, of which a considerable number of species are parasitic upon 
Protozoa, Anguillule, Rotifera, Alge and Saprolegnia; 2, the Aucylistacea, 
parasitic upon Conjugate, Chlorophycee and Anguillule; 3, the Monodle- 
pharidacee, nearly all saprophytes; 4, the Peronosporacee, of which one 
genus, Pythium, has species parasitic on water plants and saprophytic on 
organic substances; and 5, the Saprolegniacee, the order of greatest interest 
to the fish-culturist, as of all the above, this group and the Peronosporacee 
are, to greater or lesser degree, aquatic at some or all stages of their 
existence. Most of the Peronosporacee are aquatic only at certain stages 
and afterwards become land forms, but the Saprolegniacee are aquatic at all 
stages. 
SAPROLEGNIACEA. This group of water molds contain both fresh 
and saltwater forms, of which the genus Saprolegnia is widely dessemi- 
nated in all bodies of freshwater. “he most generally distributed genera 
are Saprolegnia, Pythiopsis, Dichtyuchus, Achlya, Aphanomyces, Leptomitus and 
Apodachlya, present as saprophytes on dead and decaying aquatic animals 
and vegetal substances, and as parasites on all aquatic fauna, including the 
spawn and young and mature fishes, whenever the conditions favor their 
active development. This occurs on skin abrasions, bruises, wounds, loss of 
a scale, or on a torn or congested fin. When fishes are enfeebled and the 
mucus coating affected, when they are kept under unsanitary conditions or in 
too cold water, these fungi may develop to cover the entire body, first as 
a film and later as white or colored blotches on the head and body, in the 
mouth and gills, on the fins and on and under the scales, which they 
often force out of place; as, when once established upon and into the 
living tissue, they ultimately cause its destruction. Investigators have 
determined that the Saprolegniacee on fishes can be communicated to 
dead insects and those growing on dead insects and other low forms of 
aquatic fauna are communicated in their turn to living and healthy fishes. 
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