
AILMENTS AND DISEASES 

The Saprolegniacee have the merit of scavengers in consuming the organic 
compounds of dead animal matter and when this source of nutrition is 
exhausted it is usually followed by a disappearance of the fungi; but 
under favorable conditions some species of this genus become active 
parasites on fishes, amphibia, insects and plants, and have caused epidemics 
of diseases in rivers and lakes, as well as among fishes in the confines of 
the aquarium and breeding tank. | 
SAPROLEGNIA. Fig. r11. The most common species of this genus 
is Saprolegnia ferax a minute vegitative body without stem or leaf, 
which may exist as a saprophyte and develop its spores. These drift 
about in the water, to immediately under- 
go a change in contact with a fitting animal 
surface not protected from their ravages. 
A rootlike nucleus or rhizoid is formed 
from which threadlike hyphe grow, each 
bearing a Sporangium or brood-sac filled 
with spores,and forminga white cottony felt 
over a malignant sore. These ulcers, if 
not checked, spread over the surface and 
sap the vitality of the victim until death 
ensues. This parasitic fungus is one of the 

FIG. 111. Saprolegniacee, the most common 
Vegetal parasites of Freshwater. commonest and most frequent causes of 
Greatly enlarged. 4 5 
Rata acl) Saprolegnia ferax! epidemics among fishes. Other more or 
46 to 49. Saprolegnia tor ulosa. 
ple less common species of the eastern section 
50. <Achlya apiculata. 
gt. Achlya eee: - ofthe Wnited: States, ated. wxta, 0: 
I to 4. yp. @ with spores. 5 : , . 
52. Dictyuchus polysporus. monoica, S. torulosa, S.declina, 8. astorophora 
53. Leptomerus lacteus, Blea S f , 
ee eared and S. ¢rileaseana. Spores of one or more 
EE Se forms of these saprophytes are always 
present in all freshwater and are therewith introduced into the aquarium. 
Pyruiopsis. The most common species of this genus is Pythiopsis 
cymosa, a minute vegitative body similar to the foregoing, but with more 
slender hyphz; which occurs in stagnant water and is parasitic upon low 
forms of vegetal life and saprophytic on organic substances. 
Dicryucuus. This fungus produces a skin disease on cold-blooded 
animals and lower forms of aquatic life. In appearance it resembles Sap- 
rolegnia, but the sporangia are more fusiform. The most common species 
are Dichtyuchus polysporus and D. magnusii; the former.as frequently present 
as an animal parasite as S. ferax. Usually they are associated on the 
same host. 
Acuyta. This fungus is one of the most malignant of the Sap- 
rolegniacee. It attacks marine fishes during their freshwater spawning 
163 
