AILMENTS AND DISEASES 



The Saprolegniaceae 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. iii. 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 hyphse grow, each 

 bearing a Sporangium or brood-sac filled 

 withspores,andforminga 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 

 commonest and most frequent causes of 

 epidemics among fishes. Other more or 

 less common species of the eastern section 

 of the United States are S. mixta, S. 

 monoica, S. torulosa, S.declina, S. astorophora 

 and S. trileaseana. Spores of one or more 

 forms of these saprophytes are always 

 present in all freshwater and are therewith introduced into the aquarium. 

 Pythiopsis. The most common species of this genus is Pythiopsis 

 cvmosa,. a minute vegitative body similar to the foregoing, but with more 

 slender hyphse; which occurs in stagnant water and is parasitic upon low 

 forms of vegetal life and saprophytic on organic substances. 



DiCTYUCHUs. 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. 



AcHYLA. This fungus is one of the most malignant of the Sap- 

 rolegniacese. It attacks marine fishes during their freshwater spawning 



163 



FIG. III. Saprolegniacese, the most common 

 Vegetal parasites of Freshwater. 



Greatly enlarged. 

 43 to 45. Saprolegnia ferax, 

 46 to 49. Saprolegnia to'ulosa, 



50. Acklya apiculata. 



51. Achlya americana. 



I to 4. Hyphae with spores. 



52. Dictyuchus polysporus. 



53. Leptometus lacieus. 



54. Apkanomyces la-vis. 



a to c. Budding spores. 



