SAPROLEGNIALES 1 



The order Saprolegniales includes what are probably the best and 

 most widely known species of aquatic Phycomycetes. Its members 

 have long been the object of extensive morphological, physiological, 

 and taxonomic studies. Indeed, the terms "water mold" and "fish mold" 

 as ordinarily used refer only to members of one family, the Saproleg- 

 niaceae. Most of the species belonging to the order are saprophytic on 

 plant and animal debris in fresh water or in soil. A few are parasitic on 

 fresh-water and marine algae, especially diatoms, and on the roots of 

 terrestrial flowering plants. Sommerstorffia spinosa is a predaceous par- 

 asite of microscopic animals, particularly rotifers. Tiffany 2 (1939a, 

 1939b) reviewed the relationship of species of Saprolegnia to diseases 

 of fish and amphibia and added new experimental evidence on the 

 parasitism of these fungi. 



More recently Vallin (1951) has given a clear account of an epidemic 

 in the northern Baltic, among members of a single species of copepod, 

 Eurytemara hirundoides, that is caused by a saprolegniaceous fungus, 

 probably a species of Leptolegniella or Leptolegnia. 



Nearly all the members of the largest family, the Saprolegniaceae, 

 may be grown in pure culture on artificial media. 



Although the designation "water mold" 3 suggests that the Saproleg- 

 niaceae occur exclusively in water, investigations have shown otherwise. 

 Numerous species have been isolated from the soil and some are thus 

 far known only from that habitat. This leads naturally to the specu- 

 lation : are they not primarily soil organisms and merely adventitious 



1 The Saprolegniaceae has not been treated here in full. A key to the genera, the 

 diagnoses of genera, and references to. any new taxa (except for Achlya) published 

 since Coker (1923) and Coker and Matthews (1937) are included. A comprehensive 

 study of Achlya has recently appeared (Johnson, 1956) and for complete accounts 

 of other genera, see the two aforementioned monographs. The original generic de- 

 scriptions are mostly cited from recognized authors. The others lay no claim to be 

 critical analyses. It is hoped the keys and figures are sufficiently informative to be of 

 service for identification at the generic level. 



- See also Vishniac and Nigrelli (1957). 



;! See Bock (1956). 



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