Chapter IX — 133 — Yeasts and Molds 



mal sea water. With one exception the entire group developed best in 

 media with an initial pH above 7.6, and, unHke most terrestrial molds, 

 growth was detinitely unfavorable in acid media. Their response to salin- 

 ity and hydrogen-ion concentration was interpreted as a physiological 

 modification to marine conditions. All species cultured made an appre- 

 ciable growth at 5° C, although the most favorable temperature for 

 growth on complex synthetic media was between 22.5° and 27.5° C. 



Special attention is directed to the slime mold Labyrinthula, a genus 

 of Myxomycetes. According to Whipple (1927), no aquatic species of 

 Myxomycetes had been reported as late as 1927. This may be because 

 labyrinthulae are regarded by some as rhizopods, since they possess 

 pseudopodia and exhibit remarkable powers of amoeboid movement. 

 Sparrow (1936) described two species of marine Labyrinthula^ one of 

 which is parasitic and the other saprophytic. The latter is not unlike 

 L. macrocystis which Cienkowsky isolated from marine algae in 1867. 

 It also resembles the Lahyrinthula species which Renn (1936) found asso- 

 ciated with diseased eel grass. Jepps (193 i) observed, in debris which 

 collects in the bottom of aquaria containing marine algae, species of 

 Labyrinthula, which infect and eventually destroy diatom cultures. In- 

 jured Laminaria are also infected, but Miss Jepps found no evidence 

 that uninjured Laminaria were parasitized by Labyrinthula. Two or 

 more fungi may be involved. Sparrow (1943) relates that a Labyrinthula, 

 along with Pyrrhosorus marinus and a Woronina-Wke fungus, has often 

 been found in decaying marine algae. 



In his monograph on aquatic Phycomycetes, Sparrow (1943) states 

 that most of the Phycomycetes discovered thus far in marine environ- 

 ments are members of the orders Saprolegniales, the so-called water molds, 

 and Lagenidiales. The Chytridiales, Plasmodiophorales, and Perono- 

 sporales also have marine representatives. Most of these are chytrid-like 

 forms living in or on algae. Sparrow points out that in many cases there 

 are no hard and fast distinctions between aquatic, amphibious, and ter- 

 restrial fungi. Representatives of all groups occur in both salt and fresh 

 water. 



Significance of yeasts and molds in the sea : — Exclusive of parasitic 



varieties, the importance of yeasts and molds in modifying the marine 

 environment is strictly secondary to that of the ubiquitous and more ver- 

 satile bacteria. Most yeasts and molds require a medium rich in organic 

 nutrients, particularly the simple carbohydrates, and the sea is notori- 

 ously poor in organic matter. However, when associated with plants or 

 animals or their products, aquatic fungi may be very active in the sea. 



As the causative agents of diseases of marine plants and animals, fungi 

 may be extremely important. Fresh- water animals including fish are 

 extensively parasitized by Saprolegnia and other aquatic fungi, and it may 

 develop that many marine animals are also the victims of parasitic fungi. 

 Sparrow (1936) described a fungus, Peter senia sp., which parasitizes 

 rotifer eggs. 



Malformed sardine eggs collected and preserved for us by the Cali- 

 fornia Fish and Game Commission were found to be filled with fungi. 

 This research project was interrupted by the War before it could be estab- 

 lished whether the fungi were responsible for the malformation of the 

 sardine eggs or if the fungi attacked only moribund eggs. The preliminary 

 observations suggest the possibility of fungus infections accounting for 

 extensive failure of sardine crops. 



