Revisiting the aquatic phycomycete biota of the Douglas Lake region since the time of Dogma and Sparrow

Fredrick K. Sparrow and his students, including Irineo J. Dogma, conducted many surveys of the aquatic phycomycete biota of the Douglas Lake region in Michigan, United States of America. Following the tradition of Sparrow and Dogma, we undertook an inventory of the aquatic phycomycete biota of the Douglas Lake region with an emphasis on Chytridiomycota. Cognizant of the difficulties of relying solely on light microscopy, we used a combination of light microscopy, culturing, and single cell techniques. We observed a total of 42 taxa. We successfully cultured Terramycetaceae sp., Physocladia obscura, and Rhizoclosmatium globosum. Using single cell techniques, we obtained molecular sequence data for Rhopalophlyctis sarcoptoides, Rhizophydium echinocystoides and an unidentified parasite of Desmidium. Our inferred maximum likelihood phylogeny placed Rhopalophlyctis sarcoptoides in the Chytridales as sister to Chytriomyces hyalinus. Rhizophydium echinocystoides was placed in the Rhizophydiales but did not group with the type of the genus. The unidentified parasite of Desmidium surprisingly grouped with members of Synchytrium. Our results provide a pilot study for demonstrating how light microscopy, culturing, and single cell techniques to obtain molecular sequences of chytrid taxa could be used to create a local aquatic fungal inventory based on molecular techniques, discover novel taxa, and potentially revise current taxonomy.

Ultrastructure of Mitosis in the Aquatic Phycomycete Chytriomyces Hyalinus

The aquatic Phycomycetes, particularly the Chytridiales, are a group of fungi with a rather simple life cycle and morphology. With the advent of ultrastructural investigations on these organisms, two stable characteristics (zoospore ultrastructure and nuclear division) have proven helpful in elucidating relationships in this perplexing taxon. The latter is described in this communication. Conventional techniques were employed in the preparation of the material. Interphase nuclei of C. hyalinus are essentially spherical in shape, measure approximately 2.8 μm in diameter, and have a single, centrally located, nucleus. Prophase nuclei, while not exhibiting condensed chromatin, are characterized by the presence of migrating centrioles and a fusiform or spindle-shape to the nuclear profile (Fig. 1). Nuclear pores predominate near the polar ends of the nuclear envelope. No evidence has been found to indicate that centrioles replicate during prophase.

Physiological studies with the fungus Saprolegnia megasperma isolated from the freshwater nematode Neomesomermis flumenalis

The aquatic phycomycete Saprolegnia megasperma Coker is recorded for the first time from the freshwater nematode Neomesomermis flumenalis (Welch) Nickle. The optimum temperature for growth of the fungus is between 13 and 19 °C, and the optimum pH is between 5.2 and 5.7. The pH indicators tested were non-toxic to this isolate. The optimum concentration of phosphate was 15 mM. The optimum concentration of lactalbumin hydrolyzate under the conditions used was 4 g/litre. Glucose utilization occurred readily; 40% of the original level was utilized by day 3, and by day 4 the glucose level had dropped to 9.6% of the day 0 level. All of the detectable glucose in the medium had been utilized by day 5 under the test conditions. The utilization of ninhydrin-positive substances from media that contained lactalbumin hydrolyzate with and without glucose was determined. Under both conditions the following substances were taken up from the medium: glycerophosphoethanolamine, L-methionine sulfoxide, L-aspartic acid, L-threonine, L-serine, L-proline, L-glutamic acid, glycine, L-alanine, DL-cystathionine, L-methionine, L-isoleucine, L-leucine, L-tyrosine, L-phenylalanine, L-lysine, L-histidine, L-tryptophan, L-arginine, and L-valine. Ammonia and urea were produced in both media by the isolate. The polyamines, putrescine, cadaverine, spermidine, and spermine, were not detected as being released during autolysis.