Aquatic Myxomycetes

Mitsunori Tamayama Morioka Chuo High School, 4-26-1 Mitake Morioka City, Iwate Prefecture 020-0122, Japan and Harold W. Keller Botanical Research Institute of Texas, 1700 University Drive, Fort Worth, Texas 76107-3400 and University of Central Missouri, Department of Biology and Earth Science, Warrensburg, Missouri 64093, U.S.A. Correspondence to: [email protected] twigs, or woody fragments. Ground sites had a grayish peridium with calcium attract most myxomycete collectors but carbonate. The sessile sporangia had Abstract aquatic habitats may also harbor all life deposits of calcium carbonate that Ward Phaneroplasmodia of Diderma cycle stages, especially the microscopic (1886) described as being amorphous, effusum were observed feeding on swimming swarm cells, the amoeboid granules, or crystals that clearly green algae and diatoms submerged myxamoebae and the microscopic or places this taxon in the Physarales and in water in an aquarium. This is macroscopic plasmodia and possibly Didymiaceae. This taxon was assigned the first recorded description of the fruiting bodies. Water, either in the to Diderma difforme (now considered this species submerged in water temporary form of a thin film on the a synonym of Didymium difforme) and growing on agar culture. surface of water-soaked bark of living with the cautionary statement that “… Portions of the plasmodium were trees, or on decaying wood or leaves it seems very likely to belong to the also observed adhering to the skin found on ground sites, or submerged genus Diderma, having several of the surface of an eel-like fish swimming vegetation under standing water, or in characters of that genus well marked” in the aquarium, suggesting that natural or artificial wetland areas, are (Ward, 1886). There are discrepancies accidental contact may serve as potential sites for life cycle myxomycete here, however, based on the presence an agent of dispersal in aquatic stages. This includes the margins of lakes of calcareous nodes that interconnect habitats. Collectors are encouraged and ponds and self-contained bodies of a network of capillitial threads more to explore aquatic habitats that water in cement ponds, stock tanks, roof typical of the Physaraceae and the genus include the margins of lakes, ponds, eaves, and fish aquaria that may support Physarum. The presence of calcareous and in Sphagnum bogs, swamps, aquatic myxomycetes. granules and crystals raises questions and wetland areas. Species of the Review of Past Literature about assignment to the genus Physaraceae are noted and discussed Physarum, Diderma, or Didymium. as occurring more frequently in There are scattered reports of aquatic The presence of “calcareous nodes” aquaria and in aquatic habitats. myxomycetes, the earliest being that of in the capillitium would rule out the Field observations are described for Ward (1886). He observed the growth genera Diderma and Didymium since collections of a Trichia sp. on cattails of a myxomycete identified as Diderma both genera typically lack calcium and Badhamia lilacina on Sphagnum difforme on roots of hyacinths cultured carbonate in the capillitium that moss. Examples of taxa found in in nutrient solutions. Apparently the follows current classification. This may aquaria are Didymium difforme, D. plasmodia grew in size and developed be a species of Physarum – possibly iridis, and D. nigripes. Color images fruiting bodies completely submerged in Physarum cinereum. document the development of the the water. Plants were grown vertically Additional species of myxomycetes plasmodia in the aquarium and on with the roots hanging down in water identified as Physarum gyrosum, P. the agar surface. where tiny black spots thought to be nutans, Fuligo cinerea, and F. septica sporangia of a myxomycete appeared were grown submerged in water and on the surface of the submerged roots the plasmodial stage observed by and on the leaves exposed to dry air Parker (1946). All of these taxa are Introduction outside. Description of sessile sporangia members of the family Physaraceae in included a capillitial network with nodes Myxomycetes are typically found in the order Physarales. that had deposits of granules or crystals moist terrestrial habitats as plasmodia There are few reports of plasmodia or of calcium carbonate. Sporangia that or fruiting bodies on decaying logs or fruiting bodies in natural aquatic habitats developed at the water-air interface among forest litter of decaying leaves, but noteworthy is Didymium aquatile 18 FUNGI Volume 6:3 Fall 2013 described by Gottsberger and Nannenga- of an aquarium. This plasmodium was Color pictures illustrate a yellow Bremekamp (1971). The plasmodium carefully removed and maintained in phaneroplasmodium changing to was observed as a greenish-yellow agar culture by feeding it oat flakes. white that eventually formed stalked phaneroplasmodium growing in a stream Microscopic observation revealed a sporangia typical of Didymium nigripes. submerged at a depth of 10-20 cm on unicellular green alga present throughout The myxomycete species observed leaves and twigs and sometimes floating the protoplasm in the fan and veins. growing thus far in submerged aquatic on the water surface. This stream was The plasmodium was maintained for environments are: Didymium aquatile, in a secondary forest in the district of several months, and during this time, the D. iridis, D. nigripes, Fuligo cinerea, Botucatu, Sao Paulo state, Brazil. These alga thrived and became incorporated F. septica, Physarum gyrosum, and P. observations were made several times as into the normal rhythmic protoplasmic nutans. These species are all members of the phaneroplasmodium was growing on streaming. Some of the algal cells became the Physarales. the sandy bottom and moving against the enclosed in food vacuoles but the White plasmodia of Physarum current, sometimes leaving the water to majority were scattered throughout the didermoides and Fuligo cinerea were form fruiting bodies. The advancing and protoplasm. Attempts to isolate the green grown on sterile oat agar culture free of feeding edge of the phaneroplasmodium alga were successful and it was identified bacterial contaminants in association was “deeply incised” instead of the typical as a species of Trebouxia (Keller and with three species of green alga that even margin. Braun, 1999). formed green plasmodia. Direct It was extrapolated further that The plasmodium continued to increase microscopic observation confirmed “Should future studies reveal that the in size and maintained its green color the presence of dividing green alga plasmodium characters of this species throughout this period. These cultures cells of Chlorella xanthella apparently are fundamentally different from those were maintained on 2% water agar and establishing an endophytic myxolichen found in all other myxomycetes, then it the plasmodia were fed crushed and (Lazo, 1961). This suggested that might be desirable to refer Didymium sterilized old-fashioned oat flakes. The apparently the algal component replaced aquatile either to a new genus or to a plasmodium increased in size and was bacteria as a source of nutrients. In subgenus of its own.” This overemphasis sub-cultured by transferring portions on contrast, the yellow plasmodia of of a life cycle growth form known to be agar blocks to additional agar plates until P. polycephalum, P. gyrosum and F. highly variable gives little credibility and 10 agar cultures were maintained. These septica appear to take the algal cells justification for a new genus; even the cultures continued to grow and were also and digest them and the plasmodia status of a new species is questionable. green in color which suggested the algal do not become green. Another study In addition, the new species description cells were capable of surviving in the using white plasmodia of Fuligo cinerea is based on highly variable sporangial plasmodial protoplasm. demonstrated the exchange of 32P morphology such as the translucent To our knowledge, this is the first radioactive phosphorus between algal stalk, hemispherical spore case, scanty reported record of a myxomycete forming cells of Chlorella xanthella and the capillitium, crystal aggregates irregular an algal-myxomycete association. in shape, and spores varying from 6.5 Eventually, the plasmodium formed to 17 μm in diameter (Gottsberger and stalked sporangia typical of the genus Nannenga-Bremekamp, 1971). All of Didymium, but the stalks in this case NOW in paperback! these characters are known to be highly were bright green instead of dark brown. variable in field collections and in cultures Apparently most of the green alga cells of Didymium species. Water should be were deposited in the stalk. The sporangia considered along with premature drying were identified as Didymium iridis. Even as possible causes for this variability though the spores germinated, repeated (Keller and Schoknecht, 1989). attempts to continue the life cycle failed Myxomycetes (13 identified species) because plasmodia never formed (Keller were isolated from substrata submerged and Braun, 1999) in southern Illinois swamps (Shearer More recently Lindley et al. (2007) and Crane, 1986). One species was isolated 14 myxomycete species from new to science, Diderma diadematum. submerged vegetation of aquatic habitats Identification to species included (ponds and lakes). These samples were the Trichiales (7), Physarales (2), taken from 5 cm above and below the Stemonitales (2), and Liceales (2). water level and were cultured

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