A survey of aquatic lignicolous fungi in the area about Blacksburg, Virginia

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Virginia Polytechnic Institute

A survey of the literature reveals little information concerning the aquatic fungi associated with submerged wood debris. During the past fifteen years several mycologists have studied such lignicolous fungi, but their efforts have been confined almost entirely to marine and brackish waters. It was thought that a study of similar organisms from fresh water would make a significant addition to our knowledge of aquatic fungi. This study involves the collection, identification, and description of freshwater lignicolous fungi from the area about Blacksburg, Virginia.

To collect the fungi, sterilized panels of pine and poplar were submerged at six aquatic sites £or fifteen days or more. After submergence the wood was incubated in sterile moisture chambers and then examined with a dissecting microscope. Specimens of fungi found on the wood-surface were mounted and studied under high power.

All of the collections are described in this paper, including those that could not be identified. Generic description have been adapted. Descriptions of species have been adapted and modified from the literature when they have seemed adequate, otherwise they are the author's own. Reproductive structures are illustrated. A key to the identified fungi is provided.

The following fungi were identified and described: Dematiaceae - Alternaria sp., Bisporomyces chlamydosporis, Cacumisporium sp., Dictyosporium elegans, Dictyosporium sp., Gonytrichum macrocladum, Humicola sp., Leptographium sp., Monotospora megalospora, Piricauda sp., Septonema hormiscium, S. secedens, Sporidesmium caespitulosum, S. anglicum, Sporoschisma saccardoi, Trichocladium opacum; Moniliaceae - Arthrobotrys sp., Clathrosphaerina zalewski, Fusarium solani, Helicomyces roseus, Hobsonia mirabilis, Verticillium sp.; Tuberculariaceae - Bactrodesmium arnaudii; Sphaeropsidales - Aposphaeria agminalis, Asteromella sp., Coniothyrium sp., Stagonospora sp. (1), Stagonospora sp. (2); Actinomycetes - Nocardia sp.; Pyrenomycetes - Nectria sp. Two unidentified Dematiaceae and ten unidentified Pyrenomycetes were also collected and described.

A comparison of the results of this study with the results of other investigations on aquatic fungi indicates the existence of a distinct aquatic mycoflora associated with wood. Aquatic Hyphomycetes have been extensively collected by other workers from submerged leaves and from pond and stream scum. None of the species, not even the genera, of those collections have been found in the present survey. No lignicolous Phycomycetes were found in the present survey, although aquatic Phycomycetes are known to grow on a vast array of substrates.

The fresh-water population of lignicolous fungi may be fairly distinct from that of salt water. A survey of marine fungi reveals only five fungi - Alternaria sp., Dietyosporium elegans, Humicola sp., Trichocladium sp., Coniothyrium sp., Nectria sp. - that can be considered closely related to fungi found in the present study.

This study provides some insight into the ecology of the fresh-water lignicolous fungi, although the study itself has beer, primarily taxonomic. Perhaps the most important problem now is to determine the actual habitat of these fungi. Research so far indicates only that they grow on wood and that their spores are carried in the water. Another problem is to investigate the nutrition of these organisms, to determine if they digest lignin and if they are unique in this regard.