Labyrinthula Inside the Spores of a Vesicular—Arbuscular Mycorrhizal Fungus

SUMMARY

Approximately 20% of the ruptured spores (“spore shells”) of the vesicular-arbuscular mycorrhizal fungus Gigaspora gigantea collected from the face of a barrier sand dune contained spindle-cells of Labyrinthula sp. Single large spore shells harbored from a few to thousands of spindle-cells. Cultures of Labyrinthula were obtained by incubating surface-sterilized spore shells on a modified serum-seawater agar medium. Only spore shells from the dune face contained spindle-cells. The absence of Laybrinthula from spore shells from other areas of the dune correlates with lower salinities at these sites. Because G. gigantea spores and spore shells are common in the barrier dune, the occurrence of Labyrinthula within them may represent a significant reservoir of inoculum able to enter the waters on either side of the dune.