In 1989, a new genus was synthesized to accommodate small, water loving, green fungi from Australia and New Zealand. The genes associated with this relatively new genus are most similar to species within the genus Vibrissea. Chlorovibrissea quite literally means green Vibrissea and is still nested within the same Vibrisseaceae family. The Chlorovibrissea represent just a handful of interesting, hydrophilic species that have evolved some noteworthy, fitness enhancing adaptations to carry out its aquatic ecology. After learning about the Chlorovibrissea, I was again reassured that dainty fungi like Chlorovibrissea phialophora, hold important ecological services to both freshwater and terrestrial habitats alike.
Chlorovibrissea phialophorais known commonly as the green pinball fungus. It’s relatively new to science because of a few reasons. For one, this species only grows in specific habitats in New Zealand. Additionally, the species is rather small, only growing up to one inch in length (25mm). It does grow in small clusters, but even so, this ascomycete fungus is super tiny and tends to blend in with the forest floor. Even in this period of modern science, it has easily been overlooked with its small size and exceedingly narrow distribution. You’ll simply walk right over C. phialophora if you’re not focused on finding it.
The closely related genus Vibrissea has around 30 different species of fungi and are found in many ecosystems around the world, in both Northern and Southern hemispheres. When the current continents were once jammed together in the supercontinent Gondwana, the ancestors of fungi within the Vibrisseaceae most likely occurred throughout the ancient landmass. By looking at the global distribution of fungi within this family, we see a spatial continuity that can be explained by plate tectonics. As New Zealand broke off from Gondwana around 80 million years ago, genes stopped flowing from the mainland. The isolated fungi went through a period of speciation, which is why many species only occur in these isolated regions and nowhere else.
Gondwana.
These species are saprophytic, and almost always fruit from water-sodden woody debris. By looking at the morphology of their spores, we gain an in-depth ecological perspective. Chlorovibrissea phialophora along with other related species develop its spores in structures called asci. Unlike most ascomycete fungi that disperse spores via wind current, aquatic species like Chlorovibrissea phialophora specialize in water dispersal. Each ascus produces 8 spores, but instead of generating oval wind dispersed spores, C.phialophora form long, threadlike spores also known as filiform spores. On some spores, tiny projections called phialides form, which is unique to the species and explains its scientific name. Asexual spores called conidia arise from such regions of the sexual filiform spore.
A.) Asci. B.) Ascospores that do not have a phialide. C.) Ascopores that have a phialide. D.) Paraphyses. From Kohn 1989.
So the species has long spores, so what? Well it is these long spores that greatly enhance its fitness. Many times, this species is found on the perimeter of streams and rivers. Much of the time the fruiting bodies are submerged underwater. With its preferred substrate being water-logged sticks and twigs, when discharged, these filiform spores get carried away by the water current and can actually wrap around woody debris. Small ovoid spores would have an exceedingly difficult time attaching to potential substrate in an aquatic habitat. Flexible filiform spores have the edge in these freshwater, riparian habitats.
The decomposition of wood debris drives the function of these freshwater habitats. Without fungi breaking down these sources of carbon, aerobic bacteria would carry out this decomposer role. Similar to fungi, these aerobic bacteria use oxygen. However, they are notorious for absorbing more oxygen than fungi, especially when they rapidly divide when enough resources are available. When aerobic bacteria dominate in the absence of hydrophilic fungi like C. phialophora, the aquatic ecosystem becomes starved of oxygen. The functioning of the entire system plummets as it can no longer sustain other life that too requires oxygen. C. phialophora and other water adapted species allow nutrients to flow from the forest floor to the rivers and streams that cut through them. Without these species, carbohydrates would either stay locked up in the form of woody debris, or feed oxygen depleting bacteria.