The genus Capellomyces was first described in 2020 as part of a collaborative study that documented two Capellomyces species (Hanafy et al, 2020a). The main morphological characteristics of Capellomyces are common to several different anaerobic fungal genera: monocentric thallus, filamentous rhizoidal system, and monoflagellated zoospores.
The genus name, Capellomyces, is derived from the Latin word for goat as this is the animal the genus was first isolated from. The type species is called C. foraminis. The species name means “opening or aperture” in Latin, which refers to zoospore release occurring via a wide apical pore. The type strain for this species is BGB-1, and was isolated from a wild Boer goat in the USA.
The second Capellomyces species, C. elongatus, was isolated from a domestic goat in India. The type strain for this species is GFKJa1916. C. elongatus can be morphologically differentiated from C. foraminis due to it having extremely long sporangiophores (up to 300 μm) and multisporangiated thalli.
To date, Capellomyces has only been described in goats. Analysis of ITS1 sequences from previous culture independent surveys showed that no Capellomyces sequences had been previously detected (Hanafy et al, 2020a). Capellomyces was also not detected in a published LSU based survey (Hanafy et al, 2020b), although mismatches with the reverse primer used in the study may have prevented detection of the genus.
Images are shown above of C. foraminis strain BGB-1 (Images 1-9) and C. elongatus strain GFKJa1916 (Images 10-11).
In liquid medium, Capellomyces spp. produce a thin fungal biofilm (Image 1). On solid roll agar medium, they form small brown, circular colonies with a dark center of sporangial structures (Image 2).
Microscopically, Capellomyces spp. produce mainly monoflagellated zoospores (Image 3), although zoospores with two flagella can also be observed (Image 4). Capellomyces spp. have a monocentric thalli with filamentous anucleate rhizoidal systems (Image 5). Both endogenous (Image 6) and exogenous (Image 7) sporangia are produced.
In C. foraminis, zoospores are released through a wide apical pore (Image 8) and the sporagangial wall collapses after release (Image 9). To date, the zoospore release mechanism of C. elongatus has not been documented. C. elongatus has characteristic long thick sporangiophores (Image 10) and multisporangiated thalli (Image 11).
No sequenced genome or transcriptomes are currently available for Capellomyces.
For the C. foraminis strain BGB-1 and C. elongatus strain GFKJa1916 that are pictured above, the LSU sequences are available in the NCBI database (accession number MK881975 and MK775304, respectively).