Morphology & Thermal Preference

Batrachochytrium salamandrivorans (Bsal) is a fungus in the phylum Chytridiomycota and the order Rhizophydiales. Like B. dendrobatidisBsal has demonstrated two main life stages: a zoospore with a single posteriorly directed flagellum and a mature thallus, containing asexual zoospores, called zoosporangium (Van Rooij et al., 2015).

In vitro, Bsal produces zoospores from colonial or monocentric thalli. Colonial thalli contain more than one sporangium while monocentric thalli contain only one sporangium. Two principal distinguishing morphological features of Bsal in culture are the development of germ tubes from encysted spores and the presence of more colonial thalli than can be observed in Bd cultures (Martel et al., 2013, Van Rooij et al., 2015).

Recently Stegen et al. (2017) described an additional infectious form of Bsal spore, a robust encysted spore with the ability to persist in the environment for extended periods of time. This encysted spore is produced both in vivo and vitro and has its own specific infection, transmission and persistence strategy which contributes to its durability and hardy nature.

Bsal grows optimally between 10°C – 15°C, however, it also grows, albeit slowly at 5°C. The death of Bsal occurs at  ≥ 25°C (Martel et al., 2013).

Phylogeny and classification of the genus Batrachochytrium.
Cladogram showing the taxonomic position of Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans within the fungal kingdom (a), the phylum Chytridiomycota (b) and order of the Rhizophydiales (c). The position of the Microsporidia remains uncertain. Branch lengths are not proportional to genetic distances. (Van Rooij et al., 2015)
In vitro culture of B. salamandrivorans in TGhL broth at 15 °C. (A) Monocentric thalli predominate, with the rare presence of colonial thalli (black arrow). Sporangia develop discharge tubes (white arrow) to release zoospores (Scale bar, 100 μm.) (B) Scanning electron microscopic image of a mature sporangium with rhizoids (R), discharge tubes (D), and germ tube formation (arrow) (Scale bar, 10 μm (Martel et al., 2013)