Last September Ethan Crenson asked about two fungi he collected in New York. The first one, Trichoglossum farlowii (Fig. 1a), was the host of the second one, Gelatinopsis geoglossi (Fig. 1b, 2a-c, 3-6). Trichoglossum farlowii was described by Mordecae Cubitt Cooke (1825 – 1914) in honor of William Gilson Farlow, founder of the Farlow Library. It is found mostly in eastern of North America and Canada growing on soil in association with grass (GBIF 2020, Index Fungorum 2021). The genus Trichoglossum has flattened club-shaped fruiting structure and are commonly known as earth tongues. The fruit bodies are large enough, 1-10 cm tall, to be picked up by most collectors. In contrast, Gelatinopsis geoglossi, a parasite on Trichoglossum species, is almost unnoticeable on the hymenium of the earth tongue. It is only 0.04-0.1 mm diam. and 0.05-0.09 mm high (Fig. 2a-c). It was initially described as Hypomyces geoglossi by Job B. Ellis and Benjamin M. Everhart in 1886. The placement in Hypomyces, a pyrenomycete, reflects its fungal parasitic habit but contradicts the morphology of the fungus – it produces apothecia not perithecia. Recognizing the nature of the ascomata, Edgar V. Seeler, working at the Farlow Herbarium, proposed the genus Micropyxis for this species (Seeler 1943). Later it was referred to Gelatinopsis.

Does size matter? This is a common question in biology and one the most interesting traits studied in evolution. In the past, it was common to think that species evolved to reach larger body sizes over evolutionary time. Now we know that this general rule is not always true (Blanckenhorn 2000, Bonner 2006). In any environment on Earth there are an array of organisms of different sizes, from the smallest unicellular organisms to the largest trees or mammals (op. cit.). But what do we know about size changes in fungi?

Mycelial mass and nutrient supplies influence the development of fruit bodies. A good and stable source of nutrient supply will allow the development of larger fruit bodies. Some studies have shown that saprotrophic fungi have on average smaller fruit body than ectomycorrhizal that have less restriction on their carbon sources than saprobes because of their symbiosis with the plants (Bässler et al. 2015). Wang et al. (2009) showed saprobes produce larger fruit bodies compared to leaf endophytes that grow in a limited area with fewer resources. The same happens with dung inhabiting fungi. n quickly perishable substrates like dung, there is competition for nutrients on a limited resource and therefore fruit bodies tend to be smaller (Halbwachs et al. 2018).

In general, we can say that fungi with large fruit bodies occur where more resources are available. They live longer and produce a smaller number of fruit bodies, but each one supports more spores. Fungi that grow with limited resources (i.e. small fragments of wood, leaves, etc.) have a restricted supply of nutrients and have smaller fruit bodies. These fungi tend to have short life cycles and compensate for their small size and fewer spores by producing more fruit bodies per surface area (Halbwachs 2018).

We have a good example of these principles with Trichoglossum farlowii and Gelatinopsis geoglossi. The former is a fungus that grows on soil associated with plants (Fig. 1a) where resources are more available and therefore develop large fruitbodies. The latter is an obligate parasite with tiny fruitbodies (Fig. 1b, 2b) that completes it life cycle quickly on the mature host (Trichoglossum farlowii) before its fruitbody senesce. As noted in the literature and as seen in the examination of specimens, the parasite grows in great abundance in the hymenium of the host among the black setae (Fig. 1, 2c). Gelatinopsis compensates for its small size by producing hundreds of apothecia and covering completely the hymenium of the Trichoglossum (Fig. 1b). This does not allow the Trichoglossum to effectively discharge ascospores (Baral & Marson 2000). The parasite changes the appearance of the Trichoglossum. Healthy and infected individuals can be distinguished on sight (Fig. 1a).

Recent studies on Gelatinopsis are few as are studies of the family Helicogoniaceae to which Gelatinopsis is referred. The family has 7 genera and 38 species. They are all parasites in the hymenia of fungi (Ascomycota, Basidiomycota) distributed mostly worldwide mostly in temperate ecosystems (Jaklitsch et al. 2016). There are only a few sequences on GenBank, mostly of two gene regions ITS and LSU for four genera (Eleutheromyces, Gelatinipulvinella, Gelatinopsis, Geltingia). In the last revision and large phylogeny of the class Leotiomycetes published by Johnston et al. (2019), only two sequences of two genera (Gelatinipulvinella astraeicola, Gelatinopsis fungicola) were used. These species were placed sister to the order Phacidiales, an order with saprobic and parasitic (endophytic) species that grow on leaves, bark, and wood (Jaklitsch et al. 2016). Due to the lack of taxa sampling in the family Helicogoniaceae and the class Leotiomycetes more generally, it is still unclear if these relationships are true. Furthermore, the current information in GenBank for the three species of Gelatinopsis with sequences suggest that the genus could be paraphyletic. Further complicating the picture, there is no current sequence for the type genus Helicogonium. But we are now able to add sequences of the type species of Gelatinopsis (G. geoglossi, Fig. 1b, 2a-c, 3-6).

After colonizing and killing the host from the inside out, the fungus produces a lengthy fruiting body that emerges to spread its spores to the next unsuspecting insect. As peculiar as it may look, this specimen is not unique in our herbarium: we have over 100 collections in the genera Cordyceps and Ophiocordyceps on a variety of hosts such as ants, caterpillars, cicadas, spiders, and even other fungi.

This species of fungus has been used in Traditional Chinese Medicine for centuries and is commoditized globally today. Supplements derived from Cordyceps are marketed to treat a wide range of diseases and are sold as capsules and powders. As these treatments become more widespread and desirable to many around the world, the fungus is increasingly threatened by overharvesting. If the Cordyceps industry continues to grow unsustainably, this frightening fungus may disappear altogether.