#3 - Wrinkled Spores! Why not round? | Research Highlights (5.29.25)
- May 29, 2025
- 4 min read
During various wet periods in spring and fall, I have found the same troop of agarics munching on underground wood at my school (see above). A couple of months ago, I decided to do a spore print to identify them and mount a dry slide with the spores. Spores were brown, as seen below; the microscope slides have not been stained. I expected to see round spores, but these were odd; they were brown and wrinkled, like a deflated basketball. I did not spend much time on a proper ID, but in this article's context, it does not matter, as the focus will be on spore shape.
So, this is unremarkable. I mean - the spores are wrinkled! So what? Well, the morphology of an organism or part of an organism indicates a function. With that function comes an adaptation that has persisted so much in the genes of that species that it has become a trait of the species. So, what could wrinkly spores mean? Also, in a broader sense, gus? Something unremarkable can make a big difference in an organism's life cycle and can be easy to overlook, yet it is still important, and often surprisingly interesting to study.
I found a fantastic study, "Fungal spore diversity reflects substrate specific deposition challenges," by researchers Sara Calhim, Panu Halme, and others that looked into the correlation between size and shape in ascospores and basidiospores and the fungus's lifestyle (ectomycorrhizal, parasitic, etc.). Going in-depth on the entire study would be long, and although interesting, it would not pertain to the specific topic of spore size and shape. Instead, I have opted to provide 3 highlights from this study. I recommend reading the article if you are interested in spore morphology. Check it out at the link below!
Through analysis of 787 macrofungi (either within Basidiomycota or Ascomycota) genera, researchers analyzed the ecological statuses of each fungal taxon compared to the taxon's spore morphology. Spores, the "pollen" of fungi, or reproductive cells of fungi, are dispersed in trillions by a fruiting body. Once they find a substrate to create new mycelium to complete the life cycle, these spores undergo mitosis. The act of spores arriving on an ideal substrate depends on the spores leaving their fruiting body. Many fungi opt for the popular toadstool-with-gills, but others disperse via raindrops (like puffballs and earthstars) or other methods. Once the spores leave the nest, they must find substrate. The shape of the spores can influence this ability to find substrate.
For the first highlight, researchers discovered that round spore shapes that minimize the surface/volume ratio may increase the survival of a spore within a stressful environment. The round, globose shape may also have something to do with the differences in spore liberation types between fungal divisions, Basidiomycota (with club structures), and Ascomycota (with sac structures). The spore liberation process is when a mature spore is ejected or dropped from a macrofungus's fruiting body. Across the two incredibly diverse fungal phyla, fruiting bodies are vastly different; thus, how a spore is released differs based on that shape. However, researchers have noted that the general difference between ascomycete and basidiomycete spore release has created a morphological difference within the group's spores. Spores of an ascomycete are within a tube-like structure with a "lid" at the top that releases spores once open. Researchers state, "In the ascomycetes, where spores are discharged explosively from asci, cylindrical shapes maximize the flight speed of liberated spores." For the more adapted phyla of Basidiomycota, "...spore shape affects the size of the so-called Buller's drop, which determines the force with which spores are released from basidia" (Calhim, S. et al., 2018). The study also discussed how many fungi trade specializations (some described in further sections of this article) for less flight speed.
The second highlight pertains to spore size correlating with fruiting body size. In the agaric/gilled mushroom clade known formally as Agaricales (order) of Basidiomycota, bigger spores correlate with a bigger fruiting body. The explanation given in the study considers climate: "This suggests a co-adaptation to climatic stress, as large fruit bodies, just like large spores, are better adapted to retain humidity under dry conditions, due to the smaller surface-to-volume ratio" (Calhim, S. et al. 2018). Additionally, researchers asserted that increased spore size leads to increased spore resources that can be used to foster hyphal growth. For ectomycorrhizal fungi that need to find roots as soon as possible, this adaptation likely assists in boosting spore success rates.
Saving the best for last, researchers found an astonishing relationship between fungi and insects; spore shapes such as the ornamental shape (round with points) stick to hairy insects like ants and termites for the insects to carry the fungus's spores into the ground to form new mycelium. Fungi that form underground mycorrhiza with trees need a substrate next to a tree root, and insect spore delivery works perfectly! The study even suggests that this cross-kingdom assistance is necessary for ectomycorrhizal fungi. Similarly, most pollen is also found on the backs of insects that aid in long-distance pollination. As someone who loves to study fungi and plants, I have not thought much about how animals impact the life cycle, but now I have a larger appreciation for such creatures.
To conclude, the field of mycology is incredibly behind in understanding the causes behind these morphological differences, yet studies like the one discussed offer plenty of fascinating information to aid in understanding fungi's microscopic life cycle. Again, I heavily recommend checking out this research to learn more about spores and a fungus's life cycle. Many remarkable discoveries await in the microscopic details of something with seemingly little value, such as these infinitely small and interesting spores.
Work cited
Calhim, S., Halme, P., Petersen, J.H. et al. Fungal spore diversity reflects substrate-specific deposition challenges. Sci Rep 8, 5356 (2018). https://doi.org/10.1038/s41598-018-23292-8
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