Defensive role of cystidia against Collembola in the basidiomycetes Russula bella and Strobilurus ohshimae.

Cystidia in fruit bodies are taxonomically important characters. However, little is known about their ecological functions. The defensive role of cystidia against the collembolans Ceratophysella denisana and Mitchellania horrida was examined in fruit bodies of Russula bella and Strobilurus ohshimae. Cystidium-destruction experiments demonstrated that R. bella and S. ohshimae cystidia decrease the number of collembola found on gills, although the effects were not significant for R. bella against C. denisana. Furthermore, R. bella cystidia increased collembolan mortality in the laboratory, and in the field, collembola were found dead on parts of the fruit body of this species where cystidia were abundant. In the cystidium-destruction experiment, approximately one-third of collembola appeared to avoid R. bella. Therefore, deadly cystidia may be selected for in R. bella to avoid collembolan attack. Laboratory feeding experiments revealed that collembola can extensively damage R. bella and S. ohshimae basidiospores by feeding. These results suggest that the cystidia of R. bella and S. ohshimae may protect basidiospores from collembolan predation.