First report of potential pathogenic fungus Papiliotrema aurea in Glossiphonia complanata: Implications for leech-mediated fungal transmission

Leeches (Hirudinea), a diverse group of annelids, are primarily classified as either parasites or predators, depending on their feeding methods and life strategies. These groups differ in habitat and dispersal. This diversity plays a significant role in the functioning of aquatic ecosystems, especially in the context of epidemiological threats posed by the transmission of pathogenic fungi by leeches. Due to fungi's ability to adapt rapidly to new environments and given their dissemination through various vectors, including leeches, these diseases can spread quickly. This study examined the mycobiome of the parasitic leech Glossiphonia complanata, which has a wide range of hosts, making it a potentially effective vector for the spread of fungal diseases.

Leeches were collected from five water reservoirs located on the Morasko Campus of Adam Mickiewicz University. Anesthetized leeches were surface-sterilized with 75% ethanol, dissected into fragments, and placed on PDA medium. DNA was extracted from the cultivated fungal colonies, followed by PCR amplification of the ITS region sequences. The PCR products were sequenced, and additional morphological analyses of the fungi were conducted.

In addition to widely recognized environmental fungi such as Cladosporium spp., the fungal species Papiliotrema aurea was detected and identified within the bodies of the leeches. This species, previously isolated from the Chinese mitten crab (Eriocheir sinensis), exhibits a notable capacity for colonization in various organisms. Such findings imply that P. aurea not only possesses the ability to thrive in specific microenvironments but also raises concerns regarding its potential pathogenicity.

In summary, the ecological diversity of leeches and their ability to interact with other organisms, including pathogenic fungi, highlight their importance in aquatic ecosystems. Research on the mycobiome of leeches provides valuable insights into potential vectors of fungal diseases. Understanding these mechanisms can contribute to a better management of epidemiological risks and the protection of aquatic ecosystems from pathogen invasions.