A Tale of Two Microbiomes: Nanoplastics Exposure Disrupts Hosts but Spares Parasites--Metadata

Animal microbiomes play profound roles in many aspects of their lives, including their interactions with other animals and their environment, highlighting the need to understand whether external factors can similarly influence microbiome composition across interacting partners. In the context of the Anthropocene, one highly pervasive polluter that can penetrate animal cells are nanoplastics (NP, plastic particles of a size ≤100 nm). Therefore, quantifying the effect of NP on microbiomes of interacting animals can shed light on how this polluter may interfere with ecological associations. This study investigated whether experimental exposure to NP and the duration of the exposure period modified the bacterial alpha and beta diversities of freshwater isopods, Austridotea annectens, and of their trematode parasite, Maritrema poulini. Naturally infected isopods were assigned to three treatments in the laboratory consisting of exposure to control (0 mg/L NP), low-NP (5 mg/L), and high-NP (20 mg/L) treatments for 21 days (3 weeks) and 42 days (6 weeks). The bacterial component of the host (haemolymph) and parasite (whole body) microbiomes were characterised and compared among all three treatments between the two exposure periods. We found that both NP concentration and exposure time influenced the isopod’s microbiome composition, and longer exposure also led to a decrease in their microbiome diversity. However, NP concentration did not have impact on the parasite’s microbiome, which only showed different composition in response to longer exposure time. Our findings shed new light on the effect of NP on a three-way host-parasite-microbiome interaction and raise awareness of NP pollution in our rapidly changing world.