A rapid, non‐destructive method for sampling castrating parasites in endangered bivalve molluscs

Abstract

Bivalves are important ecosystem engineers, and there is emerging evidence that many species are afflicted with castrating parasites. Understanding the prevalence of these largely overlooked parasites is crucial in understanding the fundamental biology of bivalves, informing conservation efforts, and providing a wider understanding of host–parasite dynamics. Current techniques to assess the presence of parasites are destructive, making them untenable for endangered or protected populations. This article presents a non‐destructive method of sampling bivalve molluscs (Anodonta anatina) to detect castrating trematodes. Gonadal fluid is removed with a hypodermic needle from bivalves in situ and analysed in a laboratory setting without removing the mollusc from the field; this sampling mechanism has previously been shown not to harm the mollusc. A single 50 μl sample is sufficient to detect both the presence and developmental stage of the trematode with greater than 95% reliability, with all but the lightest infections visible. We recommend that this technique should be used to enhance knowledge on host–parasite dynamics in bivalves, and inform sensible conservation for threatened species.

Parasitism dramatically alters the ecosystem services provided by freshwater mussels

“…On the 14th of May 2021 we sampled 150 A. anatina from the River Great Ouse at King's Dyke (KD; 52.5397°N, −0.1753°E); this sampling location was selected as it has a high prevalence of the castrating trematode R. campanula . We non‐destructively assessed all mussels for trematode infection by extracting gonadal fluid using a hypodermic needle and examining it under a compound microscope (Brian & Aldridge, 2021b). R. campanula was identified using Gibson et al (1992); furthermore, it is the only digenean trematode reported using UK freshwater mussels as a first intermediate host (Brian & Aldridge, 2019).…”

Enigmatic freshwater mussel declines could be explained by the biodiversity‐disease relationship

“…Many long‐term surveys exist of mussel populations and communities in multiple locations, which likely represent a gradient of biodiversity losses over time (some sites will have undergone limited biodiversity changes, others will have lost many species). Using recently developed techniques, which can include non‐destructive sampling (Brian & Aldridge, 2021b; Richard et al, 2020), these communities should be sampled for pathogen load. We predict that those communities that have experienced higher diversity loss will have corresponding higher pathogen loads.…”

Don't move a mussel? Parasite and disease risk in conservation action

“…Within‐population variation is also important: differences in filtering behaviour or sizes of individuals can influence parasite communities (Brian & Aldridge, 2021b). Assessing these factors may be difficult for endangered species, but recently developed nondestructive methods may help (e.g., Brian & Aldridge, 2021a).…”