In situ and low-cost monitoring of particles falling from freshwater animals: from microplastics to parasites

Abstract

A simple and low-cost method of monitoring and collecting particulate matter detaching from (or interacting with) aquatic animals is described using a novel device based on an airlift pump principle applied to floating cages. The efficiency of the technique in particle collection is demonstrated using polyethylene microspheres interacting with a cyprinid fish (Carassius carassius) and a temporarily parasitic stage (glochidia) of an endangered freshwater mussel (Margaritifera margaritifera) dropping from experimentally infested host fish (Salmo trutta). The technique enables the monitoring of temporal dynamics of particle detachment and their continuous collection both in the laboratory and in situ, allowing the experimental animals to be kept under natural water quality regimes and reducing the need for handling and transport. The technique can improve the representativeness of current experimental methods used in the fields of environmental parasitology, animal feeding ecology and microplastic pathway studies in aquatic environments. In particular, it makes it accessible to study the physiological compatibility of glochidia and their hosts, which is an essential but understudied autecological feature in mussel conservation programs worldwide. Field placement of the technique can also aid in outreach programs with pay-offs in the increase of scientific literacy of citizens concerning neglected issues such as the importance of fish hosts for the conservation of freshwater mussels.

The endangered freshwater pearl mussel Margaritifera margaritifera shows adaptation to a local salmonid host in Finland

“…Huber and Geist (2019) have shown that non‐sympatric fishes can be suitable hosts for duck mussel ( Anodonta anatina ), but also, interestingly, found differences in duration of the metamorphosis/ development of glochidia between different host fish species – something that to our knowledge has not yet been studied for the freshwater pearl mussel. Determining metamorphosis success rate and juvenile quality of FPM (see Douda et al., 2020) may yield other new research directions in the area of population‐level host suitability and local adaptation. Finally, as FPM glochidia infestation may provide protection for host fish against bacterial disease (Chowdhury, Roy, et al., 2021), yet unknown features of the co‐evolutionary relationship between endangered FPM and their salmonid hosts – in addition or related to local adaptation – may be recovered through successful conservation programmes.…”

A riverine biodiversity hotspot in northern Myanmar supports three new and narrowly endemic freshwater mussel species

“…The research protocol used in that survey does not require expensive equipment and can easily be adapted for Myanmar. In the same way, a study on a cheap and mobile pontoon‐based conservation method for determining mussel–host associations, tested on Margaritifera margaritifera (Linnaeus, 1758) and its fish host Salmo trutta Linnaeus, 1758 (Douda et al, 2020), illustrates another approach that could be used in Myanmar, especially in the absence of research infrastructure.…”

Freshwater mussel conservation: A global horizon scan of emerging threats and opportunities

“…Studies identifying patterns in host‐fish suitability are needed to determine adequate management units for mussel–host resources. New technical solutions may enable simpler and more frequent intraspecific host testing in the field and areas with inadequate laboratory infrastructure (Douda et al, 2020 ). This will also lead to a better appreciation of how short‐term benefits from fish and mussel captive breeding programs might be offset by long‐term impairment of mussel–fish relationships in the wild.…”