Filtration efficiency in bivalves and examining Zebra Mussels

Queen's University Marine Research Station, Portaferry, Co. Down in June, 1989.

In the summer of 1989, I was fortunate enough to spend 5 weeks at the Queen's University (QUB) Marine Research Station in Portaferry, County Down, Northern Ireland. I lived in the hostel attached to the station - an old house called 'Barholm' next door. The staff were very helpful and committed to marine biology in all its aspects. I was able to engage in a number of research projects, and it was a happy time.

    One of the projects being undertaken there concerned filtration efficiency in bivalves (and Pacific oysters and mussels in particular) which were cultured in table ponds with a constant flow of aerated/filtered seawater. Filtration efficiency is a topic of research as filter feeders have the capacity to clean water and accumulate pollution which is especially a problem in food species such as edible mussels. 

    The method concerned removing the gill under the microscope and placing an ink drop on the gill edge and record the time taken for the ink drop to travel along the gill edge (distance measured using a graticule). Gill preparations have been continued to be made in edible mussels by Riisgård & Larsen (2007) in their comparison of the measurement of filtering efficiency in gill preparations and whole specimens. Hans Riisgård carried out an extensive review of such methods in 2001 (q.v.).

    In order to determine the effects of contaminants, some of the bivalves were placed in culture media doped with contaminants, and the bivalves dissected and kept in the doped media whilst under the microscope. The ink drops applied whilst viewing and timings are taken.  In general, it was found that with contaminants, the filtering rate was depressed with respect to controls of no contaminant, thus as hypothesized contaminants adversely affected culturing of commercial bivalves.  This method is destructive, however, so using a species other than the valuable native or cultured species would be desirable. There are other non-destructive methods such as measuring expulsion flow from mussels (Mouabad et al., 2001). 

Now fast forward to the 21st century...

I have taken the first step in repeating the work from the 1980s in the Black Sea 'Zebra mussel' - Dreissena polymorpha (Pallas, 1771), Bivalvia, Dreissenidae - which is an invasive species gaining a foothold throughout Ireland - by collecting the mussels from the wild in order to carry out the experiments. This would also benefit the native wild mollusk species at the same time! In addition, I hope to assess the potential of this species as a model for toxicology studies.

Some older specimens

The initial culture setup

Currently, I am in Step 1. - establishing the culture. Mussels were collected from slipways and jetties in the southeastern shore of Lough Sheelin (at Ross, Co. Meath) where the mussel is prevalent (tides of shells have been washed up of the northwestern shore at Crover, Co. Cavan, in the previous years). They are then accustomed to living in diluted lake water by the addition of mineral water. After a number of weeks, once the water is changed to wholly mineral water, the outer surface of the mussels will be rinsed in mineral water and washed in dilute hypochlorite (bleach). The mussels will then be placed on cleaned concrete roof tiles cut into strips for attachment (I will show this in a separate post).

The collected mussels are being cultured in polypropylene buckets in shop-bought mineral water and fed a mix of spirulina and a fish food formula. Byssus strands were deployed by the mussels and attachment to stones introduced and the buckets themselves took place.

The mussels opened and the siphons were observed in the active specimens, and have been maintained and continue to survive in 2 litres of spring water, aerated and fed with spirulina powder weekly. As the summer wears on I hope to observe the reproductive activity of this species.

I'll keep updating as I progress. The genome for D. polymorpha is available from the link below (McCartney et al., 2019).

References

McCartney, M.A. ; Benjamin Auch;  Thomas Kono; Sophie Mallez; Ying Zhang; Angelico Obille; Aaron Becker; Juan E. Abrahante; John Garbe; Jonathan P. Badalamenti; Adam Herman; Hayley Mangelson; Ivan Liachko; Shawn Sullivan; Eli D. Sone; Sergey Koren; Kevin A. T. Silverstein; Kenneth B. Beckman; Daryl M. Gohl (2019) The Genome of the Zebra Mussel, Dreissena polymorpha: A Resource for Invasive Species Research. bioRxiv preprint doi: https://doi.org/10.1101/696732 available at: https://www.biorxiv.org/content/10.1101/696732v1.full.pdf

Mouabad, A.; Ait Fdil, M.; Maarouf, A.; and Pihan, J.C. (2001) Pumping behaviour and filtration rate of the freshwater mussel Potomida littoralis as a tool for rapid detection of water contamination. Aquatic Ecology 35: 51-60

Riisgård, H.U. (2001) On measurement of filtration rates in bivalves — the stony road to reliable data: review and interpretation. MARINE ECOLOGY PROGRESS SERIES. 211: 275–291.

Riisgård, H.U. & Larsen, P.S. (2007) Viscosity of seawater controls beat frequency of water-pumping cilia and filtration rate of mussels Mytilus edulis. MARINE ECOLOGY PROGRESS SERIES. 343: 141–150.  doi: 10.3354/meps06930