Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2024 May 25;14(1):11958.
doi: 10.1038/s41598-024-62245-2.

Freshwater mussels prefer a diet of stramenopiles and fungi over bacteria

Isabella J Maggard  1 , Kayla B Deel  1 , Tina W Etoll  1 , Rachael C Sproles  1 , Tim W Lane  2 , A Bruce Cahoon  3
Affiliations

Freshwater mussels prefer a diet of stramenopiles and fungi over bacteria

Isabella J Maggard et al. Sci Rep. .

Abstract

Freshwater mussels (Mollusca: Unionidae) play a crucial role in freshwater river environments where they live in multi-species aggregations and often serve as long-lived benthic ecosystem engineers. Many of these species are imperiled and it is imperative that we understand their basic needs to aid in the reestablishment and maintenance of mussel beds in rivers. In an effort to expand our knowledge of the diet of these organisms, five species of mussel were introduced into enclosed systems in two experiments. In the first, mussels were incubated in water from the Clinch River (Virginia, USA) and in the second, water from a manmade pond at the Commonwealth of Virginia's Aquatic Wildlife Conservation Center in Marion, VA. Quantitative PCR and eDNA metabarcoding were used to determine which planktonic microbes were present before and after the introduction of mussels into each experimental system. It was found that all five species preferentially consumed microeukaryotes over bacteria. Most microeukaryotic taxa, including Stramenopiles and Chlorophytes were quickly consumed by all five mussel species. We also found that they consumed fungi but not as quickly as the microalgae, and that one species of mussel, Ortmanniana pectorosa, consumed bacteria but only after preferred food sources were depleted. Our results provide evidence that siphon feeding Unionid mussels can select preferred microbes from mixed plankton, and mussel species exhibit dietary niche differentiation.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Conductivity and pH of Clinch River Water Before and After Incubation with Mussels. River water conductivity (a) and pH (b) was measured immediately after being placed into tanks and 24 h after the introduction of mussels. Control tanks contained no mussels. Error bars represent standard deviation. Asterisks represent p-values equal or lower than 0.05 compared to river water (one-way ANOVA). Plus symbols represent p-values equal or lower than 0.05 compared to river water (one-way Kruskal–Wallis).
Figure 2
Figure 2
Estimation of the Clinch River planktonic microbiome using quantitative PCR. (a) Bacterial 16S. (b) Microeukaryotic 18S. (c) Fungal ITS. For each experiment, the amount of microbial DNA detected in each sample is expressed as a value relative to river water which was arbitrarily set to a value of 1.0. River water represents three water samples collected from the Clinch River at the beginning of the experiment. Three control tanks received no mussels and water samples were collected 24 h after its introduction. One species of mussel was placed into three replicate tanks with river water and incubated for 24 h before water samples were removed. Error bars represent standard deviation. Asterisks represent p-values equal or lower than 0.05 compared to river water (one-way ANOVA). Plus symbols represent p-values equal or lower than 0.05 compared to river water (one-way Kruskal–Wallis).
Figure 3
Figure 3
Beta diversity comparisons of the bacterial, microeukaryotic, and fungal portions of the Clinch River planktonic microbiome as principle coordinates plots. (a) 16S bacterial barcodes. (b) 18S microeukaryotic barcodes. (c) Fungal ITS directed barcode markers. River Water represents the microbiome of Clinch River water collected at the beginning of the experiment. Control represents river water incubated in three tanks for 24 h with no mussels. Each species name represents the mussel that was introduced into three replicate tanks and incubated for 24 h before water samples were analyzed. Species are color-coded.
Figure 4
Figure 4
Taxonomic composition of the planktonic microbiome in the Clinch River before and after incubation with mussels. (a–c) Bacterial phyla. (d–f) Microeukaryotic phyla. (g–i) Fungal families. Metabarcode sequences were used to identify taxa present in water samples. Metabarcode read counts were used to estimate the relative amounts of each taxon the mussels had cleared from the plankton within a 24 h incubation. The proportion of reads attributed to each taxon are expressed as values relative to those found in the Clinch River at the initiation of the experiment, which is arbitrarily set to the value of 1.0.
Figure 5
Figure 5
Conductivity of the AWCC retention pond water before and after incubation with mussels. (a) Conductivity was measured immediately after the retention pond water was placed into each tank used in this experiment. Control tanks received no mussels. (b) Conductivity as measured 24 h after mussels were introduced. (c) Conductivity as measured 48 h after mussels were introduced. (d) Conductivity as measured 96 h after mussels were introduced. Error bars represent standard deviation. Asterisks represent p-values equal or lower than 0.05 compared to river water (one-way ANOVA). Plus symbols represent p-values equal or lower than 0.05 compared to river water (one-way Kruskal–Wallis).
Figure 6
Figure 6
Quantitative PCR estimation of the microbes cleared from the AWCC retention pond plankton over the course of 4 days. (a–f) Bacterial 16S. (g–l) Microeukaryotic 18S. (m–r) Fungal ITS. Water was pumped from the AWCC retention pond into tanks and water samples removed and analyzed (Day 0). Mussel species were placed into the tanks and water samples removed and analyzed one, two, and four days after the beginning of the experiment. Control tanks received no mussels. Error bars represent standard deviation. Asterisks represent p-values equal or lower than 0.05 compared to river water (one-way ANOVA). Plus symbols represent p-values equal or lower than 0.05 compared to river water (one-way Kruskal–Wallis).
Figure 7
Figure 7
Taxonomic composition of the planktonic bacteria in the AWCC retention pond before and after incubation with O. pectorosa. (a–d) Bacterial phyla. (e) The 4 most common classes within the phylum Proteobacteria. (f) The 4 most common orders within the phylum Bacteroidota. Metabarcode sequences were used to identify taxa present in water samples when the experiment was set up (Day 0), in a control tank with no mussels (Control, Day 4), and four days after Ortmanniana pectorosa was added. The proportion of reads attributed to each taxon are expressed as values relative to those found in the Clinch River at Day 0 of the experiment, which is arbitrarily set to the value of 1.0.
Figure 8
Figure 8
Taxonomic composition of the planktonic fungi in the AWCC retention pond before and after the addition of O. pectorosa. The 5 most common fungal families are shown. Metabarcode sequences were used to identify which taxa were present in water samples when the experiment was set up (Day 0), in a control tank with no mussels (Control, Day 4), and four days after Ortmanniana pectorosa was added. The proportion of reads attributed to each taxon are expressed as values relative to those found in the Clinch River at Day 0 of the experiment, which is arbitrarily set to the value of 1.0.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Williams JD, Warren ML, Cummings KS, Harris JL, Neves RJ. Conservation status of freshwater mussels of the United States and Canada. Fisheries. 1993;18:6–22. doi: 10.1577/1548-8446(1993)018<0006:CSOFMO>2.0.CO;2. - DOI
    1. Lydeard C, et al. The global decline of nonmarine mollusks. BioScience. 2004;54:321–330. doi: 10.1641/0006-3568(2004)054[0321:TGDONM]2.0.CO;2. - DOI
    1. Strayer DL, et al. Changing perspectives on pearly mussels, North America’s most imperiled animals. BioScience. 2004;54:429–439. doi: 10.1641/0006-3568(2004)054[0429:CPOPMN]2.0.CO;2. - DOI
    1. Williams JD, et al. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshw. Mollusk Biol. Conserv. 2017;20:33–58. doi: 10.31931/fmbc.v20i2.2017.33-58. - DOI
    1. Ricciardi A, Neves RJ, Rasmussen JB. Impending extinctions of North America freshwater mussels (Unionoida) following the zebra mussel (Dreissena polymorpha) invasion. J. Anim. Ecol. 1998;67:613–619. doi: 10.1046/j.1365-2656.1998.00220.x. - DOI