Does the freshwater mussel Anodonta anatina remove the fish pathogen Flavobacterium columnare from water?

Global decline of freshwater mussels (Unionoida) is threatening biodiversity and the essential ecosystem services that mussels provide. As filter-feeding organisms, freshwater mussels remove phytoplankton and suspended particles from the water. By filtering bacteria, freshwater mussels also decrease pathogen loads in the water. The objective of this study was to evaluate whether the common freshwater bivalve Anodonta anatina (duck mussel) could remove the bacterial fish pathogen Flavobacterium columnare from the water. Mussels reduced bacteria in both of the two experiments performed, so that the bacterial concentration at the end of the 96-h monitoring in mussel treatments was only 0.3–0.5 times that of the controls. Surprisingly, mussels did not reduce algal cell concentration statistically significantly. Mussel behavior (shell openness, foot position, and movement) was not affected by the presence of bacteria or algae, except for biodeposition formation, which was greatest in algal-fed treatments, followed by bacterial-fed treatments and controls, respectively. The intestines of bacteria-incubated A. anatina harbored F. columnare, suggesting that mussels ingested the bacteria. Present results suggest that freshwater mussels may also have a potential to mitigate aquaculture pathogen problems, as well as play a role in water quality management.

Iron, Phosphorus and Trace Elements in Mussels’ Shells, Water, and Bottom Sediments from the Severnaya Dvina and the Onega River Basins (Northwestern Russia)

Trace elements in freshwater bivalve shells are widely used for reconstructing long-term changes in the riverine environments. However, Northern Eurasian regions, notably the European Russian North, susceptible to strong environmental impact via both local pollution and climate warming, are poorly studied. This work reports new data on trace elements accumulation by widespread species of freshwater mussels Unio spp. and Anodonta anatina in the Severnaya Dvina and the Onega River Basin, the two largest subarctic river basins in the Northeastern Europe. We revealed that iron and phosphorous accumulation in Unio spp. and Anodonta anatina shells have a strong relationship with a distance from the mouth of the studied river (the Severnaya Dvina). Based on multiparametric statistics comprising chemical composition of shells, water, and sediments, we demonstrated that the accumulation of elements in the shell depends on the environment of the biotope. Differences in the elemental composition of shells between different taxa are associated with ecological preferences of certain species to the substrate. The results set new constraints for the use of freshwater mussels’ shells for monitoring riverine environments and performing paleo-reconstructions.

Filter Feeding and Carbon and Nitrogen Assimilation of a Freshwater Bivalve (Unio douglasiae) on a Toxic Cyanobacterium (Microcystis aeruginosa)

We investigated the possible intake of toxic cyanobacteria (Microcystis aeruginosa) as a nutrient resource for a filter-feeder bivalve (Unio douglasiae) based on the measurement of feeding and assimilation rates of carbon and nitrogen in a limited space with no current for 72 h using 13C and 15N dual isotope tracers. With high clearance rates, the unionid rapidly removed Microcystis cells within 24 h, but only a small amount of carbon and nitrogen were incorporated into the tissues. Even with the low assimilation rates, the mussels showed more favorable uptake of carbon than of nitrogen from toxic Microcystis water, and of tissues, the gills and gut accumulated more carbon and nitrogen than the muscle and mantle. Collectively, our findings indicate that although Unio douglasiae effectively uptake toxic Microcystis cells, they can assimilate only low amounts of nutrients into tissues within three days, despite a non-flowing system.

Mussel Mass Mortality and the Microbiome: Evidence for Shifts in the Bacterial Microbiome of a Declining Freshwater Bivalve

Freshwater mussels (Unionida) are suffering mass mortality events worldwide, but the causes remain enigmatic. Here, we describe an analysis of bacterial loads, community structure, and inferred metabolic pathways in the hemolymph of pheasantshells (Actinonaias pectorosa) from the Clinch River, USA, during a multi-year mass mortality event. Bacterial loads were approximately 2 logs higher in moribund mussels (cases) than in apparently healthy mussels (controls). Bacterial communities also differed between cases and controls, with fewer sequence variants (SVs) and higher relative abundances of the proteobacteria Yokenella regensburgei and Aeromonas salmonicida in cases than in controls. Inferred bacterial metabolic pathways demonstrated a predominance of degradation, utilization, and assimilation pathways in cases and a predominance of biosynthesis pathways in controls. Only two SVs correlated with Clinch densovirus 1, a virus previously shown to be strongly associated with morality in this system: Deinococcota and Actinobacteriota, which were associated with densovirus-positive and densovirus-negative mussels, respectively. Overall, our results suggest that bacterial invasion and shifts in the bacterial microbiome during unionid mass mortality events may result from primary insults such as viral infection or environmental stressors. If so, bacterial communities in mussel hemolymph may be sensitive, if generalized, indicators of declining mussel health.

Depuration of a Freshwater Clam (Batissa Violacea) from Rewa River in Fiji Using a Bio-Filter Set-Up in Closed and Open Water Circulatory System

The effectiveness of the freshwater bivalve Batissa violacea depuration was tested in closed and open water circulatory system over a 48 h period. The closed circulatory system included a sand biofilter. Microbial levels were assessed every 4 h using Total Aerobic Plate Count (TPC) for heterotrophs and Most Probable Number (MPN) for coliforms. TPC and coliform loads in bivalve tissue reduced rapidly to low and undetectable levels in a closed circulatory system while open system showed a slower reduction. Both TPC and coliform loads remained above detectable levels throughout the depuration period. Closed system showed similar patterns of logarithmic reduction of TPC and coliforms in all cases with R2>0.95 and p<0.001. Similar results were observed for tank water however, reduction of TPC and coliforms were slower. Biofilm formation was observed in the interior walls of the aquarium tanks over 48 h in all cases. Physicochemical parameters did not show any significant change. The reduction in TPC and coliform load in B. violacea suggests that biofilter in a closed water circulatory system is a simple, cost-effective, water conserving and effective way to significantly reduce the spoilage and coliform bacterial load that is accumulated in the clams.

Inclusion of Bivalve in Carp Polyculture Ponds Managed by Small Indigenous People Under Barind Tract

The present experiment was carried out in the household ponds (0.04 to 0.08 ha in area with 1.3 to 2.4 m in depth) of small indigenous people at Barind Tract region, northwest Bangladesh during September, 2017 to June, 2018 to know the growth performance of bivalve with carp. Two different treatments with 3 replicates were used, in treatment one (T1) only the carp polyculture was performed and in treatment two (T2) carp and bivalve polyculture was performed. Good quality of carp fingerlings (Labeo rohita, Gibelion catla, Cirrhinus cirrhousus, Hypophthalmichthys molitrix and Ctenopharyngodon idella) and freshwater bivalve (Lamellidens marginalis) seeds were stocked in the ponds. Stocking density and size of the seeds were similar for all of the study ponds. During the experiment there were no significant differences was observed in growth performance of the fishes between the two different treatments (p<0.05). The weight gain was recorded for L. rohita 420.31 g in T1 and 436.25 g in T2, for G. catla 237.01 g in T1 and 329.66 g in T2, for C. cirrhosus 263.53 g in T1 and 301.74 g in T2, for H. molitrix 559.6 g in T1 and 593.57 g in T2, for C. idella 510.11 g in T1 and 619.57g in T2. The weight gain of L. marginalis was 12.3 g in T2. During this experiment the production of carp was recorded 2524.5 kg/ha in T1 and 2618.2 kg/ha in T2 and the bivalve production was 1284.4 kg/ha in T2. This study is the first report on growth performance of bivalve with carp in the Barind Tract region of northwest Bangladesh. The result of this study will be helpful for the development of bivalve aquaculture in this climatically vulnerable region. J. Bio-Sci. 29(2): 99-110, 2021 (December)

Bromatological study of the freshwater bivalve Anodontites trapesialis (Lamarck, 1819) (Unionida, Mycetopodidae)

In Brazil, Anodontites trapesialis is a mussel species that occurs spontaneously in fish breeding sites. This species feeds on the remains of cultural treatments of other aquaculture species. The objective of the work is to understand the bromatological composition of mussel A. trapesialis. Individuals were selected to compose three samples of 500 g each of A. trapesialis for chemical composition, with viscera and viscera + shells being evaluated. The species presented 40.42 to 62.76 g of viscera per individual with a moisture content of 5.16% for viscera + shells and 86.5% for viscera. The mussel contains 42.6 and 12.96% crude protein, 3.16 and 1.76 of ether extract, 0.76 and 2.5% of crude fiber for viscera and viscera + shells. The total digestible nutrients were 74.16 and 36.96% for viscera and viscera + shells and 18.43 and 52.83% of mineral material for viscera and viscera + shells. A. trapesialis has relevant characteristics in its chemical composition as high protein content that gives the species potential for the human, animal, and other byproducts production.

Ameliorating effect of L-Ascorbate on protein and ascorbic acid content in different tissues of freshwater bivalve Lamellidens marginallis on exposure to lambda-cyalothrin.

Ascorbic acid is one of the important tool to indicate the alterations induced by chemicals and pollutants. Ascorbic acid, being important constituent in cellular metabolism, the interactions of the biomolecules gives proper idea of toxicant stress and its effect. In the present investigation the freshwater bivalve Lamellidens marginalis were exposed to chronic dose of lambda-cyalothrin (0.75 PPM LC50/10 values) alone and in combination with 50mg/L L-ascorbic acid for 21 days respectively. Percent protein and ascorbic acid contents in the mantle, foot, gills, digestive glands, gonad and whole soft body of bivalve, Lamellidens marginalis on lambda-cyalothrin intoxication and in combination with 50mg/L L-ascorbic acid were observed. Protein and ascorbic acid content in all soft body tissue of lambda-cyalothrin exposed bivalve, Lamellidens marginalis showed remarkable decrease as compared to control. The maximum protein and ascorbic acid content was observed in foot and lowest in digestive gland. Animal exposed to lambda-cyalothrin intoxication in combination with 50 mg/L of L-ascorbic acid showed considerable reduction in the depletion of protein and ascorbic acid levels. Fast recovery of percent protein and ascorbic acid contents was observed in presence of L-ascorbic acid than the recovery in the normal freshwater. This study indicates the protective and curative property of the L-ascorbic acid against lambda-cyalothrin induced damage. Key Words: Lamellidens marginalis, lambda-cyalothrin, protein and L-ascorbic acid