Andrea K. Fritts

Chronic fluoxetine exposure alters movement and burrowing in adult freshwater mussels

The antidepressant fluoxetine is commonly found in aquatic fauna living near or downstream from point-sources of municipal waste effluent. Continuous release of fluoxetine results in increased effective exposure duration in surface waters, resulting in a chronic exposure for animals downstream, particularly in effluent dominated ecosystems. Fluoxetine is known to cause disruptions in reproductive behavior of freshwater mussels (order Unionoida), including stimulating release of gametes, parturition of glochidia (larvae), and changes in lure display and foot protrusion. However, the ecological relevance of these effects at environmental concentrations is unknown. We conducted a 67-d exposure of adult Lampsilis fasciola to fluoxetine concentrations of 0, 0.5, 2.5, and 22.3μg/L and assessed impacts on behavior (lateral movement, burrowing, and filtering) and metabolism (glycogen storage and respiration). Mussels treated with 2.5 and 22.3μg/L fluoxetine displayed mantle lures significantly (p<0.05) more than controls. Animals treated with 22.3μg/L fluoxetine were statistically more likely to have shorter time-to-movement, greater total movement, and initiate burrowing sooner than control animals. These observations suggest that increased activity of mussels exposed to fluoxetine may result in increased susceptibility to predators and may lead to a reduction in energy stores.

Do gill parasites influence the foraging and antipredator behaviour of rainbow darters, Etheostoma caeruleum?

Parasites are known to affect an array of characteristics of their hosts, including morphology, physiology and behaviour. We examined the foraging and antipredator behaviour of rainbow darters, Etheostoma caeruleum, that were parasitized by glochidia larvae of freshwater mussels (Ptychobranchus occidentalis and Venustaconcha pleasii: Unionidae). Glochidia attach to the gills of the host and become encapsulated in host tissue. Over a period of days or weeks the larvae develop into free-living juveniles, which then leave the host. Parasitized darters increased ventilation rates (either early in the infestation or at the height of the infestation), were less active during foraging trials, lost more body size than nonparasitized darters and showed significantly weaker responses to predation risk (signalled by the presence of a chemical alarm cue). Therefore, even for a relatively short-term infection, parasitized darters may pay a cost in terms of decreased growth and decreased probability of survival.

Critical linkage of imperiled species: Gulf Sturgeon as host for Purple Bankclimber mussels

Abstract.  One of the largest impediments to the conservation of freshwater mussels is the absence of host-fish data. Suitable hosts must be present in sufficient numbers and occur at the appropriate time for successful mussel recruitment. Habitat degradation and fragmentation caused by dams and other anthropogenic alterations may reduce host availability. Host data are lacking for the federally threatened Purple Bankclimber mussel (Elliptoideus sloatianus), which is endemic to the Apalachicola–Chattahoochee–Flint basin (ACF) in Alabama, Florida, and Georgia, and the Ochlockonee basin in Florida and Georgia. We tested 29 fish species in 7 families as potential hosts for Purple Bankclimbers and observed high metamorphosis success (79–89%) with 4 species of sturgeon: Gulf (Acipenser oxyrinchus desotoi), Atlantic (Acipenser oxyrinchus oxyrinchus), Lake (Acipenser fulvescens), and Shortnose (Acipenser brevirostrum). Metamorphosis was less successful with Blackbanded Darters (Percina nigrofasciata) and Halloween Darters (Percina crypta) as hosts (34–36% metamorphosis), and the remainder of the fishes we tested were not suitable hosts. The federally threatened Gulf Sturgeon is the only sturgeon species present in the ACF, but access of this migratory fish to most of the basin is blocked by Jim Woodruff Dam on the Apalachicola River. In the absence of sturgeon upstream of Jim Woodruff Dam, darters appear to have facilitated persistence of this mussel species, but at abundances far lower than historical conditions. This relationship between the Purple Bankclimber and Gulf Sturgeon is the first description of a federally protected fish serving as a host for a federally protected mussel and is an archetypal example of the role of habitat fragmentation in the ecology of listed species. Recovery of the Purple Bankclimber and other mussel species probably will require restoration of habitat connectivity for fish passage.

Host Identification and Glochidia Morphology of Freshwater Mussels from the Altamaha River Basin

Abstract Recovery of imperiled freshwater mussels requires knowledge of suitable host fishes and other early life-history traits. We provide quantitative host information for 6 mussel species from the Altamaha River Basin, GA, 3 of which previously had no host information. Glochidia of Alasmidonta arcula (Altamaha Arcmussel) metamorphosed on 2 species of suckers (Moxostoma spp.); Elliptio hopetonensis (Altamaha Slabshell) on Lepomis macrochirus (Bluegill), Pimephales promelas (Fathead Minnow), and Micropterus salmoides (Largemouth Bass); E. shepardiana (Altamaha Lance) on 2 species of Bullheads (Ameiurus spp.) and L. macrochirus; Lampsilis dolabraeformis (Altamaha Pocketbook) on Bluegill and Largemouth Bass; and L. splendida (Rayed Pink Fatmucket) and Villosa delumbis (Eastern Creekshell) on Largemouth Bass. We also provide descriptions of glochidia morphology for the above mussel species and E. spinosa (Altamaha Spinymussel). Glochidia were correctly identified to species in 88.7% of cases by discriminant function analysis of 3 shell dimensions. Glochidia morphology may be useful for identification of glochidia attached to wild fish, thereby providing additional host information.

Freshwater mussel shells (Unionidae) chronicle changes in a North American river over the past 1000 years

The Illinois River was substantially altered during the 20th century with the installation of navigational locks and dams, construction of extensive levee networks, and degradation of water quality. Freshwater mussels were affected by these changes. We used sclerochronology and stable isotopes to evaluate changes over time in age-and-growth and food sources for two mussel species: Amblema plicata and Quadrula quadrula. Specimens were collected in years 1894, 1897, 1909, 1912, 1966, and 2013, and archeological specimens were collected circa 850. The von Bertalanffy growth parameter (K) was similar between 850 and 1897, but it increased by 1912 and remained elevated through 2013. Predicted maximum size (Linf) increased over the past millennium, and 2013 individuals were over 50% larger than in 850. Growth indices showed similar patterns of continual increases in growth. Shells were enriched in 13C and 15N during the 20th century, but exhibited a partial return to historical conditions by 2013. These patterns are likely attributable to impoundment, nutrient pollution and eutrophication beginning in the early 20th century followed by recent water quality improvement.

Survey of Intersex Occurrence in Largemouth Bass (Micropterus salmoides) from the Upper Illinois River Waterway

Abstract Intersex condition (ooctyes in testicular tissue) has been documented in many watersheds among a diverse variety of fishes worldwide. However, few studies have tested for the occurrence of the condition in fishes from rivers of the American Midwest. Midwestern watersheds, such as the Illinois River Waterway, U.S.A. may provide important new information about the effects of endocrine disrupting chemicals (EDCs) on fishes because of the variety of urban, industrial, and agricultural land uses within the watersheds. A first step in the study of EDCs in any ecosystem is a survey to document the symptoms of EDC exposure, such as intersex condition. Our objective was to test for intersex condition in male largemouth bass Micropterus salmoides in the lower Des Plaines River, an area directly affected by surface runoff and wastewater effluents from the Chicago Metropolitan Area. Histological analysis indicated that testicular oocytes were present in 21 of 51 (41%) largemouth bass sampled and oocyte numbers ranged from 1–25/thin section among intersex individuals. Our study details the severity of intersex in a population of largemouth bass near a major metropolitan area, which represents an important contribution to the understanding of fish reproductive ecology in ecosystems with a history of environmental disturbance and recovery such as the Illinois River Waterway.

Freshwater mussel shells (Unionidae) describe anthropogenic changes to trace element cycling within a North American river

Bivalve shells provide an unparalleled opportunity for understanding the history of bioavailable trace elements in aquatic systems. The present study analyzed the elements Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, U, V and Zn in freshwater mussel shells collected from a large floodplain river. Shells were collected fresh, sampled from a historic archive, and retrieved from pre-Columbian archeological sites. The elements As, Co, Cu and Ni varied with time over the course of the 20th century. When compared to the pre-Columbian shells, 20th century shell concentrations for these elements were either consistently higher (Co, Cu and Ni) or lower (As). The 20th century shells also had consistently lower concentrations of Mn and Zn when compared to the pre-Columbian period, however diagenesis is the most likely cause of this difference in Mn. The elements Cd and Fe had little spatial or temporal variation in this data set. Several elements (Al, Cr, Hg, Pb, Se, U, and V) were below method detection limits in most shells. This study demonstrated that mussel shells can be used as archives of environmental history in river systems.

The Mussel–Fish Relationship: A Potential New Twist in North America?

Abstract North American freshwater mussels are critically imperiled organisms that generally require fish hosts in order to complete their life cycle. Although numerous studies have focused on the parasitic relationship between mussels and fishes, few have examined the benefits that mussels provide to other organisms. During sampling of Altamaha River, Georgia, we observed foreign eggs occurring within body cavities of native mussels across a 253-km reach of the river basin. Eggs were recovered from 6% of the 757 mussels examined among seven sites. Foreign eggs were present in 17% and 18% of examined mussels at two sites. Using molecular techniques, eggs were identified as American Shad Alosa sapidissima. This discovery appears to be the first documented occurrence of native fish eggs in live North American mussels. Further research into the nature and mechanism of this symbiosis is warranted to assess whether this relationship is amensalistic, mutualistic, or commensalistic as American Shad and many fres...

Freshwater mussel (Unionidae) shells document the decline of trace element pollution in the regional watersheds of Chicago (Illinois, USA)

The present study analyzed trace element concentrations from the shells of native freshwater mussels collected from the headwater tributaries of the Illinois River (USA). These analyses were conducted to determine whether (A) anthropogenic enrichment could be observed and (B) whether enrichment had decreased following the enactment of Clean Water Act legislation in the 1970s. Collections archived in museums allowed comparison of the pre-Columbian period, the mid-20th century, and the early 21st century. The element Cu was consistently elevated above pre-Columbian baselines, while the elements As, Cd, Fe, and Zn were elevated in some collections. Although higher than baseline, concentrations Zn consistently declined from the mid-20th century to modern times, although differences occurred at individual sites. There was evidence for food web influence: the element Mn was significantly negatively correlated to sediment primary productivity as indexed by shell δ13C and Cu was positively correlated to trophic position as reflected by shell δ15N. Zn correlated to stream order across all time periods. We conclude that a mixture of historic factors affecting pollution control and land use patterns in the watershed led to sometimes conflicting effects on trace element bioaccumulation in mussel shells.