Paul D. Johnson

Alabama Department of Conservation and Natural Resources, Alabama, United States, Montgomery · Alabama Aquatic Biodiversity Center

The gut microbiome is influenced by host species and the environment, but how the environment influences the microbiome of animals introduced into a new ecosystem has rarely been investigated. Freshwater mussels are aquatic fauna, with some threatened or endangered species propagated in hatcheries and introduced into natural systems as part of cons...

Unionoid freshwater mussels (Bivalvia: Unionidae) are free-living apart from a brief, obligately parasitic, larval stage that infects fish hosts, and gravid female mussels have evolved a spectrum of strategies to infect fish hosts with their larvae. In many North American species, this involves displaying a mantle lure: a pigmented fleshy extension...

We herein describe Proterometra wigglewomblen. sp. (Digenea: Azygiidae: Azygiinae) from the Cahaba River, Alabama, USA, which asexually reproduces in the compact elimia, Elimia showalteri (Lea, 1860) (Cerithioidea: Pleuroceridae) and matures in the oesophagus of the blackbanded darter, Percina nigrofasciata (Agassiz, 1854) (Perciformes: Percidae)....

Unionoid freshwater mussels (Bivalvia: Unionidae) are free-living apart from a brief, obligately parasitic, larval stage that infects fish hosts, and gravid female mussels have evolved a spectrum of strategies to infect fish hosts with their larvae. In many North American species, this involves displaying a mantle lure: a pigmented fleshy extension...

Freshwater mussels are important indicators of the overall health of their environment but have suffered declines that have been attributed to factors such as habitat degradation, a loss of fish hosts, climate change, and excessive nutrient inputs. The loss of mussel biodiversity can negatively impact freshwater ecosystems such that understanding t...

This document has been prepared in cooperation with Federal, Indigenous, and State malacologists (mollusk scientists), environmental toxicologists, restoration specialists, and other subject matter experts to provide best practices for freshwater mussel injury determination, early identification of restoration opportunities, injury quantification...

Juga is a genus of freshwater snails distributed from northern Washington to central California. The taxonomy and classification of the genus has a long and complex history, driven mainly by the features of their highly variable shells. The number of recognized species has fluctuated from ~9 to 11; however, it has been claimed that the actual diver...

The continued global loss of biodiversity highlights the importance of understanding how species loss may impact ecosystem function. Shifting temperatures will accelerate species loss, but will affect species differently. We investigated effects of temperature (10°C, 20°C, or 30°C) on resource acquisition and assimilation (clearance rate, respirati...

Phylogenomic studies with hundreds or thousands of loci are rare for most invertebrate groups, including freshwater gastropods. This can prevent understanding of phylogeny, which hinders many areas of research. Pleuroceridae is a family of freshwater snails that is highly imperiled and plays an essential role in the ecology of many freshwater syste...

Freshwater mussels are an important element of freshwater biodiversity and provide essential ecosystem services. However, mussels are among the most imperilled groups of organisms in the world. Although research has increased in recent years, information about range‐wide genetic diversity and historical demography of most species is lacking. One su...

With the biodiversity crisis continuing unchecked, we need to establish levels and drivers of extinction risk, and reassessments over time, to effectively allocate conservation resources and track progress towards global conservation targets. Given that threat appears particularly high in freshwaters, we assessed the extinction risk of 1428 randoml...

Margaritifera hembeli is a federally threatened freshwater mussel species restricted to three central Louisiana drainages. Currently, management efforts are being formulated without an understanding of population-level genetic patterns, which could result in sub-optimal conservation outcomes. In particular, information about riverscape genetic patt...

Herein, we characterized the digestive gland (‘gut’) bacterial community (microbiome) of the Ohio pigtoe, Pleurobema cordatum (Rafinesque, 1820), using 16S rRNA gene sequencing. Two populations were compared: wild P. cordatum (n = 5) from the Tennessee River and P. cordatum (n = 9) relocated to artificial mesocosms and exposed to various thermal re...

Many freshwater gastropod species face extinction, including 79% of species in the family Pleuroceridae. The Oblong Rocksnail, Leptoxis compacta , is a narrow range endemic pleurocerid from the Cahaba River basin in central Alabama that has seen rapid range contraction in the last 100 years. Such a decline is expected to negatively affect genetic d...

Many freshwater gastropod species face extinction, including 79% of species in the family Pleuroceridae. The Oblong Rocksnail, Leptoxis compacta , is a narrow range endemic pleurocerid from the Cahaba River basin in central Alabama that has seen rapid range contraction in the last 100 years. Such a decline is expected to negatively affect genetic d...

Margaritifera hembeli is a federally threatened freshwater mussel species restricted to three central Louisiana drainages. Currently, management efforts are being formulated without an understanding of population-level genetic patterns, which could result in sub-optimal conservation outcomes. In particular, information about riverscape genetic patt...

Within riverine systems, headwater populations are hypothesized to harbor higher amounts of genetic distinctiveness than populations in the main stem of a river and display increased genetic diversity in large, downstream habitats. However, these hypotheses were mostly developed with insects and fish, and they have not been tested on many invertebr...

Here we characterize the digestive gland microbiome from wild and cultured (hatchery-reared) Alabama rainbows (Villosa nebulosa) using 16 S rRNA gene pyrosequencing in order to understand the effects of propagation on microbial community structure in freshwater mussels. Digestive glands from nine Alabama rainbows were analysed, five from the wild a...

Loss of freshwater mollusk populations nationally has prompted the use of these species in establishing USEPA water quality criteria (WQC). The objectives of this study were to determine the sensitivity (EC50) of 5 at-risk mollusk species endemic to the Mobile River Basin to chloride, potassium, nickel, and zinc. Villosa nebulosa (Alabama Rainbow)...

The Duck River basin located in south-central Tennessee has long been established as an area of high freshwater mussel diversity. The Duck River is 442 km long with a large reservoir, Normandy Dam oper-ated by the Tennessee Valley Authority (TVA) placed at river km 420 controlling discharge throughout the remaining river (􀀀 95􀀁 total length). This...

The Painted Rocksnail, currently known as Leptoxis taeniata, is a federally threatened species native to the Mobile River basin in Alabama, USA. Presently restricted to four disjunct populations, the species is at considerable risk of extinction after a range decline of over 95% in the 20th century because of habitat alteration following impoundmen...

Tulotoma magnifica is a federally threatened freshwater gastropod endemic to the Mobile Basin in Alabama. It was considered extirpated from the Alabama River until its rediscovery there in 2006. Tulotoma occurs primarily in colonies in large interstitial spaces beneath boulders and in bedrock crevices. We used side-scan sonar to identify boulder ha...

Freshwater mussels, aquatic keystone species, are in global decline. Long life spans, sedentary lifestyles, and unique reproductive strategies involving obligate parasitic stages make unionid freshwater mussels particularly sensitive to environmental perturbations resulting from global climate change. A greater understanding of the mechanisms by wh...

Anthropogenically caused physical and chemical habitat degradation, including water pollution, have caused dramatic declines in freshwater mollusk populations. Sodium dodecyl sulfate (SDS), a surfactant with no USEPAWater Quality Criteria (WQC), is commonly used in industrial applications, household cleaners, personal hygiene products, and herbicid...

With a historical diversity comprising 182 species, representing 20% of the global species richness (≈ 890 species), Alabama is home to the greatest diversity of freshwater mussels on the planet. Species diversity is primarily the result of 10 separate river basins occurring within the state. Over the last century, wholesale physical modification a...

Although habitat alteration and degradation in riverine systems are the major threats to overall mussel assemblages to date, no or few studies have been able to document significant differences in habitat variables between species. The purpose of this study was to evaluate microhabitat associations of three federally threatened freshwater mussel sp...

Life histories of the imperilled freshwater gastropod genus Leptoxis are poorly known, and this information is required to achieve a basic understanding of the evolution of this diverse group and to develop management strategies for species conservation and recovery. We describe egg-laying behaviours and associated traits for all 13 extant Leptoxis...

The Paint Rock River (PRR) drainage in northern Alabama and southern Tennessee historically supported 58 freshwater mussel species. This study semi-quantitatively examined the mussel assemblage at 42 sites in the Paint Rock mainstem and 5 sites in Estill Fork, a headwater tributary. A total of 1825 live mussels were collected over 78.9 person-hours...

This is the first American Fisheries Society conservation assessment of freshwater gastropods (snails) from Canada and the United States by the Gastropod Subcommittee (Endangered Species Committee). This review covers 703 species representing 16 families and 93 genera, of which 67 species are considered extinct, or possibly extinct, 278 are endange...

The Mobile River Basin is a hotspot of molluscan endemism, but anthropogenic activities have caused at least 47 molluscan extinctions, 37 of which were gastropods, in the last century. Nine of these suspected extinctions were in the freshwater gastropod genus Leptoxis (Cerithioidea: Pleuroceridae). Leptoxis compacta, a Cahaba River endemic, has not...

Background: A third of all known freshwater mollusk extinctions worldwide have occurred within a single medium-sized American drainage. The Mobile River Basin (MRB) of Alabama, a global hotspot of temperate freshwater biodiversity, was intensively industrialized during the 20(th) century, driving 47 of its 139 endemic mollusk species to extinction...

We examined the effects of four levels of chronic hypoxic stress at three temperatures on the survivorship of Dreissena polymorpha and Corbicula fluminea to assess the efficacy of O2 deprivation as a macrofouling control treatment and examine if critical hypoxia limits support reported distribution patterns. At 25°C, the hypoxia tolerance was exami...

Margaritifera hembeli, the Louisiana pearl shell, is a threatened mussel with a distribution limited to the headwaters of three tributaries of the Red River in central Louisiana, U.S.A. We assessed the role that several habitat characters played in determining its abundance and distribution. Pearl shell mussels were more common in second-order stre...

Freshwater mollusks are highly imperiled, with 70% of the North American species extinct, endangered, or at risk of extinction. Impoundments and other human impacts on the Coosa River of Alabama, Georgia and Tennessee of the southeastern USA alone are believed to have caused 50 mollusk species extinctions, but uncertainty over boundaries among seve...