Figure 2 - uploaded by Nathan Johnson
Content may be subject to copyright.
Photographs of egg (A) and larva (B) conglutinate segments released by Ptychobranchus jonesi 3243. Lines indicate the dimension measured (mm) in our study: dashed vertical/red 5 total length of the conglutinate, solid vertical/blue 5 total length of the visible glochidial mass within the conglutinate, and dotted/ green 5 area of the visible glochidial mass within the conglutinate.
Source publication
Conservation of imperiled species is frequently challenged by insufficient knowledge of life history and environmental factors that affect various life stages. The larvae (glochidia) of most freshwater mussels in the family Unionidae are obligate ectoparasites of fishes. We described the early life history of the federally endangered Southern Kidne...
Context in source publication
Context 1
... or as separate egg and larva mimics (egg or larva segments; see Results for full description) during our study. We split intact conglutinates into separate segments. We used ImageJ software (Rasband 1997) to measure the total length of each segment and the length (mm) and area (mm 2 ) of the visible glochidial mass contained within each segment ( Fig. 2A, B). Photographs of all conglutinates, associated measurements, and glochidial counts are available online (http://dx.doi.org/10.5066/F7 FT8J5T) or by request from the corresponding ...
Similar publications
Freshwater mussels (Unionida) are globally imperiled, in part due to largely unexplained mass mortality events (MMEs). While recent studies have begun to investigate the possibility that mussel MMEs in the Eastern USA may be caused by infectious diseases, mussels in the Western USA have received relatively little attention in this regard. We conduc...
Citations
... We produced a conservation status assessment map using ArcMap 10.8.2 (ESRI) following the protocol produced by Georgia Department of Natural Resources (2014) to evaluate spatiotemporal changes in the distribution of P. riddellii. Conservation status maps play an important role in conservation planning for mussels by identifying range size, survey needs, and high priority areas for protection , McLeod et al. 2017, Smith et al. 2021a. We plotted all known records using the Mussels of Texas database (MOTX; Randklev et al. 2021) and recent survey data from Arkansas, Louisiana, Mississippi, Oklahoma, and Texas. ...
Accurate taxonomic and distributional information are arguably the most critical components of conservation status assessments but can be greatly affected by misidentifications. The Louisiana pigtoe Pleurobema riddellii is a freshwater mussel proposed as threatened under the US Endangered Species Act. The species belongs to the tribe Pleurobemini, which includes multiple taxa that are inherently challenging to identify without molecular data. We validated historical and recent survey records of P. riddellii using a combination of DNA sequence data and morphological characters to provide a more definitive assessment of range and spatiotemporal trends in distribution. Our comprehensive assessment identified specimens collected from the Pearl drainage as P. riddellii , extending the species’ known range into eastern Gulf of Mexico drainages. Contemporary records were unavailable from the Trinity drainage; however, we designed novel minibarcode PCR primers and used historical DNA from a specimen collected in the late 1800s to confirm the historical presence of P. riddellii at the species’ type locality in the Trinity River near Dallas, Texas, USA. Our range-wide genetic diversity assessment provides strong support for 2 main geographic groups, the Ouachita and all remaining populations, with individuals from the Pearl and Trinity drainages sharing haplotypes with conspecifics from other drainages. Available data suggest P. riddellii has been extirpated from a significant portion of the historical range, including the entire Trinity drainage. Additional surveys in Lake Pontchartrain, Trinity, and other drainages in the eastern periphery of the species’ range may provide additional clarity on the distribution and conservation status of P. riddellii .
... Fecundity requires 'destructive' sampling of potentially sensitive species in cases where artificial inoculations are not an option (Haag & Staton, 2003). It is also difficult to obtain accurate estimates for conglutinate-releasing species (McLeod et al., 2017). The same ordinations were run without fecundity to see if similar results could be obtained. ...
• Freshwater mussels are among the most critically endangered taxa globally. In the United States, 91 out of nearly 300 species are listed as Threatened or Endangered under the Endangered Species Act.
• Freshwater mussel species exhibit a range of life-history traits. Owing to the large number of North American species, the rarity of many listed species and the often limited data available for those species, it can be difficult to gather all of the information necessary to develop ecological risk assessments and effective management plans for freshwater mussel species.
• The primary objective of this study was to categorize North American freshwater mussel species into life-history categories to aid in the identification of representative species for risk assessment.
• To achieve these objectives, a literature review was conducted to identify available life-history data for a large range of mussel species. Using this dataset, two ordinations were performed, non-metric multidimensional scaling and discriminant analysis, to classify mussel species into previously described life-history categories. Both analyses facilitated species classification into life-history categories.
• Significant data gaps in basic life-history information still exist for many species, but previously described life-history categories were found to be robust and additional analysis allowed quantitative classification of additional species.
... In brief, glochidia encyst on the gills and/or fins of the host where they transform into juveniles over the period of several weeks before dropping off into the substrate (Haag 2012). A single mussel species may have an array of suitable host fishes or may be specialized to only complete metamorphosis on a single host species McLeod et al. 2017). Amblema plicata is considered a host generalist, known to parasitize at least 25 fishes from 10 families for the purpose of glochidial metamorphosis . ...
Recent freshwater mussel research has resulted in rediscovery of several species presumed extinct. We report the rediscovery of Amblema plicata (Say, 1817) in 2019 from the Choctawhatchee River, Florida, USA. Amblema plicata has not been reported in the Choctawhatchee river basin since 1958, more than 61 years ago. This species was collected during the long-term monitoring of freshwater mussels in Florida streams. We provide genetic confirmation of our voucher identification using a DNA barcoding approach and discuss potential risks to A. plicata populations in the Choctawhatchee river basin.
... Finally, we multiplied the total number of glochidia by the percentage of viable glochidia to determine the total number of viable glochidia available. The target viable glochidia concentration for infecting potential host fish was 2,000-4,000 viable glochidia/L of water (Dodd et al. 2006;Johnson et al. 2012;Johnson et al. 2016;McLeod et al. 2017). We used four narrow pigtoe for host trials in this study: one individual for the 2014 trials, one individual for trials 1 and 2 in 2015, one individual for trial 3 in 2015, and one individual for trial 4 in 2015. ...
... Many studies conduct one or two host fish trials, and each trial includes several replicates for each fish species. This method works well when larger numbers of glochidia (. 4,000) can be collected from a mussel in a short amount of time before glochidia viability declines (McLeod et al. 2017). However, some mussels, like narrow pigtoe in this study, release conglutinates fractionally over several days or weeks, making it difficult to collect sufficient numbers of glochidia in a short amount of time (McLeod et al. 2017). ...
... This method works well when larger numbers of glochidia (. 4,000) can be collected from a mussel in a short amount of time before glochidia viability declines (McLeod et al. 2017). However, some mussels, like narrow pigtoe in this study, release conglutinates fractionally over several days or weeks, making it difficult to collect sufficient numbers of glochidia in a short amount of time (McLeod et al. 2017). Therefore, we conducted six trials over the course of this study to achieve replication and representation of potential host fish species. ...
The narrow pigtoe Fusconaia escambia is a freshwater mussel found only in the Escambia and Yellow river basins in northwest Florida and southern Alabama. It is listed as threatened under the U.S. Endangered Species Act. Like other freshwater mussels (Unionidae), its life cycle involves a larval stage (i.e., glochidial) in which most species are obligate parasites on the gills or fins of fishes. Knowledge of life history, population demographics, population genetics, and threats for the narrow pigtoe is lacking throughout its range, which impedes conservation of this species. Therefore, our objectives were to 1) compare historical and current distribution data using a conservation status assessment map, 2) determine period of gravidity, and 3) identify fish hosts. We used a conservation status assessment map to examine spatial and temporal changes in narrow pigtoe distribution and the possibility that the species has been extirpated from a subbasin (i.e., Hydrologic Unit Code level 10 watershed boundary; U.S. Geological Survey National Hydrography Dataset). Period of gravidity for the narrow pigtoe was determined by examining the gills of mussels in the field, and peak gravidity was considered to be the month in which the greatest number of gravid females was encountered. Fish hosts were determined by infecting individuals of 18 fish species with glochidia in a laboratory setting. Overall, the narrow pigtoe appears to be maintaining stable populations in Florida, but too few surveys have been conducted in Alabama subbasins for us to fully assess its status throughout its range. Peak months of gravidity were May-July, with the greatest percent of gravid females observed in May, although they were observed as early as 9 March and as late as 25 October. Nine fish species from five genera were identified as hosts for narrow pigtoe, with Blacktail Shiner Cyprinella venusta and Weed Shiner Notropis texanus consistently producing the greatest number of viable juvenile mussels. Host and gravidity findings from this study will be useful if propagation efforts become necessary for conservation of the narrow pigtoe.
... For most species, it is unclear how long females brood glochidia and how quickly fertilized eggs fully develop. The knowledge gaps are often wider for species of conservation concern, which presents the need for a standardized method of extracting gill contents that has been tested for non-lethal effects and can be promoted to the scientific community to supplement mainstream data collection methodologies, without posing a threat to protected populations 24,31,32 . This study had three objectives: 1) formalize a gill sampling technique and test it for lethal and non-lethal effects on female mussels in situ, 2) characterize different stages of glochidial development and describe a standardized method of identifying and reporting various larval stages, and 3) create a public repository for the data collected. ...
... Otherwise, store the contents in a 1.5 mL plastic microcentrifuge tube with designated liquid (see step 2.1) for later evaluation. NOTE: Minimize disturbance and handling of glochidia samples during transportation to avoid damage and reduced viability 32,35 . ...
Actively monitoring the timing, development, and reproductive patterns of endangered species is critical when managing for population recovery. Freshwater mussels are among the most imperiled organisms in the world, but information about early larval (glochidial) development and brooding periods is still lacking for many species. Previous studies have focused on the complex life history stage when female mussels are ready to parasitize host fish, but few studies have focused on the brooding period and timing of larval development. The protocol described here allows researchers to non-lethally evaluate the state of gravidity for female mussels. The results of this study show that this method does not affect a female mussel’s ability to stay gravid or become gravid again after sampling has been performed. The advantage of this method may permit its use on federally threatened or endangered species or other populations of high conservation concern. This protocol can be adapted for use on both preserved or live individuals and was tested on a variety of mussel species. The database provided is a repository for a breadth of information on timing of reproductive habits and will facilitate future freshwater mussel research, conservation, and recovery efforts.
... For most species, it is unclear how long females brood glochidia and how quickly fertilized eggs fully develop. The knowledge gaps are often wider for species of conservation concern, which presents the need for a standardized method of extracting gill contents that has been tested for non-lethal effects and can be promoted to the scientific community to supplement mainstream data collection methodologies, without posing a threat to protected populations 24,31,32 . This study had three objectives: 1) formalize a gill sampling technique and test it for lethal and non-lethal effects on female mussels in situ, 2) characterize different stages of glochidial development and describe a standardized method of identifying and reporting various larval stages, and 3) create a public repository for the data collected. ...
... Otherwise, store the contents in a 1.5 mL plastic microcentrifuge tube with designated liquid (see step 2.1) for later evaluation. NOTE: Minimize disturbance and handling of glochidia samples during transportation to avoid damage and reduced viability 32,35 . ...
Actively monitoring the timing, development, and reproductive patterns of endangered species is critical when managing for population recovery. Freshwater mussels are among the most imperiled organisms in the world, but information about early larval (glochidial) development and brooding periods is still lacking for many species. Previous studies have focused on the complex life history stage when female mussels are ready to parasitize host fish, but few studies have focused on the brooding period and timing of larval development. The protocol described here allows researchers to non-lethally evaluate the state of gravidity for female mussels. The results of this study show that this method does not affect a female mussel’s ability to stay gravid or become gravid again after sampling has been performed. The advantage of this method may permit its use on federally threatened or endangered species or other populations of high conservation concern. This protocol can be adapted for use on both preserved or live individuals and was tested on a variety of mussel species. The database provided is a repository for a breadth of information on timing of reproductive habits and will facilitate future freshwater mussel research, conservation, and recovery efforts.
... The viability of glochidia within a conglutinate is typically higher than the viability of free glochidia, which suggests that conglutinate membranes may confer protection ( Fritts et al., 2014). For example, conglutinates of Ptychobranchus jonesi maintained >90% viability for 3 days and only dropped below 75% by day 10 (McLeod, Jelks, Pursifull, & Johnson, 2017). Thus, thermal tolerance testing of free glochidia for species that produce conglutinates may not be entirely accurate, indicating that thermal testing should include both conglutinates and free glochidia, not just one or the other. ...
Understanding the temperature tolerances of organisms is critical because the thermal regimes of freshwater ecosystems are changing globally. Native freshwater mussels are sensitive to increasing water temperatures because of their physiology and unique life history. Detailed knowledge on lethal temperatures for mussels has been limited to less than 5% of the species known to occur in North America, and little is known about the thermal tolerances of mussel species from rivers within the south‐western USA.
To determine the effects of elevated water temperature on mussels, the upper thermal tolerances of larvae (glochidia) for the following species across four basins in Texas (Neches, Guadalupe, San Antonio, and Colorado) were tested: Amblema plicata , Cyclonaias necki , Fusconaia mitchelli , Lampsilis bracteata , Lampsilis hydiana , Lampsilis satura , Lampsilis teres , and Obovaria arkansasensis .
Glochidia were acclimated to 27°C across a range of experimental temperatures (30–39°C) in 24‐h standard acute laboratory tests. The median lethal temperature (LT50) among glochidia averaged 32.4°C and ranged from 26.9 to 36.4°C.
Thermal tolerances differed significantly among and within species, and by season. Comparing these results with current water temperatures in central and east Texas indicated that populations of the focal species studied are at risk from rising environmental temperatures and, as a consequence, their long‐term viability will be challenging in future years.
... However, this method may result in harm to the adult mussel by damaging the gills or marsupia. McLeod et al. (2017) had similar concerns when testing the imperiled species Ptychobranchus, and instead induced release by raising the temperature of the tank slowly. Although ASTM International (2006) recommends flushing the marsupium in this manner, it was extremely difficult to prise open the valves of Velesunio sp. to access the inner gills without causing damage to the adductor muscles. ...
Ammonia is recognised as a major pollutant worldwide, originating from natural and anthropogenic sources. Studies have reported that freshwater mussels are amongst the most sensitive taxa to ammonia, but there is a lack of data available on ammonia toxicity for the early life stages of freshwater mussels from tropical regions. This paper reports the modification of a 24‐h acute toxicity test protocol for tropical freshwater mussels and application of the test using ammonia. Velesunio spp. from three different sites were used to assess the toxicity of ammonia at a targeted pH of 6.0 and water temperature of 27.5°C, which were the average annual values for some slightly to moderately acidic, soft water (3‐6 mg/L as CaCO3) creeks of tropical northern Australia. The valve closure responses of mussel glochidia (larvae) to a sodium chloride solution were used to measure the survival endpoint. Acute toxicity estimates indicate that tropical Velesunio spp. were highly sensitive to ammonia with 24‐h exposures to ammonium sulfate generating LC50 estimates ranging from 6.8–14.2 mg/L Total Ammonia Nitrogen (TAN), which when adjusted to pH 7 and 20°C, were amongst the highest sensitivities yet reported for any freshwater mussel species, and amongst the highest in sensitivity for any tropical taxon. These toxicity estimates can contribute to the derivation or refinement of ammonia Guideline Values for freshwater ecosystems globally. This article is protected by copyright. All rights reserved
Bivalves commonly associate with other organisms, however, examples of true parasitic associations are described only for members of the marine superfamily Galeommatoidea (two species of approximately 500 known species, facultative parasitism) and the larvae of members of the freshwater order Unionida (almost all of 958 known species, obligate parasitism). The evolution toward such a close relationship required establishing a close association with the host’s body, resulting in being enclosed within its tissues. Clear adaptations to the host species are observed in both groups. Most galeommatoideans live in soft sediments and are associated with other benthic organisms or their burrows—settlement in a burrow or on/within the host’s body protects these little bivalves, while life activity of the host possibly ensures oxygenated water currents with a food source for the bivalve. However, a few recent examples of bivalve settlement within the body cavity of crabs (believed as accidental, nevertheless bivalves feed in the crab's hemocoel), or in the oesophagus of holothurians (common, presumably nutrition from the host is possible) indicate possible pathways for an evolutionary transition from free- or commensal-living to a parasitic lifestyle. Unionoids, large freshwater bivalves, are characterized by their tiny larvae that parasitize fish. This close relationship primarily benefits bivalves through enhanced dispersal abilities, but fish tissues may also serve as a source of nutrients for the larvae. Parasitic association likely established when close and common contact of both associates could happen, thus one may hypothesize a fish that lived close to the bottom of lakes and rivers (including durophagous species) as a likely host at the beginning of their co-evolution. Accidental contact of the larvae with the body of fishes (during predation on bivalves or caused by anti-sinking mucous or the larval threads tangled with fish) could result in increased bivalve dispersal. Subsequently, firmer attachment on fish tissues was acquired, followed by encapsulation of the larva within the host epithelium. This might have allowed for the feeding on host tissues, but required developing resistance to the host’s immune system, which might have further strengthened their association.
The first confirmed record of the native freshwater clam CYRENIDAE Cyanocyclas (Neocorbicula) paranacensis (d'Orbigny, 1835) in Santa Catarina State/ SC is available,
bringing to 35 the list of regional known limnic bivalves and the fifth representative of the family recognized so far in the State (... see pp. 37-39).
