Abstracts

IAA22 Book of Abstracts (PDF)

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Oral | Posters


Oral Presentations

 

 

Day: 2, Session: 3, Talk: 2

Variations in Morphology and Physiology of Introduced Populations of the Virile Crayfish Faxonius virilis

Jennifer Weber, Hisham Abdelrahman, James A. Stoeckel and Brian Helms

Many introduced organisms have high levels of variation in morphology, physiology, and behavior, presumably conferring a selective advantage when establishing viable populations in novel habitats. Faxonius virilis (Virile or Northern Crayfish) is native to the northern and midwestern portions of the United States and southern Canada, but has been introduced throughout the continental United States and Europe. Previous work has demonstrated F. virlis and congeners possess morphological variation that is predictable among different habitats. We tested whether observed morphological variation, quantified with geometric morphometrics (GMM) and gill surface area calculation , was associated with physiological patterns, quantified with closed respirometry, in an introduced population of F. virilis from the Cahaba River in central Alabama, USA. We used 36 individual adult F. virilis (13 male, 19 female) for respirometry trials and subsequent GMM analysis. There were no sex differences in respiration or shape patterns. Using a Regulator Index calculated from curves derived from respirometry trials, we found that the total surface area of the gill filaments increased, the RI score increased, indicating that individuals who utilized regulatory strategies also had more surface area available for gas exchange. Further, crayfish could be broadly grouped as regulators, conformers, and undetermined in regards to their respiratory strategies. Crayfish shape between these 3 groups was significantly different, with regulators generally showing a broader carapace, conformers showing a narrower more fusiform carapace, and the undetermined group displaying a shape intermediate between regulators and conformers. These data suggest that F. virilis possesses physiological variation that corresponds to morphological variation, traits which may be attributable to the success of this species in novel habitats. Whether these respiration and morphological patterns hold across other species is yet to be determined.

 

 

Day: 3, Session: 3, Talk: 2

Comparisons of Enzymatic Thermal Optima Among Narrowly and Broadly Distributed Crayfish Species

HISHAM ABDELRAHMAN, James A. Stoeckel and Jacob T. Westhoff

Previous researchers have shown that extraregional invasive crayfish possess certain biological and ecological traits that facilitate their ability to successfully invade large areas in distant regions, whereas extralimital invaders tend to remain localized and occupy smaller ranges. Physiological optima may provide additional explanatory power for realized and potential range of crayfish species. In this study, we tested for differences in enzymatic thermal optima among multiple crayfish species with narrow (i.e., Faxonius marchandi, ~2,800 km2) to broad (i.e., F. virilis, >11 million km2) native and invasive ranges. We hypothesized that species with broad ranges would be thermal generalists relative to species confined to limited ranges. To test this hypothesis, we generated thermal performance curves of respiratory enzymes in the electron transport system (ETS) for 12 individuals of each species. Optimal thermal range was defined as the temperature range within which ETS enzyme activity was within 10% of the maximum observed value. Preliminary results show that the wide-ranging, invasive F. virilis has a broader thermal optima, and higher individual variation, than a localized invader – F. neglectus – or narrow endemics such as F. eupunctus or F. marchandi. Furthermore neither the thermal optima, nor the optimal range of the localized invader – F. neglectus - was significantly different than that of an endemic (F. eupunctus) within the invaded range. Results thus far suggest that underlying physiology may provide important clues as to which species have the potential to spread broadly and which species may be limited to a relatively narrow range. Additional species are currently being analyzed to better assess the robustness of these conclusions.

 

 

Day: 3, Session: 3, Talk: 7

Burning Down the House: Effects of Prescribed Burning and Mechanical Vegetation Treatments on Primary Burrowing Crayfish Densities

SUSAN B. ADAMS and Scott G. Hereford

Prior to widespread anthropogenic habitat alteration, primary burrowing crayfishes along the Gulf of Mexico Coastal Plain in southern Mississippi and Alabama presumably occupied predominantly open pine savannas, prairies, and bogs. Among other alterations, European settlement brought increasing fire suppression and intensive pine production. The Mississippi Sandhill Crane National Wildlife Refuge was “established in 1975…to protect the critically endangered Mississippi sandhill cranes [Grus canadensis pulla] and their unique, and itself endangered, wet pine savanna habitat.” The cranes require open meadow or pine savanna habitat, now created and maintained via prescribed burning, or when burning is precluded, via mechanical treatment. The US Fish and Wildlife Service (FWS) became interested in how these land management actions affect other at-risk species, including the primary burrowing crayfishes on the refuge: Creaserinus spp. and Procambarus fitzpatricki. In 2016, we initiated a study to survey crayfishes on the refuge and to begin examining how the land management influences burrowing crayfish densities. Crayfishes were surveyed by trapping and dipnetting in perennial and intermittent water bodies and by excavating and trapping from burrows. Burrower density among management classes was addressed by surveying burrow densities in quadrats along six transects on three plot types: regularly burned, regularly mechanically treated, and infrequently managed. We collected six species, including four only from water bodies: Cambarellus diminutus, Procambarus shermani, P. clarkii, and Faxonella clypeata. Procambarus fitzpatricki, considered at-risk by the FWS, was collected from burrows but also from small, isolated, intermittent pools in prairies and savannas. The most abundant burrower was identified as Creaserinus oryktes; however, taxonomic uncertainty creates enormous difficulty in distinguishing C. oryktes (not considered at-risk) from C. danielae (considered at-risk). Preliminary results indicate that burrowers were more abundant in burned or mulched plots than in infrequently managed plots. Confounding factors include interactions between site moisture and burn frequency/intensity and between ease of locating burrows and vegetation density.

 

 

Day: 5, Session: 3, Talk: 2

Population Characteristics of Red Swamp Crayfish Procambarus clarkii from Two Hydrologically Different Large River-floodplain Systems in Southeast Louisiana

ALEXA BALLINGER and Christopher Bonvillain

Anthropogenic modifications to large river-floodplain systems can sever natural water sources, alter annual flood pulses, and disrupt population dynamics of aquatic biota. The Atchafalaya River Basin (ARB) and the upper Barataria Estuary (UBE) in southeast Louisiana are separated by only 25 km and historically shared a similar hydrologic regime. Currently, the ARB receives an annual flood pulse from the Mississippi River that typically inundates floodplain habitats in the spring and dewaters in summer, providing access to floodplain spawning and foraging habitats and environmental cues for crayfish life cycle activities. In contrast, anthropogenic modifications to the UBE have eliminated an annual riverine flood pulse from the Mississippi River and large precipitation events are now the only drivers of floodplain inundation. The purpose of this project is to compare population characteristics of red swamp crayfish Procambarus clarkii between the ARB and UBE, two hydrologically different large river-floodplain ecosystems. P. clarkii were sampled every two weeks in the ARB and UBE during the 2017 and 2018 crayfish seasons. Sex, carapace length, and male reproductive form were recorded for all captured crayfish and catch per unit effort (CPUE) was determined as the number of crayfish per trap. Water quality was recorded at all sample sites on every sample date and hemolymph samples were collected from P. clarkii at all sample locations to determine hemolymph protein concentration. During the 2017 crayfish season, mean P. clarkii CPUE (3.81 ± 0.21) and carapace length (43.41 ± 0.71 mm) were higher in the ARB compared to the UBE (1.42 ± 0.34; 35.86 ± 0.49 mm). Additionally, ARB mean P. clarkii hemolymph protein concentration (5.1 ± 0.1 g/100 mL) was slightly higher than individuals from the UBE (4.8 ± 0.09 g/100 mL). These results indicate that the modification or absence of a flood pulse can have adverse effects on crayfish populations, threatening the ecological and economical importance of this species in river-floodplain ecosystems. The results from this research will provide a foundation for assessment of future anthropogenic modifications to river-floodplain hydrology and its effect on local aquatic biota.

 

 

Day: 5, Session: 4, Talk: 3

Crustacyanin Genes of Cambarus Crayfish

PAUL R. CABE, Morgan Trimas, Jeronimo Reyes-Olmedo and Christian Kim

Decapod crustaceans, including crayfish, exhibit a tremendous range of coloration. These various colors are all produced by a combination of diet-derived carotenoid pigments with proteins coded by the crustacyanin genes, a crustacean-specific evolutionary innovation. In general, peptides from two different crustacyanin genes, crustacyanin A and crustacyanin C, combine in multi-unit proteins with carotenoids, shifting the absorption spectra of carotenoids to produce a range of colors. Despite their evolutionary and ecological importance, little is known about these genes in crayfish. We attempted to determine the sequence of these genes in Cambarus longulus and Cambarus bartonii (family Cambaridae) using an RNA-seq approach. RNA was extracted from tissues on the inner surface of the carapace (endocuticle, epithelium, hypodermis) and converted to cDNA. The cDNA pool was sequenced on the Illumina platform, yielding more than 7 million paired-end reads per species, which were assembled into transcripts. These transcripts were searched using crustacyanin sequences from other decapods. The sequence data suggest there are three different crustacyanin A genes in these species which differ primarily in non-coding regions. Using primers designed from these sequences, we were able to amplify these genes directly from genomic DNA, which confirmed the transcript sequences and revealed the presence of short introns. Likewise, the data also suggest both species have several distinct crustacyanin C genes. Direct knowledge of the sequence of these genes opens the possibility for comparative study of these evolutionary important genes in crayfish of the family Cambaridae.

 

 

Day: 5, Session: 4, Talk: 4

Detectable Effects of Impoundments on the Genetic Structure of Crayfish (Faxonius spp.) in Alabama 43-Years After Dam Closure

ZANETHIA C. BARNETT, Ryan C. Garrick, Clifford A. Ochs and Susan B. Adams

Numerous freshwater species have highly fragmented populations due to barriers created by impoundments. Dams and impoundments can prevent or reduce dispersal by physically blocking movement of individuals, reducing floodplain-river connectivity, and creating a lentic zone and tail waters unfavorable to stream organisms. The loss of longitudinal and lateral connectivity can lead to population isolation, failed recruitment, and local extinction. Using population genetic analyses, we assessed fragmentation of crayfish populations caused by impoundments in the southern Appalachians, a global center of crayfish diversity and a region with numerous impoundments. We sampled one unimpounded and two impounded streams. Six to 10 sites were sampled along each stream between 2015 and 2017, with at least four sites sampled up- and downstream of impoundments. Faxonius erichsonianus and F. validus, two of the most abundant and widespread species in the streams, were collected for genetic analyses. For all individuals, a portion of the mitochondrial cytochrome oxidase subunit I (COI) gene was amplified via polymerase chain reaction, and sequenced. Analyses of F. erichsonianus are in progress. Faxonius validus genetic diversity was lower in unimpounded than impounded streams. Local populations of F. validus up- versus downstream of impoundments differed genetically from one another, but up- and downstream populations in the unimpounded stream did not differ. Directionality of gene flow analyses indicated that in the unimpounded stream, F. validus individuals moved both up and downstream. However, as expected, this connectivity was asymmetric, with greater gene flow originating from upstream sources. Notably, whereas downstream gene flow occurred in both impounded streams, upstream gene flow occurred in only one of these streams. Overall, the magnitude of genetic connectivity among local populations was higher in unimpounded than impounded streams.


 

Poster Presentations

 

 

POSTER 52

History of Spring River Crayfish (Faxonius roberti) Collections in the Strawberry River, Arkansas

BRIAN K. WAGNER

The Spring River Crayfish (Faxonius roberti) was recently distinguished from the Coldwater Crayfish (Faxonius eupunctus). It encompasses former F. eupunctus range in the Spring and Strawberry river drainages of Missouri and Arkansas. The species was first detected in the Strawberry River basin in a tributary stream in 1972 and the main river in 1974, neither of which have yielded specimens in more recent sampling efforts. The next reported observation was in 2006 from the main stem at a low water crossing 17.6 km downstream. A 2010-11 range-wide study of F. eupunctus only collected 4 individuals from one site in the basin using a quantitative kick-seine method that was much more effective in the other basins, suggesting a much lower abundance in the Strawberry. Additional effort in 2011 utilizing snorkeling and hand capture of crayfish was able to extend the documented range downstream an additional 14.3 km from the 2006 collection. Beginning in 2016 efforts began to attain a more detailed understanding of the species' range in this river by kayaking between access points and conducting snorkel searches by 2-3 divers at every 2nd to 3rd riffle encountered. These efforts documented 8 additional sites, including one 9 km upstream of the 2006 site. In 2017 efforts continued by making kayak trips above and below the area surveyed in 2016, requiring kayaking back to the put-in point at the end of the survey. In the upstream collection this included searching an additional 2 km above the site of the 1974 collection, but did not locate any occupied sites in this direction. Downstream searches were more productive, extending the occupied stream reach by 17.1 km. Combined this documents that F. roberti currently occupies at minimum 15 sites over a 40.4 km section of the Strawberry River.

 

 

POSTER 65

Analysis of Species-environmental Relationships with Variance Partitioning and Distance-based Moran Eigenvector Maps: Application for Crayfish Distribution and Community Models

WILLIAM R. BUDNICK, Sophia I. Passy and Michael D. Kaller

Advances in numerical ecology have developed robust modeling techniques that can include spatial information in analyses of species-environmental relationships. We demonstrate how variance partitioning and distance-based Moran eigenvector maps (dbMEM) can determine which spatial scales that environmental factors structure crayfish communities and distributions. We sampled 56 streams from 5 major Louisiana river drainages from 2013-2014. Variance partitioning with redundancy analyses of environmental factors and geographic spatial distances produced a poor model fit and great environmental-spatial covariance, which confounded interpretation. However, including orthogonal spatial variables obtained from dbMEM not only improved model fits, but elucidated which environmental variables constrained community composition across spatial scales, namely among drainages (broad scale), within drainages (intermediate scale) and within stream (small scale). Presence of sand, specific conductance, and stream depth were important community drivers across scales, but presence of clay and grassy banks were more locally important. Temperature, a climatic factor, was important at broad scales. Our methods provided valuable insight into the relevant scales of environmental influence on crayfish and it is our hope that we see wider adoption of these methods for future work.

 

 

POSTER 66

Dispersal and a Large River: Patterns of Genetic Diversity in an Imperiled, Small-stream Adapted Crayfish, Cambarus pristinus

BROOKE A. GRUBB, John W. Johansen and Rebecca E. Blanton

Crayfishes are a diverse group of freshwater decapods. Many North American crayfishes have small geographic ranges and are considered imperiled due to a variety of factors that threaten their persistence. Several factors, including fragmented habitats and corridor quality, affect dispersal ability and gene flow. Decreases in gene flow among populations can contribute to increasing genetic drift and inbreeding depression, which leads to a loss of genetic variability within populations and can reduce the adaptive potential of a species. Cambarus pristinus (Pristine Crayfish) has a small range on the Cumberland Plateau of Tennessee, where it occupies small tributaries of the Caney Fork River and lower order (<4th) reaches of the mainstem Caney Fork. Because the majority of the mainstem is larger than 4th order, it may limit dispersal and gene flow among populations of the different tributary systems. To examine contemporary and historic levels of genetic structure across the Caney Fork River mainstem, chelae from 20-30 individuals from two localities in each tributary will be collected. DNA extracted from the muscle of the chelae will be used to examine patterns of genetic structure using 20 microsatellite loci amplified from species-specific primers and the mitochondrial COI gene. Preliminary data summarizing progress on microsatellite primer optimization and locus identification and genetic structure among populations based on the COI gene will be presented and discussed.

 

 

POSTER 76

A New Species of Faxonius Crayfish from the Red River System of Kentucky and Tennessee

ERIN T. BLOOM, Brittany McCall, Guenter A. Schuster and Rebecca E. Blanton

Faxonius barrenensis is a crayfish endemic to the Green River system of Kentucky and Tennessee and is closely related to F. mirus, which is restricted to Tennessee River tributaries in Tennessee and Alabama. A morphologically similar but undescribed crayfish, Faxonius sp., occurs in the Red River system (Cumberland River) of Kentucky and Tennessee. Whether the latter represents a disjunct population of F. barrenensis or F. mirus, or alternatively, a distinct, species is unknown. Furthermore, whether the shared morphological traits reflected shared ancestry or convergence has not been tested. We used molecular and morphological data, including two mitochondrial (COI and 16s) and two nuclear (28s and GAPDH) genes and a standard suite of phenotypic measurements and meristics to examine phylogenetic relationships and the taxonomic status of Faxonius sp. relative to F. barrenensis, F. mirus and other Faxonius. Results from the concatenated and individual gene datasets supported a close relationship among the three focal taxa, implying their gross morphological similarities likely reflect recent shared ancestry. In all mitochondrial and combined gene trees, Faxonius sp. was recovered as a genetically divergent clade from F. barrenensis and F. mirus. Additionally, Faxonius sp. is phenotypically distinguished from F. barrenensis and F. mirus based on several characteristics. Given these findings, we propose Faxonius sp. represents a distinct species of crayfish that is closely related to F. mirus and F. barrenensis. However, our data does not resolve which of the latter is its sister species; additional molecular markers are needed to resolve this question. The new species has only been collected at four different localities within the Red River system (Cumberland), three of those located on the Ft. Campbell Army Base along the Tennessee/Kentucky state line. Several other streams have been searched, but no other populations have been identified, suggesting it has a small range and warrants conservation concern.


Oral Presentations from IAA22

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