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Crayfish are ecologically important in freshwater systems worldwide and are imperiled in North America and globally. We sought to examine landscape- to local-scale environmental variables related to occupancy and detection probability of a suite of stream-dwelling crayfish species. We used a quantitative kickseine method to sample crayfish presence at 102 perennial stream sites with eight surveys per site. We modeled occupancy (psi) and detection probability ( P ) and local- and landscape-scale environmental covariates. We developed a set of a priori candidate models for each species and ranked models using (Q)AICc. Detection probabilities and occupancy estimates differed among crayfish species with Orconectes eupunctus , O. marchandi , and Cambarus hubbsi being relatively rare (psi < 0.20) with moderate (0.46–0.60) to high (0.81) detection probability and O. punctimanus and O. ozarkae being relatively common (psi > 0.60) with high detection probability (0.81). Detection probability was often related to local habitat variables current velocity, depth, or substrate size. Important environmental variables for crayfish occupancy were species dependent but were mainly landscape variables such as stream order, geology, slope, topography, and land use. Landscape variables strongly influenced crayfish occupancy and should be considered in future studies and conservation plans.

We summarize the distribution, ecology, threats, and conservation status of Faxonius marchandi (Hobbs, 1948), the Mammoth Spring crayfish, a limited-range endemic species to the Spring River drainage of Missouri and Arkansas, USA. The species is known from 51 locations on lower-order perennial and intermittent streams in only the eastern portion of the drainage. Faxonius marchandi is found in larger rocky substrates in shallower, slower-velocity habitats of well-buffered, mineral-rich streams. The invading alien crayfish Faxonius neglectus chaenodactylus (Williams, 1952) is the most likely threat to F. marchandi. These compiled data should serve as a baseline for future comparison, and facilitate discussion about future management, conservation, and research efforts.

The microsporidian parasite Thelohania contejeani causes porcelain disease and has been implicated in mass mortalities in populations of the endangered European crayfish Austropotamobius pallipes. However, the route of parasite transmission is not known. This paper investigates the horizontal transmission of T. contejeani between A. pallipes hosts as well as its transmissibility to the invasive signal crayfish (Pacifastacus leniusculus). Field collected juvenile A. pallipes and P. leniusculus were assigned to 1 of 3 experimental treatments; fed heavily infected A. pallipes tissue, exposed to water from tanks housing heavily parasitized A. pallipes, and a control group to provide an estimate of the baseline infection levels in the field. After 26 weeks, abdominal muscle samples were screened by PCR for T. contejeani. Infection was significantly higher in the treatment groups (83% in the cannibalism treatment, 42% in the water exposure treatment) than in the control group (4%), providing evidence for horizontal transmission of the parasite between A. pallipes hosts. Cannibalism and scavenging are common amongst crayfish, providing transmission opportunities in the field. The study also provides the first direct evidence for transmission of the parasite from an indigenous European crayfish species to the invasive signal crayfish, with 50% of P. leniusculus in each treatment, and 8% of control animals infected. We discuss the possibility that high density populations of the invasive signal crayfish may serve either as reservoirs or sinks for the parasite.

Reports of alien crayfish invasions are increasingly common and often associated with well-documented ecological effects including native crayfish biodiversity declines. Because most regions in the U.S. and Canada have not been surveyed to detect the presence and gauge the threat status of such invasions, management agencies lack information on the magnitude of problems in their respective jurisdictions. Our objectives were to catalog, confirm and summarize suspected crayfish invasions that were reported in one U.S. state in recent years. Data were also examined for potential spatial patterns, prevalence of certain species as invaders and effects to native crayfishes. We collected reports of crayfish introductions/invasions from 1998–2014, and attempted to confirm them via sampling. We catalogued 34 reports and confirmed 31 as suspected invasions involving 6 invading species. Procambarus acutus was easily the most frequent invader, and all invading species were native to at least part of Missouri. Most suspected invasions involved species that were legal for commercial sale in the state, but many also involved non-commercial species that are described as “narrow-range endemics.” Invading species were abundant, dominating crayfish communities, at several sites. Native species have apparently declined or been displaced at several locations. Our results suggest the potential for many unreported crayfish invasions in the U.S. and Canada, including those caused by shorter-range (e.g., intrastate) translocations. Ecoregions featuring high crayfish diversity could be threatened with significant declines of native species with narrow ranges. Increased survey efforts in these regions are warranted to estimate threat levels and provide agencies with information to support management actions.

Despite the prevalence and importance of intermittent streams, few studies have examined their use by crayfishes. We documented persistence in an intermittent stream and use of the hyporheic zone by 2 imperiled crayfishes, Orconectes williamsi and Orconectes meeki meeki, upon stream drying. During 2005 to 2007, we monitored summer flows and crayfish densities in 10 riffles in a Missouri (US) Ozark stream to document stream drying and crayfish persistence. Stream drying variables were riffle wetted area (m2) and current velocity (m/s). Crayfish density estimates were obtained with a quadrat sampler. We sampled monthly (May–August 2006) to examine crayfish response to decreased flows, and excavated dry quadrat samples (to 30 cm depth) after surface flows ceased. Over 2 periods during summer 2007, we used baited traps in the stream and a downstream reservoir where the stream terminates to examine whether crayfish migrated from the stream to permanent water in response to drying. Riffles dried significantly by July, few had surface water present by August, and all were rewetted by the following June. Annual June densities of O. williamsi remained stable throughout the study, whereas densities of O. m. meeki were lower in 2007 than 2005. Both species burrowed to the hyporheic zone during drying, and crayfish densities were similar to those estimated in riffles before drying. We found no evidence that either species migrated to permanent water in the reservoir during drying. Use by crayfish of the hyporheic zone during drying and interannual persistence in intermittent streams suggests that hyporheic habitats are important for conservation of these crayfishes. Our study contributes to the increasing body of knowledge that indicates the importance of intermittent streams for conservation of freshwater biodiversity.

The diversity of motor units arises from differences in the contractile properties of muscle fibers and the intrinsic electrical properties of their motoneurons. In mice, however, this relationship has not been quantitatively defined, and conventional classification often relies on subjective thresholds. Here, we combined in vivo intracellular recordings with supervised and unsupervised machine-learning methods to test whether motoneuron electrophysiology can predict the physiological identity of mouse motor units. Unbiased clustering identified four groups corresponding to slow (S), fast fatigue-resistant (FR), intermediate (FI), and fast fatigable (FF) types. A multinomial logistic regression model performed well, with most errors occurring between FI and FF types, which showed substantial overlap. Reducing the task to three classes improved accuracy. Feature selection revealed that four electrophysiological properties (input conductance, rheobase, AHP duration, maximal frequency) were sufficient for high predictive performance. Overall, this study provides a quantitative description of mouse motor-unit properties and a framework for incorporating motor-unit diversity into future investigations of neuromuscular physiology and disease.

Src homology 2 domain-containing inositol 5-phosphatase 1 (SHIP1), encoded by the gene INPP5D, is a lipid phosphatase that negatively regulates immune receptor signaling in hematopoietic cells and microglia. Here, we describe a pyridyl-pyrazole-piperidine scaffold and the lead compound 3-((2-chlorobenzyl)oxy)-5-(1-(piperidin-4-yl)-1H-pyrazol-4-yl)pyridine ( ), which demonstrates SHIP1 target engagement, brain exposure, and evidence of a central pharmacodynamic response . Structure-activity relationship studies, guided by biochemical and cellular assays using multiple human and murine protein constructs and cells, identified SHIP1-active ligands. A thermal shift assay using full-length SHIP1 was used to assess compounds for cellular target engagement, while studies in IL-4 conditioned THP-1 cells was used to demonstrate changes in downstream AKT signaling. Targeted lipidomics revealed changes in the overall phosphoinositide pool consistent with SHIP1 target engagement and reduction of phospho-AKT levels. In a protein-lipid overlay assay, compound induced changes in the relative association of SHIP1 with multiple phosphatidylinositols on a membrane surface. In high-content cellular imaging assays, compound enhanced the uptake of myelin/membrane debris and fibrillar amyloid by primary murine microglia, phenocopying a genetic model with reduced SHIP1 expression. Finally, oral administration of compound resulted in brain exposure sufficient to alter gene expression and reduce IL-1β levels as pharmacodynamic markers of microglial activation and neuroinflammation in an amyloidosis mouse model of Alzheimer's disease. Collectively, these results define a scaffold with SHIP1 target engagement, CNS exposure, and activity, providing a foundation for the optimization of brain-penetrant SHIP1 ligands suitable for further mechanistic studies and therapeutic development for the treatment of Alzheimer's disease.