Fastloc-GPS reveals daytime departure and arrival during long-distance migration and the use of different resting strategies in sea turtles

Determining the time of day that animals initiate and end migration, as well as variation in diel movement patterns during migration, provides insights into the types of strategy used to maximise energy efficiency and ensure successful completion of migration. However, obtaining this level of detail has been difficult for long-distance migratory marine species. Thus, we investigated whether the large volume of highly accurate locations obtained by Argos-linked Fastloc-GPS transmitters could be used to identify the time of day that adult green (n = 8 turtles, 9487 locations) and loggerhead (n = 46 turtles, 47,588 locations) sea turtles initiate and end migration, along with potential resting strategies during migration. We found that departure from and arrival at breeding, stopover and foraging sites consistently occurred during the daytime, which is consistent with previous findings suggesting that turtles might use solar visual cues for orientation. Only seven turtles made stopovers (of up to 6 days and all located close to the start or end of migration) during migration, possibly to rest and/or refuel; however, observations of day versus night speed of travel indicated that turtles might use other mechanisms to rest. For instance, turtles travelled 31% slower at night compared to day during their oceanic crossings. Furthermore, within the first 24 h of entering waters shallower than 100 m towards the end of migration, some individuals travelled 72% slower at night, repeating this behaviour intermittently (each time for a one-night duration at 3–6 day intervals) until reaching the foraging grounds. Thus, access to data-rich, highly accurate Argos-linked Fastloc-GPS provided information about differences in day versus night activity at different stages in migration, allowing us, for the first time, to compare the strategies used by a marine vertebrate with terrestrial land-based and flying species

Single-cell RNA sequencing profiling of mouse endothelial cells in response to pulmonary arterial hypertension.

AIMS: Endothelial cell (EC) dysfunction drives the initiation and pathogenesis of pulmonary arterial hypertension (PAH). We aimed to characterize EC dynamics in PAH at single-cell resolution. METHODS AND RESULTS: We carried out single-cell RNA sequencing (scRNA-seq) of lung ECs isolated from an EC lineage-tracing mouse model in Control and SU5416/hypoxia-induced PAH conditions. EC populations corresponding to distinct lung vessel types, including two discrete capillary populations, were identified in both Control and PAH mice. Differential gene expression analysis revealed global PAH-induced EC changes that were confirmed by bulk RNA-seq. This included upregulation of the major histocompatibility complex class II pathway, supporting a role for ECs in the inflammatory response in PAH. We also identified a PAH response specific to the second capillary EC population including upregulation of genes involved in cell death, cell motility, and angiogenesis. Interestingly, four genes with genetic variants associated with PAH were dysregulated in mouse ECs in PAH. To compare relevance across PAH models and species, we performed a detailed analysis of EC heterogeneity and response to PAH in rats and humans through whole-lung PAH scRNA-seq datasets, revealing that 51% of up-regulated mouse genes were also up-regulated in rat or human PAH. We identified promising new candidates to target endothelial dysfunction including CD74, the knockdown of which regulates EC proliferation and barrier integrity in vitro. Finally, with an in silico cell ordering approach, we identified zonation-dependent changes across the arteriovenous axis in mouse PAH and showed upregulation of the Serine/threonine-protein kinase Sgk1 at the junction between the macro- and microvasculature. CONCLUSION: This study uncovers PAH-induced EC transcriptomic changes at a high resolution, revealing novel targets for potential therapeutic candidate development

Fish assemblage recovery along a riverine disturbance gradient

Artificial fluctuations in streamflow have been documented to alter the composition andstructure of stream communities. This study tests the hypothesis that a spatial recovery gradientin fish assemblage structure exists downstream of a hydroelectric dam, and that recovery can be identified by the presence and abundance of species largely restricted to flowing-water habitats(fluvial specialists). A longitudinal gradient of change in a shoreline fish assemblage wasquantified in a 66-km reach of a mid-sized, species-rich river (Tallapoosa River, Alabama) withdaily flow fluctuations from hydropower generation. The shoreline fish assemblage in a nearbyand similar river (Cahaba River, Alabama) was quantified as a regional reference for theoccurrence of fish assemblage gradients. Fish were collected with prepositioned areaelectrofishers in 240 randomly located sampling sites, and physical habitat was quantified. Usingdistributional and habitat use information, fish species were categorized as fluvial specialists ormacrohabitat generalists (species that occur in a wide variety of aquatic systems). Sampledhabitats were similar between rivers and along each study reach. The longitudinal pattern ofspecies occurrence and fish abundance was consistent in the free-flowing river. A longitudinalgradient of increasing abundance and richness of only fluvial specialist species existeddownstream of the hydroelectric dam. No similar spatial gradient existed for macrohabitatgeneralists in either river. Although a fish community recovery gradient was identified, a recoveryendpoint was not evident because assemblage change was gradual and possibly incomplete.The preservation and management of riverine fish faunas will partly depend on incorporatingspatial recovery into decisions about permitting and siting of anthropogenic changes like hydroelectric dams. http://dx.doi.org/10.2307/194192