Finding of Gordius austrinus De Villalobos, Zanca & Ibarra - Vidal, 2005 (Gordiida, Nematomorpha) in the stomach of Salmo trutta (Salmoniformes) in Patagonia

Field observations revealed, for the first time, cases of predation on Gordius austrinus by Salmo trutta in Risopatrón Lake, Aysén Region, Chile. Reinvestigation by SEM of the characteristics of the posterior end and of the cuticle of the specimens of horsehair worms collected inside the stomach of brown trout allow us to assign the specimens to the species Gordius austrinus. Also we could show that in some specimens the cuticle of mid body and terminal end presented structural alterations, due to the action of the digestive juices of the fish. This finding implies the extension of the distribution range of G. austrinus.Facultad de Ciencias Naturales y Muse

Finding of Gordius austrinus De Villalobos, Zanca & Ibarra - Vidal, 2005 (Gordiida, Nematomorpha) in the stomach of Salmo trutta (Salmoniformes) in Patagonia

Field observations revealed, for the first time, cases of predation on Gordius austrinus by Salmo trutta in Risopatrón Lake, Aysén Region, Chile. Reinvestigation by SEM of the characteristics of the posterior end and of the cuticle of the specimens of horsehair worms collected inside the stomach of brown trout allow us to assign the specimens to the species Gordius austrinus. Also we could show that in some specimens the cuticle of mid body and terminal end presented structural alterations, due to the action of the digestive juices of the fish. This finding implies the extension of the distribution range of G. austrinus.Facultad de Ciencias Naturales y Muse

Drones and digital photogrammetry: from classifications to continuums for monitoring river habitat and hydromorphology

Recently, we have gained the opportunity to obtain very high-resolution imagery and topographic data of rivers using drones and novel digital photogrammetric processing techniques. The high-resolution outputs from this method are unprecedented, and provide the opportunity to move beyond river habitat classification systems, and work directly with spatially explicit continuums of data. Traditionally, classification systems have formed the backbone of physical river habitat monitoring for their ease of use, rapidity, cost efficiency, and direct comparability. Yet such classifications fail to characterize the detailed heterogeneity of habitat, especially those features which are small or marginal. Drones and digital photogrammetry now provide an alternative approach for monitoring river habitat and hydromorphology, which we review here using two case studies. First, we demonstrate the classification of river habitat using drone imagery acquired in 2012 of a 120 m section of the San Pedro River in Chile, which was at the technological limits of what could be achieved at that time. Second, we review how continuums of data can be acquired, using drone imagery acquired in 2016 from the River Teme in Herefordshire, England. We investigate the precision and accuracy of these data continuums, highlight key current challenges, and review current best practices of data collection, processing, and management. We encourage further quantitative testing and field applications. If current difficulties can be overcome, these continuums of geomorphic and hydraulic information hold great potential for providing new opportunities for understanding river systems to the benefit of both river science and management

Surviving historical Patagonian landscapes and climate: molecular insights from Galaxias maculatus

<p>Abstract</p> <p>Background</p> <p>The dynamic geological and climatic histories of temperate South America have played important roles in shaping the contemporary distributions and genetic diversity of endemic freshwater species. We use mitochondria and nuclear sequence variation to investigate the consequences of mountain barriers and Quaternary glacial cycles for patterns of genetic diversity in the diadromous fish <it>Galaxias maculatus </it>in Patagonia (~300 individuals from 36 locations).</p> <p>Results</p> <p>Contemporary populations of <it>G. maculatus</it>, east and west of the Andes in Patagonia, represent a single monophyletic lineage comprising several well supported groups. Mantel tests using control region data revealed a strong positive relationship when geographic distance was modeled according to a scenario of marine dispersal. (<it>r </it>= 0.69, <it>P = 0.055</it>). By contrast, direct distance between regions was poorly correlated with genetic distance (<it>r </it>= -0.05, <it>P </it>= 0.463). Hierarchical AMOVAs using mtDNA revealed that pooling samples according to historical (pre-LGM) oceanic drainage (Pacific vs. Atlantic) explained approximately four times more variance than pooling them into present-day drainage (15.6% vs. 3.7%). Further <it>post-hoc </it>AMOVA tests revealed additional genetic structure between populations east and west of the Chilean Coastal Cordillera (coastal vs. interior). Overall female effective population size appears to have remained relatively constant until roughly 0.5 Ma when population size rapidly increased several orders of magnitude [100× (60×-190×)] to reach contemporary levels. Maximum likelihood analysis of nuclear alleles revealed a poorly supported gene tree which was paraphyletic with respect to mitochondrial-defined haplogroups.</p> <p>Conclusions</p> <p>First diversifying in the central/north-west region of Patagonia, <it>G. maculatus </it>extended its range into Argentina via the southern coastal regions that join the Pacific and Atlantic oceans. More recent gene flow between northern populations involved the most ancient and most derived lineages, and was likely facilitated by drainage reversal(s) during one or more cooling events of the late Pleistocene. Overall female effective population size represents the end result of a widespread and several hundred-fold increase over approximately 0.5 Ma, spanning several climatic fluctuations of the Pleistocene. The minor influence of glacial cycles on the genetic structure and diversity of <it>G. maculatus </it>likely reflects the access to marine refugia during repeated bouts of global cooling. Evidence of genetic structure that was detected on a finer scale between lakes/rivers is most likely the result of both biological attributes (i.e., resident non-migratory behavior and/or landlocking and natal homing in diadromous populations), and the Coastal Cordillera as a dispersal barrier.</p

Finding of Gordius austrinus De Villalobos, Zanca & Ibarra - Vidal, 2005 (Gordiida, Nematomorpha) in the stomach of Salmo trutta (Salmoniformes) in Patagonia

Field observations revealed, for the first time, cases of predation on Gordius austrinus by Salmo trutta in Risopatrón Lake, Aysén Region, Chile. Reinvestigation by SEM of the characteristics of the posterior end and of the cuticle of the specimens of horsehair worms collected inside the stomach of brown trout allow us to assign the specimens to the species Gordius austrinus. Also we could show that in some specimens the cuticle of mid body and terminal end presented structural alterations, due to the action of the digestive juices of the fish. This finding implies the extension of the distribution range of G. austrinus.Facultad de Ciencias Naturales y Muse

New Insights into the Distribution, Physiology and Life Histories of South American Galaxiid Fishes, and Potential Threats to this Unique Fauna

South American galaxiids occupy both Patagonia and the ichthyogeographic Chilean Province, encompassing glacial Andean deep lakes, shallow plateau lakes, reservoirs, short Pacific rivers and long Atlantic rivers. The total fish fauna includes 29 species, comprising Neotropical fishes (siluriforms and characids), galaxiids, percichthyids, atherinopsids and mugilids, two lamprey species, and several exotic fishes (salmonids, Gambusia spp. and common carp). The family Galaxiidae shares a common ancestry with the Gondwanan temperate fish fauna, played a major role in the post-glacial colonization of Andean lakes and streams, and contributes key species to the food webs. Galaxiid species occupy an enormous latitudinal gradient, show a wide variety of life history patterns and are the southernmost native freshwater fishes of the world. Knowledge of South American galaxiids has improved notably, but new challenges arise due to climate change, biological invasions, damming, aquaculture and contamination. In this changing environment, the future of South American galaxiids should be carefully considered as a legacy of the old Gondwana and a unique attribute of the freshwaters of southern South America.Fil: Cussac, Victor Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales. Universidad Nacional del Comahue. Instituto Andino Patagónico de Tecnologías Biológicas y Geoambientales; ArgentinaFil: Barrantes, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Boy, Claudia Clementina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Górski, Konrad. Universidad Austral de Chile; ChileFil: Habit, Evelyn. Universidad de Concepción; ChileFil: Lattuca, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Rojo, Javier Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin