A new species of bufonid frog, Rhinella bernardoi sp. nov., belonging to the granulosa group, is described from moderately high elevation (1400 m) at Ischigualasto Provincial Park, San Juan, Argentina. The morphology of the new species is compared to and diagnosed from other closely related species of the same group (R. bergi, R. fernandezae, and R. granulosa). We also describe the osteology of the skull and the vertebral column of the new species and present data on its geographic distribution and natural history.

Background: Rhea pennata is classified internationally as a near-threatened species, with the subspecies R. p. garleppi being listed as endangered. Finding: The aim of this study was to provide updated information on the density and abundance of R. p. garleppi in the southern Puna ecoregion of Argentina. Density was estimated indirectly on the basis of monthly feces counts during 2011 and 2012, using line-transect surveys. Monthly abundance was calculated by multiplying the density of each month by the area of the reserve (400 km 2 ). Population size range was calculated considering the average of the months with the highest abundance (and density) as the upper limit and the average of the months with the lowest abundance (and density) as the lower limit. The population size of this subspecies varied between 300 individuals (±60), with a density of 0.75 individuals/km 2 (±0.15) during the non-breeding season, and 188 individuals (±40), with a density of 0.47 individuals/km 2 (±0.10), during the reproductive season.

Locomoting organisms often carry loads such as captured prey or young. Load-carrying effects on high-Reynolds-number flight have been studied, but the fluid dynamics of load carrying by low-Reynolds-number microorganisms has not. We studied low-Reynolds-number load carrying using unicellular choanoflagellates, which wave a flagellum to swim and create a water current transporting bacterial prey to a food-capturing collar of microvilli. A regularized Stokeslet framework was used to model the hydrodynamics of a swimming choanoflagellate with bacterial prey on its collar. Both the model and microvideography of choanoflagellates showed that swimming speed decreases as number of prey being carried increases. Flux of water into the capture zone is reduced by bacteria on the collar, which redirect the water flow and occlude parts of the collar. Feeding efficiency (prey captured per work to produce the feeding current) is decreased more by large prey, prey in the plane of flagellar beating and prey near microvillar tips than by prey in other locations. Some choanoflagellates can attach themselves to surfaces. We found that the reduction in flux due to bacterial prey on the collars of these attached thecate cells was similar to the reduction in flux for swimmers.

ResumenEl presente trabajo reporta la ampliación de la distribución de Sephanoides sephaniodes hacia el centro-oeste de Argentina. Se analizan posibles causas de la dispersión y consecuencias ecológicas de la misma.Palabras clave: Aves, Distribución, Sephanoides sephaniodes, San Juan, Argentina. AbstractThe present work report the expansion of the distribution of Sephanoides sephaniodes toward the west-central of Argentina. It discusses possible causes of dispersion and ecological consequences of them.