A Novel Method for Comparative Analysis of Retinal Specialization Traits from Topographic Maps

Abstract Vertebrates possess different types of retinal specializations that vary in number, size, shape, and position in the retina. This diversity in retinal configuration has been revealed through topographic maps, which show variations in neuron density across the retina. Although topographic maps of about 300 vertebrates are available, there is no method for characterizing retinal traits quantitatively. Our goal is to present a novel method to standardize information on the position of the retinal specializations and changes in retinal ganglion cell (RGC) density across the retina from published topographic maps. We measured the position of the retinal specialization using two Cartesian coordinates and the gradient in cell density by sampling ganglion cell density values along four axes (nasal, temporal, ventral, and dorsal). Using this information, along with the peak and lowest RGC densities, we conducted discriminant function analyses (DFAs) to establish if this method is sensitive to distinguish three common types of retinal specializations (fovea, area, and visual streak). The discrimination ability of the model was higher when considering terrestrial (78%–80% correct classification) and aquatic (77%–86% correct classification) species separately than together. Our method can be used in the future to test specific hypotheses on the differences in retinal morphology between retinal specializations and the association between retinal morphology and behavioral and ecological traits using comparative methods controlling for phylogenetic effects

A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes

Chimaeroid fishes (Holocephali) are one of the four principal divisions of modern gnathostomes (jawed vertebrates). Despite only 47 described living species1, chimaeroids are the focus of resurgent interest as potential archives of genomic data2 and for the unique perspective they provide on chondrichthyan and gnathostome ancestral conditions. Chimaeroids are also noteworthy for their highly derived body plan1,3,4. However, like other living groups with distinctive anatomies5, fossils have been of limited use in unravelling their evolutionary origin, as the earliest recognized examples already exhibit many of the specializations present in modern forms6,7. Here we report the results of a computed tomography analysis of Dwykaselachus, an enigmatic chondrichthyan braincase from the ~280 million year old Karoo sediments of South Africa8. Externally, the braincase is that of a symmoriid shark9,10,11,12,13and is by far the most complete uncrushed example yet discovered. Internally, the morphology exhibits otherwise characteristically chimaeroid specializations, including the otic labyrinth arrangement and the brain space configuration relative to exceptionally large orbits. These results have important implications for our view of modern chondrichthyan origins, add robust structure to the phylogeny of early crown group gnathostomes, reveal preconditions that suggest an initial morpho-functional basis for the derived chimaeroid cranium, and shed new light on the chondrichthyan response to the extinction at the end of the Devonian period

Understanding the retinal basis of vision across species

The vertebrate retina first evolved some 500 million years ago in ancestral marine chordates. Since then, the eyes of different species have been tuned to best support their unique visuoecological lifestyles. Visual specializations in eye designs, large-scale inhomogeneities across the retinal surface and local circuit motifs mean that all species' retinas are unique. Computational theories, such as the efficient coding hypothesis, have come a long way towards an explanation of the basic features of retinal organization and function; however, they cannot explain the full extent of retinal diversity within and across species. To build a truly general understanding of vertebrate vision and the retina's computational purpose, it is therefore important to more quantitatively relate different species' retinal functions to their specific natural environments and behavioural requirements. Ultimately, the goal of such efforts should be to build up to a more general theory of vision

Social preferences and network structure in a population of reef manta rays

Understanding how individual behavior shapes the structure and ecology ofpopulations is key to species conservation and management. Like manyelasmobranchs, manta rays are highly mobile and wide ranging species threatened byanthropogenic impacts. In shallow-water environments these pelagic rays often formgroups, and perform several apparently socially-mediated behaviors. Group structuresmay result from active choices of individual rays to interact, or passive processes.Social behavior is known to affect spatial ecology in other elasmobranchs, but this isthe first study providing quantitative evidence for structured social relationships inmanta rays. To construct social networks, we collected data from more than 500groups of reef manta rays over five years, in the Raja Ampat Regency of West Papua.We used generalized affiliation indices to isolate social preferences from non-socialassociations, the first study on elasmobranchs to use this method. Longer lastingsocial preferences were detected mostly between female rays. We detectedassortment of social relations by phenotype and variation in social strategies, with theoverall social network divided into two main communities. Overall network structurewas characteristic of a dynamic fission-fusion society, with differentiated relationshipslinked to strong fidelity to cleaning station sites. Our results suggest that fine-scaleconservation measures will be useful in protecting social groups of M. alfredi in theirnatural habitats, and that a more complete understanding of the social nature of mantarays will help predict population response

Hinkley Point 'C' power station public inquiry Proof of evidence on landscape and architecture

Report also known as CEGB--15Available from British Library Document Supply Centre- DSC:Alphafiche(INIS-GB--220) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Deprivación sociocultural y violencia barrial en adolescentes con disrupción escolar en la ciudad de Pasto–Colombia

Objetivos: Conocer las manifestaciones de la deprivaciónsociocultural y la violencia barrial en adolescentes que presentandisrupción escolar en la ciudad de Pasto - Colombia.Materiales y métodos: En el estudio se utilizó la escala FAPDESO,los grupos focales y la observación participante lascuales contribuirán de forma secuencial al abordaje del estudiode la deprivación sociocultural, la violencia barrial y ladisrupción escolar como ejes de análisis. Para el análisis dedatos en la fase cuantitativa se procedió al análisis descriptivoa partir de estadísticos de tendencia central, estadísticosde dispersión y los descriptivos de distribución como la asimetríay curtosis. Se realizó una investigación de enfoquemixto con status dominante cualitativo en la ciudad de Pasto-Colombia de una Institución Educativa Pública. Para ladeterminación de los sujetos en la fase cuantitativa se trabajócon 80 estudiantes, seleccionados a través de un muestreoaleatorio simple, tomando como referencia aquellos adolescentesque presentaban reportes de convivencia escolar yposteriormente en la fase cualitativa mediante muestreo porconveniencia se eligieron a 27 estudiantes que presentabanreportes de disrupción escolar reiterativas y puntuaban altoen la escala FAPDESO. En la fase cualitativa se organizó einterpretó la información recogida por los investigadores paraestablecer relaciones, identificar los significados y proyectarlas conclusiones.Resultados: Se identifica una destacada relación entre barriosmarcados por la violencia, la marginalidad y la exclusiónsocial con diversos factores de deprivación socioculturalacoplados a los principales ambientes de influencia de losjóvenes, familia, barrio - comunidad y escuela.Conclusiones: Se evidencia que el conjunto de experienciaspositivas o negativas de los adolescentes determinanmayores o menores niveles en el funcionamiento cognitivo,la adaptación a contextos normativos y competencias sociales,siendo la deprivación sociocultural un predictor delfracaso escolar y la disruptividad en el aula y una necesidadde atención