Gradients in cytoarchitectural landscapes of the isocortex: Diprotodont marsupials in comparison to eutherian mammals

Although it has been claimed that marsupials possess a lower density of isocortical neurons compared with other mammals, little is known about cross‐cortical variation in neuron distributions in this diverse taxonomic group. We quantified upper‐layer (layers II–IV) and lower‐layer (layers V–VI) neuron numbers per unit of cortical surface area in three diprotodont marsupial species (two macropodiformes, the red kangaroo and the parma wallaby, and a vombatiform, the koala) and compared these results to eutherian mammals (e.g., xenarthrans, rodents, primates). In contrast to the notion that the marsupial isocortex contains a low density of neurons, we found that neuron numbers per unit of cortical surface area in several marsupial species overlap with those found in eutherian mammals. Furthermore, neuron numbers vary systematically across the isocortex of the marsupial mammals examined. Neuron numbers under a unit of cortical surface area are low toward the frontal cortex and high toward the caudo‐medial (occipital) pole. Upper‐layer neurons (i.e., layers II–IV) account for most of the variation in neuron numbers across the isocortex. The variation in neuron numbers across the rostral to the caudal pole resembles primates. These findings suggest that diprotodont marsupials and eutherian mammals share a similar cortical architecture despite their distant evolutionary divergence

Espécies do gênero Munida Leach (Crustacea, Decapoda, Galatheidae), distribuídas na costa do Brasil Species of the genus Munida Leach (Crustacea, Decapoda, Galatheidae) with distribution in the Brazilian coast

<abstract language="eng">The purpose of this work is to analyse the taxonomy and distributional patterns of the species of the genus Munida Leach, 1820 which occur along the Brazilian coast. The species of Munida present some peculiar characteristics, rarely found in any other marine group. They live in groups with great number of individuals (gregariousness) and with several species found together in the same population (sintopy). In addition, they exhibit a great degree of intraspeciftc variation and, paradoxally, a little variability among the species. These factors make a better understanding of the systematics of this group very difficult. In the present study the utilization of non variable characters was emphasized. As a corollary of this study, "species-complexes" were defined including groups of species morphologically very similar but yet well characterized. Sixteen species with distribution along the Brazilian coast were studied. An identification key is provided. A general discussion where the main problems on taxonomy and distributional patterns of species were analysed was done