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Porco David - One of the best experts on this subject based on the ideXlab platform.

Stoev Pavel - One of the best experts on this subject based on the ideXlab platform.

Rebecca T. Kimball - One of the best experts on this subject based on the ideXlab platform.

  • Supplementary data
    2014
    Co-Authors: T. Kimball, Keping Sun, Kelly A. Meiklejohn, Brant C. Faircloth, Travis C. Glenn, Edward L. Braun, Rebecca T. Kimball
    Abstract:

    a phylogenomic approach The evolution of peafowl and other taxa with Ocelli (eyespots)

  • a molecular phylogeny of the peacock pheasants galliformes polyplectron spp indicates loss and reduction of ornamental traits and display behaviours
    Biological Journal of The Linnean Society, 2001
    Co-Authors: Edward L. Braun, Rebecca T. Kimball, David J Ligon, Vittorio Lucchini, Ettore Randi
    Abstract:

    The South-east Asian pheasant genus Polyplectron is comprised of six or seven species which are characterized by Ocelli (ornamental eye-spots) in all but one species, though the sizes and distribution of Ocelli vary among species. All Polyplectron species have lateral displays, but species with Ocelli also display frontally to females, with feathers held erect and spread to clearly display the Ocelli. The two least ornamented Polyplectron species, one of which completely lacks Ocelli, have been considered the primitive members of the genus, implying that Ocelli are derived. We examined this hypothesis phylogenetically using complete mitochondrial cytochrome b and control region sequences, as well as sequences from intron G in the nuclear ovomucoid gene, and found that the two least ornamented species are in fact the most recently evolved. Thus, the absence and reduction of Ocelli and other ornamental traits in Polyplectronare recent losses. The only variable that may correlate with the reduction in ornamentation is habitat, as the two less-ornamented species inhabit montane regions, while the ornamented species inhabit lowland regions. The implications of these findings are discussed in light of models of sexual selection. The phylogeny is not congruent with current geographical distributions, and there is little evidence that Pleistocene sea level changes promoted speciation in this genus. Maximum likelihood and maximum parsimony analyses of cytochrome b sequences suggest that the closest relatives of Polyplectron are probably the peafowl and the argus pheasants.

Roland R. Melzer - One of the best experts on this subject based on the ideXlab platform.

  • wiring a periscope Ocelli retinula axons visual neuropils and the ancestrality of sea spiders
    PLOS ONE, 2012
    Co-Authors: Tobias Lehmann, Martin Hes, Roland R. Melzer
    Abstract:

    The Pycnogonida or sea spiders are cryptic, eight-legged arthropods with four median Ocelli in a ‘periscope’ or eye tubercle. In older attempts at reconstructing phylogeny they were Arthropoda incertae sedis, but recent molecular trees placed them as the sister group either to all other euchelicerates or even to all euarthropods. Thus, pycnogonids are among the oldest extant arthropods and hold a key position for the understanding of arthropod evolution. This has stimulated studies of new sets of characters conductive to cladistic analyses, e.g. of the chelifores and of the hox gene expression pattern. In contrast knowledge of the architecture of the visual system is cursory. A few studies have analysed the Ocelli and the uncommon “pseudoinverted” retinula cells. Moreover, analyses of visual neuropils are still at the stage of Hanstrom's early comprehensive works. We have therefore used various techniques to analyse the visual fibre pathways and the structure of their interrelated neuropils in several species. We found that pycnogonid Ocelli are innervated to first and second visual neuropils in close vicinity to an unpaired midline neuropil, i.e. possibly the arcuate body, in a way very similar to ancestral euarthropods like Euperipatoides rowelli (Onychophora) and Limulus polyphemus (Xiphosura). This supports the ancestrality of pycnogonids and sheds light on what eyes in the pycnogonid ground plan might have ‘looked’ like. Recently it was suggested that arthropod eyes originated from simple Ocelli similar to larval eyes. Hence, pycnogonid eyes would be one of the early offshoots among the wealth of more sophisticated arthropod eyes.

  • Mechanisms of eye development and evolution of the arthropod visual system: The lateral eyes of myriapoda are not modified insect ommatidia
    Organisms Diversity & Evolution, 2007
    Co-Authors: Steffen Harzsch, Roland R. Melzer, Carsten Müller
    Abstract:

    Abstract The lateral eyes of Crustacea and Insecta consist of many single optical units, the ommatidia, that are composed of a small, strictly determined and evolutionarily conserved set of cells. In contrast, the eyes of Myriapoda (millipedes and centipedes) are fields of optical units, the lateral Ocelli, each of which is composed of up to several hundreds of cells. For many years these striking differences between the lateral eyes of Crustacea/Insecta versus Myriapoda have puzzled evolutionary biologists, as the Myriapoda are traditionally considered to be closely related to the Insecta. The prevailing hypothesis to explain this paradox has been that the myriapod fields of lateral Ocelli derive from insect compound eyes by disintegration of the latter into single ommatidia and subsequent fusion of several ommatidia to form multicellular Ocelli. To provide a fresh view on this problem, we counted and mapped the arrangement of Ocelli during postembryonic development of a diplopod. Furthermore, the arrangement of proliferating cells in the eyes of another diplopod and two chilopods was monitored by labelling with the mitosis marker bromodeoxyuridine. Our results confirm that during eye growth in Myriapoda new elements are added to the side of the eye field, which extend the rows of earlier-generated optical units. This pattern closely resembles that in horseshoe crabs (Chelicerata) and Trilobita. We conclude that the trilobite, xiphosuran, diplopod and chilopod mechanism of eye growth represents the ancestral euarthropod mode of visual-system formation, which raises the possibility that the eyes of Diplopoda and Chilopoda may not be secondarily reconstructed insect eyes.

Akkari Nesrine - One of the best experts on this subject based on the ideXlab platform.

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