Molecular characterization and embryonic origin of the eyes in the common house spider Parasteatoda tepidariorum

Abstract

BackgroundTwo visual systems are present in most arthropod groups: median and lateral eyes. Most of our current knowledge about the developmental and molecular mechanisms involved in eye formation in arthropods comes from research in the model system Drosophila melanogaster. Here, a core set of retinal determination genes, namely, sine-oculis (so), eyes absent (eya), dachshund (dac), and the two pax6 orthologues eyeless (ey) and twin of eyeless (toy) govern early retinal development. By contrast, not much is known about the development of the up-to-eight eyes present in spiders. Therefore, we analyzed the embryonic expression of core retinal determination genes in the common house spider Parasteatoda tepidariorum.ResultsWe show that the anlagen of the median and lateral eyes in P. tepidariorum originate from different regions of the non-neurogenic ectoderm in the embryonic head. The median eyes are specified as two individual anlagen in an anterior median position in the developing head and subsequently move to their final position following extensive morphogenetic movements of the non-neurogenic ectoderm. The lateral eyes develop from a more lateral position. Intriguingly, they are specified as a unique field of cells that splits into the three individual lateral eyes during late embryonic development. Using gene expression analyses, we identified a unique combination of determination gene expression in the anlagen of the lateral and median eyes, respectively.ConclusionsThis study of retinal determination genes in the common house spider P. tepidariorum represents the first comprehensive analysis of the well-known retinal determination genes in arthropods outside insects. The development of the individual lateral eyes via the subdivision of one single eye primordium might be the vestige of a larger composite eye anlage, and thus supports the notion that the composite eye is the plesiomorphic state of the lateral eyes in arthropods. The molecular distinction of the two visual systems is similar to the one described for compound eyes and ocelli in Drosophila, suggesting that a unique core determination network for median and lateral eyes, respectively, might have been in place already in the last common ancestor of spiders and insects.Electronic supplementary materialThe online version of this article (doi:10.1186/s13227-015-0011-9) contains supplementary material, which is available to authorized users.

Ancient default activators of terminal photoreceptor differentiation in the pancrustacean compound eye: the homeodomain transcription factors Otd and Pph13

“…It is therefore equally exciting to note a new generation of molecular developmental studies in the structurally and evolutionarily complex visual systems of chelicerates [67–69], opening further testing grounds for examining the conserved roles of Otd and Pph13 in photoreceptor differentiation.…”

Antero-posterior patterning of Drosophila ocelli requires an anti-repressor mechanism within the hh-pathway mediated by the Six3 gene Optix

“…This work has expanded our understanding of the general mechanisms by which the conserved Wnt and Hh signaling pathways interact (Royet and Finkelstein, 1997) and of the development and evolution of the eyes and dorsal head of arthropods (Posnien et al, 2010(Posnien et al, , 2011Samadi et al, 2015;Schomburg et al, 2015), and has helped in establishing parallels between head patterning across phyla. For instance, members of both the Wnt and Otx gene families are involved in anterior head/ neural tube patterning in both invertebrates and vertebrates (Lichtneckert and Reichert, 2005;Rhinn et al, 2005;Schinko et al, 2008;Steinmetz et al, 2011;Fu et al, 2012).…”

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Sex differences in spiders: from phenotype to genomics

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