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Compound Eyes (compound + eye)
Selected AbstractsCell-type specific utilization of multiple negative feedback loops generates developmental constancyGENES TO CELLS, Issue 7 2005Masaki Iwanami Signaling pathways generally contain multiple negative regulators that are induced by the signal they repress, constructing negative feedback loops. Although such negative regulators are often expressed in a tissue- or cell-type specific manner during development, little is known about the significance of their differential expression patterns and possible interactions. We show the role and interplay of two cell-type specific negative feedback loops during specification of photoreceptor neurons in the Drosophila compound eye, a process that occurs via epidermal growth factor (EGF)-mediated sequential induction through the activation of the Ras/MAPK signaling pathway. Inducing cells secreting EGF express a negative regulator Sprouty (SPRY) that lowers Ras/MAPK signaling activity, and as a consequence reduces the signal-dependent expression of a secreted EGF inhibitor, Argos (AOS). Induced cells in turn express an orphan nuclear receptor Seven-up (SVP), which represses SPRY expression thereby allowing expression and secretion of AOS, preventing further induction. When this intricate system fails, as in spry mutants, sequential induction is no longer constant and the number of photoreceptor neurons becomes variable. Thus, cell-type specific utilization of multiple negative feedback loops not only confers developmental robustness through functional redundancy, but is a key component in generating consistent patterning. [source] The non-conserved C-terminal segments of Sine Oculis Homeobox (Six) proteins confer functional specificityGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 8 2009Brandon P. Weasner Scanning electron microscope image of a fly head, showing an extra eye field (red) lying on the ventral surface adjacent to the normal compound eye (red). This field results from the forced expression of mouse Six6, the vertebrate ortholog for the Drosophila optix gene. Please see the article by B. Weasner and J.P. Kumar in this issue. [source] Cell diversity in the retina: more than meets the eyeBIOESSAYS, Issue 10 2003Tiffany Cook Over 10 years ago, Pax-6 was shown to play an evolutionarily conserved role in controlling eye formation from Drosophila to humans.1 Since then, the identification of an entire cascade of conserved eye determination genes has brought a new understanding to the developmental relationship between the insect compound eye and the vertebrate camera eye.2 Additional studies are now beginning to suggest that even late aspects of eye development, including cell type specification, also share common molecular machinery. In this commentary, I will discuss some of these findings, with a particular focus on the recent study by Dyer et al.3 describing a novel role for the Prox1 transcription factor in specifying horizontal cells in the mouse retina. As Prospero, the Drosophila homolog of Prox1, also participates in retinal cell specification, these data provide a forum for asking new questions concerning pathways that may regulate retinogenesis across evolution. BioEssays 25:921,925, 2003. © 2003 Wiley Periodicals, Inc. [source] A new look at an old visual system: structure and development of the compound eyes and optic ganglia of the brine shrimp artemia salina linnaeus, 1758 (branchiopoda, anostraca)DEVELOPMENTAL NEUROBIOLOGY, Issue 2 2002Miriam Wildt Abstract Compared to research carried out on decapod crustaceans, the development of the visual system in representatives of the entomostracan crustaceans is poorly understood. However, the structural evolution of the arthropod visual system is an important topic in the new debate on arthropod relationships, and entomostracan crustaceans play a key role in this discussion. Hence, data on structure and ontogeny of the entomostracan visual system are likely to contribute new aspects to our understanding of arthropod phylogeny. Therefore, we explored the proliferation of neuronal stem cells (in vivo incorporation of bromodeoxyuridine) and the developmental expression of synaptic proteins (immunohistochemistry against synapsins) in the developing optic neuropils of the brine shrimp Artemia salina Linnaeus, 1758 (Crustacea, Entomostraca, Branchiopoda, Anostraca) from hatching to adulthood. The morphology of the adult visual system was examined in serial sections of plastic embedded specimens. Our results indicate that the cellular material that gives rise to the visual system (compound eyes and two optic ganglia) is contributed by the mitotic activity of neuronal stem cells that are arranged in three band-shaped proliferation zones. Synapsin-like immunoreactivity in the lamina ganglionaris and the medulla externa initiated only after the anlagen of the compound eyes had already formed, suggesting that the emergence of the two optic neuropils lags behind the proliferative action of these stem cells. Neurogenesis in A. salina is compared to similar processes in malacostracan crustaceans and possible phylogenetic implications are discussed. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 117,132, 2002 [source] Subterranean species of the ant genus Crematogaster in Asia (Hymenoptera: Formicidae)ENTOMOLOGICAL SCIENCE, Issue 3 2010Shingo HOSOISHI Abstract Three Crematogaster ant species, C. (Orthocrema) javanica Menozzi, C. (O.) myops Forel and C. (O.) masukoi sp. nov., share reduced compound eyes which characterizes them among Asian species of the subgenus Orthocrema. The new species is described based on material from Borneo. It can be distinguished from C. javanica and C. myops by its smooth surface of clypeus and acutely produced subpetiolar process. Reduced compound eyes and yellowish body suggest that these three species are subterranean. [source] Winged presoldiers induced by a juvenile hormone analog in Zootermopsis nevadensis: Implications for plasticity and evolution of caste differentiation in termitesJOURNAL OF MORPHOLOGY, Issue 1 2003Toru Miura Abstract To elucidate the switching mechanism of caste differentiation in termites and to examine the possible induction of soldier-reproductive intercastes experimentally, we investigated the effects of juvenile hormone on the morphologies of soldier caste by applying a juvenile hormone analog (JHA) to nymphs of the damp-wood termite Zootermopsis nevadensis (Isoptera : Termopsidae). JHA treatment for about 2 weeks induced a variety of intermediate castes, showing both alate and soldier morphological features. The principal component analysis (PCA) of those morphological characters showed that those intercastes were a deviation from the developmental line into alates to soldier differentiation, which is known to be triggered by juvenile hormone. Detailed morphological examination of the compound eyes, wing joint, and mandibles showed that those intercastes expressed soldier features, although they had started to develop alate characteristics. The morphology of the resultant intercastes seemed to be determined by the nymphal stage, at which JHA treatment was applied. The induced intercastes with exaggerated soldier-specific characteristics (e.g., mandibles) repressed alate-specific characteristics (e.g., wings), namely, the alate and soldier morphological characteristics in induced intercastes show opposite responses against the application of JHA. On the other hand, ovarian development was not suppressed by the JHA application, even in the soldier-like individuals. Naturally differentiated presoldiers also possessed developed ovarioles, although ovaries of mature soldiers were degenerated. Our results suggest that the juvenile hormone plays complicated roles in the expression of caste morphologies and ovarian development in termites. J. Morphol. 257:22,32, 2003. © 2003 Wiley-Liss, Inc. [source] Divided and undivided compound eyes in Ascalaphidae (Insecta, Neuroptera) and their functional and phylogenetic significanceJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2006K. Fischer Abstract The external morphology of the compound eyes of 13 species of the Ascalaphidae family (Insecta, Neuroptera) from Africa, Asia and Europe was studied in relation to the habitat, phylogeny and time of activity during the day. The six species with undivided eyes (Haplogleniinae) are nocturnal; four inhabit more or less open terrain, while two inhabit more or less dense vegetation. Of the seven species with divided eyes (Ascalaphinae), three are diurnal, one is crepuscular and nocturnal, and three are nocturnal. It was found that two of the diurnal species inhabit open terrain and open forest, and one inhabits dense vegetation; the crepuscular and nocturnal species inhabits open terrain; and two of the nocturnal species inhabit open terrain, while one inhabits dense vegetation. The results are discussed in relation to the hypothesis that divided eyes evolved from undivided eyes, originally serving as an adaptation to daytime vision in open terrain. Zusammenfassung Bei 13 Arten aus der Familie der Ascalaphidae (Insecta, Neuroptera) aus Afrika, Asien und Europa wurde die externe Morphologie der Komplexaugen im Zusammenhang mit der tageszeitlichen Aktivität, dem Habitat und der Phylogenie untersucht. Alle sechs Arten mit ungeteilten Augen (Haplogleniinae) sind nachtaktiv. Vier kommen im mehr oder weniger offenen Gelände und zwei kommen in mehr oder weniger dichter Vegetation vor. Von den sieben Arten mit geteilten Augen (Ascalaphinae) sind drei tagaktiv, eine ist dämmerungs- und nachtaktiv und drei sind nachtaktiv. Zwei von den tagaktiven Arten kommen im offenen Gelände und in lichten Baumbeständen vor, eine Art bewohnt dichte Vegetation. Die dämmerungs- und nachtaktive Art kommt im offenen Gelände vor.Von den drei nachtaktiven Arten kommen zwei im offenen Gelände vor, eine bevorzugt dichte Vegetation. Die Ergebnisse werden im Zusammenhang mit der Hypothese diskutiert, dass sich im Verlauf der Evolution die geteilten Augen aus ungeteilten Augen entwickelt haben und ursprünglich eine Anpassung an das Sehen bei Tag im offenen Gelände darstellen. [source] Behavioural environments and niche construction: the evolution of dim-light foraging in beesBIOLOGICAL REVIEWS, Issue 1 2009William T. Wcislo Abstract Most bees forage for floral resources during the day, but temporal patterns of foraging activity vary extensively, and foraging in dim-light environments has evolved repeatedly. Facultative dim-light foraging behaviour is known in five of nine families of bees, while obligate behaviour is known in four families and evolved independently at least 19 times. The light intensity under which bees forage varies by a factor of 108, and therefore the evolution of dim-light foraging represents the invasion of a new, extreme niche. The repeated evolution of dim-light foraging behaviour in bees allows tests of the hypothesis that behaviour acts as an evolutionary pacemaker. With the exception of one species of Apis, facultative dim-light foragers show no external structural traits that are thought to enable visually mediated flight behaviour in low-light environments. By contrast, most obligate dim-light foragers show a suite of convergent optical traits such as enlarged ocelli and compound eyes. In one intensively studied species (Megalopta genalis) these optical changes are associated with neurobiological changes to enhance photon capture. The available ecological evidence suggests that an escape from competition for pollen and nectar resources and avoidance of natural enemies are driving factors in the evolution of obligate dim-light foraging. [source] | ||||||||||||||||||||||