| 1 Silk Proteins: Breakdown and Evolutionary Pathways |
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3 | (28) |
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Silks and fibrous proteins are made up of amino acids that exhibit diverse secondary and tertiary configurations |
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3 | (4) |
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Current hypotheses suggest that fibrous proteins produced by the Chelicerata and Hexapoda evolved independently |
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7 | (7) |
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Comparative phylogenetic analyses pinpoint the taxa most likely to yield insight into the origins and biology of silk-producing systems |
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14 | (4) |
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The ability to secrete fibrous proteins is a primitive character of the hexapods and first evolved in the Diplura |
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18 | (2) |
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The ability to secrete silk fibroins correlates with the evolution of spinning behavior |
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20 | (5) |
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The structural organization of spider silk is correlated with the evolution of a muscular and innervated spinneret |
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25 | (2) |
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Silk production in insects and spiders is hypothesized to have evolved via two pathways: a systemic gland pathway and a surficial gland pathway |
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27 | (2) |
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29 | (2) |
| 2 The Comparative Architecture of Silks, Fibrous Proteins, and Their Encoding Genes in Insects and Spiders (with C. Riekel) |
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31 | (20) |
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The known silk fibroins and fibrous glues are encoded by members of the same gene family |
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32 | (3) |
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Most silk fibroins contain crystalline and noncrystalline regions |
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35 | (3) |
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All of the sequenced fibroin silks (Fhc, MA, and Flag) are made up of hierarchically organized, repetitive arrays of amino acids |
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38 | (3) |
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Fhc fibroin genes (and perhaps MA genes) are characterized by a similar molecular genetic architecture of two exons and one intron, but the organization and size of these units differ |
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41 | (2) |
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The Flag, Ser, and BR genes are made up of multiple exons and introns |
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43 | (3) |
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Sequences coding for crystalline and noncrystalline protein domains are integrated in the repetitive regions of Fhc and MA exons, but not in the protein glues Ser1 and BR-1 |
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46 | (1) |
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Genetic "hot-spots" promote recombination errors in Fhc, MA, and Flag |
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46 | (1) |
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Codon bias, structural constraint, point mutations, and shortened coding arrays are alternative means of stabilizing precursor mRNA transcripts |
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47 | (1) |
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Differential regulation of gene expression and selective splicing may allow rapid adaptation of silk functional properties to different environments |
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48 | (1) |
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49 | (2) |
| 3 The Mechanical Functions of Silks and Their Correlated Structural Properties (with C. Riekel) |
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51 | (33) |
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Ancestral araneomorph spiders spin "dry" capture silks into irregular webs; derived araneomorph spiders (here, the Orbiculariae) spin dry and "wet" capture silks into symmetrical webs |
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55 | (5) |
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The Orbiculariae spin nets that are suspended under tension and that approximate minimum volume architectures |
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60 | (3) |
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Web function is determined by the interaction between web architecture and the material properties of silks |
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63 | (5) |
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The webs and silks spun by the ancestral Deinopoidea are stiff; their ability to both withstand prey impact and to retain prey is a function of fiber strength |
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68 | (1) |
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The diversification of the Araneoidea correlates with a shift in web functional mechanism |
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69 | (1) |
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Silk fibroins produced by derived spiders contain either highly oriented crystalline regions or no crystalline regions at all |
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70 | (11) |
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Despite the advantages of araneoid webs and silks, the cribellate spiders have persisted through evolution |
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81 | (1) |
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82 | (2) |
| 4 Insect Spatial Vision Is a Potential Selective Factor on the Evolution of Silk Achromatic Properties and Web Architecture (with M. Lehrer) |
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84 | (24) |
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Insect spatial resolution is a function of the anatomy and the optics of the eye |
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84 | (2) |
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Contrast resolution is the prerequisite of object detection |
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86 | (1) |
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Insects possess a high temporal resolution capacity |
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87 | (3) |
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Motion parallax cues provide the insect with depth information |
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90 | (1) |
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Insect vision and flight maneuverability function as potential selective forces on silk and web properties |
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91 | (1) |
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Distorted and oscillating webs may enhance insect interception |
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92 | (4) |
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The translucent properties of frame (MA) and spiral (Flag) silk minimize contrast between webs and their background |
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96 | (2) |
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Insects' response to webs is independent of ambient light conditions |
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98 | (5) |
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Web visibility is determined by specific web-background combinations in specific ambient light conditions |
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103 | (3) |
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Visible and invisible webs might have evolved in parallel |
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106 | (2) |
| 5 Insect Color Vision Is a Potential Selective Factor on the Evolution of Silk Chromatic Properties and Web Design (with M. Lehrer) |
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108 | (15) |
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Most insects have UV-, blue-, and green-sensitive photoreceptors |
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108 | (5) |
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Detection of colored objects is based on their contrast against the background |
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113 | (1) |
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The perceptions of chromatic contrast and achromatic contrast are independent processes |
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114 | (1) |
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Webs of ancestral and derived spiders differ in their spectral reflectance |
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115 | (7) |
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Do the differences in UV-reflection of silks result from selective effects of insect color vision? |
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122 | (1) |
| 6 Insect Learning Capacity Is a Potential Selective Factor in the Evolution of Silk Color and the Decorative Silk Patterns Spun by Spiders |
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123 | (33) |
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Insect responses to visual cues are either innate or learned |
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124 | (1) |
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Some silks possess particular spectral or spatial features that vary with ambient light |
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125 | (4) |
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Some silks and webs possess particular spectral or spatial features that might be attractive to insects |
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129 | (5) |
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Drosophile may be attracted to UV-reflecting silk due to their spontaneous open-space response |
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134 | (2) |
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Studies on web avoidance learning show that bees are able to dissociate color cues from the information with which it is paired |
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136 | (5) |
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Web decorations attract prey and their variable orientations may disrupt insect pattern learning |
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141 | (11) |
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Decorative silk patterns that attract prey are also likely to attract the predators of spiders |
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152 | (4) |
| 7 Inter-Gland Competition for Amino Acids and the ATP Costs of Silk Synthesis |
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156 | (17) |
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The amino acids organisms synthesize are those needed in large quantities and on a predictable basis |
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157 | (1) |
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The central metabolic pathways provide a common currency, ATP, through which the costs of protein synthesis can be compared |
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158 | (7) |
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The amino acid compositions of silks spun by arthropods vary in proportions of alanine, glycine, and serine |
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165 | (2) |
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Direct comparison of amino acid costs suggests that dragline (MA) silks produced by araneomorph spiders are more costly than cocoon (Fhc) silks produced by herbivores |
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167 | (1) |
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Comparison of MA silk produced by ancestral and derived species suggests a trend toward reduced silk costs among the cribellates and between the MA and Flag silks of the Araneoidea |
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168 | (1) |
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Spider silk glands may have evolved through intra-gland competition for amino acids that the spiders synthesize |
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169 | (2) |
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Gene organization that allows selective expression and/or selective editing of proteins may allow spiders to reduce silk costs during periods of food stress |
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171 | (1) |
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The ability to recycle silks allows the araneoids to reduce the metabolic costs of producing silk |
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172 | (1) |
| 8 A One-Dimensional Developmental System and Life-Long Silk Synthesis May Preclude the Evolution of Higher Eusociality in Spiders |
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173 | (20) |
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Multiple selective factors favor the evolution of eusociality |
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174 | (5) |
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Insects have three developmental pathways, but spiders have only one |
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179 | (2) |
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Ecdysteroids regulate metamorphosis in the absence of JH |
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181 | (2) |
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Ecdysteroids regulate silk synthesis in the Lepidoptera |
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183 | (2) |
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JH inhibits the action of ecdysone |
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185 | (3) |
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Ecdysone may regulate silk synthesis in some spider glands, but silk production in the MA gland seems to be neurally regulated |
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188 | (1) |
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Developmental flexibility may be a precondition for the evolution of caste systems |
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189 | (2) |
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191 | (2) |
| 9 Conclusions and Looking Forward |
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193 | |
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Natural selection, the repetitive organization of silk genes, and energy exchange are the major factors that direct the evolution of silk proteins and the spiders that produce them |
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194 | (2) |
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Evolutionary analyses of silk protein evolvability, the effects of predators on prey sensory systems, and cost selection are three promising avenues for future evolutionary research and specifically for evolutionary research on spiders |
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196 | (2) |
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The accessibility of silk systems allows us to link evolutionary effects from gene to organism |
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198 | (1) |
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199 | (24) |
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223 | |
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