![\"\"](\"https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-675x506.jpg\" "\\"\\"")
<\/figure>\n\n\n\nThose longest legs, the second pair from the front, are covered in hair-like growths that work as sensory organs. They\u2019re also divided, like fingers with many knuckles, into articulable sections called tarsomeres. In the case of the species Phalangium opilio, the focus of a study Gainett and UW\u2013Madison professor of integrative biology Prashant Sharma published this week in the journal Proceedings of the Royal Society B, their longest legs have 80 tarsomeres.<\/p>\n\n\n\n
\u201cOther arthropods have tarsomeres,\u201d says Sharma, \u201cbut only harvestmen use them in such a broad range of behaviors \u2014 sensing, climbing, fighting, courtship.\u201d<\/p>\n\n\n\n
To find the genes that give harvestmen such unique legs, the researchers used a technique called RNA interference to \u201cknock down\u201d \u2014 turn off or reduce the expression of \u2014 several genes, called Hox genes, known to be involved in organizing body structure in developing embryos in all sorts of animals.<\/p>\n\n\n\n
\u201cWhat we have been able to show is that two Hox genes acting in combination are sufficient to specify the identity of the first three pairs of legs,\u201d Gainett says. \u201cThey tell them, \u2018You\u2019re going to be a walking leg,\u2019 and, \u2018You’re not going to be a pedipalp,\u2019 which is the small food-manipulating appendage.\u201d<\/p>\n\n\n\n
When they knocked down Hox genes known as \u201cDeformed\u201d and \u201cSex combs reduced\u201d in Phalangium eggs, they ended up with embryonic harvestmen whose first three pairs of legs were transformed into short appendages more like pedipalps.<\/p>\n\n\n\n
Disrupting another set of genes, which have been associated with the development of leg sections in fruit flies and other insects, took away the daddy longlegs\u2019 exceptional tarsomeres.<\/p>\n\n\n\n
\u201cThis is the first data outside of insects that points to how it is that these structures are made,\u201d Sharma says. \u201cAnd we see that evolution is not really coming up with new solutions here. It\u2019s recycling the same genetic platform to make these organs even as they evolve independently in different species.\u201d<\/p>\n\n\n\n
They are genetic platforms that appear to come in handy for even more differentiation \u2014 and may have helped Phalangium opilio spread upward, in a very local sense, and outward in more global terms.<\/p>\n\n\n\n
While the UW\u2013Madison researchers collected their study specimens from the stone walls of their own campus building in Wisconsin, Phalangium is probably the most widespread of all harvestmen species. It has expanded from a native range in Eurasia to North America, Africa and New Zealand.<\/p>\n\n\n\n
\u201cThere’s a very tight correlation to having a large number of tarsomeres and being able to climb, and climbing groups also tend to be much more diverse,\u201d says Sharma, whose work is supported by the National Science Foundation. \u201cThe most diverse family of harvestmen by far happens to be the one that has the most tarsomeres. So, it\u2019s providing some sort of ecological advantage.\u201d<\/p>\n\n\n\n
The researchers hope to use the results of the study, which included collaborators at the Smithsonian Institution\u2019s Global Genome Initiative and Eastern Connecticut State University, to examine genes involved in the number and locations of eye structures in spiders and their relatives.<\/p>\n","protected":false},"excerpt":{"rendered":"
The first genome of a daddy longlegs, sequenced by University of Wisconsin\u2013Madison researchers, is giving up clues to the evolution of the gangly appendages that give members of the order Opiliones their common name.<\/p>\n","protected":false},"author":2,"featured_media":21130,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-21129","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",775,581,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-200x200.jpg",200,200,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-534x400.jpg",534,400,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-768x576.jpg",750,563,true],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-675x506.jpg",675,506,true],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",775,581,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",775,581,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",775,581,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",760,570,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",600,450,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",600,450,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-760x490.jpg",760,490,true],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-550x360.jpg",550,360,true],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs-95x65.jpg",95,65,true],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",640,480,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",96,72,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2021\/08\/daddylonglegs.jpg",150,112,false]},"author_info":{"info":["RevoScience"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/21129","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=21129"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/21129\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/21130"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=21129"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=21129"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=21129"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}