{"id":25091,"date":"2014-06-01T16:14:04","date_gmt":"2014-06-01T13:14:04","guid":{"rendered":"https:\/\/bilimvegelecek.com.tr\/?p=25091"},"modified":"2018-05-10T16:25:39","modified_gmt":"2018-05-10T13:25:39","slug":"fosillerden-dev-sperm-cikti","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2014\/06\/01\/fosillerden-dev-sperm-cikti","title":{"rendered":"Fosillerden dev sperm \u00e7\u0131kt\u0131"},"content":{"rendered":"

Bir grup antik kabuklu, g\u00fcn\u00fcm\u00fcze dek ke\u015ffedilmi\u015f en eski sperm fosillerinin bulunmas\u0131na \u00f6nayak oldu. En az 16 milyon ya\u015f\u0131ndaki bu \u00f6rnekler, ayn\u0131 zamanda \u015fimdiye dek bulunanlar\u0131n en b\u00fcy\u00fcklerinden biri. Ayr\u0131ca fosille\u015fmi\u015f sperm h\u00fccreleri, canl\u0131n\u0131n al\u0131\u015f\u0131lmam\u0131\u015f b\u00fcy\u00fckl\u00fckteki gametlerinin baz\u0131 yap\u0131lar\u0131n\u0131 ortaya koyacak yeterlilikte korunmu\u015f halde. Bu sayede yap\u0131lar ara\u015ft\u0131rmac\u0131lar taraf\u0131ndan X-\u0131\u015f\u0131n\u0131 verileriyle \u00fc\u00e7 boyutlu olarak yeniden olu\u015fturulabildi.<\/p>\n

Ostrakodlar kabuklular\u0131n g\u00fcn\u00fcm\u00fczde de var olan bir s\u0131n\u0131f\u0131. Karidese benzeyen bu hayvanlar, tipik olarak 1 mm uzunlu\u011fundad\u0131r, fakat spermlerinin uzunlu\u011fu kendileriyle orant\u0131s\u0131z bir bi\u00e7imde 1 cm\u2019ye kadar \u00e7\u0131kar. M\u00fcnih\u2019teki Ludwig Maximilian \u00dcniversitesi\u2019nde \u00e7al\u0131\u015fmalar\u0131n\u0131 y\u00fcr\u00fcten ve kendini ostrakodolog olarak tan\u0131mlayan Renate Matzke-Karasz, Avustralya\u2019da bir ma\u011farada bulunan tatl\u0131 su ostrakodlar\u0131n\u0131n i\u00e7indeki dokular\u0131 g\u00f6zler \u00f6n\u00fcne sermek i\u00e7in sinkrotron X-\u0131\u015f\u0131n\u0131 kulland\u0131.<\/p>\n

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Ara\u015ft\u0131rmac\u0131lar X-\u0131\u015f\u0131n\u0131 yard\u0131m\u0131yla g\u00f6r\u00fcnt\u00fcledi\u011fi, fosille\u015fmi\u015f sperm h\u00fccrelerinin uzunluklar\u0131n\u0131 1,2 mm -insan sperm h\u00fccresinin yakla\u015f\u0131k 20 kat\u0131- olarak tahmin etti. (G\u00f6rsel: Renate Matzke-Karasz)<\/figcaption><\/figure>\n

Fosille\u015fmi\u015f sperm h\u00fccrelerinden bir\u00e7o\u011fu birbirine dola\u015f\u0131k bir haldeydi ve bu nedenle uzunluklar\u0131n\u0131n tam olarak tespit edilmesi zordu. Fakat ara\u015ft\u0131rmac\u0131lar uzunluklar\u0131n\u0131 1,2 mm -insan sperm h\u00fccresinin yakla\u015f\u0131k 20 kat\u0131- olarak tahmin ettiler. Ara\u015ft\u0131rman\u0131n sonu\u00e7lar\u0131 Proceeding of the Royal Society B1<\/em> dergisinde yay\u0131mland\u0131.<\/p>\n

Normalde etin kayala\u015fmas\u0131 s\u00fcreci yumu\u015fak dokuyu yok eder, ama bu ostrakodlar\u0131n i\u00e7 k\u0131sm\u0131 m\u00fckemmel bir bi\u00e7imde korunmu\u015f. Ara\u015ft\u0131rmac\u0131lar, fosillerin \u00e7oklu X-\u0131\u015f\u0131n\u0131 g\u00f6r\u00fcnt\u00fclerini al\u0131p, bunlar\u0131 \u00fc\u00e7 boyutlu bir g\u00f6rsel olu\u015fturacak bi\u00e7imde birle\u015ftirirken, yaln\u0131zca sperm \u00e7ekirdeklerini de\u011fil, antik hayvanlar\u0131n yeniden \u00fcretim sistemlerini ve kaslar\u0131n\u0131 da g\u00f6r\u00fcnt\u00fcledi.<\/p>\n

\u0130\u00e7erideki spermleri bulduklar\u0131nda olduk\u00e7a heyecanland\u0131klar\u0131n\u0131 belirten Matzke-Karasz, ara\u015ft\u0131rma sonu\u00e7lar\u0131n\u0131n, X-\u0131\u015f\u0131n\u0131 ile g\u00f6r\u00fcnt\u00fcleme teknolojisinin paleontoloji biliminde daha yayg\u0131n kullan\u0131labilece\u011fini g\u00f6sterdi\u011fini s\u00f6yl\u00fcyor.<\/p>\n

Ara\u015ft\u0131rmac\u0131lar \u00f6nceden, Romanya\u2019da bulunan fosiller sayesinde ostrakod spermini tan\u0131mlam\u0131\u015flard\u0131. Fakat bunlar 15 biny\u0131ldan daha az\u0131na tarihleniyordu. Matzke-Karasz\u2019\u0131n makalesinde tan\u0131mlanan fosillerin ya\u015flar\u0131n\u0131n ise 16 milyon ila 23 milyon aras\u0131nda de\u011fi\u015fti\u011fi tahmin ediliyor. Matzke-Karasz\u2019a g\u00f6re bu, dev spermlerin az\u0131msanmayacak bir zaman aral\u0131\u011f\u0131nda varl\u0131k g\u00f6sterdi\u011finin bir kan\u0131t\u0131.<\/p>\n

Boyutlar\u0131n\u0131n b\u00fcy\u00fckl\u00fc\u011f\u00fcne ra\u011fmen ostrakodlar en b\u00fcy\u00fck sperm h\u00fccresi rekorunun sahibi de\u011fil. Bu nitelik, sperm uzunlu\u011fu birka\u00e7 santimetreyi bulan baz\u0131 meyve sine\u011fi t\u00fcrlerine ait. Ostrakodlar\u0131n neden bu kadar uzun gametlere sahip olduklar\u0131n\u0131n belirsiz oldu\u011funu belirten Matzke-Karasz, \u015fimdi canl\u0131 ostrakodlarla \u00e7al\u0131\u015farak, onlar\u0131n yeniden \u00fcretimine ili\u015fkin daha iyi bir kavray\u0131\u015f geli\u015ftirmeyi hedefliyor.<\/p>\n

New York\u2019taki Syracuse \u00dcniversitesi\u2019nde reprodaktif biyoloji alan\u0131nda \u00e7al\u0131\u015fan Scott Pitnick, spermlerin olduk\u00e7a \u00e7abuk evrimle\u015fti\u011fi i\u00e7in evrimsel biyologlar\u0131n ilgisini \u00e7ekti\u011fini s\u00f6yl\u00fcyor. Fakat biliminsanlar\u0131 her ne kadar g\u00fcn\u00fcm\u00fczde var olan binlerce t\u00fcr\u00fcn spermini inceleyebilse de, ge\u00e7mi\u015fte ne oldu\u011funa ili\u015fkin s\u0131kl\u0131kla sadece tahmin y\u00fcr\u00fctebiliyorlar. Son makalesinde \u201cG\u00f6rmek, \u00a0inanmakt\u0131r\u201d yazan Pitnick, \u201cEvrimsel biyologlar i\u00e7in g\u00f6zlerinin \u00f6n\u00fcne serilmi\u015f iyi bir fosil gibisi yoktur\u201d diye ekliyor.<\/p>\n","protected":false},"excerpt":{"rendered":"

Bir grup antik kabuklu, g\u00fcn\u00fcm\u00fcze dek ke\u015ffedilmi\u015f en eski sperm fosillerinin bulunmas\u0131na \u00f6nayak oldu. En az 16 milyon ya\u015f\u0131ndaki bu \u00f6rnekler, ayn\u0131 zamanda \u015fimdiye dek bulunanlar\u0131n en b\u00fcy\u00fcklerinden biri. Ayr\u0131ca fosille\u015fmi\u015f sperm h\u00fccreleri, canl\u0131n\u0131n al\u0131\u015f\u0131lmam\u0131\u015f b\u00fcy\u00fckl\u00fckteki gametlerinin baz\u0131 yap\u0131lar\u0131n\u0131 ortaya koyacak yeterlilikte korunmu\u015f halde. Bu sayede yap\u0131lar ara\u015ft\u0131rmac\u0131lar taraf\u0131ndan X-\u0131\u015f\u0131n\u0131 verileriyle \u00fc\u00e7 boyutlu olarak yeniden […]<\/p>\n","protected":false},"author":448,"featured_media":25097,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[161,19],"tags":[816,3189,3188,2765],"class_list":["post-25091","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-124-sayi","category-bilim-gundemi","tag-fosil","tag-ostrakod","tag-sperm","tag-x-isini"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t