{"id":9329,"date":"2009-12-01T01:15:48","date_gmt":"2009-11-30T23:15:48","guid":{"rendered":"http:\/\/109.232.216.219\/~bilimvegelecek\/?p=9329"},"modified":"2017-07-18T10:41:55","modified_gmt":"2017-07-18T07:41:55","slug":"bilinen-en-sogukkanli-memeli-nesli-tukenmis-bir-keci-myotragus-balearicus","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2009\/12\/01\/bilinen-en-sogukkanli-memeli-nesli-tukenmis-bir-keci-myotragus-balearicus","title":{"rendered":"Bilinen en so\u011fukkanl\u0131 memeli, nesli t\u00fckenmi\u015f bir ke\u00e7i: Myotragus balearicus"},"content":{"rendered":"
\"\"
Myotragus balearicus\u2019un iskeleti, 02.03.2006, Francisco Valverde<\/figcaption><\/figure>\n

Co\u011frafik olarak adalar, Darwin\u2019in yakla\u015f\u0131k bir bu\u00e7uk as\u0131r \u00f6nce ke\u015ffetti\u011fi gibi, asl\u0131nda k\u0131talarla k\u0131yasl\u0131\u011f\u0131nda evrimin en iyi g\u00f6zlemlenebildi\u011fi laboratuvarlard\u0131r. Co\u011frafik izolasyon, s\u0131n\u0131rl\u0131 yiyecek kayna\u011f\u0131 ve avc\u0131 say\u0131s\u0131 gibi temel nedenlerden \u00f6t\u00fcr\u00fc, adalarda, k\u0131talarda g\u00f6rd\u00fc\u011f\u00fcm\u00fcz hayvanlardan farkl\u0131, \u00f6rne\u011fin Yeni Zelanda\u2019da Dev Moa Ku\u015fu, California Channel Adalar\u0131\u2019nda C\u00fcce T\u00fcyl\u00fc Mamut gibi garip hayvanlar ortaya \u00e7\u0131km\u0131\u015ft\u0131r (1).<\/p>\n

\u00d6zerk Barcelona \u00dcniversitesi Katalan Paleontoloji Enstit\u00fcs\u00fc\u2019nden Meike K\u00f6hler ve Salvador Moy\u00e0-Sol\u00e0\u2019n\u0131n yapt\u0131\u011f\u0131 ve \u201cAmerikan Bilimler Akademisindeki Geli\u015fmeler\u201d adl\u0131 derginin hen\u00fcz sadece online versiyonunda (pnas.org) yay\u0131nlanan makaleye g\u00f6re Myotragus balearicus<\/em> s\u0131cakkanl\u0131 bir memeliden \u00e7ok (ki bir t\u00fcr hari\u00e7 g\u00fcn\u00fcm\u00fczdeki t\u00fcm memeliler s\u0131cak kanl\u0131d\u0131r (6)), so\u011fukkanl\u0131 bir s\u00fcr\u00fcngenin metabolizmas\u0131na evrilmi\u015ftir. \u00a0(2). Myotragus balearicus<\/em> bu yeni bulu\u015ftan \u00f6nce de hayli ilgin\u00e7 bir canl\u0131yd\u0131. \u00d6rne\u011fin, \u00f6nceki \u00e7al\u0131\u015fmalar Myotragus balearicus<\/em>\u2019un g\u00fcn\u00fcm\u00fczdeki ke\u00e7ilerden daha k\u00fc\u00e7\u00fck oldu\u011funu (yakla\u015f\u0131k 45 cm), yavrular\u0131n\u0131n b\u00fcy\u00fck bir \u015f\u0131\u00e7an kadar oldu\u011funu, g\u00fcn\u00fcm\u00fcz ke\u00e7ileri kadar atletik olmad\u0131\u011f\u0131n\u0131, hatta iskeletinin z\u0131plamaya uygun olmad\u0131\u011f\u0131n\u0131, 5,2 milyon y\u0131l varl\u0131\u011f\u0131n\u0131 s\u00fcrd\u00fcrd\u00fc\u011f\u00fcn\u00fc ve yakla\u015f\u0131k g\u00fcn\u00fcm\u00fczden 3000 y\u0131l \u00f6nce neslinin t\u00fckendi\u011fini g\u00f6stermekteydi (4).<\/p>\n

Myotragus balearicus<\/em>\u2019un fosili \u0130spanya\u2019n\u0131n Majorca adas\u0131nda \u00fcnl\u00fc \u0130ngiliz arkeozoolog Dorothea Bate taraf\u0131ndan 1909 y\u0131l\u0131nda bulunmu\u015ftu (5). Yiyecek kaynaklar\u0131n\u0131n k\u0131s\u0131tl\u0131 oldu\u011fu ve bulundu\u011fu yerden ayr\u0131lmas\u0131n\u0131n m\u00fcmk\u00fcn olmad\u0131\u011f\u0131 Majorca adas\u0131nda Myotragus balearicus<\/em>\u2019un milyonlarca y\u0131l nas\u0131l hayatta kald\u0131\u011f\u0131 bilim insanlar\u0131n\u0131n merak etti\u011fi konular aras\u0131ndayd\u0131. Meike K\u00f6hler ve Salvador Moy\u00e0-Sol\u00e0\u2019n\u0131n yapt\u0131\u011f\u0131 ara\u015ft\u0131rman\u0131n bulgular\u0131, Myotragus balearicus<\/em>\u2019un adada a\u00e7l\u0131k ve so\u011fuk durumlar\u0131nda milyonlarca y\u0131l nas\u0131l hayatta kalm\u0131\u015f olabilece\u011fine dair bug\u00fcne kadar memeliler aleminde e\u015fine hi\u00e7 rastlanmayan kan\u0131tlar ortaya koydu (4).<\/p>\n

Do\u011frudan olmasa da bulunan kan\u0131tlar, Myotragus balearicus<\/em>\u2019un bir memeli olmas\u0131na ra\u011fmen g\u00fcn\u00fcm\u00fcz memelilerinin aksine metabolizmas\u0131n\u0131 so\u011fukkanl\u0131 hayvanlar (\u00f6rne\u011fin s\u00fcr\u00fcngenler) gibi yava\u015flatarak, y\u0131ll\u0131n belli zamanlar\u0131nda b\u00fcy\u00fcmesini durdu\u011funu g\u00f6stermektedir (2). Oysa ki, tekrar hat\u0131rlatal\u0131m, g\u00fcn\u00fcm\u00fczdeki memeliler bilinen bir t\u00fcr hari\u00e7 hepsi s\u0131cakkanl\u0131 hayvanlard\u0131r. V\u00fccut s\u0131cakl\u0131klar\u0131n\u0131 neredeyse sabit tutarlar. Ortam so\u011fudu\u011funda metabolizmalar\u0131 h\u0131zlan\u0131r. S\u0131cakl\u0131klar\u0131n\u0131 ortam s\u0131cakl\u0131\u011f\u0131n\u0131n \u00fczerinde tutmak i\u00e7in s\u00fcrekli besine yani enerjiye ihtiya\u00e7 duyarlar. Bunun bedeli olarak da s\u00fcrekli besin bulmak zorundad\u0131rlar. Dolay\u0131s\u0131yla h\u00fccreleri s\u00fcrekli b\u00f6l\u00fcn\u00fcr. \u00d6rne\u011fin s\u00fcr\u00fcngenler gibi so\u011fukkanl\u0131 olan hayvanlar ise, ortam so\u011fudu\u011funda memelilerin aksine metabolizmalar\u0131n\u0131 yava\u015flat\u0131rlar ve h\u00fccre b\u00f6l\u00fcnmesi durur. Ortam \u0131s\u0131nd\u0131\u011f\u0131nda metobolizma h\u0131zlan\u0131r ve h\u00fccreler tekrar b\u00f6l\u00fcnmeye ba\u015flar. Bu strateji besinin s\u0131n\u0131rl\u0131 oldu\u011fu b\u00f6lgelerde onlar\u0131n hayatta kalmas\u0131n\u0131 sa\u011flar (6). Daha da ilginci s\u00fcr\u00fcngenlerin kemiklerinde t\u0131pk\u0131 a\u011fa\u00e7lar\u0131n g\u00f6vdelerinde bulunan halkasal yap\u0131lar gibi mevsimlere ba\u011fl\u0131 d\u00f6ng\u00fcsel b\u00fcy\u00fcmenin izleri bulunmaktad\u0131r (LAG denen yap\u0131lar) (2, 4).<\/p>\n

Meike K\u00f6hler ve Salvador Moy\u00e0-Sol\u00e0\u2019n\u0131n bulgular\u0131 Myotragus balearicus<\/em>\u2019un metabolizmas\u0131n\u0131 bu strateji ile y\u00f6netti\u011fini desteklemektedir. Bulgular ise k\u0131saca \u015f\u00f6yledir: Ara\u015ft\u0131rmac\u0131lar Myotragus balearicus<\/em>\u2019un fosil \u00f6rneklerini, yani kemik kesitlerini yine ayn\u0131 zamanda ayn\u0131 b\u00f6lgede ya\u015fayan s\u00fcr\u00fcngen fosilleri ile mikroskop alt\u0131nda k\u0131yaslad\u0131r. Bir \u00f6nceki paragrafta s\u00f6z edildi\u011fi gibi bug\u00fcne kadar sadece s\u00fcr\u00fcngenlerin kemiklerinde g\u00f6zlemlenen y\u0131ll\u0131k halkasal yap\u0131lar\u0131 Myotragus balearicus<\/em>\u2019un kemiklerinde de g\u00f6zlemlediler. Bu halkasal yap\u0131lar ise tamamen, so\u011fuk mevsimlerde metabolizman\u0131n yava\u015flamas\u0131, kemikteki h\u00fccrelerin b\u00f6l\u00fcnmesini durdurmas\u0131 ve takiben \u0131s\u0131nan havalar nedeniyle olaylar\u0131n tersine d\u00f6nmesi ile h\u00fccre b\u00f6l\u00fcnmesinin ba\u015flamas\u0131 sonucu olu\u015fan kesikli b\u00fcy\u00fcmenin izidir. Oysa memelilerin kemiklerinde b\u00f6yle bir halkasal yap\u0131ya rastlanmaz, \u00e7\u00fcnk\u00fc s\u00fcrekli h\u00fccreleri yenilenir yani b\u00f6l\u00fcn\u00fcr. Kemik dokular\u0131nda kesintisiz bir yap\u0131 g\u00f6zlemlenir. K\u0131saca Myotragus balearicus<\/em>\u2019un kemiklerindeki halkasal yap\u0131lar metabolizmas\u0131n\u0131n so\u011fukkanl\u0131 hayvanlara benzedi\u011fi konusunda ipu\u00e7lar\u0131 vermekte. Sonu\u00e7 olarak Myotragus balearicus<\/em>\u2019un k\u0131s\u0131tl\u0131 kaynaklarla birlikte so\u011fuk ge\u00e7en devirleri de i\u00e7eren 5,2 milyon y\u0131l\u0131 nas\u0131l ge\u00e7irdi\u011fi hakk\u0131nda bilim insanlar\u0131n\u0131n elinde art\u0131k \u00e7ok daha sa\u011flam kan\u0131tlar bulunmakta (2, 4).<\/p>\n

\"\"
Myotragus balearicus\u2019un \u0130spanya\u2019n\u0131n Barcelona \u015fehrindeki Cosmo Caixa m\u00fczesindeki maketi. 20.12.2007, Xavier V\u00e1zquez<\/figcaption><\/figure>\n

Ne yaz\u0131k ki, evrimsel olarak \u00e7ok yak\u0131n bir zamana kadar neslini s\u00fcrd\u00fcrmekte olan bu t\u00fcr\u00fcn ada ya\u015fam\u0131nda kazand\u0131\u011f\u0131 adaptasyonlar (uzun \u00f6m\u00fcr dolay\u0131s\u0131yla yava\u015f \u00fcreme aral\u0131klar\u0131, k\u00fc\u00e7\u00fck boyut, atletik olmayan yap\u0131), avc\u0131lar\u0131n olmad\u0131\u011f\u0131 ada ya\u015fam\u0131 i\u00e7in son derece geli\u015fmi\u015f \u00f6zellikler olmas\u0131na ra\u011fmen, b\u00f6lgeye avc\u0131lar\u0131n gelmesiyle bir dezavantaja d\u00f6n\u00fc\u015ft\u00fc. Myotragus balearicus<\/em>\u2019un 3000 y\u0131l \u00f6nce adaya gelen Homo sapiens<\/em> kar\u015f\u0131s\u0131nda hi\u00e7bir \u015fans\u0131 yoktu (2).<\/p>\n

 <\/p>\n

KAYNAKLAR<\/strong><\/p>\n

1)”Cold-blooded” goat grew like a reptile, http:\/\/www.examiner.com\/x-29167-SF-Science-News-Examiner~y2009m11d18-Coldblooded-goat-grew-like-a-reptile, 18\/11\/2009, 20:12<\/p>\n

2)K\u00f6hler, M. ve Moy\u00e0-Sol\u00e0, S., Physiological and life history strategies of a fossil large mammal in a resource-limited environment, www.pnas.org\/cgi\/doi\/10.1073\/pnas.0813385106, 18\/11\/2009, 20:21<\/p>\n

3) Dwarf Goat More Reptile Than Mammal, http:\/\/news.discovery.com\/animals\/dwarf-goat-reptiles-mammals.html, 18\/11\/2009, 20:30<\/p>\n

4) Extinct goat was cold-blooded, http:\/\/www.physorg.com\/news177755291.html, 18\/11\/2009, 20:38<\/p>\n

5) Myotragus, http:\/\/en.wikipedia.org\/wiki\/Myotragus_balearicus, 18\/11\/2009, 20:45<\/p>\n

6) Buffenstein, R. et al.<\/em>, Cold-induced changes in thyroid function in a poikilothermic mammal, the naked mole-rat, Am J Physiol Regulatory Integrative Comp Physiol, 2001, 280, 149-155.<\/p>\n","protected":false},"excerpt":{"rendered":"

Co\u011frafik olarak adalar, Darwin\u2019in yakla\u015f\u0131k bir bu\u00e7uk as\u0131r \u00f6nce ke\u015ffetti\u011fi gibi, asl\u0131nda k\u0131talarla k\u0131yasl\u0131\u011f\u0131nda evrimin en iyi g\u00f6zlemlenebildi\u011fi laboratuvarlard\u0131r. Co\u011frafik izolasyon, s\u0131n\u0131rl\u0131 yiyecek kayna\u011f\u0131 ve avc\u0131 say\u0131s\u0131 gibi temel nedenlerden \u00f6t\u00fcr\u00fc, adalarda, k\u0131talarda g\u00f6rd\u00fc\u011f\u00fcm\u00fcz hayvanlardan farkl\u0131, \u00f6rne\u011fin Yeni Zelanda\u2019da Dev Moa Ku\u015fu, California Channel Adalar\u0131\u2019nda C\u00fcce T\u00fcyl\u00fc Mamut gibi garip hayvanlar ortaya \u00e7\u0131km\u0131\u015ft\u0131r (1). \u00d6zerk […]<\/p>\n","protected":false},"author":778,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[107,19],"tags":[],"class_list":["post-9329","post","type-post","status-publish","format-standard","hentry","category-70-sayi","category-bilim-gundemi"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts\/9329","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/users\/778"}],"replies":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/comments?post=9329"}],"version-history":[{"count":0,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts\/9329\/revisions"}],"wp:attachment":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/media?parent=9329"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/categories?post=9329"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/tags?post=9329"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}