{"id":13634,"date":"2020-03-18T18:03:39","date_gmt":"2020-03-18T18:03:39","guid":{"rendered":"https:\/\/www.lifescienceart.com\/?p=13634"},"modified":"2020-03-18T18:03:39","modified_gmt":"2020-03-18T18:03:39","slug":"sharks-10-fascinating-discoveries","status":"publish","type":"post","link":"https:\/\/www.lifescienceart.com\/cs\/science\/zoology\/sharks-10-fascinating-discoveries\/","title":{"rendered":"10 fascinuj\u00edc\u00edch objev\u016f o \u017eraloc\u00edch: Od nejd\u00e9le \u017eij\u00edc\u00edch obratlovc\u016f sv\u011bta a\u017e po tajn\u00e9 vojensk\u00e9 zbra\u0148ov\u00e9 projekty"},"content":{"rendered":"

\u017draloci: 10 fascinuj\u00edc\u00edch objev\u016f<\/h2>\n\n

Gr\u00f3nsk\u00fd \u017eralok: Nejd\u00e9le \u017eij\u00edc\u00ed obratlovec<\/h2>\n\n

Gr\u00f3nsk\u00fd \u017eralok, kter\u00fd se vyskytuje v chladn\u00fdch vod\u00e1ch pobl\u00ed\u017e Arktidy, m\u00e1 d\u00e9lku \u017eivota p\u0159es 400 let, co\u017e z n\u011bj d\u011bl\u00e1 nejd\u00e9le \u017eij\u00edc\u00edho obratlovce, jak\u00fd byl kdy objeven. Jeho pomal\u00fd metabolismus, \u201ejen o n\u011bco rychlej\u0161\u00ed ne\u017e u kamene\u201c, p\u0159isp\u00edv\u00e1 k jeho extr\u00e9mn\u00ed dlouhov\u011bkosti. Tento pomal\u00fd \u017eivotn\u00ed styl v\u0161ak tak\u00e9 znamen\u00e1, \u017ee se rozmno\u017euje velmi pomalu, co\u017e ho vystavuje riziku vyhynut\u00ed, pokud budou jeho populace vy\u010derp\u00e1ny.<\/p>\n\n

Stra\u0161ideln\u00ed \u017eraloci: Z\u00e1hadn\u00ed tvorov\u00e9 s v\u00fdsuvn\u00fdmi pohlavn\u00edmi org\u00e1ny<\/h2>\n\n

U stra\u0161ideln\u00fdch \u017eralok\u016f, pojmenovan\u00fdch podle jejich hlubinn\u00e9ho prost\u0159ed\u00ed a vz\u00e1cnosti, bylo ned\u00e1vno zji\u0161t\u011bno, \u017ee maj\u00ed v\u00fdsuvn\u00e9 pohlavn\u00ed org\u00e1ny na hlav\u011b. Tyto org\u00e1ny maj\u00ed h\u00e1\u010dky, kter\u00e9 samci stra\u0161ideln\u00fdch \u017eralok\u016f pou\u017e\u00edvaj\u00ed k uchopen\u00ed samic b\u011bhem p\u00e1\u0159en\u00ed, co\u017e je z\u00e1\u017eitek, kter\u00fd \u00fadajn\u011b nen\u00ed pro samice p\u0159\u00edli\u0161 p\u0159\u00edjemn\u00fd. Samice stra\u0161ideln\u00fdch \u017eralok\u016f mohou uchov\u00e1vat sperma po mnoho let ve speci\u00e1ln\u00edch \u00falo\u017en\u00fdch bank\u00e1ch ve sv\u00fdch t\u011blech a \u010dekat na spr\u00e1vn\u00fd \u010das k po\u010det\u00ed.<\/p>\n\n

Objevena \u0161kolka pro b\u00edl\u00e9 \u017eraloky u pob\u0159e\u017e\u00ed New Yorku<\/h2>\n\n

V srpnu 2017 objevila ochran\u00e1\u0159sk\u00e1 skupina Ocearch vz\u00e1cnou \u0161kolku b\u00edl\u00fdch \u017eralok\u016f v m\u011blk\u00e9 vod\u011b u pob\u0159e\u017e\u00ed New Yorku. Byla to prvn\u00ed takov\u00e1 \u0161kolka, kter\u00e1 byla nalezena v severn\u00edm Atlantick\u00e9m oce\u00e1nu, a v\u011bdci se domn\u00edvaj\u00ed, \u017ee \u017eraloci tam tr\u00e1v\u00ed prvn\u00edch 20 let sv\u00e9ho \u017eivota. O migra\u010dn\u00edch vzorc\u00edch mlad\u00fdch \u017eralok\u016f se v\u00ed jen m\u00e1lo, co\u017e d\u011bl\u00e1 tento objev v\u00fdznamn\u00fdm pr\u016flomem.<\/p>\n\n

\u00datesov\u00ed \u017eraloci: Nejsou to vrcholov\u00ed pred\u00e1to\u0159i, za kter\u00e9 jsme je pova\u017eovali<\/h2>\n\n

\u00datesov\u00ed \u017eraloci byli \u010dasto zobrazov\u00e1ni jako alfa pred\u00e1to\u0159i ve sv\u00fdch stanovi\u0161t\u00edch, podobn\u011b jako lvi v africk\u00e9 savan\u011b. V\u00fdzkum v\u0161ak tento m\u00fdtus zpochybnil. Studie uk\u00e1zaly, \u017ee v mnoha oblastech, kde byli \u017eraloci vyloveni, se popula\u010dn\u00ed hladiny b\u00fdlo\u017erav\u00fdch ryb v\u00fdrazn\u011b nezm\u011bnily, co\u017e nazna\u010duje, \u017ee vliv \u017eralok\u016f na jejich prost\u0159ed\u00ed je men\u0161\u00ed, ne\u017e se d\u0159\u00edve myslelo. Pouze n\u011bkolik z nejv\u011bt\u0161\u00edch druh\u016f \u017eralok\u016f, jako jsou \u017eraloci tyg\u0159\u00ed, skute\u010dn\u011b hraje roli vrcholov\u00e9ho pred\u00e1tora.<\/p>\n\n

Megalolamna paradoxodon: Ob\u0159\u00ed \u017eralok z minulosti<\/h2>\n\n

Megalolamna paradoxodon, nov\u011b popsan\u00fd druh ob\u0159\u00edho \u017eraloka, kter\u00fd \u017eil p\u0159ed 20 miliony let, dorostl do velikosti auta. V\u011bdci odhadli jeho d\u00e9lku na asi 12 stop, d\u00edky \u010demu\u017e je mnohem v\u011bt\u0161\u00ed ne\u017e v\u011bt\u0161ina lid\u00ed, ale men\u0161\u00ed ne\u017e nechvaln\u011b zn\u00e1m\u00fd b\u00edl\u00fd \u017eralok. Tento druh mohl b\u00fdt bl\u00edzk\u00fdm p\u0159\u00edbuzn\u00fdm dal\u0161\u00edch prav\u011bk\u00fdch \u017eralok\u016f, kte\u0159\u00ed dor\u016fstali do p\u011btin\u00e1sobku t\u00e9to velikosti.<\/p>\n\n

Z\u00e1chrana \u017eralok\u016f povzbuzov\u00e1n\u00edm rybolovu: Kontroverzn\u00ed \u0159e\u0161en\u00ed<\/h2>\n\n

Mnoho druh\u016f \u017eralok\u016f je ohro\u017eeno neleg\u00e1ln\u00edm rybolovem kv\u016fli jejich masu a ploutv\u00edm, ale tak\u00e9 vedlej\u0161\u00edm \u00falovkem v s\u00edt\u00edch zam\u011b\u0159en\u00fdch na jin\u00e9 ryby. V\u011bdci navrhli kontroverzn\u00ed \u0159e\u0161en\u00ed: podpo\u0159it leg\u00e1ln\u00ed rybolov \u017eralok\u016f. Studie zjistila, \u017ee v sou\u010dasn\u00e9 dob\u011b je udr\u017eiteln\u011b \u0159\u00edzeno pouze asi 4 % rybolovu \u017eralok\u016f. Politika rybolovu \u017eralok\u016f, kter\u00e1 zohled\u0148uje v\u011bk a reproduk\u010dn\u00ed cykly ur\u010dit\u00fdch \u017eralok\u016f, by mohla pomoci udr\u017eet populace \u017eralok\u016f zdrav\u00e9.<\/p>\n\n

B\u00edl\u00ed \u017eraloci z Kalifornie: Z\u00e1hadn\u00e1 pou\u0165<\/h2>\n\n

Ka\u017ed\u00fd rok se b\u00edl\u00ed \u017eraloci z Kalifornie vyd\u00e1vaj\u00ed na z\u00e1hadnou pou\u0165 do odlehl\u00e9 \u010d\u00e1sti oce\u00e1nu. V\u011bdci se sna\u017e\u00ed odhalit d\u016fvod tohoto chov\u00e1n\u00ed. Biolog Salvador Jorgensen vyvinul odoln\u00e9 kamery, kter\u00e9 lze p\u0159ipevnit na ploutve \u017eralok\u016f, aby zaznamen\u00e1valy jejich pohyby a vrhly sv\u011btlo na tento z\u00e1hadn\u00fd jev.<\/p>\n\n

Dvouhlav\u00ed \u017eraloci: Zn\u00e1mka environment\u00e1ln\u00edch probl\u00e9m\u016f?<\/h2>\n\n

Ryb\u00e1\u0159i a v\u011bdci se v posledn\u00edch letech setk\u00e1vaj\u00ed s \u010d\u00edm d\u00e1l v\u00edce dvouhlav\u00fdmi \u017eraloky. P\u0159\u00ed\u010dina tohoto n\u00e1r\u016fstu mutac\u00ed st\u00e1le nen\u00ed jasn\u00e1, ale n\u011bkte\u0159\u00ed biologov\u00e9 se domn\u00edvaj\u00ed, \u017ee m\u016f\u017ee souviset s infekcemi, zne\u010di\u0161t\u011bn\u00edm nebo poklesem populace kv\u016fli nadm\u011brn\u00e9mu rybolovu \u017eralok\u016f.<\/p>\n\n

Tajn\u00fd projekt americk\u00e9ho n\u00e1mo\u0159nictva na vyu\u017eit\u00ed \u017eralok\u016f jako zbran\u00ed<\/h2>\n\n

B\u011bhem studen\u00e9 v\u00e1lky americk\u00e9 n\u00e1mo\u0159nictvo provedlo p\u0159\u00edsn\u011b tajn\u00fd projekt s c\u00edlem vyvinout \u017eraloky jako zbran\u011b. Pl\u00e1n spo\u010d\u00edval v tom, \u017ee elektrick\u00e9 \u0161oky navedou \u017eraloky nesouc\u00ed bomby k jejich c\u00edl\u016fm a odp\u00e1lily je. Projekt, kter\u00fd prob\u00edhal od roku 1958 do roku 1971, nakonec nebyl \u00fasp\u011b\u0161n\u00fd.<\/p>\n\n

Citr\u00f3nov\u00ed \u017eraloci: Neochv\u011bjn\u00ed tvorov\u00e9<\/h2>\n\n

Citr\u00f3nov\u00ed \u017eraloci jsou zn\u00e1m\u00ed svou odolnost\u00ed. Ned\u00e1vn\u00e1 studie zdokumentovala citr\u00f3nov\u00e9ho \u017eraloka, kter\u00fd spolkl kus ryb\u00e1\u0159sk\u00e9ho vybaven\u00ed z oceli, kter\u00fd mu prop\u00edchl \u017ealudek. \u017dralok nejen p\u0159e\u017eil zran\u011bn\u00ed, ale tak\u00e9 se mu poda\u0159ilo vylou\u010dit kovov\u00fd p\u0159edm\u011bt k\u016f\u017e\u00ed ven. Jin\u00e1 studie zjistila, \u017ee tyg\u0159\u00ed \u017eraloci zkonzumovali \u0161irokou \u0161k\u00e1lu podivn\u00fdch p\u0159edm\u011bt\u016f, v\u010detn\u011b pt\u00e1k\u016f, netop\u00fdr\u016f, dikobraz\u016f, s\u00e1\u010dk\u016f s chipsy a dokonce i kondom\u016f.<\/p>","protected":false},"excerpt":{"rendered":"

\u017draloci: 10 fascinuj\u00edc\u00edch objev\u016f Gr\u00f3nsk\u00fd \u017eralok: Nejd\u00e9le \u017eij\u00edc\u00ed obratlovec Gr\u00f3nsk\u00fd \u017eralok, kter\u00fd se vyskytuje v chladn\u00fdch vod\u00e1ch pobl\u00ed\u017e Arktidy, m\u00e1 d\u00e9lku \u017eivota p\u0159es 400 let, co\u017e z n\u011bj d\u011bl\u00e1 nejd\u00e9le…<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[280],"tags":[254,265,1302,401,73],"class_list":["post-13634","post","type-post","status-publish","format-standard","hentry","category-zoology","tag-wildlife","tag-marine-life","tag-oceanography","tag-conservation","tag-sharks"],"_links":{"self":[{"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/posts\/13634","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/comments?post=13634"}],"version-history":[{"count":1,"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/posts\/13634\/revisions"}],"predecessor-version":[{"id":13635,"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/posts\/13634\/revisions\/13635"}],"wp:attachment":[{"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/media?parent=13634"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/categories?post=13634"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifescienceart.com\/cs\/wp-json\/wp\/v2\/tags?post=13634"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}