Focus-Science and Technology - - DISCOVERIES -

New hope for the sur­vival of the north­ern white rhino has emerged with the cre­ation of the first in vitro, hy­brid rhino em­bryos.

With only two fe­males left alive, the north­ern white rhino is clas­si­fied as be­ing func­tion­ally ex­tinct. But an in­ter­na­tional team of sci­en­tists has com­bined cry­op­re­served se­men from north­ern white rhino males with egg cells har­vested from south­ern white rhi­nos to pro­duce a vi­able em­bryo.

“These are the first in vitro pro­duced rhi­noc­eros em­bryos ever. They have a very high chance of es­tab­lish­ing a preg­nancy once im­planted into a sur­ro­gate mother,” said Prof Thomas Hilde­brandt of the Leib­niz In­sti­tute for Zoo and Wildlife Re­search in Ber­lin.

The team adapted a tech­nique used for as­sisted cat­tle and horse re­pro­duc­tion to har­vest oocytes (im­ma­ture egg cells) from cap­tive south­ern white rhino fe­males. Harvesting oocytes from rhi­nos is tricky be­cause their ovaries can’t be reached by hand and lie next to a ma­jor artery that could cause a fa­tal bleed if punc­tured. To get around this the team de­vel­oped a two-me­tre­long, ul­tra­sound guided de­vice to safely ex­tract the oocytes.

The ex­tracted oocytes were then com­bined with north­ern white rhino sperm and cul­tured un­til a blas­to­cyst, an early form of an em­bryo, de­vel­oped.

“Our re­sults are solid, re­pro­ducible and very promis­ing. Now we’re well pre­pared to go to Kenya and col­lect oocytes from the last two north­ern white rhino fe­males to pro­duce pure north­ern white rhino blas­to­cysts,” said Hilde­brandt.

But hav­ing only four males’ frozen sperm and two liv­ing fe­males means sub­se­quent gen­er­a­tions of north­ern white rhi­nos won’t have the ge­netic di­ver­sity nec­es­sary to prop­a­gate the species. So the sci­en­tists are plan­ning to use stem cell tech­nol­ogy and north­ern white rhino tis­sue to cre­ate new re­pro­duc­tive cells that can be trans­planted into the rhi­nos’ sperm and eggs.

Fatu ( pic­tured) and her mother Na­jin are the only north­ern white rhi­nos left

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