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Agence France-Presse

<div><span class="fr-img-caption fr-fic fr-dib" style="width:900px"><span class="fr-img-wrap"><img src="https://od2-image-api.abs-cbn.com/prod/editorImage/1722479761448marijan-sivric-lkASuxWN1s8-unsplash.jpg" style="width:900px" class="fr-fic fr-dib"/><span class="fr-inner" style="text-align:left"><span id="isPasted" style="white-space:pre-wrap">Marijan Sivric, Unsplash</span></span></span></span></div><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Italian researchers have noted the first case of &quot;virgin birth&quot;, or reproduction without fertilisation, in an endangered shark species, a scientific journal reported this week.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">The findings published in Scientific Reports concern the first case of the phenomenon in the common smooth-hound shark, Mustelus mustelus, a species threatened by illegal fishing that inhabits the Mediterranean and other warm waters.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Researchers from the Experimental Zooprophylactic Institute of Piedmont, Liguria and the Aosta Valley found that two female M. mustelus sharks under observation in captivity had exhibited parthenogenesis -- in which a female can reproduce asexually without the need of sperm to fertilise the egg -- each year since 2020.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">The two 18-year-old sharks have been at the Cala Gonone Aquarium in Sardinia since 2010.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">&quot;Remarkably, this finding reveals that parthenogenesis can occur annually in these sharks, alternating between two females, and conclusively excludes long-term sperm storage as a cause,&quot; the study&#x27;s authors wrote.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Cycling parthenogenesis, in which progeny can be born either from fertilised eggs or asexually with unfertilised eggs, occurs in over 15,000 species, yet is not fully understood.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Parthenogenesis, which is more common in invertebrates than vertebrates, has not yet been seen in mammals.</p><div><a href="https://news.abs-cbn.com/classified-odd/2024/7/25/sharks-off-rio-de-janeiro-test-positive-for-cocaine-616">Sharks off Rio de Janeiro test positive for cocaine</a></div><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Reptiles and some sharks, rays and skates are able to &quot;modify their adaptive strategy according to the surrounding circumstances&quot;, the authors wrote.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">&quot;Although the mechanisms driving parthenogenesis remain unclear, it is suggested that male population reduction could be a pivotal factor,&quot; they said.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Sharks in the wild pose challenges to understanding the phenomenon, but conditions in captivity are ideal for long-term monitoring, they noted.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">Aquariums in the United States, United Arab Emirates and Australia have documented the phenomenon in other shark species in the past two decades.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">M. mustelus, a midsize shark found in shallower waters that can potentially live up to 25 years, is classified as endangered, with estimates showing the population could decline by as much as a half in the next several decades, according to the study.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">The study tracked two 18-year-old female sharks in the aquarium for 13 years, without the presence of males.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">&quot;Nonetheless, a nearly annual production of young was observed in the absence of males,&quot; the authors wrote.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">The researchers studied the DNA of the offspring to exclude the possibility they were conceived because of long-term storage of sperm by the mothers.</p><p style="margin-top:1em;margin-bottom:1em;padding:0px;border:0px;-webkit- line-height:1.3;color:rgb(0, 0, 0);orphans:2;widows:2">The authors also noted that only one of the sharks born from parthenogenesis at the aquarium is still alive today. The two adults &quot;are in good health&quot;, sharing their large exhibition tank with other Mediterranean marine species.</p><div><a href="https://news.abs-cbn.com/life/01/22/24/the-meg-shark-was-actually-quite-thin-scientists-say">&#x27;The Meg&#x27; shark was actually quite thin, scientists say</a></div><div><strong>© Agence France-Presse</strong></div><div><br/></div>

<p>Italian researchers have noted the first case of "virgin birth", or reproduction without fertilisation, in an endangered shark species, a scientific journal reported this week.</p>

Italian researchers have noted the first case of "virgin birth", or reproduction without fertilisation, in an endangered shark species, a scientific journal reported this week.

Who needs males? Female sharks make babies alone in Italy

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Who needs males? Female sharks make babies alone in Italy

Agence France-Presse

Published Aug 01, 2024 10:40 AM PHT

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