smalltooth sawfish (Photo : Facebook)
The first animal virgin births in the wild, performed by sawfish, have been documented in Florida bodies of water. The endangered fish with "saw" sharp teeth is the first case of asexual reproduction among sexual animals, and has helped them to escape extinction.
Andrew Fields, the study's lead author from Stony Brook University, told Discovery News that the female smalltooh sawfish, Pristis pectinate, are likely having problems finding male sexual partners, due to their "fragmented habitat" and small population. Fields and his team believe that some female fish have found a way to perform asexual reproduction.
The recent discovery was published in the June 1 issue of Current Biology.
Sawfish are world-famous for their long noses that resemble a saw tool. The unique-looking fishes are a type of ray, and are sharks' cousins.
Fields and his university colleagues were in a Florida estuary (river-sea junction) performing DNA fingerprinting of sawfish when they noticed signs of parthenogenesis (virgin births). This was among almost 4 percent of the cold-blooded animals, according to Nature.
Researchers believe this very rare phenomenon occurs when an unfertilized egg absorbs a sister cell that is an exact genetic copy. The offspring have around 50 percent of their mothers' genetic diversity, and frequently die, according to Discovery.
The non-sexually reproduced sawfish were different. These fish "parthogens" looked perfectly healthy, so the Florida scientists tagged and then released the sawfish.
Scientists know of five animal species of rays and sharks in which parthenogenesis exists. Virgin births have also been verified in captivity among birds and reptiles (e.g. snakes), through DNA testing.
The asexual reproduction among the fish species is a warning about their shrinking population. Fields said that sawfish are near the "brink of extinction."
The population size of the smalltooth sawfish is at 1-5 percent of its historical levels. Main threats include fishing entanglements and habitat loss.
Sawfish also produce few offspring during their mating season. This makes saving the sawfish from species extinction a greater challenge.
However, scientists are searching for various conservation methods to trigger virgin births in species like the smalltooth sawfish. That includes testing "artificial sperm" in lab mice.
