Baby balloon shark at a Louisiana aquarium:
The arrival of a baby balloon shark at a Louisiana aquarium has caused a great stir, after the egg hatched even though it seems that no male shark was involved. The baby shark Yoko was born in early January, according to the Shreveport aquarium, after hatching from an egg in a tank that contained two female sharks, but no males.
In fact, none of the specimens that could have laid the egg had had contact with a male for over three years, the aquarium said.Despite the lack of male sharks in the enclosure, there are two possible ways that the egg could have produced an offspring, it suggested.
Parthenogenesis
A phenomenon called parthenogenesis could have occurred, a form of asexual reproduction in which the embryo develops from an egg without fertilization, said the aquarium.Alternatively, late fertilization may have taken place, that is, when fertilization occurs much after mating, it suggested.
Kevin Feldheim, director of the Pritzker Laboratory of Molecular Systematics and Evolution, whose research focuses on the mating system and the biology of shark populations, told share4all that parthenogenesis has been observed in several species of sharks, such as the zebra shark and the white-spotted bamboo shark. It is also believed to have occurred in a species of ray.
Parthenogenesis usually occurs when females are isolated from males, Feldheim said, although there are examples of females giving birth this way even in the presence of males.
“It is still to be discovered how parthenogenesis is activated or what signals are given to the females… to initiate the process,” Feldheim pointed out, adding that “in general, we believe that this is a final effort by the female to transmit her genes.”
“This demonstrates how adaptable sharks are in terms of reproduction,” he said.
Feldheim also said that scientists currently “know almost nothing about how long females of each species can store sperm.” In one species of shark, it was found that a female had stored sperm for at least 45 months, he said.
The Shreveport aquarium said it will conduct genetic testing on Yoko when the pup is old enough to determine exactly how it came to be.
“This situation is incredible and shows the resilience of this species,” said Greg Barrick, the live animal curator at the aquarium, in a press release.
“We are very excited to confirm in the coming months whether this is really a case of parthenogenesis or delayed fertilization. It truly shows that life… finds a way.”
Animals
