Examples of cases in which sharks separated from males spawned alone, and the breeding strategy was quickly changed from sexual reproduction to asexual reproduction

BySigmund

It was confirmed that the female sharks that had once oviposited and married once succeeded to lay eggs alone on several years after being isolated from male. Sharks in a short time to leave descendantsSexual reproductionFromAsexual reproductionThere is a possibility that the breeding strategy was switched to.

Switch from sexual to parthenogenetic reproduction in a zebra shark: Scientific Reports
http://www.nature.com/articles/srep40537

Female shark learns to reproduce without males after years alone | New Scientist
https://www.newscientist.com/article/2118052-female-shark-learns-to-reproduce-without-males-after-years-alone/

Mr. Christine D'Ajaeon of the University of Queensland and his research team observed a phenomenon which has not been so far as a females lay eggs alone after several years from being separated from male.

This shark is a fish of a trough shark named "Leone" and is an individual bred at the Reef Aquarium in Australia. Leoney was mated with a male partner in 1999 and a total of 24 children were hatching after several egg laying. After that, partners were transferred to another aquarium in 2012, and they were spending their time in male-free environment, but in 2016 they succeeded in laying eggs alone.


Asexual reproduction animals themselves who lay eggs with females without mating with male are not uncommon in themselves, but it is extremely rare for animals that are sexual reproduction to turn into asexual reproduction. Especially, in the case of individuals with experienced egg laying in sexual reproduction, the example of switching to asexual reproduction afterwards has been observed only in some flying fish and bore, it became the first observation example as a shark.

Daejaeon suspected the possibility of fertilizing again using the male spermatozoa which was a merger a few years ago, but as a result of examining the genes of the birth fry, only the ones derived from mother Leonie were found The possibility has disappeared. Leonie has left offspring in parthenogenesis.


Dajaeon believes that switching sharks from sexual reproduction to asexual reproduction is a significant thing in survival competition. Originally, asexual reproduction of creatures leaving descendants in sexual reproduction is considered to be genetically disadvantageous for inbreeding when referring to inbreeding. However, it is extremely superior as a short-term survival strategy to leave descendants with only their own genes temporarily by asexual reproduction if they do not meet male and can not be mated, Dr. thinks.

By the way, a trough shark showing a breeding strategy of switching from sexual reproduction to asexual reproduction within an extremely short time is a creature designated as an endangered species on the IUCN red list.