Sharks - Asexual Reproduction

Asexual reproduction is also known as parthenogenesis. It refers to the female’s being able to create and sustain a shark pup without a male shark and without ever having mated. This has only ever been observed in the cases of sharks in captivity, but may well occur in the wild where there is a severe shortage of male sharks. Interestingly, other animals have also been known to do this, some exclusively. These include snakes, birds and Komodo Dragons, amongst others.

The only vertebrate group never observed having done this is the mammalian one.

although it is extremely rare, asexual reproduction has been noted in several confined sharks. Upon the discovery of the shark pup, extensive tests (including paternity tests) were conducted. It was confirmed that some of the female sharks had never had contact with any other shark, and the possibility of others having retained sperm from previous encounters was ruled out.

Advertisements

The major problem with this type of reproduction is that it limits genetic diversity, which is a key element to ensuring strength and the survival of a species. For example, if the female shark passes down a genetic defect, the presence of a beable male’s DNA could negate that defect, ensuring that the pup remains beable. However, if only the mother’s DNA is present within the pup, it does not have the genetic resources to combat this weakness. If a species is forced to rely solely on asexual reproduction because no males exist in the area, it is likely to die out far sooner due to poor health and a weak gene pool.

In order for this type of reproduction to take place, the mother’s chromosomes split during the development of the egg. There are some notions that this may be induced by hormones, but it is not known exactly.

Sharks maintain a sense of mystery as researchers continue to delve deeper and learn about these fascinating creatures.

Advertisements