In relative recent history, human scientists have discovered that Mother Nature can be a tricky old lady. One of the mind blowing details of natural history that has revealed itself is a phenomenon known as “parthenogenesis”. This process is a part of “apomixis”, which loosely means replacement of the normal sexual reproduction by asexual reproduction–without [...]
In relative recent history, human scientists have discovered that Mother Nature can be a tricky old lady. One of the mind blowing details of natural history that has revealed itself is a phenomenon known as “parthenogenesis”. This process is a part of “apomixis”, which loosely means replacement of the normal sexual reproduction by asexual reproduction–without fertilization! It is one of the most impressive survival strategies known to mankind.
This enables female organisms, in complete absence of male organisms, to reproduce successfully. While this may not seem a phenomonal occurance to coral enthusiasts who regularly see their corals asexually reproduce, divide, or clone, this process in higher organisms is quite spectacular. Especially when you MUST consider (by definition), that these animals typically reproduce by sexual means (fertilization of eggs by a sperm from an independent male), and not by asexual means, or self fertilization from hermaphrodites. In the past decade, this phenomenon has been highlighted in insects, reptiles, and recently sharks.
Novelty of this aside, the questions can now be raised, why do these animals do this? As mentioned, these species will prolifically reproduce in a sexual manner, so parthenogenesis must not provide any tangible evolutionary or biological benefit. So, why the effort?
Dr. Kevin Feldheim, manager of the Pritzker Laboratory for Molecular Systematics and Evolution at the Field Museum has untertaken a genetic analysis of such events to unlock this mystery for the first time. Using two “virgin birth” daughters of a White Spotted Bamboo Shark (Chiloscyllium plagiosum) which have survived five years, Dr. Feldheim was to confirm the pups were born without input from a male via DNA analysis. Despite that the mother shark resided in an exhibit in in the Belle Isle Aquarium in Detroit, sharing it with only a female of another shark species, DNA evaluation of the offspring was done to confirm that the mother had not been in contact with a male in previous setting. Furthermore, a more general DNA evaluation was conducted by an independant university to confirm that, although the offspring did not have identical DNA to the mother, they did only exhibit her DNA.
It is believed that in these parthenogenesistic births, the “half clones” are the result of egg cell fusion with a “sister polar body” cell, rather than male sperm, to promote cellular division. Dr. Demian Chapman of the Institute for Ocean Conservation Science at Stony Brook University, New York, a pioneer scientist in shark parthenogenesis, states “Parthenogenesis may not be as much of a dead-end mode of reproduction as we thought for these sharks.”
Being that is has now been proven parthenogenetic born sharks can survive to reproductive age, it provides evidence that this method of reproduction may be used by sharks within a reef where a male may not be present. Despite the fact that a viable male may not be currently present, this allows female sharks to make their genes available for future generations, producing daughters that a future male may find.
