In defining the general topic of a-sexuality, the Britannica Encyclopedia explains that parthenogenesis is the

“biological reproduction that involves development of a female (rarely a male) gamete (sex cell) without fertilization. It occurs commonly among lower plants and invertebrate animals, particularly rotifers, aphids, ants, wasps, and bees. An egg produced parthenogenetically may be either haploid (i.e., with one set of dissimilar chromosomes) or diploid (i.e., with a paired set of chromosomes).” In larger animals, however, few are able to parthenogenetically produce offspring that will flourish to the same extend as sexually-produce offspring. One species that has the ability to reproduce without the male gamete is the Komodo dragon. The “reproductive plasticity” indicates that the female Komodo Dragons have the ability to switch between asexual and sexual reproduction, depending on the availability of a mate. Similarly to the dragons, some species of snakes maintain similar abilities. Parthenogenesis, although noted in various reptiles, is most notably seen in New World lizards of the Teiidae family, Old World lizards of the Lacertidae family, and the Brahminy blind snake, and within these populations, all of the snakes are composed entirely of genetically identical female individuals, or clones. Although recent research has shown other types of snakes to reproduce asexually and still maintain males, I found the first three to be the most interesting. The populations lack the necessity of males as they can reproduce perfectly without the male gamete, and each offspring has identical DNA. Sharks, however, primarily rely on sexual reproduction of offspring, with some exceptions (cases in which no males are available for mating). A recent study shows that some parthenogenetically reproduced sharks are viable offspring, with life spans similar to sexually produced sharks. After studying the first known case of a virgin female shark producing multiple offspring that survived, scientists found that two of the offspring have survived five years since birth. Earlier research found that the offspring of parthenogenetically reproduced sharks did not survive, making the recent study the first known of its kind. In order to be certain that the sharks indeed had no father, scientists examined the DNA of the offspring and found all areas of the genome to be inherited from the mother. The new development in shark studies indicates that parthenogenesis is an active participant in shark life, and not merely a death sentence for the offspring.

Nature Journal, viewed February 10, 2010

http://www.nature.com/nature/journal/v444/n7122/abs/4441021a.html

Gordon W. Schuett on September 16, 1997, as reported in The Sonoran Herpetologist, the Newsletter of the THS, Vol.11, No.9, September, 1998.

Science Daily, viewed February 8, 2010

http://www.sciencedaily.com/releases/2010/01/100125094518.htm

Britannica Encyclopedia. Viewed on February 8, 2010. http://www.britannica.com/EBchecked/topic/444810/parthenogenesis

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