Article Review: Parthenogensis in Copperheads

        I have always been fascinated by lesser-known forms of reproduction, parthenogenesis in particular. When I came across the article entitled "An Independent Observation of Facultative Parthenogenesis in the Copperhead (Agkistrodon contortrix)" in the Journal of Herpetology, I was immediately intrigued. Jordan, Perrine-Riplinger, and Carter have contributed their research to an otherwise non-existent pool of evidence for facultative parthenogenesis (FP) in Copperheads. They used molecular tools, statistical analysis, and the common characteristics of FP in snakes (male, homozygous, clutch with aborted ova) to research their hypothesis.
       Long term sperm storage (LTSS) has been proven to be an alternative mating tactic in Copperheads. Females can store sperm for up to 10 years in captivity, have a variety of mates and sperm donors, leading to sperm competition and the production of offspring from the "most fit" sperm. One study, other than this one, has been conducted on FP in Copperheads even though FP has been proven to be a reproductive techniques in other Squamates. The authors of this paper wanted to continue this research. To begin the study, a female Copperhead was captured in Indiana in 2001 and put on display in a park without having contact with any other snake. In 2010, the female produced 4 aborted ova and one stillborn male neonate. The authors' hypothesis was that the neonate produced by this wild-caught mother was produced via facultative parthenogenesis and not by LTSS.
       The authors retrieved the neonate and sampled its tissue, sampled the mother's tissue, and also sampled tissue from multiple wild Copperheads in Indiana in the same park where the mother was caught. All caught Copperheads were measured, sampled, and then released immediately. These tissue samples from the wild Copperheads were to be used for allele frequencies to compare to the neonate's genotype. After the sampling was completed, the authors performed extremely complicated molecular analysis (PCR and gene mapping) and statistical analysis to identify 10 loci (9 were utilized in the analysis) and to come up with an equation for paternal probability.
        The authors found that, at all 9 loci in the wild population (the mother's population of origin), heterozygosity was high. The captive mother was heterozygous at four out of the 9 loci. The neonate was completely homozygous for the maternal alleles at all 9 loci leading the authors to conclude that the paternity probability was extremely low once they utilized their equation. Combining these results with the previously known characteristics of FP allowed the authors to conclude that their hypothesis that the neonate had been produced via FP was supported. The clutch that the mother produced when the neonate was stillborn was mostly aborted ova, the paternity probability was very low, and the neonate was male and homozygous for maternal alleles.
       This solid support of an instance of FP in Copperheads is only the second of its kind. Booth et. al. in 2011 (where the authors of this article got much of their supporting information) also performed a similar study with similar results. Since this research is brand new and almost unheard of, it is much too soon to make any conclusions on why females utilize FP. The authors acknowledge that FP in female Copperheads leads to the loss of genetic variation, but they point out that it could be useful in the colonization of new territories by females without access to suitable mates. Also, since the majority of parthenogenic offspring (in all species of snakes, not just Copperheads) are not viable, there is no reason to fear for the loss of genetic diversity in the species.
       Since our climate is changing so much, I feel this research is extremely important to the future of Copperheads. With the planet warming and environments changing, species are seeking out new habitats. Copperheads could be among these and since the authors believe FP could be a result of the lack of available mates, FP could become a more common reproductive method for Copperheads. Much more research needs to be done to find out why females choose FP and if there is any hope for more viable offspring via parthenogenesis like there has been in other squamate species.

Article: http://content.ebscohost.com.nuncio.cofc.edu/ContentServer.asp?T=P&P=AN&K=101643902&S=R&D=a9h&EbscoContent=dGJyMMvl7ESeqLU4v%2BbwOLCmr02ep7JSsKy4TbKWxWXS&ContentCustomer=dGJyMPGuslCzr7dMuePfgeyx44Dt6fIA