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Wow! It has been a while since I posted something in this blog!

I guess it is time that I talk about something... or at least update you on what I am doing currently. This is my current obsession, the hellbender.

Last August I got started on my PhD in conservation genetics at Purdue University. I currently am working with the creature in the picture above. It is known as North America's giant salamander, or hellbender. Populations of this species have dropped more than 70% accross its range within the past 30 years. Reasons for its decline include habitat loss, pollution, collection, and disease. I am particularly interested in observing the immunogenetics of this species, due to the fact that one of the subspecies of hellbenders (the Ozark hellbender, native to the Ozark region of Missouri and part of Arkansas), suffers of pathogenic infections on the skin. Most infections occur in the extremities causing necrosis, and most adult Ozark hellbenders have no feet because of this. Pathogens (such as chytrid fungus and ranavirus) have already threatened the health of many of the world's amphibians. My goal is to look at one set of immune genes (Major Histocompatibility Complex or MHC) of both hellbender subspecies (Ozark and eastern hellbenders), and try to see if there is a genetic cause behind the Ozark hellbender higher risk for infection. MHC genes are involved in the recognition of self and non-self. Your body uses these genes in order to recognize pathogens, and present them to the immune system. They have also been found to be involved in mate selection, kin recognition, and pregnacy success. High diversity in the alleles within your MHC protects you against a large array of pathogens, and low diversity limits the amount of pathogens that you are protected against. Diversity within these genes is maintained by heterozygous andvantage or frequency dependent seleciton. My theory is that because of their small population size, Ozark hellbenders have a low diversity within their MHC genes, and thus have a decreased immune response to pathogens. Picture of an MHC molecule presening a pathogen to a lymphocyte
Similar results have already been seen in the axolotl. The axolotl is an aquatic salamander endemic to the Xochimilco Lake, MX. It is the model specimen for caudata (order of salamanders), and its MHC genes have been well studied. These studies have shown that there is no diversity within the genes. This animal is immunosuppressed. However, my reseach goal is to find at least one allele that confers resistance to a common pathogen in hellbenders. Zamudio et al. 2012 were able to detect an MHC class II allele that provided resistance to chytrid in frogs, which gives some hope for the hellbender. If we are able to find such alleles, we might be able to direct breeding programs to artificially select for such traits and increase the beneficial allele frequency in the population. ﻿

The journey just begins, but I will try to keep you posted on how this adventure goes! I'm holding an eastern hellbender from Missouri, with permision of Jeff Briggler MDC Herpetologist
Posted by Obed H. G. at 2:24 PM No comments: