The hellbender (Cryptobranchus alleganiensis) is North America’s largest aquatic salamander. These peaceful creatures inhabit fast-flowing, cool streams from Missouri extending northwest through New York. Amphibians, including hellbenders, are currently experiencing a range wide population decline as a result of a number of and anthropocentric sources. One of the most prevalent sources of population stress affecting the world is rising air and water temperatures associated with global climate change.
The Immune System
Vertebrate immune systems are comprised of a number of cell types and glands containing cells that will eventually give rise to immune cells. Leukocytes, or white blood cells, patrol the body in search of foreign invaders. Bacteria, fungi and viruses that gain entry into the body are detected by these leukocytes and trigger an immune response by binding to the invader and producing antibodies. Antibodies bind to the original pathogen, “tagging” the invader so that the immune system can detect and destroy it. Without a fully functioning immune system, organisms are susceptible to bacterial, fungal and viral pathogens which may impair fitness or even cause death (Sherwood et al., 2012).
Hellbender Immunity
The amphibian immune system has long been understood to be affected by temperature. However, the immune response of species differs considerably. To determine the effect of temperature on the hellbender immune system, researchers exposed a number of hellbenders in a controlled setting to cycles of temperature warming and cooling (lasting about 7 days). The immune system of hellbenders exposed to variable temperatures ( i.e. a cold winter with a warm summer) was able to more effectively kill bacteria and pathogens than that of individuals exposed to a constant temperature (Terrell et al., 2013). These results illustrate how important the fluctuation of temperature is to hellbender fitness.
Prognosis?
Rising stream temperatures as a result of global climate change could have a negative effect on the immune system of hellbenders, which are currently at risk from exotic 
diseases (Kaushal et al., 2010). Chytrid fungus, (the pathogen responsible for fungal chytridiomycosis, a deadly infection in amphibians -illustrated to the right) and Rana virus have been documented to cause disastrous population declines in other amphibians (Daszak et al., 1999, Souza et al., 2012). Currently, hellbenders seen to be able to survive chytridiomycosis infections, but global climate modulated immune systems may not be able to combat this foreign invader. Populations will likely decline with the remaining populations found in streams that maintain this seasonal water temperature shift.
What can you do to help?
Help the Hellbender and The Ohio Hellbender Partnership are two organizations dedicated to public outreach and hellbender conservation through creating partnerships with zoos and aquariums and local landowners. Their goals are to educate the public on hellbender ecology and importance as well as propagate captive populations of hellbenders for release.
Visit the Columbus, St. Louis, Toledo, or Akron Zoo today to support the institutions that are rearing and releasing hellbenders back into the wild to bolster population numbers.
Photo Credit
David Herasimtschuk – retrieved from http://www.davidherasimtschuk.com/#a=0&at=0&mi=2&pt=1&pi=10000&s=14&p=4
“Chytrid Fungus” – retrieved from https://microbiologybytes.wordpress.com/2006/09/12/chytrid-fungus/
Sources
Daszak P, Berger L, Cunningham AA, Hyatt AD, Green DE, Speare R (1999) Emerging infectious diseases and amphibian population declines. Emerg Infect Dis 5: 735.
Kaushal SS, Likens GE, Jaworski NA, Pace ML, Sides AM, Seekell D, Belt KT, Secor DH, Wingate RL (2010) Rising stream and river temperatures in the United States. Front Ecol Environ 8: 461–466.
Sherwood L, Klandorf H, Yancey P (2012) Animal Physiology: From Genes to Organisms. Cengage Learning.
Souza MJ, Gray MJ, Colclough P, Miller DL (2012) Prevalence of infection by Batrachochytrium dendrobatidis and Ranavirus in eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) in eastern Tennessee. J Wildl Dis 48: 560–566.
Terrell KA, Quintero RP, Murray S, Kleopfer JD, Murphy JB, Evans MJ, Nissen BD, Gratwicke B (2013) Cryptic impacts of temperature variability on amphibian immune function. J Exp Biol 216: 4204–4211.