Update: John Cooley shared his thoughts about this article about the Hodgkinia symbionts. There is a lot more work in this area of research yet to be done.
Update: McCutcheon (Matthew A. Campbella, James T. Van Leuvena, Russell C. Meister, Kaitlin M. Carey, Chris Simon, and John P. McCutcheon) has a new paper that shows Magicicada may have between 20 to 50 variants of Hodgkinia in their gut! Read the paper here. It would seem that the longer the life cycle, the more variants of Hodgkinia will be present in cicadas.
Here is the species used in the study: Magicicada tredecim:
From the October 5th, 2014 post:
Most people know how termites rely on microbes in their gut to break down the wood they consume into nutrients their insect bodies can use. Even human beings benefit from bacteria to help digest certain carbohydrates, fight pathogens and produce certain vitamins (like K and B12).
Cicadas also benefit from microbial endosymbionts. Cicadas, for most of their lives, consume a diet of xylem sap, drawn from the roots of trees. There are two types of sap: xylem and phloem. Phloem is the delicious, sugary one — in Maples, it’s Maple Syrup. Xylem is the “Diet” version of that. Thankfully cicadas have bacteria in their gut that process the xylem sap into nutrients cicadas can actually use.
Recently it was discovered that one such bacteria (Hodgkinia) has become two distinct bacteria in some cicadas belonging to the genus Tettigades. This discovery was documented in the paper Sympatric Speciation in a Bacterial Endosymbiont Results in Two Genomes with the Functionality of One by James T. Van Leuven, Russell C. Meister, Chris Simon, John P. McCutcheon (link http://www.cell.com/cell/abstract/S0092-8674(14)01037-X).
What’s interesting is the Hodgkinia bacteria became two distinct species for no particular discernible reason (nonadaptive evolution). Separate, either of the species would be useless to the cicada because they produce an incomplete set of nutrients, but together they produce the compete set of nutrients. Two function as one, that once was just one. Ed Yong does a thorough job of explaining this on National Geographic. According to Yong’s article McCutcheon thinks they know how it happened (explained in the article and paper). Why it happened is another matter — of course how and why might be the same thing deep in the soggy bowels of a cicada.
Chris Simon, let me know that she is working on a paper that will discuss bacteria found in Magicicada. It will be interesting to learn what they find in the bellies of those long-living cicadas.