Wolf Spiders, Mayflies and DNA: Wes Northram '10, Alsam Scholar

Wes Northam and others with headlamps on a search for wolf spiders. At night, spiders' eyes shine as tiny green lights.Wes Northam is one of four Biology/Neuorscience undergraduates awarded an ALSAM scholarship this year.  Wes Northam spent several years on research that crosses over interests of professors Liz Allison, a molecular biologist, and Dan Cristol, working on ecological problems that affect birds. After his research, Wes finds himself an expert on mayfly mitochondrial DNA, spider gut anatomy, arachnid/insect, predator/prey relationships, and adaptive lab techniques (e.g., using human pathogen detection products for spider DNA sequence procedures).

Northam’s job has been to answer the questions: Have wolf spiders been eating mayflies? and if so, How can we document it?  These research questions began when Dan Cristol and his students published a paper in Science that demonstrated the transfer of the toxic metal mercury from its source, the South River in the Shenandoah Valley, to the terrestrial ecosystem in the bodies of birds (swallows). Investigation into the birds’ diet found an intriguing culprit: wolf spiders! By studying the diet of swallows, Cristol found they ate a disproportionately large amount of wolf spiders. Cristol looked at the food chain and hypothesized that mayflies were the source of mercury in the wolf spiders; mayflies begin life as aquatic larvae in streams and then emerge from the water in episodic large swarms as flying insects.

To Wolf spider trapped for studyshow that wolf spiders actually eat mostly mayflies is not a simple task. It’s hard because the insides of a wolf spider look like orange goo, not like young mayflies—according to Wes, one of few who would know. Since visual analysis of wolf spiders’ stomach contents won’t work, Wes uses forensic tools gleaned from DNA analysis used in Liz Allison’s research. For two summers he collected wolf spiders and mayflies (stored in freezers for study the rest of the year). A good way to catch wolf spiders is to don a head lamp and find their pin-point characteristic green eyes that eerily reflect the light. Wes also ran time trial experiments in terrariums to characterize the predator/prey relationship between the spiders and mayflies—watching spider-predators at work. “Wolf spiders eat almost anything—including themselves!”  He characterized how long he could detect the mayflies in the spiders’ gut tissue: “the DNA signal was surprisingly strong for up to 24 hours”.

In the biology laboratories, Wes extracted mitochondrial DNA sequences from the spiders and mayflies—not an easy task, since unlike humans, fruit flies and a hand full of model organisms, mayflies haven’t been the subject of extensive DNA studies. Wes used polymerase chain reaction (PCR) technology to identify a range of spider and mayfly DNA sequences. “I  developed a small database of these [wolf spider and mayfly] sequences and designed primers to extract the DNA sequences needed. Because my ultimate goal is to take spider gut contents and identify the presence of mayflies. Can my primers account for them, with the large morphological diversity of all the mayflies?”

A challenge to developing the primers was that “I must amplify the mayfly DNA we’ve found, but exclude all the spiders’ DNA sequences”. Another challenge for Wes was that commercial DNA sampling materials haven’t been developed for mayflies and spiders, as they have for human lab work. Wes found a product “QIAmp”, designed for use by hospital laboratories to detect fecal pathogens from human stool sample to help prep his samples “that worked well to remove the many substances in spider and mayfly tissues that inhibit PCR.”

Wes Northam using the vacuum hoodWes currently works in Liz Allison’s lab, and uses the shared common equipment room where the genetic technique specialist Lidia Epp maintains a plethora of equipment needed by faculty, staff and students working with microscopy and DNA studies. “It’s a nice set-up. We have a new dead-air PCR hood that great because there’s such small levels of DNA I’m trying to amplify, that any other kind of DNA can contaminate the sample.”

Wes considers himself very fortunate to benefit from funding available for research at William and Mary. “It was so great to have the entire summer to do field work and research in the lab. During the year it’s a challenge with classes but I’m here [in the lab] all the time.” Costs for his supplies and summer funding have come from the Howard Hughes Medical Institute (HHMI) grant and now from the ALSAM foundation. The ALSAM funds paid for research supplies and a stipend, facilitating Wes’s work as he brings this story of biological and ecological investigation to completion. After writing up his work as an Honors Thesis, and graduating in 2010, Wes plans to attend medical school, and to pursue a career in clinical and laboratory research.