Host and a Parasite: Battle of Sand Field Crickets vs. Horsehair Worms

If you were a sand field cricket, you would not like horsehair worms.

"The horsehair worm (Paragordius varius) is a long-lived parasite that infects arthropods, including the sand field cricket, Gryllus firmus," says biologist Amy Worthington, assistant professor, Creighton University, Omaha, Neb. "This parasite lives inside its host for upwards of 28 days and can grow as long as 30 cm, presenting a significant challenge for its host's own growth, survival, and reproduction."

You can learn more about Worthington's work when she delivers a UC Davis Department of Entomology and Nematology seminar--it will be both in-person and virtual--on "A Host of Hardships: The Costs of Harboring a Long-Lived Parasite."

Worthington will speak at 4:10 p.m., Wednesday, March 8 in 122 Briggs Hall. Her seminar also will be virtual. The Zoom link:

"Parasites often manipulate their hosts'  behavior and physiology, resulting in detrimental effects on host fitness," Worthington says in her abstract. In her research, "we tested the ability of infected male crickets to invest in immunity, somatic growth, and reproductive structures. We also compared courtship behaviors, calling abilities, and mating success rates between infected and healthy males to identify how host reproductive fitness is affected by this large, long-lived parasite. Our results demonstrate surprisingly few physiological trade-offs, yet preliminary research suggests a reproductive burden on infected males, where even when host male crickets are able to survive horsehair worm infection, they will likely suffer from significantly reduced lifetime reproductive fitness."

UC Davis doctoral candidate Lindsey Mack, who studies with major professor Geoffrey Attardo, medical entomologist-geneticist, is the seminar host. "Dr. Worthington was my undergraduate research advisor," said Mack, adding. "She studies reproduction/immune trade-offs in crickets. Currently, her work focuses on the reproductive costs of high parasitic loads in field crickets, but she has experience with stalk=eyed flies, rhinoceros beetles, horsehair worms, and many other organisms. Generally, she is interested in wild sexually selected morphologies and behaviors."

"Additionally, she teaches at a religiously affiliated, primarily undergraduate institution (Creighton is a private Jesuit research university) and would be a great person to talk to about this type of career," Mack said.  A pre-seminar coffee takes place from 3:30 to 4:10 p.m. in 158 Briggs. 

Worthington, who joined Creighton's Department of Biology in the fall of 2016, holds a bachelor's degree in biology from the University of South Dakota (USD), and also received her master's degree at USD, studying the anti-predator behaviors of stalk-eyed flies and managing a long-term project dedicated to conserving the federally endangered Hine's Emerald dragonfly. 

Worthington completed her doctorate in ecology and evolutionary biology at Iowa State University, researching mating behavior in field crickets. She then transitioned into a postdoctoral fellowship at Washington State University where she worked on the development of sexually selected weapons in rhinoceros beetles and the hormonal mechanisms mediating wing polymorphism in crickets.

"Broadly, I am fascinated by bizarre morphologies and behaviors that are the result of sexual selection," Worthington says on her website. "Specifically, I am interested in the functional and physiological costs of these traits. I focus on trade-offs between reproduction and immunity, but also investigate topics such as sperm competition, the benefits of polyandry, and the molecular/hormonal mechanisms responsible for life-history tradeoffs. I have worked with a diverse array of invertebrate taxa (stalk-eyed flies, jumping spiders, dragonflies, crayfish, snails, and rhinoceros beetles), but currently focus my research on Gryllus firmus crickets. One particular interest is how individuals respond to long-term parasitic infections by the horsehair worm Paragordius varius, and how this infection impacts life-long fitness in its host."

The UC Davis Department of Entomology and Nematology's winter seminars are held on Wednesdays at 4:10 p.m. in 122 Briggs Hall. All are virtual. Urban landscape entomologist Emily Meineke, assistant professor, coordinates the seminars. (See schedule.) She may be reached at for technical issues.