Kistenmacher ’12 Cultivates Seed Beetle Study with Faculty Collaboration

September 13, 2011 Sarah Schwartz

Sarah Kistenmacher ’12 spent the summer pioneering a lab-based research under the supervision of Dr. Chad Hoefler, Assistant Professor of Biology. Her study “Congruence between host preference and reproductive success in Callosobruchus maculatus seed beetles” revolves around host preferences and differential reproductive success in a species that uses stored beans and legumes as both a nutritional and gestational agent.

“One of the most important factors influencing the life-history of an organism is parental investment in reproduction, and reproductive decisions invariably have trade-offs,” says Hoefler. “Therefore, reproductive decisions should be beneficial in terms of increased offspring number. For example, egg-laying decisions in many insects can influence resource availability, speed of development, survival, and the types of hosts that will be sought when offspring mature.”

Kistenmacher initially became involved in Hoefler’s laboratory by volunteering to clean and care for the test spiders during the summer of 2010. At the conclusion of the fall 2010 semester, she had built a close enough working relationship with Hoefler to ask him for help in formulating a research project of her own.

“I’ve never run my own experiment before,” says Kistenmacher. “Dr. Hoefler has been really helpful in helping me cultivate the idea and determine the testing methods,” she says. “There were I wasn’t really sure what aspect, I just knew that I wanted to do a lab-based thesis rather than a library based thesis. I met with him on numerous occasions and he helped me narrow down my project.”

“When the male and female Callosobruchus maculatus seed beetles mate, the larva dig into the bean, where they will remain until fully grown,” she says. “This makes it a cosmopolitan pest of stored pulses and legumes.”

Kistenmacher’s process is twofold. The first portion requires her to explore of offspring success on a variety of environments. Kistenmacher measured 10 grams of either dried pulses and legumes including mung, black beans, black-eyed peas, lentils, and adzuki beans into small test cups, distributing one male and one female Callosobruchus maculates to each site. At the end of eight weeks, Kistenmacher will quantify and compare reproductive success and offspring sex ratio of the beetles on these hosts.

After investigating host/bean preferences of the adult beetles, Kistenmacher will derive a hypothesis from the results discovered in part one of her project. Should the beetles be significantly more successful on one or a few host types, she will expect there to be a strong selection pressure for preferences for those specific hosts when the beetles are given a choice. Kistenmacher will conduct simultaneous choice tests of hosts to determine if male and female beetles have preferences in a manner that is congruent with reproductive success.

Kistenmacher plans to use her research as part of her Senior Capstone project. In the future, she hopes to continue her studies at Arcadia pursuing a master’s degree in Public Health.

“One of the very best things that Arcadia offers its students is the opportunity to conduct state-of-the-art research one-on-one with our gifted faculty,” said Arcadia’s President Carl (Tobey) Oxholm III.

“Here, discovery and innovation are not just read about in books—they are experienced with the hands and a mentor. These experiences prepare our students well for graduate schools and careers and help to ensure that our country will have creative minds eager to take on new challenges. But these experiences also create informed citizens, as our students know firsthand how difficult true scientific inquiry is and are better able to evaluate and participate in public discourse about scientific issues that will have local, national and global significance in the coming decades.”

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