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Lisa
Dorn Jonathan Coddington, Ph.D.
"Learning about the different areas of natural history and working in the museum environment has really helped me to focus on my career goals. The RTP help reaffirm how important it is to have a broad knowledge of science." |
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Designing a Method for Freezing Spiders In-copula Work was done to develop a method for freezing spiders in-copula. The spiders used in the experiment were collected in the area surrounding Washington, DC. In addition to freezing, an attempt was made to freeze dry the spiders for study under the Scanning Electron Microscope (SEM). This project was originally titled "the functional morphology of spider genitalia"; however, at the start of the project, it was decided to shift the focus slightly and concentrate on designing a method for freeze drying spiders in-copula. The first step in this project was to collect spiders, which would later be mated in the lab. Three collecting trips were performed in the DC area. One of the trips was at night. Early in the program, Linyphiid spiders were provided. Because there were so many pairs of these spiders, most experimentation was done on them. This study is not concerned with species from the collecting trips. The focus was on mature animals or animals in their last instar, so that matings would occur in the course of weeks, and on collecting male/female pairs. Spiders were housed in dixie cups. Sand or paper towel was placed in the bottom of the cup to provide the spiders with a humid environment. Plastic wrap was used for the lids. Drosophila maintenance supplies were obtained from Nate Erwin and Joe Smith in the Insect Zoo and Drosophila was raised in the lab. The Drosophila served as food for most of the spiders, although some of the larger spiders required crickets or smaller spiders. They were fed and watered daily. The next step in the project involved a lot of experimentation on different freezing devices. It was decided to use liquid nitrogen as the freezing mechanism because it freezes on contact. Two containers were used for the liquid nitrogen, one with a diameter of 2" and one with a diameter of 6". The cage was designed to fit the 6" thermos as the spiders would not build webs in anything smaller. The goals was to have a cage that would allow the spiders to be plunged into the nitrogen as this method worked best for freezing single spiders during the experiment. The final cage had a diameter which fit a petri dish so that these could be used as the top and bottom. Sand was placed in the bottom dish. A long upright handle was attached to the side of the cage. This handle gave the most control over the cage and allowed the cage to be moved into the nitrogen in one fluid motion. Finally, the cage had a height of only 3.6cm. This not only minimized the vibration in the cage due to the boiling of the nitrogen, when it contacted the cage, but also the spiders to be put into the nitrogen faster as they would build their webs at the tops of the cages. In order to freeze the copulatory pair, the female was first introduced to the cage. After a few days, the male was introduced and, at the right phase of copulation, the pair was submerged into the nitrogen. In addition to freezing, a freeze dryer was designed to dry the specimens in. Both the freezing and the freeze drying were successful. However, the pair did not stay together. In addition to this work, much was read about spider biology and behavior to help in the design of this project. Much was also learned from raising the spiders. Although this technique still needs some refinements, it may be a useful tool to researchers who want to study the functional morphology of spider genitalia.
This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates (Award: BIR-9300225). |