Abstracts for Oral Presentations
Influence of Nitrogen on Root Morphology in Corn and Soybeans
Anthony Cancro, Thiel College
Plants adjust their root morphology when faced with the scarcity of such nutrients as nitrogen and phosphorus. The present study aimed to determine if different concentrations of nitrate would affect the total root length of common corn Zea mays and soybean Glycine max. One hundred seeds were germinated for five days, and grown in sand for twenty five days. Different nitrate concentrations (.04, .4, 2, and 4 mM) were supplied to the corn and soybean crop over a twenty five day growing period. The entire root biomass was measured. No correlation existed between nitrate concentration and root morphology.
Estimating white-tailed deer populations using infrared-triggered cameras
Joseph Laslo, Washington & Jefferson College
This study investigates the effectiveness of using infrared-triggered cameras, as opposed to more costly and labor intensive methods, to estimate population size and structure of white-tailed deer (Odocoileus virginianus) on a 22 hectare forested property in southwest Pennsylvania. Three baited camera stations were set up on the property and photographed deer during two separate two week periods in November, 2006 and January, 2007. Following the population model developed by Jacobsen et al. (1997), individual branch-antlered bucks were identified, and the populations of spike-antlered deer, does, and fawns were then estimated using ratios derived from the total number of pictures of each age class of deer. The November survey period yielded an estimate of 25 (13 antlered and 12 antlerless) deer at the property, while the January survey revealed a greater number of antlerless deer and substantial changes in feeding behavior at the camera stations. Overall, camera surveys appear to be a viable option for estimating deer populations, although there are some problems inherent with using this method in such a small area.
Is Male Territoriality Influenced by Cover in Betta splendens?
Lonnie Lindberg, Thiel College
There are several reasons why animals defend territories. One reason maybe to protect resources. Another is to defend a territory that is attractive to potential mates. A third possibility is that they offer shelter and safety from predators and potential challengers. The Siamese Fighting fish, Betta splendens, is strongly territorial and is an excellent model for testing hypotheses about territoriality. In this study, I compared the aggressiveness of the domesticated male Betta splendens with and without a place of refuge. My hypothesis for this experiment was that male betta fish with a refuge will be more aggressive than those without a refuge. After a dominance hierarchy was established, aggressiveness was determined by counting how many times a male betta attempted to attack another male betta within the three minute time limit. Results showed that there is no clear link between male aggression and a place of refuge.
The Influence of Incubation Temperature on Sex Determination in the Veiled Chameleon, Chameleo calyptratus
Jamie Long, Thiel College
The sex of an organism can be determined by a variety of mechanisms, depending on its species. Commonly, sex is fixed at conception by sex chromosomes through genetic sex determination (GSD). However, there are many species in which environmental factors influence the differentiation of bipotential gonads into either ovaries or testes as the embryo develops. Incubation temperature plays a vital role in sex ratio outcomes of many animals, especially reptiles, by what is known as temperature-dependent sex determination (TSD). During TSD, temperature affects steroid metabolism of the embryo within the egg, eventually establishing sex irreversibly part way through development. It was the intention of this study to demonstrate whether or not the Veiled Chameleon, Chameleo calyptratus, is subject to the mechanism of TSD. Seven clutches of chameleon eggs were divided into three groups and incubated at one of three carefully controlled temperatures, 29, 26.5 and 24.5°C, throughout the duration of their 6 to 9 month development period until hatching. Sex data from over 350 live hatchlings was included in the study, and an overall mortality rate of less than 2% assured that failure of eggs to hatch did not affect the final results. The length of incubation time was significantly impacted by temperature, with lower temperatures increasing the duration of development. However, because there was no statistical difference, according to the Chi-squared analysis, between the sex ratios of the three groups, the study suggests that the sex of Chameleo calyptratus is not governed by incubation temperature, but most likely fixed at conception by genetic factors.
Innervation Pattern in the Ventral Diaphragm Muscle of Manduca sexta
Steven Punzell, Washington and Jefferson College
Control of muscle contraction can be done in two ways; neurogenically and myogenically. Neurogenic control requires innervation and innervation patterning can have some interesting results when working with an organism that undergoes metamorphosis like the tobacco hornworm Manduca sexta. A specific muscle of interest in this insect is the ventral diaphragm muscle (VDM). The VDM is a circulatory muscle that controls oscillations of its abdominal nerve cord; however, the pattern of innervation in this muscle has yet to be elucidated. In this study adult animals were dissected and stained with either methylene blue or rabbit anti synaptotagmin antibody and viewed via microscopy. It was shown that synpatotagmin immunoreactivity occurred only in segments A3 and A6-10 with no staining in segments A4 or A5. From this it was clearly visible that the VDM was innervated with similarities to that of the dorsal vessel (heart) and it is hypothesized that the innervation pattern on the VDM acts as a pacemaker does, as is seen in the dorsal vessel.
Effects of the Herbal Agents Australian Tea Tree Oil and Jamaican Nutmeg Oil and the Antimicrobials Polymyxin B and Colistin on the Cell Envelope of Escherichia coli K-12
Michael G. Gresock - Saint Vincent College
Current research suggests that E. coli K-12 is developing antibiotic resistance mechanisms to traditional, synthetic antibiotics, so the exploration of alternative treatment methods for opportunistic E. coli K-12 infections is becoming increasingly significant. The traditional antibiotics polymyxin B and colistin increase the permeability of the outer and cell membranes of Gram-negative bacteria such as E. coli beyond normal levels, leading to osmotic instability and death. Tea tree oil (TTO) and nutmeg oil both contain large proportions of terpene alcohols that also disrupt cell membranes. However, the antimicrobial properties of these herbal agents have not been extensively studied. It was hypothesized that the herbal agents would actually cause more membrane damage because E. coli K-12 has probably not developed resistance mechanisms for these rarely used herbal agents. To test the hypothesis, E. coli K-12 was grown in Luria-Bertani broth in the presence of varying concentrations of polymyxin B, colistin, TTO, or nutmeg. Growth was measured over an eight-hour period through spectrophotometry readings and population analyses, and the minimum inhibitory concentration (MIC) of each agent was noted. Analyses with SYTOX Green nucleic acid stain, a stain that specifically binds to the DNA within cells that have compromised plasma membranes, were performed to corroborate the growth curve results. Both polymyxin B and colistin produced the same MIC value at 2.00 ?g/ml, meaning that both are equally effective at disrupting membrane structure. The MIC for TTO was 0.08%, but even a solution containing 2.5% nutmeg oil did not halt at least some visible growth. SYTOX Green fluorescent tests revealed no significant difference between the membrane-compromising abilities of polymyxin B, colistin, and TTO (p <0.05). However, nutmeg consistently produced significantly lower fluorescent readings than the other three compounds, meaning that nutmeg did not permeabilize membranes as well. Overall, it appears that TTO was as effective as polymyxin B and colistin while nutmeg was certainly less effective, refuting the hypothesis that the herbal agents would be more effective at causing damage to the cell envelope.