Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3A Abstracts
6. INTRASPECIFIC VARIATION IN RESISTANCE AND ADAPTATION TO
DESICCATION AND CLIMATIC GRADIENTS IN THE PACIFIC BANANA SLUG
(Ariolimax columbianus). Kyle Crawford and Chris Medina, Department of Biological Sciences,
Saddleback College, Mission Viejo, CA, 92692, USA
Pacific banana slugs, Ariolimax dolichophallus, of California are subject to desiccating
conditions in their terrestrial habitats depending on seasonal weather patterns. A slug risks a
significant loss of body mass when placed in desiccating environments due to high relative body
water content and osmosis permeable skin. It was tested that banana slugs are prone to become
more resistant to dehydration after several periods of exposure to desiccating environments. The
experiment was performed on banana slugs in four controlled humidities including a control
group in order to determine the amount of water loss and the ability to adapt to each environment
over a period of three trials. The results supported the hypothesis that by the third dehydration
the slugs retained more water and were less susceptible to desiccation. After the third trial the
slugs retained 92.5% (± se, N = 4) of their original body mass in a 0% relative humid
environment, retaining 12.5% more than the first desiccation, 91.2% (± se, N = 4) in a 33%
relative humid environment retaining 4.5% more than the first desiccation, and 91.6% (± se, N =
4) in a 75% relative humid environment retaining 4.8% more than the first desiccation. Three
independent ANOVA’s indicated a significant difference between the first and final desiccation
in each environment, (p = 4.71 × 10 -6 , p = 8.73 × 10 -4 , and p = 7.04 × 10 -3 ).
7. CRUDE ONION (Allium cepa) JUICE SHOWS NO SIGNIFICANT ANTIBACTERIAL
EFFECT ON Escherichia coli AND Staphylococcus aureus. Daria Cubberley and Arshan
Ferdowsian. Department of Biological Sciences, Saddleback College, Mission Viejo, CA, 92692,
USA
Since many researchers found that some plants possess antibacterial substances, this study
investigated the effect of onion (Allium cepa) juice on the growth of a strain of gram-negative
bacteria, Escherichia coli, and a strain of gram-positive bacteria, Staphylococcus aureus. As
gram-negative bacteria have the outer membrane which makes them more resistant to antibiotics,
it was predicted that the antibacterial effect of crude onion juice would be significantly greater
on S. aureus than on E. coli. The experiment was performed using aseptic technique. The broth
cultures of bacteria were spread on the surface of the agar. Four sterile filter paper disks 6.0 mm
in diameter were dipped into onion juice and placed equidistant from each other on each of the
10 Petri dishes with E. coli and on each of the 10 Petri dishes with S. aureus. The controls were
prepared in the same manner by dipping filter paper disks into sterile deionized water and
placing them on the agar. After incubating the Petri dishes for 72 hours in 37 °C, the diameters
of the zones of inhibition were measured. The results did not support either of the hypotheses.
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Saddleback Journal of Biology
Spring 2010