Saddleback Journal of Biology - Saddleback College

Spring 2010 Biology 3B Paper
investigation were acclimated to temperatures
averaging about 20 ˚C ± 5 ˚C; therefore, investigators
hypothesized that Hyla regilla collected from more
temperate climates would not exhibit significant
increases in plasma glucose associated with cold
temperature.
Blood glucose levels significantly increased
as the temperature decreased (Figure 2). The mean
glucose level of the control group after protocol was
31.70 ± 2.29 mg • dL -1 (±SEM, n=10), and the mean
glucose level of the near freezing group was 50.20 ±
3.10 mg • dL -1 (±SEM, n=10).
The significant findings in this experiment
were unexpected and did not support the investigators
hypothesis. The increase in blood glucose levels
suggests that glucose, a cryoprotectant, accumulates
in order to prevent cellular damage by stabilizing
proteins and maintaining membrane structure.
Glucose may also limit intracellular dehydration via
osmotic and water-binding effects. As a result, the
investigators were interested in furthering their
research to determine why Hyla regilla, living in
Southern California, were able to survive exposure to
near freezing temperatures when they had not
previously been acclimated to these conditions.
Therefore, the questions is, why is this adaptation
observed in species that are not subjected to colder
temperatures?
Investigators wanted to determine if Hyla
regilla increased their blood glucose levels as a
response to environmental changes that may cause
great stress on their body. They wanted to expose the
Hyla regilla to a high saline environment, a different
environmental variable that the species had not been
acclimated to, in order to determine if the frogs
would increase blood glucose levels. The
investigators hypothesized that the blood glucose
levels of Hyla regilla would increase as a response to
an environment of high salinity as a protective
mechanism against cellular damage.
Twelve Hyla regilla were collected at a
freshwater pond in Irvine, California on April 7,
2010. One control group (freshwater) and three
experiment groups, consisting of three frogs each,
were used in this experiment. The frogs were placed
in individual petri dishes containing either water from
the freshwater pond or dilutions of normal saline (50
mM NaCl, 100 mM NaCl, and 150 mM NaCl). The
blood glucose levels of all the frogs were recorded
before experimentation, after three hours and after 48
hours of continuous exposure to either pond water
(control) or saline solutions (experimental groups).
Multiple one-tailed, paired t-tests (p 0.05) were
used to analyze the data.
P values were analyzed to determine if the
changes in blood glucose levels were significant.
Investigators looked at p values that were obtained by
comparing the initial blood glucose levels of each
group and the blood glucose levels after three hours
of continuous exposure to the solutions. In addition, p
values were calculated between the initial blood
glucose levels and the blood glucose levels after 48
hours of continuous exposure. There was no
significant increase in the blood glucose levels in any
group. Figure 3 illustrates the mean blood glucose
levels of the control and experimental groups.
Although unexpected, the insignificant
results found in the study of exposure to a saline
environment may actually provide more support
towards the preliminary study. The evidence of the
initial study suggested that frogs in warmer climates
possess the same freeze adaptation as frogs in cold
climates. However, the investigators did not put the
frogs in any other stressful situations and this left the
investigators’ speculation vulnerable to other
arguments. The new data, showing the frogs
subjected to a different environmental change with no
significant increase in glucose, may reinforce the
researchers’ results that suggest that a widespread
distribution of the freeze tolerance adaptation exists
in this species.
43
Saddleback Journal of Biology
Spring 2010