Blood Glucose Levels in Crickets
Abstract: The experiment was conducted to determine the blood glucose levels in male and female house crickets. A solution of o-dianisdine that contained the enzymes glucose oxidase and peroxidase was combined with the hemolymph samples. The color change was quantified using a spectrophotometer and compared to a standard containing a known amount of glucose. Glucose levels were not significantly different from males and females (p=50%-70%). Glucose level in male house crickets was 89.508 mg/dl and was 79.144 mg/dl in female house crickets.
Insects have a high level of carbohydrates in their hemolymph compared to vertebrae species. Carbohydrates are extremely important to insects because it gives them their energy needed to survive and are a major exoskeleton component. Some carbohydrates that can be found in hemolymph include trehalose, hexosmaines, various sugars, glycogen, and glucoronic acid. (Mullins, 1985).
Blood sugar levels vary in many insect species. In unfed parasitoid wasps, glucose levels are higher in males than in females. Even in some non-insect species levels vary between species, this can be seen in the shrimp Palaemonetes argentiuns (Kaisa, 2010). Glucose is found in larger amounts in female insects than in male insects. In male and female cockroaches females reportedly had more trehalose and more glucose than males. The males had 28.56 mM/l of glucose and the females had 38.89 mM/l glucose. In regards to trehalose the female cockroaches had 24.45 mM/l and the males had approximately 19.03 mM/l (Bedford, 1977).
Although there have been many studies on the blood sugar levels in hemolymph of various insects, none have tested common house crickets. The purpose of this study was to find the blood glucose level in crickets and to determine if there was a difference between the males and females. We tested the null hypothesis that there was no difference between the blood sugar levels in male and female house crickets.
METHODS AND MATERIALS
We first obtained hemolymph samples from both male and female house crickets. We then transferred 50 μL of each sample in to two different cuvettes. After, 0.5mL of o-dianisidine-enzyme solution was added to each cuvette. A blank was then prepared by adding 50μL of PBS to a cuvette and then 0.5 mL of o-dianisidine-enzyme solution was added. Next, the cuvettes were incubated for 30 minutes at 37°C. Once incubation was complete, the glucose levels were determined using a spectrophotometer with the wave length set a 450 nm. A chi-square median test was used to test for differences in glucose levels between the sexes.
The blood glucose level in female house crickets was 89.508 mg/dL and 79.144 mg/dL in male house crickets (Table 1). The chi-square median test showed the difference in glucose levels between the sexes was 0.133. There was no significant difference between male and female house crickets (p=50%-75%).
Although female house crickets had a higher blood glucose level than males, there was no significant difference. Our results did not agree with previous findings. In the experiment run by Bedford, female insects had high glucose levels than male insects (Bedford, 1977). A reason our glucose levels did not vary significantly would be that we only ran one test. If we ran multiple tests with different crickets we could have come up with a better blood glucose level average.
There were several weaknesses in the experiment. The average blood glucose levels were determined from multiple lab groups. Each lab group could have set up the experiment differently, rounded their numbers, or did a poor job at running the experiment. If this experiment was done by a professional, with multiple trials, the data could possibly be much more accurate. Also, glucose levels could depend on the age, activity, health, and genes of each cricket. Different crickets were used for each group, with no known information about them (besides their gender). To obtain better results, we could have closely observed and created our own group of crickets who were fed the same food, received the same amount of sunlight, and were bred from the same family line.
One possible future study might be to determine how much being in a certain environment (higher temperature, low food supply, limited space, etc) affects the blood glucose level in male and female house crickets. Another future study might be to determine if female glucose levels are higher because of their reproductive organs or how many offspring they have had.
Bedford, J. 1977. The carbohydrate levels of insect haemolymph. Comparative Biochemistry and Physiology 57A:83-86.
Kaisa, T.R. 2010. Biology 106 laboratory manual. Hayden-McNeil, Publishing, Inc., Plymouth, MI.
Mullins, D.E. 1985. Chemistry and physiology of the hemolymph. Pp. 355-400 in G.A. Kerkut and L.I. Gilbert, eds. Comprehensive Insect Physiology, Biochemistry and Pharmacology, vol 3. Oxford: Pergamon Press.
Table 1. Blood glucose levels in female and male house crickets.
Blood Glucose Level (mg/dL)