Alessandra Jimenez, Whitworth University
Have you ever wondered what it’s like to be a lab researcher who works with live animals? Through this internship, I am experiencing this firsthand in Hollings Marine Laboratory, along with all the responsibilities involved!
A normal workday in the life of a “shrimp intern” is like this: A big part of it is animal care and maintenance. It starts in the morning with a daily visit to the wet lab, where approximately 80 brown shrimp juveniles are kept in four large tanks with circulating water. After feeding them a round of commercial shrimp pellets, I test the salinity of the water in each tank using a refractometer to make sure that each tank has a certain salinity value: 30 parts per thousand, to be exact. I use dechlorinated freshwater and seawater to adjust this value if needed. Besides salinity, I also need to watch out for harmful levels of ammonia (it’s a part of shrimp waste!), nitrates, etc. In usual circumstances, I conduct a water change (replacing old water with new) once a week in order to dilute these chemicals. For the past couple of weeks, however, I have been conducting water changes daily in order to keep ammonia levels neutral in three tanks. Ah, the life of a caretaker of tons of baby shrimp!
Besides animal husbandry, I work on my experiment involving the effects of injection of bacteria on tail flipping (Want to learn more about what I’m doing? click here). I have two shrimp at a time in separate, well-aerated tanks, and they are both from the same treatment group. Shrimp are randomly assigned to one of four treatment groups. These treatment groups are designated according to the treatment type (injection of bacteria or saline) and according to the amount of time between the moment of injection and the tail-flipping procedure (4 or 24 hours). I randomly select two shrimps from the wet lab, weigh them, and keep them in the two experimental tanks overnight so they can get used to the new environment, temperature, etc. The next day, I take each shrimp out of the tank momentarily and quickly inject them with bacteria, or a saline buffer if they are part of the control group. Then, I give them 4 or 24 hours (depending on group type) to rest before conducting the actual tail-flipping experiment. Using a stir-rod (basically, a straight stick), I poke the shrimp lightly to induce tail-flipping, and count how many flips they perform before fatigue. The number of flips here is called ‘initial activity’. Then, I give them 20 minutes to recover in the tank before tail-flipping them again. The number of flips this time is called ‘recovery activity’.
Why tail-flip them twice? Well, we hypothesize that recovery activity will be impaired in bacteria-injected shrimp versus the controls, while initial activity would probably not be. This is based on how recovery from tail-flipping activities involves aerobic (or oxygen-fueled) metabolism. Since bacteria accumulate in the gills of shrimp and block oxygen uptake (want to learn more? click here), it would make sense that recovery activity would be reduced. Stay tuned for results later on!
Gruschczyk, B., Kamp, G., 1990. The shift from glycogenolysis to glycogen resynthesis after escape swimming: studies on the abdominal muscle of the shrimp, Crangon crangon. J Comp Physiol B, 753-760.
Scholnick, D. A., Burnett, K. G., & Burnett, L. E. (2006). Impact of exposure to bacteria on metabolism in the penaeid shrimp Litopenaeus vannamei. Biological Bulletin, 211(1), 44-49.
Many thanks to College of Charleston for hosting my project, Dr. Karen Burnett and Hollings Marine Laboratory for guidance and work space, and NSF for funding the REU program.