To Gain an Understanding – Krista Soderlund

June, 2014 –The Honors Experiential Scholarship has contributed to my research concerning Ceratomyxa shasta spore prevalence in post-spawned adult Chinook salmon. This term was a continuation of research that was initiated at the beginning of this year; I primarily took samples from intestinal epithelial tissue of salmon and did spore counts for the first two terms, and focused on reading literature regarding C. shasta and the salmon life cycle this term (as a basis for my senior thesis), in addition to taking more counts from samples that had inconclusive results from last term. The method for taking spore counts is highlighted below:

“There were four samples that were looked at for each fish that included To anterior, To posterior , T7 anterior, T7 posterior . The To or T7 indicates whether the sample was from an intestinal piece that was preserved immediately after the fish died or whether it was frozen a week (7 days) following the death of the fish. The anterior and posterior labels indicate what section of the intestine the sample was from: the front or the back. Samples were viewed under a microscope at a magnification of 20x to look for the C. shasta spores using a hemocytometer.”

The length of the intestinal piece and the number of spores found were compared in a statistical ratio to find a value of spore prevalence that could then be compared to other samples using a p-value (null hypothesis test) and a q-value (false discovery rate). The false discovery rate is a stricter means of determining whether there is a statistical significance in the data; there were more fish that demonstrated an increase in spore prevalence a week after dying compared to immediately after death using the null hypothesis value than when compared with a false discovery rate but it is better to use both values because a q-value holds a lot of weight, even if the results are fairly accurate using a null hypothesis test. There were some salmon that had inconclusive results last term, and more numbers were taken this term. Here are the spore count numbers for those fish so far (the first four numbers were the original counts, the last two for every sample were done this term):

Figure 1:

Fish 1: AT0 0 0 0 0 1 3
Fish 1: AT7 1 5 3 3 0 7
Fish 1: PT0 0 0 5 1 0 1
Fish 1: PT7 3 3 5 4 7 2
Fish 13: AT0 2 4 6 4 5 2
Fish 13: AT7 3 7 5 9 5 4
Fish 13: PT0 6 3 4 2 5 3
Fish 13: PT7 35 25 33 39 19 31

 

A null hypothesis test needs to be conducted for these fish again to determine whether the results were significant. More numbers could also be recorded to give a more accurate value before a p- value or q-value is determined again. However, by simply looking at the numbers we can see a surprisingly high increase in spores in the Posterior T7 numbers for Fish #13. Initially I thought there may have been an error on this sample but indeed it was clear in the recount that the high numbers continued in that sample for Fish #13.

This is an image of a spore taken this term under 20x magnification. It has a kidney bean shape and is binucleated, so under higher magnification you can often determine that it is a spore by the shape of multiple circles within the shape of the object.

Figure 2:KristaFigure2

It will be interesting to conduct statistical measurements on the fish that had more samples counted to see what the results are. While it definitely seems like there is a noticeable difference in the spores, having a more precise comparison will be very helpful.

Additionally, this term I began literary research to gain knowledge in describing the life cycle of Chinook salmon and the current situation with their health in the Willamette River Valley. Maintaining the health of Chinook salmon populations is crucial in the Pacific Northwest, and research recently conducted by Kent et al (2011) has illustrated that a significant portion of the King salmon population is suffering from pre-spawning mortality. Factors that contribute to pre-spawning mortality include “stress, disease loads, poor energetic condition and exposure to stressful water temperatures” as noted by Kent et al (2011). High water temperature is an extremely detrimental multi-faceted component to the health of the salmon (Shreck et al, 1994) as it not only directly impacts the fish but also creates an environment that is more conducive to parasite exposure, especially the actinospore stages of Ceratomyxa shasta (Bartholomew et al. 2013).

Keeping this in mind while reviewing spore counts puts the research into perspective and serves as a reminder of why we are doing this: to gain an understanding of a parasite and how it affects a species that is very important to us. Having this research funded by the Experience Scholarship has taken a huge financial burden off me and made it possible for me to simultaneously put my best effort into my academic endeavors and continue research!

 


 

References:

Bartholomew, J., & Ray, R. (2013). Estimation of transmission dynamics of the Ceratomyxa shasta actinospore to the salmonid host. Cambridge University Press 140, 907-916.doi: 10.1017/S0031182013000127

Kent et al. (2011). Continuing Research Proposal.

Shreck, C., Snelling, J., Ewing, R., Bradford, C., Davis, L., & Slater, C. (1994). Migratory behavior of adult spring Chinook salmon in the Willamette river and its tributaries. Oregon Cooperative Fishery Research Unit, Oregon State University, Corvallis, OR.

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