Sunday, July 1, 2012

Thomas - Parasites and More Fun!

Thomas Stinson here to give you a brief overview of who I am and what I am doing here at Hatfield Marine Science Center (HMSC). I am a current student at Rogue Community College (RCC). Having completed my two years of pre-requisites I am preparing to transfer to OSU in the fall in pursuit of a degree in Fisheries and Wildlife Science. After completing the biology series at RCC I applied to the COSEE PRIME internship program to work with Dr. Kym Jacobson on parasites and their effects on juvenile salmon in the Pacific Ocean. Much to my delight I was accepted!

The study that I am working on with Dr. Jacobson focuses on one particular parasite that goes by the name of Nanaphyetus salmincola. Infection by this parasite has been proven to have negative effects on the health of Salmon and some mammals. One of the interesting facts about this parasite is that it is drawn to the posterior end of the kidney in the salmon, which is where we are studying it in this case. My part in this study (so far) is to examine that section of kidney of the collected Salmon which were captured in the estuary using a purse seine.
The posterior half of the kidney from the captured fish is preserved by freezing in whirlpak bags for later analysis. I thaw the specimens and analyze them for infection.

This is done by placing the kidney between two plates of glass and examining them under a 100X dissecting microscope. Identifying the metacercariae (encysted worms) can be difficult to distinguish from bubbles and other contaminants at first but with practice and good instruction I am getting pretty good.  Some of the specimens have no metacercariae, some have one or two. To date the most I have found on a single specimen is 1526. The below is a picture taken through the eye piece of the microscope zoomed in on one square cm. Inside each of the spheres is one worm.
 That’s it for now; I have plenty of samples to analyze and hopefully more exciting parasite news to come. 


  1. Parasites are pretty amazing organisms with fascinating life cycles. I did not know about Nanaphyetus. Is salmon the terminal host and is there an intermediate host? How do eggs or larvae get out of the salmon and make it to another host? I am looking forward to hearing more about this little critter!

  2. Salmon is not the definitive host, it is usually skunks and raccoons, some other mammals and birds. The intermediate host is a snail called Juga. The worm is not consumed by the snail or the fish, it burrows its way into the host. Inside of the snail it does asexual reproduction and the snail sheds many eggs. These eggs develop and eventually hatch. Salmon are infected while swimming in the same waters with the cercaria. Inside of the fish the worms encyst and await consumption by the definitive host. Inside the final host the trematode reproduce sexually and the eggs are released to start the process over again.