Hook, Line and Sinker

Sierra Duca, Goucher College

Spotted seatrout, Cynoscion nebulosus, are important recreational fish that range from the Atlantic coast to the Gulf of Mexico. They are also good indicators of environmental changes in estuarine habitats since all of their life stages are found in estuaries1. To reiterate, I am studying muscle softness in spotted seatrout induced by the parasite Kudoa inornata. Several Kudoa species are notorious for causing this muscle softening, which makes the meat of the fish go bad faster than in uninfected fish2. This is an issue with fish that are consumed by people, such as the commercially important farmed Atlantic salmon2. seatrout for blogg

Fig 1. Spotted seatrout that were caught via trammel netting (PC: Sierra Duca).

First of all, to study this I need fish. While the mode of infection of Kudoa parasites is not well understood, it is presumed that wild spotted seatrout have a higher rate of infection of Kudoa inornata; therefore, I needed some wild spotted seatrout. In addition to the traditional hook and line approach of fishing for spotted seatrout, I was able to join a group at the South Carolina Department of Natural Resources (SCDNR) as they went trammel netting. In comparison to other nets, trammel nets have three layers of netting that vary in size in order to catch fish of various sizes. trammel net for blog

Fig 2. This illustration depicts the basic function and structure of a trammel net. A similar such device is used by the SCDNR to catalogue fish in specific sites over time in order to study the changing population dynamics of various fish species.

Once I have the fish I fillet, refrigerate, and take muscle biopsies at time points between 0-6 days, which is the most likely time that the fish would be consumed. I test the firmness of these muscle biopsies, as well as the parasite density. What I am trying to accomplish is to establish whether or not there is a link between parasite density and accelerated muscle softness (which causes the meat to go bad faster in infected fish), and if the rate of muscle softening changes over the course of 6 days. Ultimately the project will help increase our understanding of the effects of Kudoa inornata on the muscle of spotted seatrout. plasmodia for blog

Fig 3. This image (under 100x magnification) displays a plasmodium structure that contains a cluster of spores (known as myxospores) of Kudoa inornata in the muscle tissue of spotted seatrout. One way that I quantify parasite density is by looking at the average area of plasmodia. I can do this because generally larger plasmodia are found in the more infected fish  (PC: Sierra Duca).

Literature Cited 1Bortone SA (ed) 2003: Biology of the Spotted Seatrout. CRC Press. Boca Raton, FL, 328 pp 2Henning SS, Hoffman LC, Manley M (2013) A review of Kudoa-induced myoliquefaction of marine fish species in South Africa and other countries. S Afr J Sci. 109: 1-5

Photo Source (Fig 2): http://thewikibible.pbworks.com/w/page/22174694/Fishing%20in%20the %2Bible%20and%20the%20Ancient%20Near%20East

Acknowledgments The Fort Johnson REU Program is funded by the National Science Foundation. This research is made possible through the mentorship of Dr. Eric McElroy and Dr. Isaure de Buron.  In addition, I would like to thank the College of Charleston and the South Carolina Department of Natural Resources for providing the help and facilities necessary for my project.

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Shrimp kabob, shrimp gumbo…shrimp sickness?

 

Alessandra Jimenez, Whitworth University

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Are you a fan of shrimp? You’re not the only one – billions of people around the world depend on shrimp fisheries and aquaculture for this wonderful source of food. Other predators in the sea rely on shrimp for their daily meals. Here’s the catch: shrimp may not last long enough to make it to your plate. Like us and other animals, crustaceans in general have to deal with so many obstacles that threaten their survival. One obstacle that is not often thought about is bacterial infection. Did you know that seawater is literally teeming with hundreds of millions of bacteria? The only way a shrimp can make it is by using its immune response – the “quick, potent, and effective” way of defending against a huge, microscopic army! Sounds like the perfect shield, right?

shrimp food

Shrimp is a common food source for many people. @Leslie Fink

Turns out that, like everything else in the science world, immunity comes at a big cost. It has been recently discovered that the immune response in crabs and shrimp against bacteria actually has a bad side effect: metabolic depression. In fact, the way the shrimp gets rid of bacteria in its bloodstream is by moving the bacteria to the gills, where it gets lodged and stays there for quite some time. The consequence? The lodged bacteria block blood flow through the gills, and the shrimp can’t get enough oxygen from the water. (Want to learn more? Click here)

Ouch, talk about a double whammy – fighting sickness plus oxygen blockage. One basic question comes to mind: can the shrimp still do what it needs to do while under such metabolic stress? This is where I come in. This summer, I am working under Dr. Karen Burnett in Hollings Marine Laboratory as an intern through the Research Experience for Undergraduates (REU) program in marine biology. We will be testing whether or not a shrimp’s immune response to a common bacteria affects its ability to perform daily activities. The activity of interest is called ‘tail-flipping’ (fancy name: caridoid escape reaction. Want to learn more? Click here)This really fast, reflex-like action needs to be in top shape for the shrimp to survive from predator attacks and to help it during feeding time.

Caridoid_escape_reaction

Also known as the ‘tail-flip’ reaction, this response is a shrimp’s primary means of escape. @Uwe Kils

The shrimp species of interest is Farfantepenaeus aztecus, or ‘Atlantic brown shrimp’. This fella is a familiar catch for fishermen throughout the Southeastern US and the Gulf of Mexico. This is the first time that a study like this is going to be done on a wild shrimp species in general, let alone this specific type!

Penaeus aztecus

Farfantepenaeus aztecus, aka ‘Atlantic brown shrimp’. @Virginia Living Museum

So, can an immune response impact tail-flipping in wild shrimp? If ‘yes’, would the potentially handicapped shrimp be able to survive in its natural environment? We will soon find out!

Happy shrimping!

Alessandra Jimenez

REFERENCES:

Burnett, L. E., Holman, J. D., Jorgensen, D. D., Ikerd, J. L., & Burnett, K. G. (2006). Immune defense reduces respiratory fitness in Callinectes sapidus, the Atlantic blue crab. Biological Bulletin, 211(1), 50-57.

Fuhrman, J. A. (1999). Marine viruses and their biogeochemical and ecological effects. Nature, 399(6736), 541-548.

Latournerie, J.R., Gonzalez-Mora, I.D., Gomez-Aguirre, S.G., Estrada-Ortega, A.R., & Soto, L.A. (2011).                   Salinity, temperature, and seasonality effects on the metabolic rate of the brown shrimp Farfantepenaeus Aztecus (Ives, 1891) (Decapoda, Penaeidae) from the coastal Gulf of Mexico.Crustaceana 84(12-13), 1547-1560. doi: 10.1163/156854011X605738

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.

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