Crikey! What’s in the Water?

Julianna Duran, Virginia Tech

1B7047D7-DD01-4D65-B081-9D809AC07271The Problem: South Africa is home to some of the most extraordinary wildlife and culture. This diverse ecotourism plays a major role in their economy and conservation efforts.

Crocodile

Nile Crocodile (Photo credit: Darren Poke)

The Olifants River System in the Mpumalanga Province is a large source of water that provides a habitat for several species. Over the last 30 years in this region, there have been dramatic declines of Nile Crocodile (Crocodylus niloticus), fish, and waterfowl.

The cause of this is a disease called Pansteatitis. It is hypothesized that contaminants from coal mining and agriculture contributed to the emergence of the disease. Invasive species and the stagnant water may also be enhancing the intensity of its effects.

Pansteatitis is an inflammatory disease that affects the lipids, or fats, of an animal. The fats become tough which cause pain and a reduction in mobility that can make the species easier prey or unable to hunt for food.

Mozambique Tilapia (Oreochromis mossambicus) have been frequently diagnosed with pansteatitis and maintain a large population size. These characteristics make them a perfect model organism to use for researching pansteatitis – which is why they were selected for my project. I will be analyzing muscle tissue samples of these fish to compare the fatty acid profiles between healthy and diseased specimen; infected Nile Crocodile muscle will also be key in understanding how pansteatitis affects different organisms.

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Mozambique Tilapia – Photo taken from John Snow

It is important that we study Mozambique Tilapia to influence management efforts for top predators like Nile Crocodile, whose presence and actions impact the food web. In addition, tilapia and other fish are harvested and I want to ensure that any diseased fish caught are safe to eat. Although there have been no studies that have found whether or not this disease can directly affect humans, I hope that my study can give us an indication of the indirect human health risks.

Research Questions

  1. What is the difference in Fatty Acid Profiles between healthy and diseased Mozambique Tilapia?
  2. What is the difference between diseased Mozambique Tilapia and Nile Crocodile?
  3. What lipids are most affected by Pansteatitis?

This Summer, I will be investigating these questions and reporting back my findings. To find more information on the topics check out these links:

Blood Chemistry of Pansteatitis-Affected Tilapia

Life History of Mozambique Tilapia

Life History of Nile Crocodile


Supported by the Fort Johnson REU Program (NSF DBI-1757899), Dr. Mike Napolitano, Dr. John Bowden, The College of Charleston, NOAA, and NIST. 


References:

Bowden, J., Cantu, T., Chapman, R., Somerville, S., Guillette, M., Botha, H., Hoffman, A., Luus-Powell, W., Smit, W., Lebepe, J., Myburgh, J., Govender, D., Tucker, J., Boggs, A. and Guillette, L. (2016). Predictive Blood Chemistry Parameters for Pansteatitis-Affected Mozambique Tilapia (Oreochromis mossambicus). PLOS ONE, 11(4), p.e0153874.

Poke, D. 5 Interesting Facts About Nile Crocodiles. https://haydensanimalfacts.com/2015/03/04/5-interesting-facts-about-nile-crocodiles/ (accessed Jun 27, 2019).

Snow, J. Mozambique Tilapia. https://www.mexican-fish.com/mozambique-tilapia/ (accessed Jun 17, 2019).

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.