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.

Parasitic Kudoa inornata causes muscle deterioration in spotted seatrout

Sierra Duca, Goucher College

pic1

This summer I am working at the South Carolina Department of Natural Resources at Fort Johnson under the mentorship of Dr. McElroy and Dr. Isaure de Buron. Being part of an REU program, I am looking forward to gaining some research experience and learning more about career possibilities in the biological sciences. In terms of my research, I am researching the effects of a microscopic parasite, Kudoa inornata, on spotted sea trout (see image below).

Seatrout

Photo source: http://www.kayaking-north-america.com

There are many Kudoa species that infect host fish worldwide. Several of the Kudoa parasites have spores (known as myxospores; see image below) that proliferate inside of the muscle fibers of the host fish (Harrel et al. 1985). In some cases the  parasites wreak havoc on the quality of the meat after the fish dies. For example, infected fish may have unsightly cysts or decreased meat quality (Moran et al.), both of which are unappealing to consumers. Don’t worry, the majority of Kudoa infected fish are not directly harmful if consumed by humans; however, if the deterioration of the muscle tissue is accelerated, like any meat, the quality will decrease sooner as compared to uninfected fish. This process of muscle deterioration is what I am studying with K. inornata infected spotted seatrout. I am looking at the rates of this deterioration during various time frames, from 0 to 6 days after the fish dies, in order to discern if there is a relationship between parasite presence in spotted seatrout and muscle softness.  Ultimately, this research can be used to better understand the biology of K. inornata and to determine the best time frame to consume infected spotted seatrout.

picc     Individual spores of Kudoa inornata (Photo source: Dyková et al., 2009).

Literature Cited

Dyková I, de Buron I, Fiala I, Roumillat WA (2009) Kudoa inornata sp. n. (Myxosporea: Multivalvulida) from the skeletal muscles of Cynoscion nebulosus (Teleostei: Sciaenidae). Folia Parasitology 56: 91-98

Harrel LW, Scott TM (1985) Kudoa thyrsitis (Gilchrist) (Myxosporea: Multivalvulida) in Atlantic salmon, Salmo salar L. Journal of Fish Diseases 8: 329-332

Moran JDW, Whitaker DJ, Kent ML (1999) A review of the myxosporean genus Kudoa Meglitsch, 1947, and its impact on the international aquaculture industry and commercial fisheries. Aquaculture 172: 163-196

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.