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Lymphoreticular Histology and Innate Immunity on Cultured Black Sea Bass

PIs: Randal L. Walker (UGA Marine Extension Service), Kenneth Latimer, and Donald Evans (College of Veterinary Medicine, Univ of Georgia, Athens, GA, USA)

Support: Sea Grant College Program (R/FS-6-A)

Timeframe: 3/01 - 2/03 (complete)

Project Overview.  The objective of this project was to determine the parasitic fauna and seasonality of parasites for the commercially important black sea bass from offshore Georgia stocks. By determining the seasonality and parasite fauna, live pot-trapped fish to be used for black sea bass aquaculture can be treated to kill external parasites prior to stocking them in land-based grow out ponds or tanks.

Accomplishments and Findings:
Field sampling has been completed. Parasites from external samples, gills, internal organs, and meat have been sorted and counted. Nine parasite species (two internal and seven external) have been collected: one nematode, one trematode, 3 copepods, one branchiura and three unknowns.

The greatest incidence of natural disease appears to occur in groups of fish that resided in relatively shallow water during the warmer months of the year; however, the incidence of disease is very low based upon histological examinations. The primary diseases observed included gill necrosis with copepods, intestinal trematodiasis, metacercariae within mesenteric fat, and multifocal gastric granulomas that were devoid of organisms. Processed and mounted intact gill copepods and intestinal flukes indicate that these organisms apparently are unique. They differ morphologically from any previously described species of copepods and trematodes, respectively. Further study of these organisms will be necessary for their proper taxonomy and to investigate their life cycles. In general, the black sea bass that were trapped for this investigation were generally healthy, robust fish.

Putative nonspecific cytotoxic cells were purified from single cell suspensions of spleen and anterior kidney and were identified readily in immunostained sections of the same tissue types. A lower percentage of nonspecific cytotoxic cells cells was detected by immunohistochemistry as compared to flow cytometry. Formalin fixation and tissue processing for immunohistochemistry are more harsh than
for flow cytometry and tend to mask membrane antigens via protein cross-linking. However, nonspecific cytotoxic cells can still be evaluated by immunohistochemistry. This immunohistochemical staining technique was found to be applicable to other species of fishes as well.

Tooke, L., M. Rawson, R.L. Walker, and K. Latimer. A Survey of Parasites of the Black Sea Bass, Centropristis striatus. In preparation.

Leslie (Tooke) Hardy, MS Thesis. Parasites of Black Sea Bass (Centropristis striata).

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This page was updated October 13, 2006