February 15-18, 2009 Washington State Convention Center Seattle ...

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SUSCEPTIBILITY OF SPOTTED SEATROUT Cynoscion nebulosus AND RED SNAPPER
Lutjanus campechanus TO Amyloodinium ocellatum INFECTIONS
Ignacio Masson*, Jeffrey M. Lotz and Reginald B. Blaylock
Gulf Coast Research Laboratory
The University of Southern Mississippi
Ocean Springs, MS 39564 USA
ignacio.masson@usm.edu
Amyloodiniosis, a fish disease caused by the parasitic dinoflagellate Amyloodinium ocellatum, is one of the most devastating
diseases in warm water marine aquaculture. The life cycle of A. ocellatum consists of a parasitic trophont, a free-living, dividing
tomont and a free-swimming infective dinospore. Trophonts attach to the gills and skin, diminish the gills’ functional surface
area, damage the epithelium, and cause fish death. Different fish species have different susceptibilities to infection reflected in
dinospore infection rates (the proportion of dinospores that attach to the host in 24h and become trophonts), dinospore lethal
doses (the number of dinospores that results in host death), trophont lethal loads (the number of trophonts on a host after a
challenge with a lethal dinospore dose) and trophont detachment rates (the proportion of trophonts that detach from a host per
time unit after a single challenge with dinospores). In this study we compared the susceptibility of juvenile spotted seatrout
(16.36±0.82 g, mean±SE) and juvenile red snapper (17.15±2.04), two fish species with potential for culture in the Gulf of
Mexico, to A. ocellatum infections. The mean infection rates (24-h individual exposures in 3-l aquaria) for spotted seatrout and
red snapper were not significantly different (0.3552±0.0137 and 0.3414±0.0147 dinospores/d respectively, mean±SE; p>0.05).
However, there was a significant difference (p