Mass mortality of hatchery-reared milkfish (Chanos chanos) and mangrove red snapper (Lutjanus argentimaculatus) caused by Amyloodinium ocellatum (Dinoflagellida)
Abstract
Outbreaks of heavy infestation by the parasitic dinoflagellate Amyloodinium ocellatum in hatchery-reared milkfish (Chanos chanos) and mangrove red snapper (Lutjanus argentimaculatus) caused 100% mortality events in hatcheries in the Philippines. Parasites were recorded on the body surface in 14-day-old milkfish fry and on both skin and gills in 2-month-old snapper. Trophonts of A. ocellatum caused local erosions of fish skin and degeneration of epithelial cells at the sites of the parasite's attachment to the body surface. Separation and hyperplasia of gill epithelium and fusion of secondary lamellae at the distal parts of the gill filaments were common. High pathogenicity of A. ocellatum to fish may be attributed to the severe alterations of the fish gills, the disruption of the host's skin, and feeding of trophonts on hosts' epithelial cells. In-vivo treatments of A. ocellatum-infested snapper with a 1 h freshwater bath and 200 ppm H2O2 showed promising results. This is the first report of A. ocellatum infestation in milkfish and mangrove red snapper in the Philippines.
Citation
Cruz-Lacierda, E. R., Maeno, Y., Pineda, A. J. T., & Matey, V. E. (2004). Mass mortality of hatchery-reared milkfish (Chanos chanos) and mangrove red snapper (Lutjanus argentimaculatus) caused by Amyloodinium ocellatum (Dinoflagellida).Publisher
ElsevierSubject
Acknowledgment/Sponsorship
This study was done under the Regional Fish Disease Project of Government of Japan-Trust Fund. We acknowledge Dr. Yasuo Inui and Dr. Kazuya Nagasawa for technical guidance, Albert Gaitan and Angelo Marte of Aquaspec Hatchery and Marietta Duray and Jhozine Damaso of SEAFDEC Fish Hatchery for providing the fish samples, the Microtechnique Service Laboratory of SEAFDEC Aquaculture Department for assistance in histological processing of the samples, and Dr. Evelyn de Jesus for editing an earlier draft of the paper.
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Conference paper
Research on marine and freshwater fishes
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Article
Sensitivity of fertilized milkfish (Chanos chanos Forsskal) eggs to mechanical shock and simulated transport
-Aquaculture , 1998 - ElsevierNaturally-spawned milkfish eggs are routinely subjected to physical manipulation during collection and transport. To avoid unnecessary mortalities, sensitivity of milkfish eggs to mechanical shock was determined at different times after fertilization. Shock sensitivity was assessed in terms of egg mortality within 8 h after a free fall over calibrated heights. The LD50 and LD10 (drop height resulting in 50% and 10% mortality) were estimated for 11 stages of embryonic development. The corresponding force (F) imparted to eggs on impact after a free fall was also computed. LD10 estimates (cm) and their corresponding F (erg per egg) showed that shock sensitivity of milkfish eggs was high during cleavage until the early segmentation stage, rapidly declined as segmentation proceeded until the head and tail started to separate from the yolk, but returned to high levels when the embryo begun twitching and the heart beating until near-hatching. To determine the sublethal effects of mechanical shock, C-shaped embryos were subjected to a free fall over varying heights and transported to a hatchery for further incubation and hatching. The effects of varying periods of simulated transport (mobile or stationary periods) were also examined. At C-shaped embryo stage, neither mechanical shock (F, 13–127 erg per egg) nor prolonged shaking (3–9 h) simulating mobile periods of egg transport affected hatching rate, larval mortality, and incidence of deformed larvae. Exposure to still water (unshaken) simulating stationary periods of egg transport, however, tended to lower hatching rate and significantly increased the incidence of deformed larvae and the combined mortalities and deformed larvae. These results indicate that the sensitivity of milkfish eggs to mechanical shock varies during incubation and that C-shaped embryos may be manipulated or transported with minimum risk of injury. Some recommendations are given regarding proper handling and transport of fertilized eggs.
