AB 11:201-211 (2011)  -  doi:10.3354/ab00295

Clearance effects of the Pacific oyster Crassostrea gigas on the fish-killing algae Chattonella marina and Chattonella antiqua

Sou Nagasoe1,2, Kengo Suzuki1, Tatsuya Yurimoto1,3, Reiko Fuseya1,6, Tsuyoshi Fukao1, Toshifumi Yamatogi4,5, Katsunori Kimoto1, Yukio Maeno1,3,*

1Seikai National Fisheries Research Institute, Fisheries Research Agency, Nagasaki, Nagasaki 851-2213, Japan
2National Center for Stock Enhancement, Fisheries Research Agency, Miyazu Station, Miyazu, Kyoto 626-0052, Japan
3Japan International Research Center for Agricultural Sciences, Tsukuba, Ibaraki 305-8686, Japan
4Nagasaki Prefectural Institute of Fisheries, Nagasaki, Nagasaki 851-2213, Japan
5Nagasaki Prefectural Tsushima District Office, Fisheries Division, Tsushima, Nagasaki 817-8520, Japan
6Present address: National Research Institute of Fisheries Engineering, Fisheries Research Agency, Kamisu, Ibaraki 314-0408, Japan

ABSTRACT: We exposed Pacific oysters Crassostrea gigas to the harmful algal species, Chattonella marina and C. antiqua, at various initial algal cell densities for up to 24 h. None of the oysters died, even after exposure to high cell densities of both Chattonella species. Oysters filtered Chattonella from the aquarium water within 24 h, depending on initial algal cell densities. The oyster clearance rates peaked at a specific cell density for each algal species (about 100 cells ml–1 for C. marina and about 10 cells ml–1 for C. antiqua). However, because of differences in cell sizes between the algal species, the algal biovolume per unit water volume varied widely at the same cell density. The relationships between clearance rates and biovolumes of exposed algae were similar between the 2 algal species; clearance rates by the oysters peaked at about 1.0 × 106 µm3 mm–3. The filtration activity of the oysters was fundamentally affected by their exposure to algal biovolume and not algal cell density. No histological lesions were found after the oysters were exposed to either Chattonella species. Furthermore, immunohistological observations of the digestive glands of the oysters and analysis of their phytopigment content revealed that Chattonella cells that were cleared from the water during exposure entered the cytoplasm of the oyster digestive glands by phagocytosis.

KEY WORDS: Clearance rate · Raphidophyte · Harmful algae · Chattonella spp.

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Cite this article as: Nagasoe S, Suzuki K, Yurimoto T, Fuseya R and others (2011) Clearance effects of the Pacific oyster Crassostrea gigas on the fish-killing algae Chattonella marina and Chattonella antiqua. Aquat Biol 11:201-211

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