MEPS 446:107-118 (2012)  -  DOI: https://doi.org/10.3354/meps09476

Allelopathy of the raphidophyte Heterosigma akashiwo against the dinoflagellate Akashiwo sanguinea is mediated via allelochemicals and cell contact

Xuchun Qiu1, Yasuhiro Yamasaki2, Yohei Shimasaki1,*, Hiroaki Gunjikake1, Masato Honda1, Mayumi Kawaguchi1, Tadashi Matsubara3, Sou Nagasoe4, Takuya Etoh5, Shigeaki Matsui5, Tsuneo Honjo6, Yuji Oshima1

1Laboratory of Marine Environmental Science, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
2National Fisheries University, 2-7-1 Nagata-Honmachi, Shimonoseki 759-6595, Japan
3Saga Prefectural Ariake Fisheries Research and Development Center, 2753-2 Nagata, Ashikari-cho, Ogi, Saga 849-0313, Japan
4Miyazu Station, National Center for Stock Enhancement, Fisheries Research Agency, 1721 Oda Shukuno, Miyazu, Kyoto 626-0052, Japan
5Fukuoka Fisheries and Marine Technology Research Center, 1141-1 Imazu, Nishi-ku, Fukuoka 819-0165, Japan
6Seto Inland Sea Regional Research Center, Kagawa University, Saiwaichou 1-1, Takamatsu, Kagawa 760-8521, Japan

ABSTRACT: Growth interactions between the raphidophyte Heterosigma akashiwo and the dinoflagellate Akashiwo sanguinea were examined by using bi-algal culture experiments under axenic conditions. There was a lethal effect of H. akashiwo (initial cell density: 1 × 102 or 1 × 104 cells ml−1) on A. sanguinea at an initial cell density of 1 × 102 cells ml−1. Growth of both species was suppressed concurrently when initial cell densities of H. akashiwo and A. sanguinea were 1 × 102 and 2 × 103 cells ml−1, respectively. A mathematical model was used to simulate growth and interactions in bi-algal cultures. The model predicted that H. akashiwo would outcompete A. sanguinea over time. A cell-free enriched filtrate prepared from dense culture of H. akashiwo reduced both maximum growth rate and maximum yield of A. sanguinea. A filtrate of A. sanguinea prepared in the same manner only reduced maximum yield of H. akashiwo but did not affect its maximum growth rate. Growth of A. sanguinea in bi-algal cultures under contact conditions was significantly lower than that in mono-algal culture and in bi-algal cultures under non-contact conditions. Morphologically abnormal A. sanguinea cells occurred at high frequency only when A. sanguinea was cultured together with H. akashiwo under direct cell contact condition. Moreover, growth inhibition and formation of morphologically abnormal cells of A. sanguinea were induced in a concentration-dependent manner by allelochemicals (including allelochemical polysaccharide−protein complexes) produced by H. akashiwo. These results suggest that growth inhibition effects, via allelochemicals and direct cell contact by Heterosigma akashiwo, influence bloom formation of Akashiwo sanguinea in the field.


KEY WORDS: Heterosigma akashiwo · Akashiwo sanguinea · Allelopathy · Polysaccharide−protein complex · Cell contact · Growth interaction · Growth simulation


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Cite this article as: Qiu X, Yamasaki Y, Shimasaki Y, Gunjikake H and others (2012) Allelopathy of the raphidophyte Heterosigma akashiwo against the dinoflagellate Akashiwo sanguinea is mediated via allelochemicals and cell contact. Mar Ecol Prog Ser 446:107-118. https://doi.org/10.3354/meps09476

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