Successful cultivation of the toxic dinoflagellate Dinophysis caudata (Dinophyceae)

Abstract

IntroductionIn the dinoflagellate genus Dinophysis, some species are known to cause diarrhetic shellfish poisoning (DSP). The physiological and ecological characteristics of this genus are not yet fully understood due to difficulties in culturing the organisms.Dinophysis caudata Saville-Kent is one of the toxic species that causes DSP. Okadaic acid (OA) and dinophysistoxin-1 (DTX1) were detected from D. caudata cells (Ͻ76.3 pg cell Ϫ1 of OA and DTX1 in total) in Sapian Bay, the Philippines (Marasigan et al. 2001). This species is widely distributed in tropical and temperate waters and can appear abundantly in coastal waters, with a red tide of this species associated with mass mortalities of fish being reported in the Seto Inland Sea, Japan (Okaichi 1967). Holmes et al. (1999) reported that D. caudata was the main species causing DSP in green mussels in Singapore. Thus, D. caudata might be one of the main causative species of DSP in the future, especially in tropical regions. The establishment of cultures is crucial to study the physiology and toxicology of this species. Recently, Park et al. (2006) succeeded in cultivating Dinophysis acuminata Claparède et Lachmann at high cell densities (Ͼ11,000 cell mL Ϫ1 ) and maintained them for a long period (Ͼ6 months) by feeding the ciliate Myrionecta rubra (Lohmann 1908) grown with a cryptophyte Teleaulax sp. In this report, we followed their experimental design, and succeeded in cultivating D. caudata. We report here the conditions necessary for cultivation of D. caudata and describe their feeding strategy. Materials and MethodsThe marine ciliate Myrionecta rubra and the cryptophyte Teleaulax amphioxeia (Conrad) Hill were isolated from Inokushi Bay (131°53ЈE, 34°47ЈN) at the end of February 2007 in Oita Prefecture, Japan. Myrionecta rubra and T. amphioxeia were identified by their morphology and sequence data from the nuclear small subunit rDNA. The sequences are deposited in GenBank under accession num- (2006) succeeded in cultivating the toxic dinoflagellate Dinophysis acuminata and maintaining them by feeding the ciliate Myrionecta rubra grown with a cryptophyte Teleaulax sp. After this report, the present study is the second report of propagation of a Dinophysis species (Dinophysis caudata) under laboratory conditions and describes the maintenance of several clonal strains kept at high abundance (Ͼ5,000 cells mL Ϫ1) for a relatively long period (Ͼ4 months) when fed on M. rubra with the addition of Teleaulax amphioxeia. We confirmed that D. caudata swam actively around its ciliate prey and inserted its peduncle (feeding tube) into the ciliate. Thereafter, the prey became immobile and rounded. Dinophysis caudata actively ingested the cytoplasm of the prey through the peduncle. Dinophysis caudata grew at a growth rate of 1.03 divisions day Ϫ1 when supplied with M. rubra as prey, reaching a maximum concentration of ca. 5,000 cell well Ϫ1 (810 mL) during a 9 day growth experiment. In contrast, a culture of D. caudata was not able to be established in the absence of the...

Successful cultivation of the toxic dinoflagellate Dinophysis tripos (Dinophyceae)

“…1). Dinophysis tripos swam around the prey and inserted its peduncle, which extends from around the flagellar pore region, into the cell of M. rubra, as has been previously reported for D. rotundata Claparède & Lachmann (Hansen 1991), D. acuminata (Park et al 2006), D. caudata (Nishitani et al 2008a) and D. fortii (Nagai et al 2008). Soon after D. tripos inserted its peduncle into the cell of M. rubra, the ciliate became immobile and its cilia were shed from the cell within 1-5 minutes.…”

“…This species can also be confused with D. caudata; some cells of D. caudata (see fig. 3B in Nishitani et al 2008a), bearing a short hypothecal process, can superficially resemble D. tripos. However, D. tripos can be fundamentally distinguished by the presence of two posterior projections (Larsen & Moestrup 1992, Steidinger & Tangen 1996.…”

“…Myrionecta rubra (a clonal strain MR-INO01) and Teleaulax amphioxeia (a clonal strain TA-INO01) were isolated from Inokushi Bay in Oita Prefecture, Japan (131°89′E, 32°79′N) at the end of February 2007 (Nagai et al 2008, Nishitani et al 2008a, and other clonal strains of both species (Meso-A4 and Tel-D5, respectively) were isolated from Matsushima Bay, Miyagi Prefecture, Japan (141°2.7′E, 38°19.5′N) in 2006. The M. rubra culture was maintained by mixing 50 mL of the culture (7.0-9.0 10 3 cells mL 1 ) with 100 mL of a modified f/2 medium (Guillard 1975, Nagai et al 2004, with the addition of 25-100 μL of T. amphioxeia culture (containing 0.5-2.0 10 4 cells) as a food source.…”

“…fortii Pavillard, 1923/D. infundibulus Schiller, requiring the ciliate M. rubra grown on Teleaulax/Geminigera as prey for their propagation (Park et al 2006, Kim et al 2008, Nagai et al 2008, Nishitani et al 2008a, b, Kamiyama & Suzuki 2009, Hackett et al 2009, Riisgaard & Hansen 2009, Kamiyama et al 2010.…”

Morphological Transition in Kleptochloroplasts after Ingestion in the Dinoflagellates Amphidinium poecilochroum and Gymnodinium aeruginosum (Dinophyceae)

“…are known to obtain kleptochloroplasts by myzocytosis from Mesodinium rubrum that in turn possesses kleptochloroplasts derived from the cryptomonad genus Teleaulax Nishitani et al 2008;Park et al 2006). Dinophysis fortii, heavily fed on M. rubrum, possesses solitary kleptochloroplasts (= restricted to chloroplasts only) and several food vacuoles that contain membrane-like and mitochondria-like structures.…”