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INTRODUCTION Two major groups are found within the dinoflagellates: Naked or athecate cell forms (e.g. Gyrodinium spp., Gymnodinium spp., Noctiluca scintillans) and armoured or thecate cells with thecal plates made of cellulose (e.g. Protoperidinium spp., Ceratium spp., Dinophysis spp.) (Figure 2). The arrangement of the plates is used for species identification in thecate forms (Dodge, 1982, Tomas, 1996, Kraberg et al., 2010). Also characteristic of dinoflagellates is their large nucleus known as the dinokaryon. This contains chromosomes in a highly condensed form which do not decondense during the interphase of cell division. Vegetative cells of dinoflagellates grow by asexual cell division (Taylor, 1987). They display maximum specific growth rates up to ~2 d -1 , depending on the species, but in general a division rate about 0.5-1 d -1 is common. Feeding strategies Heterotrophic dinoflagellates are known to catch and consume prey by a variety of different feeding mechanisms (Schnepf & Elbrächter, 1992, Hansen & Calado, 1999). Many naked genera (Figure 3) are able to ingest whole intact prey cells via direct engulfment (e.g. Gyrodinium spp., Gymnodinium spp.) (Hansen, 1992). This strategy is widespread and has recently also been described for some thecate species (Jeong et al., 1999) (e.g. Fragilidium cf. mexicanum, Peridiniella danica). A common feeding strategy within thecate forms is pallium feeding (Figure 4): The prey is surrounded by a pseudopodium, the pallium, reaching out of the flagellar pore of the dinoflagellate’s cell, and is digested outside the theca (Protoperidinium spp., the Diplopsalis group) (Jacobson & Anderson, 1986, Hansen & Calado, 1999). Figure 3: Direct engulfment: Gyrodinium dominans with an ingested Scrippsiella trochoidea cell (arrow). Scale bar 50 µm. 6
INTRODUCTION Figure 4: Diplopsalis lenticula digesting a Thalassiosira rotula chain in its pallium (arrow). Scale bar 50 µm. Figure 5: Dinophysis acuminata feeding on Myrionecta rubra with a peduncle (arrow). Scale bar 10 µm. Photo: Myung Gil Park (Park et al., 2006) Another group of dinoflagellates takes up food by feeding tubes (Figure 5), used to pierce the prey cell and suck out its cytoplasm (e.g. Amphidinium spp., Dinophysis spp.). Two different types of feeding tubes have been described: Peduncle and phagopod (Schnepf & Elbrächter, 1992) Food spectrum A wide range of prey items are reported for dinoflagellates, including almost every kind of organic particle present in the marine habitat. Food particles range from bacteria to nanoflagellates, all size classes of microalgae, especially chain-forming diatoms, marine snow, microzooplankton as well as copepod eggs and even injured metazoans (Jeong, 1999). However, the prey used by a particular species of dinoflagellate most probably depends on different factors such as their size, chemo-attraction and swimming behaviour (Hansen, 1992). Laboratory determined predator:prey size ratios within heterotrophic dinoflagellates show that they can feed and grow on predator:prey size 7
Page 1 and 2: The role of heterotrophic dinoflage
Page 3: “What we know is a drop, what we
Page 7 and 8: INTRODUCTION INTRODUCTION Understan
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Page 20 and 21: RESEARCH AIMS Apart from the pure g
Page 22 and 23: OUTLINE OF THE THESIS the two diffe
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Page 29 and 30: CHAPTER I INTRODUCTION Marine resea
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Page 46 and 47: CHAPTER II ABSTRACT Grazing experim
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CHAPTER II ACKNOWLEDGEMENTS This st
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CHAPTER III 58
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CHAPTER III ABSTRACT Mesocosm exper
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CHAPTER III the prey (Cowles et al.
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CHAPTER III The mesocosms were stir
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CHAPTER III Net growth of plankton
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CHAPTER III prior to the experiment
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CHAPTER III incubation bottles with
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CHAPTER III Data analysis To monito
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CHAPTER III General development of
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CHAPTER III Ciliate community After
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CHAPTER III Other microzooplankton
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CHAPTER III Microzooplankton Experi
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CHAPTER III Figure 6: (6a) General
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CHAPTER III Table 3: Temora longico
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CHAPTER III Table 4: Temora longico
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CHAPTER III The comparison of mesoc
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CHAPTER III Flagellates contributed
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CHAPTER III The effort to capture,
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CHAPTER III in words and deeds. Man
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CHAPTER III Table 2 Microzooplankto
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CHAPTER III Table 3b Temora longico
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CHAPTER III Table 4b Temora longico
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CHAPTER IV 102
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CHAPTER IV ABSTRACT The intra-speci
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CHAPTER IV Hansen, 1997). In turn,
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CHAPTER IV out in F/2 medium over 7
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CHAPTER IV the same patterns in G.
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CHAPTER IV Figure 1: General develo
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CHAPTER IV Favella ehrenbergii (Fig
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CHAPTER IV (24, 48, 72 hours of inc
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CHAPTER IV Growth response of G. do
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CHAPTER IV due to pre-conditioning
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CHAPTER IV This was also confirmed
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DISCUSSION described by competition
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DISCUSSION to know who they are. Th
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DISCUSSION Microzooplankton grazers
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DISCUSSION Figure 1: A rather simpl
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DISCUSSION 1986, Tillmann, 2004) co
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DISCUSSION To my knowledge similar
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DISCUSSION transported around the w
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SUMMARY by its larger competitor. T
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REFERENCES Buskey, E.J. & Stoecker,
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REFERENCES Gentsch, E., Kreibich, T
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REFERENCES Jeong, H.J., Yoo, Y.D.,
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REFERENCES Montagnes, D.J.S., 2003.
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REFERENCES Rose, J.M. & Caron, D.A.
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REFERENCES Teixeira, I.G. & Figueir
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