Spatial distribution of symbiont-bearing dinoflagellates in the Indian Ocean in relation to oceanographic regimes

Abstract

The spatial distribution of symbiont-bearing dinoflagellates was investigated during a cruise from Cape Town, South Africa to Broome, Australia. Endo-and ectosymbionts were only found in the order Dinophysiales. The genera Ornithocercus, Histioneis, Parahistioneis and Citharistes had cyanobacteria as ectosymbionts, while the genera Amphisolenia and Triposolenia contained both intact cyanobacterial and eukaryotic endosymbionts. The symbiont-bearing dinoflagellates were mainly found in the upper 100 m of the water column. Their distribution was restricted to water temperatures exceeding 16.5°C, and the highest species diversity and cell concentrations were found at temperatures around 20 to 30°C. The symbiont-bearing dinoflagellates were always associated with water masses with low nutrient (N-limited) and chl a concentrations. Special attention was given to the ectosymbiont-bearing dinoflagellates. Under light microscopy, some of the food vacuoles of Ornithocercus spp. resembled ectosymbionts in size, shape and colour. Transmission electron microscopy of O. magnificus and O. quadratus revealed the presence of a peduncle and many rhabdosomes; both may serve in prey capture. Also, numerous food vacuoles were present, but their content was generally too degraded for a proper identification of prey type. However, occasionally remnants of eukaryotes were observed, indicating that Ornithocercus spp. may feed on ciliates. Thus, our data suggest that the ectosymbiont-bearing dinoflagellates use a multi-resource strategy (photosynthesis and phagotrophy) to cope with a low-nutrient environment.

Putative N2-fixing heterotrophic bacteria associated with dinoflagellate–Cyanobacteria consortia in the low-nitrogen Indian Ocean

“…Recently, we found that symbiont-bearing dinoflagellates were most common in the photic zone of the Indian Ocean characterized by low nutrients and low phytoplankton biomass (Tarangkoon et al 2010). This is consistent with previous observations from the Indian Ocean (Jyothibabu et al 2006) and the Red Sea (Gordon et al 1994).…”

An exploratory study of heterotrophic protists of the mesopelagic Mediterranean Sea

“…Amphisolenia species, whilst known from surface water samples (e.g. Gó mez et al, 2011), are most abundant in sub-surface waters (100-200) but occur in down to 400 m depth (Tarangkoon et al, 2010). With regard to phaeogromid radiolarians, the species we denoted as common in the mesopelagic are also known from the mesopelagic of the Adriatic Sea (Kr sini c and Kr sini c, 2012) and the western and central Pacific Ocean (Yamashita et al, 2002).…”

Feeding behavior, spatial distribution and phylogenetic affinities of the heterotrophic dinoflagellate Oxyphysis oxytoxoides

“…were also observed feeding on Myrionecta rubra by myzocytosis (Park et al 2006, Nishitani et al 2008. Very recently, Tarangkoon et al (2010) observed, with transmission electron microscopy, that Ornithocercus magnificus and Ornithocercus quadratus have a peduncle. Further, they observed that Ornithocercus spp.…”

“…are they true, permanent chloroplasts or kleptoplastids derived from chrysophyte or prymnesiophyte symbionts (Hallegraeff & Lucas 1988)? Aside from Clade B, the other 2 clades (A and C) are characterized by the presence of phycobilin-containing plastids or cyanobacterial endo-(or ecto-)symbionts, although eukaryotic endosymbionts within Amphisolenia and Triposolenia have also been observed (Tarangkoon et al 2010). Taylor (2004) thought that the phycobilin-containing dinophysoids Dinophysis, Amphisolenia and Triposolenia seemed more closely related to each other than to more morphologically complex (i.e.…”

“…argus were distantly related to the other Phalacroma species in Clade B. It is unclear whether the genus Dinophysis is monophyletic, as species belonging to the genus formed 4 lineages within Clade C. According to the phylogenetic analyses, Clades A and C included species containing phycobilin-pigmented endosymbionts (Amphisolenia) (Lucas 1991, Tarangkoon et al 2010, cyanobacterial ectosymbionts (Histioneis, Ornithocercus and Citharistes) (Carpenter 2002, Tarangkoon et al 2010, or mixotrophic species having phycobilin pigment (Dinophysis) (Park et al 2006(Park et al , 2008, whereas Clade B contained mostly heterotrophic species (Oxyphysis and Phalacroma) (present study; Inoue et al 1993, Jensen & Daugbjerg 2009). …”