Transmission electron micrographs of <i>Symbiodinium</i> cells in the giant clam <i>Tridacna crocea</i>.

<p>(a) and (b) Noticeable crystalline clusters in random arrangements are found (arrows). The structure is far different from that found in cultured motile stage cells, and the crystalline deposits are tightly packed within vacuoles. Abbreviations: Dinokaryotic nucleus (N), pyrenoid (Py), chloroplast (Ch).</p

Transmission electron micrographs of crystalline layers found in the motile stage of <i>Symbiodinium</i>.

<p>Transmission electron micrographs showing close-ups of the crystalline layers found in the gymnodinioid motile stage in cultured <i>Symbiodinium</i> (CS-156 & FKM0207). (a) and (b) Arrangements of crystalline layers underlying the sulcus (Su). (c)–(e) Clusters with multiple layers of crystalline deposits. Five layers were most commonly found. (f) Two sections of a flagellar basal body can be seen (arrows) near the crystalline cluster. (g) Close-up of the flagellar basal body, showing circularly arranged triplet microtubules (right arrow).</p

Light micrographs of cultured <i>Symbiodinium</i> cells.

<p>The upper row shows strain CS-156, and the lower row shows FKM0207. (a) and (c) Motile stage cells showing gymnodinioid morphology with transverse and longitudinal flagella (arrows) at 10:00. (b) and (d) Coccoid stage cells showing non-flagellated spherical shapes at 00:00.</p

Northern- (a) and Western- (b) blot analyses showing a <i>Symbiodinium</i> (CS-156) opsin.

<p>(a) Northern dot blot analysis using a digoxigenin-labeled opsin cDNA probe for a dinoflagellate <i>Alexandrium tamarense</i>, showing a positive signal in the <i>Symbiodinium</i> total RNA. (b) Western blot analysis using an antibody against the partial <i>A. tamarense</i> opsin peptide, showing positive single band (arrow) in the <i>Symbiodinium</i> total protein. MW: Molecular weight marker.</p

Cultured <i>Symbiodinium</i> motile cells viewed with differential interference contrast (DIC) microscope without the DIC analyzer.

<p>(a) CS-156. (b) FKM0207. Bright areas near the sulcus (arrows) indicate that strong light reflection and polarization may occur in this area corresponding to the location of the clusters as revealed by transmission electron microscopy.</p

Transmission electron micrographs of <i>Symbiodinium</i> cells in animal hosts.

<p><i>Symbiodinium</i> cells in (a) a sea anemone <i>Aiptasia</i> sp., (b) a giant clam <i>Tridacna crocea</i>, (c) a soft coral <i>Sinularia lochmodes</i>, and (d) a stony coral <i>Ctenactis echinata</i>. All samples were fixed at 10:00. There is no diurnal morphological change, and the cells are very similar to the coccoid stage cell in cultured strains. There are no crystalline layer clusters, while individual crystalline deposits can be scantily seen (arrows). Abbreviations: Dinokaryotic nucleus (N), mitochondrion (M), pyrenoid (Py), chloroplast (Ch), starch (S), accumulation body (A).</p

Transmission electron micrographs of cultured <i>Symbiodinium</i> cells.

<p>(a) Longitudinal section of strain CS-156 fixed at 10:00. (b) Longitudinal section of strain FKM0207 fixed at 10:00. In both (a) and (b) a cluster of crystalline deposit layers (white arrows) is located in the hypocone of the dinoflagellate cell. (c) Transverse section of CS-156 fixed at 00:00. (d) Transverse section of FKM0207 fixed at 00:00. These represent the thick-walled spherical morphology. Note that the crystalline deposits are not arranged in layers, but are sparsely scattered (black arrows). (e) Transverse section of CS-156 fixed at 10:00 showing the crystalline layers (a white arrow) underlying the sulcus region (Su) of the cell. Abbreviations: Dinokaryotic nucleus (N), mitochondrion (M), pyrenoid (Py), chloroplast (Ch), cingulum (Ci).</p

Light micrographs of cultured <i>Symbiodinium</i> motile cells under normal light and specific-wavelength light.

<p>(a)–(c) Normal light supply. The white arrows show the eye-spot like area. (d) Equivalent image field to (a) using a band-pass filter transmitting 365–400 nm (UV), attached to the microscope light port, (e) equivalent image field to (b) using a band-pass filter transmitting 410–492 nm (blue), and (f) equivalent image field to (c) using a band-pass filter transmitting 470–560 nm (green). Obvious black spots can be seen at the eye-spot like areas (black arrows), most visibly under UV.</p

<i>Symbiodinium</i> cell numbers observed in the attraction tests using PCR tubes with and without <i>Acropora tenuis</i> larvae.

(a)<p>The infected larvae/total observed larvae are shown in parentheses.</p

<i>Symbiodinium</i> compositions of water column and naturally settled <i>Acropora</i> coral recruits.

<p>The water samples were collected during the coral mass spawning period in 2011 (gray bars), and the recruits were collected approximately 2 weeks after spawning (black bars). Left histograms show that the clade composition of the recruits did not reflect that of the water column (p<0.05). Clades A and D were detected in both the water and recruit samples, and these <i>Symbiodinium</i> clones were further sorted into ITS2 types. Type A1 was the dominant clade A type within the recruits (middle histogram). Right histogram showing clade D ITS2 type compositions; type D1 and D4 group sequences were predominant in both water and recruit samples. Type D3 relative sequences were only detected from water samples. In clade A and D, <i>Symbiodinium</i> type compositions were differ between recruits and environments (p<0.05).</p