Effects of environmental and physical factors on the shell infiltration density of free-living conchocelis of three Pyropia species (Bangiales, Rhodophyta)

Shell infiltration of free-living conchocelis of the three commercial <i>Pyropia</i> species (<i>P. yezoensis</i>, <i>P. seriata</i>, and <i>P. dentata</i>) were examined in various conditions of temperatures (20–25°C), light intensities (1, 10, 40, and 80 μmol photons m<sup>-2</sup> s<sup>-1</sup>), conchocelis quantities (100, 150, 200, 250, and 300 mg) and sizes (108, 209, 324, 411, and 519 μm). The optimal shell infiltration conditions were 20°C and 40 μmol photons m<sup>-2</sup> s<sup>-1</sup> in all species. The infiltration densities were 44.81–146.15 conchocelis cm<sup>-2</sup> for <i>P. yezoensis</i>, 51.40–190.49 conchocelis cm<sup>-2</sup> for <i>P. seriata</i>, and 22.24–92.49 conchocelis cm<sup>-2</sup> for <i>P. dentata</i>. Inefficient shell infiltration was observed with the different conchocelis quantities from 100 to 300 mg. A positive corelationship was observed between shell infiltration density and the amount of conchocelis. The optimal blending time for maximizing infiltration density was 40 s for <i>P. yezoensis</i> and <i>P. seriata</i> and 25 s for <i>P. dentata</i>. This blending time correlated with a cell count of 5–7 cells. Total conchocelis lengths of 5–7 cells were approximately 300 μm for <i>P. yezoensis</i> and <i>P. seriata</i> (with cell size of about 45 μm) and approximately 400 μm for <i>P. dentata</i> (with a cell size of about 65 μm). These results suggest that, to achieve optimal shell infiltration density for <i>P. dentata</i>, the blending time should be reduced by half, and the amount of conchocelis should be increased twofold, making it comparable to the other two <i>Pyropia</i> species.