Developmental and physiological properties of Pyropia dentata (Bangiales, Rhodophyta) conchocelis in culture

Abstract

Pyropia dentata is a promising species for aquaculture in South China. To develop an efficient protocol for seedling culture, the growth, development, and physiological changes of P. dentata conchocelis were investigated under different temperatures, irradiances, photoperiods, and salinity. After 25 days, conchosporangia formation at 28 °C was 5–7-fold of that at 25 and 31 °C. The percentage of conchosporangia increased as day length increased from 8 to 12 h and then decreased sharply under day length ≥14 h, with no conchosporangia observed under 24L:0D. By contrast, long day length (≥14 h) and lower temperature (≤25 °C) favored the vegetative growth of conchocelis. Conchosporangia formation peaked at 28 °C, 12L:12D, and 40–60 μmol photons m−2 s−1. The highest F v /F m , P n , and P n /R d also occurred at 28 °C and/or 12L:12D, which might provide energy for conchosporangia formation. Total soluble proteins (TSPs) content decreased while relative growth rate increased as irradiance and day length increased. Increasing irradiance and day length, and at temperatures of 31 °C caused a reduction in phycoerythrin and chlorophyll a content. However, allophycocyanin content increased at 31 °C and the content of phycocyanin, carotenoids, and TSPs remained steady from 25 to 31 °C. Growth, development, P n , content of TSPs and pigments were similar at 25–40 ppt. F v /F m decreased and R d increased significantly at salinities ≥35 ppt. These findings provide informative data on the mechanisms of Pyropia conchocelis development, and help establish an efficient seedling culture protocol for this P. dentata strain.