EFFECT OF PHOSPHORUS CONDITION ON GROWTH AND INGESTION IN PSEUDODIAPTOMUS ANNANDALEI

The growth, development and ingestion of the Pseudodiaptomus annandalei were investigated by using Platymonas subcordiformis with different phosphorus contents as food. The growth rates of Pseudodiaptomus annan-dalei were (0.04370.0030)/d and (0.03390.0049)/d when using Platymonas subcordiformis with low P content (C/P=197 or 375 in molar) as food. The growth rate was (0.10400.0395)/d when using Platymonas subcordiformis with high P content (C/P=78 in molar) as food. Furthermore, the period of naupliar stage under low P condition was pro-longed by 1.52 times compared to those under the P-sufficiency condition. The P content was 0.30%0.33% of dry weight in the animals under P-sufficiency condition, while it decreased to 0.08%0.28% in the low P condition. There was a close linear significant correlation between the growth rates and P contents in the copepodite. The ingestion rates of nauplius, copepodites and adults decreased significantly in low P condition compared with those under P-sufficiency, which changed from790, 720 and 728 cells/(ind?h) in the P-sufficiency condition to 150370, 695703 and 648733 cells/(ind?h) in the low P condition, respectively. It was concluded that the nutritional quality (C/P and C/N ratio) of algae was degraded in low P condition, which led to the significant impairment on the growth and ingestion of the Pseudodiaptomus annandalei. Therefore, the P-limitation in marine copepods was verified.