He, X.J., L.Y. Han, B.D. Lu, X.D. Wang & J.Q. Yin. (2015). Nucleic acid proxies for growth and response to changing prey species in Pseudodiaptomus annandalei. Journal of Tropical Oceanography. 34(4):65-73.

220972

10.3969/j.issn.1009-5470.2015.04.009 [view]

He, X.J., L.Y. Han, B.D. Lu, X.D. Wang & J.Q. Yin

2015

34(4):65-73.

Publication

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Nauplii, copepodids and adults of Pseudodiaptomus annandalei were fed with Chaetoceros debilis and Thalassiosira weissflogii at the saturated food concentration. Biochemical indices were then measured and described including mass specific RNA content, DNA conten, RNA︰DNA, RNA︰protein, and DNA︰protein, as well as the elemental compositions (mass specific phosphorus content, nitrogen content, atomic C︰P, and C︰N ratios). Their growth rates were also determined for different developmental stages. The relationships between growth rate and three RNA-related indices were analyzed. It was shown that RNA︰protein (RNA︰PRO), varying with developmental stage in the same trend as growth rate, was correlated with growth rate significantly in a positive linear manner for all life stages of P. annandalei on C. debilis and for older stages than nauplii on T. weissflogii. Thus, RNA︰ PRO could be applied as an indicator of P. annandalei growth. In the experiment of changing diet, the CII copepodids with a 24 h feeding history on C. debilis continued to be fed with Skeletonema costatum or Phaeoecystis globosa for another 48 h, and then showed remarkable differences in RNA content and RNA︰PRO ratio, which ranked as S. costatum > C. debilis> P. globosa treatment. Differently, RNA︰DNA ratios ranked as S. costatum =C. debilis>P. globosa treatment. On the other hand, elemental compositions of those copepodids in different treatments differed in phosphorus content and atomic C︰N ratio, which ranked as C. debilis >S. costatum = P. globosa. It can be deduced that RNA-related indices can respond immediately to food change within 48 h while elemental compositions only reflect feeding history. It was concluded that RNA︰PRO can be applied in field investigation as an indicator of growth in copepod, and RNA-related indices can be used to indicate nutrition status.

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