Rotifers Manipulation of fatty acid composition in phospholipids

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					                                                           Rotifers: Manipulation of fatty acid composition in
                                                                              phospholipids and triglycerides

                                                                                             The rotifer Brachionus plicatilis has been widely used as live to fish larvae since
                                                                                             it was introduced in Japan in the 1960`s. However, very little n-3 highly
                                                                                             unsaturated fatty acids are synthesised by the rotifer, and must therefore be
                                                                                             enriched in order to satisfy requirements of the fish larvae. Several studies have
                                                                                             shown that dietary phospholipids increase the efficiency of the digestion process
                                                                                             in fish larvae and are beneficial for growth and survival of the larvae. The main
                                                                                             objective of the present study was to investigate the effects of different
                                                                                             enrichments on the rotifers, especially with regard to lipid class composition and
                      Foto: Tora Bardal, NTNU                                                the ability to control the fatty acid composition in two lipid classes (phospholipids
                                                                                             and triglycerides).

                                                                                             The rotifers used in this study were long term enriched (7 days) and short term
                                                                                             enriched (up to 72 hours) with different diets; Isochrysis galbana, Tetraselmis sp.,
                                                                                             cod roe, oil emulsions (Super Selco; Inve, Be) and yeast/oil emulsions (Super
                                                                                             Selco; Inve, Be). In addition the effect of starvation on rotifers was investigated.

                                          % in PL                                                                             % in TG
                                                                                                                                                              •   A positive correlation between the lipid
                      30                                   sum saturated                              30   sum saturated                                          content in rotifers and the feed was observed.
                      25                                                                              25                                                          Low lipid diets resulted in high relative levels
% of sum FA in PL




                                                                                  % of sum FA in TG




                      20                                                                              20
                                                                                                                                                                  of phospholipids and low relative level of
                                                                                                                                                                  triglycerides in the rotifers.
                      15                                                                              15
                                                                                                                                                              •   For all the diets there was greater variation in
                      10                                                                              10
                                                                                                                                                                  the fatty acid composition of triglycerides
                      5
                            0   10   20   30    40    50     60    70
                                                                                                      5
                                                                                                              0    10    20       30     40    50   60   70       compared to in the phospholipid fraction in the
                                          Hours                                                                                   Hours
                      70
                                                  sum monounsaturated
                                                                                                      70
                                                                                                           sum monounsaturated
                                                                                                                                                                  rotifers. In addition, a higher relative level of
                      60                                                                              60                                                          polyunsaturated fatty acids was found in
  % of sum FA in PL




                                                                             % of sum FA in TG




                      50                                                                              50
                                                                                                                                                                  phospholipids compared to triglycerides,
                                                                                                                                                                  except for short time enriched rotifers with oil
                      40                                                                              40
                                                                                                                                                                  emulsion.
                      30                                                                              30                                                      •   The fatty acid composition in the triglycerides
                      20                                                                              20                                                          of rotifers was better correlated to the
                            0   10   20   30    40    50     60    70                                         0    10    20       30     40    50   60   70
                      80
                                          Hours
                                                                                                      80
                                                                                                                                   Hours                          composition in the diets than it was for the
                                                   sum polyunsaturated                                     sum polyunsaturated
                      70                                                                              70                                                          phospholipid fraction. Lower relative levels of
                                                                                                                                                                  DHA (22:6 n-3) were found in the
                                                                               % of sum FA in TG
  % of sum FA in PL




                      60                                                                              60

                      50                                                                              50                                                          phospholipids than in the triglycerides, while
                      40                                                                              40                                                          EPA (20:5 n-3) was approximately equal. As a
                      30                                                                              30
                                                                                                                                                                  result the DHA/EPA ratio was higher in the
                      20                                                                              20
                                                                                                                                                                  triglycerides than in the phospholipids.
                                                                                                                                                              •
                      10                                                                              10
                            0   10   20   30
                                          Hours
                                                40    50     60    70
                                                            I. galbana
                                                                                                              0    10
                                                                                                           Super Selco2
                                                                                                                         20       30     40
                                                                                                                                       Hours
                                                                                                                                               50   60   70       The use of microalgae resulted in increased
                                                            Tetraselmis sp.
                                                            Yeast + Super Selco1
                                                                                                           Starved
                                                                                                           Yeast + Super Selco2
                                                                                                                                                                  nitrogen content per individual rotifer and an
                                                                                                                                                                  increased protein level.
                      Contents of saturated, monounsaturated and
                      polyunsaturated fatty acids (% of total fatty acids)                                                                                    ⇒ These results show possibilities also to adjust
                      in phospholipids (PL) and triglycerides (TG) in                                                                                         the fatty acid composition in the phospholipid
                      rotifers enriched up to 24 and 72 hours. In two                                                                                         fraction of rotifers through selection of diet and
                      trials separated by solid and broken lines.FA:                                                                                          enrichment length.
                      Fatty Acids.


                                                                                                                                                 Contact: Ingrid Overrein
                                                                                                                              SINTEF Fisheries and Aquaculture, N-7465 Trondheim, Norway
                                                                                                             Tel: +47 73596391 - Fax: +47 73595660 - E-mail: ingrid.overrein@sintef.no - Web: www.fish.sintef.no