61.1 50.8 49.6 46.8 46 46 43.2 44.5 44 50 25.8 29.1 28.8 27.1 31 26.5 28 32 29 13.1 21.6 21.3 24.5 26.9 22 28.8 28.8 26.8 23 nI3 33 11.3 16.8 16.7 16.7 18.7 18 24.4 22.2 17.9 18 Materials and methods

pre-washed in methanol, and then the filter was stored in a clean glass vial with Ž . chloroformrmethanol qbutyl hydroxyl toluene 2:1 solution. The vials were stored at y408C. All the glassware used were pre-washed with chloroform to avoid lipid contamina- tion. The lipids were extracted using a modification of the method of Bligh and Dyer Ž . 1959 ; fatty acid methyl esters were obtained by methylation with 12 BF in 3 Ž . methanol Metcalfe et al., 1966 . A methanolic solution of C was used as an external 23:0 Table 3 Fatty acid content of M. edulis larvae obtained after 2 weeks of feeding on R. reticulata Ž . Individual FA are expressed as percentage of total identifiable fatty acids percentage TIFA . SAFA sSaturated fatty acid, MUFA s Monounsaturated fatty acid, PUFA s Polyunsaturated fatty acid. Two individual larval cultures are code-named as: Con s fed on Control diet, Un sUnfed larvae, HL s High Light, LL s Low Light, fr2 salga cultured under no nutrient limitation, P salga cultures under phosphorus limitations and Nsalga cultured under nitrogen limitation. Blanks indicate that the fatty acid was below detection levels. Two 20:1 isomers were found. Question mark after the 20:4 ny6 fatty acid indicates that although the fatty acid could not be identified on the GC trace, the GCrMS analysis suggested an identification. N.I.s fatty acid identified on the GC trace, but not integrated by the instrument. Larval length achieved is taken from Ž . Ž . Leonardos and Lucas 2000b ns60 . Ž . Ž . Fatty acid Control Unfed R. reticulata HL R. reticulata LL 1 2 1 2 fr2 1 fr2 2 P 1 P 2 N 1 N 2 fr2 1 fr2 2 P 1 P 2 N 1 N 2 14:0 5.3 3.6 5.2 4.4 6.1 5.0 4.8 5.5 4.4 4.0 3.6 3.6 2.4 4.2 5.4 2.7 15:0 2.1 1.3 3.5 4.1 3.9 3.5 2.6 2.7 3.6 2.7 2.3 2.7 2.6 4.1 1.2 1.0 16:0 31 22 30 34 26.1 26.9 24.7 24.5 27 25 22.8 24.3 24 28 23 22.6 18:0 9.8 8.1 10 12 9.4 9.0 9.3 8.4 8.7 10 9.2 9.7 9.8 9.3 7.3 7.3 22:0 4.5 2.6 8.4 5.7 5.4 5.3 5.3 4.9 2.7 1.6 5.3 4.3 5.1 3.8 2.7 3.4 SAFA 52.7 37

57.5 61.1 50.8 49.6 46.8 46 46

44.8 43.2 44.5 44 50

39 37.1 16:1ny7 4.8 6.4 8.6 7.1 7.8 8.0 6.5 6.2 5.6 4.8 8.1 6.8 7.7 8.6 4.7 3.5 18:1ny9 3.6 3.8 12 11 9.1 8.4 8.7 9.7 7.2 6.1 8.6 10.8 9.3 8.4 13 15.6 18:1ny7 3.8 4.7 5.2 3.2 5.6 6.3 6.6 7.0 10 10 6.8 6.8 7.7 7.1 7.0 6.7 20:1 1 2.3 3.4 0.0 1.1 1.9 1.9 2.3 0.3 2.3 0.7 0.7 0.8 2.3 1.8 3.7 2.6 2 20:1 5.0 2.6 N.I. 1.4 2.3 3.0 3.0 2.8 4.4 2.6 2.3 1.9 4.1 1.9 2.4 2.8 22:1ny11 1.8 0.9 1.8 1.8 0.9 1.5 1.7 1.2 1.4 1.6 1.5 1.7 1.9 1.7 1.5 MUFA 21.2 21 27.6 25.8 27.6 29.1 28.8 27.1 31 26.5 28

28.7 32 29

31 32.7 18:2 ny6 2.5 3.2 2.7 2.2 3.3 2.8 5.0 5.5 1.7 2.2 4.7 7.2 2.5 1.6 5.2 4.6 18:3ny3 1.1 4.2 1.1 0.9 1.2 1.4 3.3 3.6 1.8 2.1 2.3 1.8 1.7 1.5 9.2 9.0 18:4 ny3 1.3 2.3 0.3 0.3 0.9 1.1 1.3 1.6 1.5 1.8 2.4 1.9 1.7 1.4 4.2 3.8 20:4 ny6? 2.0 3.4 0.9 1.1 1.5 1.9 2.7 2.8 1.8 2.2 1.8 1.8 2.2 2.0 1.4 1.2 20:5ny3 7.3 11 3.7 2.5 4.0 4.9 4.0 4.2 5.7 7.5 6.8 5.4 5.4 4.3 3.6 4.2 22:5ny3 1.0 1.0 0.7 0.7 1.4 0.9 0.7 0.6 0.5 0.8 1.1 0.5 0.5 0.5 0.2 0.3 22:6 ny3 10 14 5.5 5.4 9.4 8.3 7.5 8.6 9.2 12 9.5 8.2 9.2 9.1 5.1 7.1 PUFA 26.1 40

14.9 13.1 21.6 21.3 24.5 26.9 22 28.8 28.8 26.8 23

20 28

30.2 nI3

21.6 33 11.3

9.8 16.8 16.7 16.7 18.7 18 24.4 22.2 17.9 18

16 22 24.4 Larval 199 192 138 137 162 172 168 180 198 184 205 181 161 163 178 172 length in microns SD 26.5 31.2 15.1 15.1 20.4 21.4 17.0 26.1 28.4 21.5 20.6 21.4 18.6 19.5 21.4 22.4 Ž . standard. Equipment and instrumentation of gas chromatography GC and gas chro- Ž . Ž . matography–mass spectroscopy GCrMS are as in Leonardos and Lucas 2000a . Identification was carried out by comparison with known cod liver oil traces. To determine the quality of fatty acid, Mass Lab software, supplied with the instrument, was used. All statistical analyses were carried out with the aid of the Minitab w . To investigate the use of larval fatty acids as an index of growth, correlation analysis was used. This type of analysis was used rather than regression analysis because the assumptions of model I regression analysis do not hold true with this type of data. For a more detailed discussion and useful examination of various aspects of regression and correlation Ž . analysis, the reader is referred to Sokal and Rohlf 1987 .

3. Results