THE FATE OF THE CAROTENOID PIGMENT FUCOXANTHIN DURING PASSAGE THROUGHTHE COPEPOD GUT - PIGMENT RECOVERY AS A FUNCTION OF COPEPOD SPECIES, SEASON AND FOOD CONCENTRATION

The amount of fucoxanthin, a taxonomically diagnostic carotenoid, reco vered after passage through the guts of the copepods Acartia californi ensis and Calanus pacificus, was determined after the copepods had fed on low (50 mu g C l(-1)) and high (350 mu g C l(-1) for Acartia; 500 mu g C l(-1) for Calanus) concentrations of the diatom Thalassiosira w eissflogii, during spring (May) and winter (December). Changes in pigm ent concentrations and cell abundances were assessed in experimental ( with copepods) and control (without copepods) samples by standard incu bation experiments. Pigment recovery was assessed by (i) comparing the amount of ingested pigment recovered in the experimental groups with that predicted to have been ingested from cell count data and (ii) com paring fucoxanthin/cell ratios in control and experimental samples. Bo th techniques suggested that pigment loss is substantial (usually 60-1 00%), regardless of species, food availability or season. Patterns of pigment conservation differed between species, although pigment recove ry was always higher at high, than at low, food concentrations. Pigmen t recovery in Acartia was higher (9.4-28.0%) in the spring than during the winter (0 recovery), regardless of food concentration. In Calanus , however, pigment recovery was always higher at high (34.9-67.8%) tha n at low (0 recovery) food concentrations, regardless of season.