DEGRADATION OF GUT PIGMENT DURING FEEDING BY A SUB-ANTARCTIC COPEPOD - IMPORTANCE OF FEEDING HISTORY AND DIGESTIVE ACCLIMATION

Gut pigment degradation by females of the subantarctic copepod Drepanopus pectinatus was established by measurements of gut fluorescence prior to fecal pellet production. The total amount of pigment lost varied from 0 to 17% while the Chl a unrecovered as pheopigment ranged from 0 to 92%. A linear relationship was observed between food concentration and mean pigment loss per copepod but not with the level of pigment loss as a percentage of total ingestion (pigment destruction efficiency) which varied without clear pattern. A nested ANOVA indicated that pigment destruction efficiency was influenced primarily by the trophic history of the animals (66% of the total variance) and to a minor extent by the experimental food concentrations (12% of the total variance). The hypothesis that gut pigment loss could be related to digestive activity and influenced by digestive acclimation processes (trophic history) was confirmed by the significant exponential relationship between food concentration at the time of copepod capture and the experimentally derived destruction efficiency. Careful consideration should be given to the quantitative or qualitative nature of gut pigment measurements as an in situ index of ingestion.