PIGMENT INGESTION AND EGG-PRODUCTION RATES OF THE CALANOID COPEPOD TEMORA-LONGICORNIS - IMPLICATIONS FOR GUT PIGMENT LOSS AND OMNIVOROUS FEEDING

We examined the relationship between egg production rate (E) and pigme nt ingestion rate (I, from gut content corrected for 33% loss) for adu lt female Temora longicornis in Long Island Sound on 47 occasions. Lin ear regression of E on I [both variables expressed in mass of nitrogen (N) female(-1) day(-1)] was: E(N) = 0.0016 + 0.770 x I-N. The slope, 0.77, is the apparent gross efficiency of egg production, equivalent t o the gross growth efficiency (GGE) assuming that females partition al l nitrogen for growth into egg production. Published work suggests tha t a GGE of 0.37 would be expected for herbivorous copepods. The discre pancy between the expected value of 0.37 and observed value of 0.77 co uld result from unquantified losses of gut pigment or because T.longic ornis ingested a significant amount of nitrogen by feeding as a carniv ore. We suggest that if T.longicornis females derive all of their nitr ogen for growth by feeding on phytoplankton, and if no correction for pigment loss is employed, then the gut pigment method underestimates p igment ingestion by no more than a factor of two.