Short-term feeding of Temora longicornis Müller in the laboratory and the field

Abstract

Short-term feeding (min to h) of the copepod Temora longicomis (Müller) was investigated in the laboratory and in the field by monitoring the increase in gut fluorescence of adult females. Laboratory feeding studies using the diatoms Thalassiosira pseudonana (Hust.), T. weissflogii (Hust.) and Ditylum brightwellii (West) showed that ingestion rates increased with increased food concentration and cell size. The maximum ingestion rate was 9.5 ng chl. equiv. female −1. h −1 on a diet D. brightwellii. Clearance rates decreased with increased food concentration and decreased cell size. Maximum clearance rate was 1.9 ml. female −1·h −1 also on a diet of D. brightwellii. On two of three occasions, ingestion and clearance rates in the field were twice as high at night as during the day. Night rates were similar to laboratory rates in the chlorophyll range found in the field. Diel differences in feeding activity in the field appeared to have been behaviorally induced rather than being related to vertical migration of individuals into food rich layers.