The long and short term feeding condition in field‐caught Calanus pacificus, as determined from the lipid content

Abstract

The wax ester and triglyceride contents of Calanus pacificus were measured as indices of feeding condition. The copepod was reared to copepodite V on 100, 300, and 900 µg C·liter‒1 of the diatom Thalassiosira weissflogii and also subjected to changing food concentrations at the fifth copepodite stage. The resulting lipid content was measured. The naupliar stages did not appear to benefit from a food concentration higher than 100 µg C·liter‒1 although there was an increasing difference in wax ester content after C III among the three food concentrations. The triglyceride content seemed a good indicator of recent feeding, being completely lost after 3 days of starvation. The wax ester content was a good indicator of feeding over a period of a week.Field samples were collected on six occasions off San Diego, in summer 1982 and spring 1983. At five of the six stations the field‐caught animals were very well fed, having a much higher wax ester content than at 300 µg C·liter‒1 of T. weissflogii in the laboratory. On one occasion the wax ester and triglyceride contents indicated that the field population was more poorly fed. The variability in lipid content was measured at each station.Data are shown to suggest that quality of food is very important and that Chl a or particulate carbon are poor indicators of food for late stage C. pacificus.