Nauplii of Calanus helgolandicus were raised from eggs, laid within a 12 h period, to Copepodite Stage I (CI) on 5 different species of algae at high concentrations at 15°C. The diets used were Isochrysis galbana (5 µm spherical diameter), Rhodomonas baltica (7 µm), the coccolithophorid Pleurochrysis carterae (12 µm), the diatom Thalassiosira weissflogii (14 µm) and the dinoflagellate Prorocentrum micans (30 µm). Each day a sample was taken and preserved for later cohort analysis. Growth was estimated from CHN samples collected almost daily, from which naupliar stages were also distinguished. Ingestion was measured for each naupliar feeding stage. The fastest development was obtained with I. galbana and P. micans. We found the highest value of carbon and nitrogen content of Naupliar Stages NV to CI for individuals reared on the smallest algae, I. galbana and R. baltica. However, ingestion rate in terms of carbon or nitrogen was lowest with these same (smallest) algae. Therefore, the gross growth efficiency was highest for the smallest algae. These results suggest the following: Firstly, that factors influencing development time and weight in stage are different; weight in stage is negatively related to algal size, whereas development time is independent of it. The quality of the algal biochemical components could be the factor influencing development. Secondly, that small algae are fully assimilated in the gut whereas larger cells, i.e. those with indigestible components around the cell (theca, frustule, calcium layer) are only partly assimilated.KEY WORDS: Calanus helgolandicus · Nauplii · Growth · Development · Ingestion · Efficiency · Food quality
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 216: [151][152][153][154][155][156][157][158][159][160][161][162][163][164][165] 2001 Some studies have found consumption of diatoms by females to result in low hatching success (Ianora & Poulet 1993, Poulet et al. 1994, Chaudron et al. 1996, Ban et al. 1997), but this is still open to discussion (Jónasdóttir & Kiørboe 1996, Jónas-dóttir et al. 1998, Irigoien et al. 2000b.Development, body size and weight of nauplii and copepodites have been negatively related to temperature (Thompson 1982, Peterson 1986, Hopcroft & Roff 1998. Ontogenetic differences in the physiological response to temperature in copepods have also been noted (Pedersen & Tande 1992). The effect of food quantity on growth processes has often been unclear (Hart 1990, Hopcroft & Roff 1998, but some studies have clearly established an effect of food limitation on wild nauplii (Lopez 1991, Melle 1998, and this has been further substantiated by laboratory studies (Green et al. 1991, Lopez 1996.Food quality is another factor which has to be considered when examining variability in naupliar growth (Mullin & Brooks 1970, Paffenhöfer 1971, 1976, Fernández 1979a,b, Diel & Klein Breteler 1986, Verity & Smayda 1989. The major algal characteristics of importance are biochemical content, morphology, and di...