Feeding rates and gross growth efficiencies of larval developmental stages of Oithona davisae (Copepoda, Cyclopoida)

Abstract

Among marine planktonic copepods, the genus Oithona is probably the most abundant and ubiquitous copepod in the world's oceans. However, knowledge about the ecophysiology of Oithonids is very scarce compared to calanoid copepods, particularly for their larval stages. We determined feeding rates and gross growth efficiencies of different developmental stages of the cyclopoid copepod Oithona davisae as related to food concentration, body weight and temperature in the laboratory.

The feeding rates of nauplii and copepodites of Oithona davisae in relation to food concentration followed a type III functional response, with feeding threshold concentrations ranging from ∼ 50 to 75 μg C L− 1, depending on the developmental stage. All feeding parameters varied according to body weight/age. The food concentration required to achieve the maximum ingestion rates increased from 200 μg C L− 1 in early nauplii to 320 μg C L− 1 in copepodites. Specific ingestion rates (d− 1) increased with increasing temperature, with a Q10 = 2.45. Growth rates were negatively related to larval size and positively related to food concentration and temperature. Gross growth efficiency ranged from 0.16 to 0.60 depending on the developmental stage, food availability and temperature.

Oithona davisae developmental stages exhibited much lower maximum specific ingestion rates than calanoid nauplii but exhibited quite similar gross growth efficiencies. This indicates that Oithona nauplii should display lower metabolic losses and consequently lower food requirements than calanoid nauplii. Together with other factors, this feeding/energetic strategy may contribute to the success of the Oithona species in marine ecosystems of contrasting trophic characteristics.