Symbion pandora is a commensal on Norway lobster (Nephrops norvegicus) with a very complicated life cycle. The species was described very recently and appointed to a new phylum, Cycliophora. Obviously nothing is known about the biology of this animal. The present study investigated the feeding biology of Symbion pandora. This was investigated by offering them two different high quality food items: Algae and mussel. Additionally, incubations with radiolabelled dissolved amino acids were done to estimate the energy contribution from DOM. A specific goal was to quantify the amount of organic matter taken in during one meal and estimate how much this contributes to the total energy requirement of internal budding, production of larvae etc. during the life cycle of the cycliophoran. This was done by autoradiography and radiolabel incorporation.
Feeding biology: First, the reaction to algae or mussel extract, were tested on initially non-filtering individuals. The timing of the opening of the bucal funnels was noted during an observational period of 15min. After the first 3min where no activity was observed the animals were administered live algal cells. After 7min the animals were additionally administered homogenised mussel filtered through a 15 microm. nitex screen at 0.5 mg/ml. There were no reaction to the algae offered. On the contrary all individuals reacted positively to the mussel extract and started filtering. Secondly, the animals were offered varying concentrations of homogenised mussel and the timing of opening and closure of the bucal funnels of 2 to 5 individuals was noted until all were ultimately closed. There was a clear functional response of filtering on the substrate concentration. Below a food concentration of 1mg/ml the total period of time in which the bucal funnel was open was inverse linearly related to food concentration. Above this concentration the length of the total feeding time was constant with increasing concentration probably depending only on maximum clearance rate. Autoradiography: The intake and distribution of organic matter from the food or DOM were investigated by offering the animals 3H-phenylalanine labelled mussel extract or diluted 3H-phenylalanine in a time series from 10min to 6h. Two different mixtures were then used to fix the animals for autoradiography: Carnoy´s fixative and glutaraldehyde/sucrose. The samples will then be sliced (1 microm.), transferred to autoradiographic film. Similar samples will be measured for total isotopic activity to quantify total intake. The study will be submitted for publication.