Feeding selectivity of the marine ascidian Styela clava

摘要

The sessile suspension feeding ascidian, Styela clava, plays an important role in the functioning of estuarine systems. The feeding selectivity of S. clava was examined using standard physiological techniques in terms of particle sizes and diet concentrations. Styela clava increased its retention efficiency (the proportion of available particles retained in ascidian) with increasing particle size at a lower diet concentration [expressed as particulate organic matter (POM)] from 2.11 to 10.06 mg POM Lp#, and the highest retention was reached for 5-20 om particles. With increasing diet concentration to 20.12 mg POM Lp#, S. clava retained small particles (<3.5 om) more efficiently and large ones (>15 om) less efficiently. The selectivity of ascidian with different sizes was similar at the same concentration. At every diet concentration, larger ascidians retained more 5-20 om cells than the smaller ones. All these results indicate that S. clava possesses a particle selection mechanism that may affect the zooplankton communities to a certain degree.