Influence of body size, temperature, and diet concentration on feeding of Styela clava

As solitary filter feeder, Styela clava shows superior water purification capacity in the integrated multi-trophic aquaculture (IMTA) model consisting of S. clava, microalgae, and sea cucumber, which should be an ideal system to reduce organic and inorganic pollution in the water. It is of great significance to study the physiological energetics of S. clava for the application of this IMTA system. The physiological energetics of S. clava was determined in a simulated natural culture system to provide information for comparing to the energetic data derived from feeding ecological studies. The ascidians were grouped into five cohorts based on body size in terms of their wet weight of 1.5-2.0 g, 2.5-3.5 g, 5.0-6.5 g, 8.0-9.5 g, and 11.0-14.0 g, respectively. Clearance rate (CR), ingestion rate (IR), and assimilation efficiency (AE) of ascidian were estimated using flow-through feeding chambers. The results showed that the CR and IR increased exponentially with the ascidians’ body size at different temperatures. Body size showed little effect on AE at the same water temperature. However, significant differences were observed between different temperature regions in the range of 12-28°C regardless of body size. S. clava performed far better in feeding behavior at 20°C than that at higher or lower temperatures. Within the range of diet concentration (as particulate organic matter, POM) from 2.11 to 6.11 mg POM/L, the CR and IR increased exponentially with POM. This study provides basic data for the application of ascidian in the IMTA system.