Abstract:To study the adaptive capability of Sipunculus nudus to three different types of sediments, we carried out a rearing experiment of S. nudus under the laboratory conditions. Treatments in quintuplicate were the sea sand (S-s), shrimp-pond sediment (S-sp) and fish-pond sediment (S-fp), respectively, with different oxidation reductive potential value, organic material content and different grain sizes. After sunlight exposure, all types of sediments were paved onto the bottom of the tanks (31 cm × 20 cm × 30 cm) to 10 cm thick, and the same water was put into each tank. Five individuals with mean weight of (2.58±0.23) g were stocked in each tank and cultured with a normal ration supply. DO content in the water was above 6.0 mg/L and no water change during the experiment. The results showed that the survival rate of S. nudus was up to 96%, 92% and 92% in S-s, S-fp and S-fp (P>0.05), respectively. Main component of the excrement of S. nudus was fine particles smaller than 0.4 mm, especially the 0.224 mm particles reached 47.70%, 85.95% and 69.99% in the treatments of S-s, S-sp and S-fp, respectively. At the end of the experiment, S. nudus presented growth to some extent in S-fp, while a little weight loss in other two groups. These results suggest that S. nudus has strong adaptive capability to the reductive condition and different grain size of sediment, while it has a higher need for the smaller size of particles (R<0.224 mm) for the restriction of its feeding organs. Meanwhile, the organic material of the sediment was a key factor to the growth of S. nudus, including the quality (source) and quantity of the food. Therefore, based on its strong adaptive capability to the different sediments, the culturing of S. nudus in the suitable ponds/beaches was an ecological-economical model with potential development.
