Abstract：Sipunculan worm (Phascolosoma arcuatum) is a famous economic animal that inhabits in the intertidal zone. At present, sipunculan worm has been artificially cultured at a small-scale. However, little is known about the characteristics of its basic physiology. In this study, the structure and features of the coelomocytes from the sipunculan worm were characterized by Giemsa staining method, scanning electron microscopy (SEM）and transmission electron microscopy (TEM), respectively. The results showed that there were seven main types of body cavity fluid cells in the sipunculan worm: erythrocyte, plate cell, basophilic granulocyte, thrombotic cell, lymphoidocyte, reticular cell and osinophilic granulocyte. Among them, the number of erythrocyte was the largest in the number of coelomocytes, the maximum diameter of the plate cell was 39-42 μm, the basophilic granulocyte was near elliptic, the basophilic granules were dyed blue after Giemsa staining, the thrombotic cell was often clustered, the nuclei of lymphoidocyte were larger and almost filled with the whole cell, multiple vacuoles in reticular cell and osinophilic granulocyte were purplish red after Giemsa staining.
2020, Vol. 33 
