Sipunculus nudus

Small ones: transparent and iridescent. Large one: pinkish red. Skin is smooth to small ones. Trunk: has no papillae; introvert is covered with triangular "scales" or large white papillae directed posteriorly. Some having 4 lobes - 2 dorsal and 2 ventral. Longitudinal muscle bands (LMBs): thick strong ridges; common 5-15 cm long with 24-34 LMBs. Refractors muscles are separate and attach at the same level, each with a broad base extending over 5 - 7 longitudinal muscle bands. Spindle muscle: attached anterior to the anus. Gut: attached to the body wall by several fixing muscles or connective tissue strands throughout its length; very thin, transparent, and fragile. Nephridia: vary in length; range from 10 to 20% of the trunk length. Nephridiopores: anterior to the anus between the 4th and 5th longitudinal muscle bands. Ventral nerve cord: loosely attached anteriorly with numerous, large, lateral offshoots to the introvert (Ref. 358).

• Sipunculus titubans Selenka & Bülow, 1883
• Sipunculus tesselatus (Rafinesque, 1814)
• Sipunculus balanophorus delle Chaiaje, 1823
• Sipunculus delphinus Murina, 1967
• Syrinx nudus Forbes, 1841
• Syrinx tesselatus Rafinesque, 1814
• Sipunculus nudus tesselatus (Rafinesque, 1814)
• Sipunculus nudus var. tessalatus (Rafinesque, 1814)
• Sipunculus eximioclatharus Baird, 1868
• Sipunculus titubans var. diptychus (Selenka & Bülow, 1883)
• Sipunculus gigas de Quatrefages, 1865