Aspidosiphon (Aspidosiphon) misakiensis Ikeda, 1904
This species has a distinct anal and caudal shield. Introvert up to three times the trunk length. The gut coils are ill defined. Unidentate and bidentate hooks are present.
External anatomy
(From Cutler and Cutler, 1989)
Introvert two to three times the trunk length.
Bidentate hooks arranged in rings on the distal portion of the introvert (25-60 µm height). Secondary tooth has normal dimensions on distal rings, but is very small in proximal ones. Unidentate compressed hooks are present at the proximal portion of the introvert (25-60 µm height).
Anal shield is composed of closely packed, irregular, granular units. Border has widely spaced, square blocks of shield material around the anterior quarter of the trunk (not sharply defined).
Caudal shield granular but does have radial grooves.
Internal anatomy
Longitudinal muscle (LM) layer is continuous in most part of the trunk but is sometimes fractured or split beyond these boundaries. LM splits into bands under the anal shield.
The intestine has ill-defined coils and is anchored anteriorly and posteriorly by a spindle muscle. The rectum bears a small caecum (Ikeda, 1904 and Migotto and Ditadi, 1988)
Nephridia length is 50-100% of the trunk length.
Retractor muscles originate close to the caudal shield.
Most about 10 mm trunk length.
Cutler & Cutler (1989) reported the largest known specimen with 25 mm trunk length.
(From Cutler 1994)
Both sides of central Japan (1-50 m); South and Western Australia, and Kermadec Island. Eastern Atlantic from the Azores, Cape Verde, and the Canary Island to the Gulf of Guinea (depths to 75 m); off Spanish Mediterranean. Western Atlantic, from Brazil, Haiti, and Cuba.
Migotto and Ditadi (1988) described the nature of the sea floor where A. misakiensis lives as composed exclusively of calcareous algae.