Aspidosiphon (Paraspidosiphon) fischeri ten Broeke, 1925

General description:

This species has a distinct anal shield composed of angled-plates regularly arranged, without furrows or grooves. Caudal shield is not well defined. Introvert up to two times the trunk length. The ill-defined muscles bands are visible through the trunk wall. Bidentate and unidentate hooks are present in rings. Compressed bidentate hooks arranged in rings; unidentate hooks may be present among the bidentates on the proximal rings. Scattered pyramidal hooks are present behind compressed hooks.

Look alikes:

Aspidosiphon misakiensis and A. gosnoldi.

Morphology:

(From Cutler & Cutler, 1989)

External anatomy

Introvert one to two times the length of the trunk.

Trunk from 4-16 mm long.

Stephen and Edmonds (1972) reported 18 tentacles, and Migotto and Ditadi (1988) described 10 small white tentacles in a small worm.

Compressed bidentate hooks (18-27 µm height) are arranged in rings. The secondary tooth is small. Unidentate hooks may be mixed among the bidentates on the proximal rings or a few rings can carry exclusive unidentate hooks. Pyramidal pale hooks (15-50 µm height) are scattered following the compressed hooks.

The anal shield has distinct margins. It is composed of regularly arranged many-angled plates (Stephen & Edmonds, 1972), and has no grooves or furrows.

Caudal shield is not clearly defined, with dark patches in its center (Stephen and Edmonds, 1972)

Internal anatomy

The trunk wall has few ill-defined muscles bands which frequently anastomose. In some specimens the posterior part of the trunk wall appears as a continuous sheet.

Intestine attached anteriorly and posteriorly by spindle muscle. A caecum is present in the last coil or in the beginning of the rectum (Migotto and Ditadi, 1988).

Nephridia length is 33-50% of the trunk length. The nepridiopores are at the level of the anus or slightly posterior to it (Migotto and Ditadi, 1988).

Retractor muscles originate at or close to the posterior end of the trunk (95-100%).

Associations:

Four miles off Fort Pierce Inlet Aspidosiphon fisheri is found in coquina rubble with the following sipunculans species: A. albus, A. parvulus, A. sp., Nephasoma pellucidum, N. rimicola, Antillesoma antillarum.

Distribution:

(From Cutler, 1994)

In shallow water common from Cuba to São Paulo, Brazil. Also found from the Pacific coast of Panama, Ecuador, James and Hood Island, and the Galapágos Islands. Throughout the Caribbean (Rice, 1975).

Habitat:

Found inside hard substrata such as coral and coquina rubble.

Life cycle:

(From Rice, 1975b)

This species follows the developmental pattern IV determined by Rice (1976), which includes a lecithotrophic trochophore and a planktotronic pelagosphera larva that often remains for several months in the plankton. The shape of the egg of A. fischeri is usually slightly oval and the size may be quite variable in relative width and length. The average length and width of the eggs is 103 by 94 µm. The egg mass appear white, but each egg has a pinkish tinge. The cleavage is spiral and unequal. The development is rapid compared to that of Phascolosoma, reared at 10 to 13 C. In 48 hours at 25ºC the lecithotrophic trochophore of A. fischeri metamorphoses into a planktothrophic pelagosphera larva. These larvae survived in the laboratory for only two weeks.

Sipuncula

Sipuncula

Aspidosiphon (Paraspidosiphon) fischeri ten Broeke, 1925

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