Aspidosiphon (Akrikos) zinni Cutler, 1969
This species description was based on 246 specimens. It is a small, fragile, deep-sea species, with an ungrooved anal shield and compressed unidentate hooks arranged irregularly. It has a transparent mid trunk, which allows viewing the internal organs through the trunk wall. Very common in the northern Atlantic Ocean in depths up to 4400 m inside foraminiferans tests.
(From Cutler 1994)
This species can be overlooked or misidentified, especially if the introvert is retracted. However, the flattened anterior ends, and the pale golden anal shield, distinguish this worm from Nephasoma diphanes, which has been collected along with A. zinni.
(From Cutler 1969, Cutler 1994)
External anatomy
Introvert is almost equal in length to the trunk.
Trunk is cylindrical and transparent except at the two extremities where there is some brown pigmentation.
Small tentacles are present in a dorsal cluster.
Compressed unidentate hooks (about 15-20 µm tall) are arranged irregularly on the distal introvert.
The anal shield is indistinct and consists of very fine grained, pale units.
The caudal shield is not evident.
Internal anatomy
Cutler (1969) reported that the attempts at dissection have been unsuccessful, but he pointed out that is possible to see the internal organs through the trunk wall due to the transparency of the wall.
The trunk wall has a continuous longitudinal muscle layer.
Intestine extends to the posterior end of the trunk.
Nephridia are usually 25 % of the trunk length and open at about the same level as the anus.
A pair of retractor muscles originates about 65-80% of the distance to the posterior end of the trunk.
This is a small species, most of them measuring 2 to 3.5 mm long by about 0.3 mm in diameter.
This is a deep-sea species, which has been reported at depth of 1100-4400 m in the northern Atlantic Ocean. However, there are two records from around 9º S off Congo River and one in the Mozambique Channel around 25º S, at 132 m (Cutler 1994).
This species lives in arenaceous foraminiferan tests (Cutler 1969).