Aspidosiphon (Paraspidosiphon) parvulus Gerould, 1913
This species has wart or conically pointed papillae on the ventral and lateral sides of the anal shield. In small worms the longitudinal muscle bands are visible through the trunk wall. Bidentate and unidentate hooks are present in rings. They are found most frequently in hard substrata like coral rubble and among or under clumps of oysters and vermetids
(From Cutler, 1973 and Cutler and Cutler, 1989)
External anatomy
Introvert longer than the trunk.
There are 10 to 12 short tentacles which may be connected with connective tissue.
Bidentate and unidentate hooks arranged in numerous rings, also scattered unidentate, and some pyramidal (25-35 µm height). The bidentate hooks are found more frequently at some distance behind the tentacles.
The anal shield is composed of broad, flat, irregular units, which sometimes appears arranged in rows giving an impression of ridges and grooves. The units becomes smaller, scattered, wart or conically pointed papillae on the ventral and lateral sides. The shields have a diffuse boundary where the units grade into coarse trunk papillae.
Caudal shield granular but does have radial grooves.
Internal anatomy
The trunk wall has about 24 anastomosing longitudinal muscle bands, generally distinct in worms longer than 5 mm, more so towards the anterior end.
Intestine attached anteriorly and posteriorly by spindle muscle. No caecum was observed.
Nephridia are 50-75 % of the trunk length, and are attached to the trunk wall for most of the their length, opening at the level of the anus or slightly posterior to it.
Retractor muscles originate close to the caudal shield (Gerould, 1913).
Trunk from 2-14 mm long (Cutler, 1973).
Often found with Nephasoma pellucidum and Themiste alutacea inside Oculina rubble (Cutler, 1973). In the Indian River lagoon A. parvulus is found in association with two other Aspidosiphon: A. fischeri, and A. steenstrupii (Rice et al. 1995).
(From Cutler 1994)
This species is found in shallow waters (5-35 m) in Western Atlantic Ocean from Cape Hatteras through the Caribbean to Venezuela.
Gerould (1913) found specimens in gray mud and broken shells. Cutler (1973) reported occurrence to be frequent in Oculina rubble and occasional in shelly sand. In the Indian River lagoon A. parvulus is found among and under clumps of oysters and vermetids (Rice et al 1995).