Childia crassum Westblad 1942

Childia crassum (Westblad, 1942)

(Figs. 1 A, B)

Paraphanostoma crassum: Westblad 1942 (p. 14); Westblad 1948 (p. 23); Marcus 1950 (p. 427); Westblad 1954 (p. 4); Marcus 1954 (p. 427); Riedl 1956 (p. 89); Dörjes 1968 (p. 112); Dörjes and Karling 1975 (p. 183); Lauckner 1980 (p. 292); Reuter et al. 2001 (p. 122); Raikova et al. 2004 (p. 72).

Childia crassum: Tekle et al. 2005 (p. 73); Raikova et al. 2006 (p. 220).

Material. Living specimens in squeeze preparations, whole mounts for fluorescence imaging of musculature.

Localities. Pond Sock Reef (9°17’17.9” N, 82°19’39.9” W), from fine-grained sand at 2 m depth collected from sediment surrounding a sunken boat; Isla Colon, Mangrove Inn (9°19.870’ N, 82°15.286’ W), from fine-grained sand at 3–4 m water depth.

Description. Mature specimens ~650 µm long and ~160 µm wide (Fig. 1 A). Anterior end rounded; posterior sometimes somewhat pointed. Body without conspicuous coloration.

Body-wall musculature with longitudinal fibers positioned outside of circular fibers. Ventral musculature with U1 and U2 muscles (sensu Tekle et al. 2005): muscles that are longitudinally oriented in the anterior half of body and wrap around posterior rim of mouth, and modified circular muscles whose mid-points line the posterior rim of the mouth and whose lateral extensions are positioned anterior to the mouth (data not shown).

Separate male and female gonopores. Male copulatory organ with fine penis stylets in cone-shaped arrangement (Fig. 1 B).

Remarks. Prior to this collection, Childia crassum was known only from the Eastern North Atlantic Ocean (see Tyler et al. 2006). Our specimens were approximately half the length of those originally described by Westblad (1942), with correspondingly smaller internal structures. Members of the genus Childia have species-specific patterns of body-wall musculature, and our specimens matched that described for C. crassum (see Tekle et al. 2005).