Orbiniella uniformis Hartman 1967

Orbiniella uniformis Hartman, 1967

Figure 55

Orbiniella uniformis Hartman, 1967: 106 –107; Rozbaczylo 1985: 130.

Material examined. Antarctic Peninsula, Anvers Island, Arthur Harbor, USCG Staten Island Sta. 6 - 63, 24 Jan 1963, 64.77°S, 64.07°W, ~ 7 m, fish trap, holotype, and 2 paratypes (USNM 47329–30).

Description. Body long, linear, holotype 6 mm long, 0.4 mm wide for 30 setigerous segments. Body generally uniform in overall appearance, with a weakly defined thoracic region only vaguely separated from an abdominal region at setiger 6.

Prostomium short, broadly rounded on anterior margin (Fig. 55 A); peristomium 3x as long as prostomium, with two smoothly rounded rings, second forming ventral oral lips. Noto- and neuropodia of setigers 1–5 with few long, thin, tapering crenulated capillaries (Fig. 55 D); capillaries from setiger 6 and subsequent segments shorter, thicker, with distinct curve or bend in shaft (Figs. 55 E–F); crenulations of thoracic setae extending along most of exposed setal shaft; in abdominal segments crenulations occuring only from bend of shaft. Abdominal neuropodia with 2–3 emergent, pointed aciculae (Figs. 55 G–H).

Setigers 16–19 swollen, with several large eggs about 150 µm in longest dimension (Fig. 55 B). Pygidium with two large ventral lobes bearing two short, dorsal cirriform appendages (Fig. 55 C).

Remarks. Orbiniella uniformis was well described by Hartman (1967). Illustrations are presented here for the first time. The long threadlike nature of this species readily distinguishes it from other orbiniids encountered in this study. Orbiniella uniformis is most closely related to four other shallow-water species (Table 2). Eyespots are reported for O. nuda, O. plumisetesa, O. annulata, and absent in O. minuta and O. uniformis. Further, while the pygidium all of these species consists of two rounded lobes, O. uniformis is the only one with two short dorsal cirri.

Distribution. Antarctic Peninsula, low water.