Figure 56
Material examined. Juan Fernandez Islands, Anton Bruun Cruise 12, Sta. 65-240, 12 Dec 1965, 33.622°S, 78.839°W, 26–29 m, holotype and 3 paratypes (USNM 1013912–3); Sta. 65-243, 12 Dec 1965, 33.62°S, 78.847°W, 0–10 m, 3 paratypes (USNM 1013914).
Description. A small species, holotype complete, 2.23 mm long, 0.29 mm wide for 23 setigers; one incomplete paratype 2.86 mm long, 0.2 mm wide for 20 setigers; other paratypes smaller. Color in alcohol: opaque white.
Prostomium smoothly rounded on anterior margin; with two crescent-shaped red eyespots (Fig. 56 A). Peristomium with two indistinct achaetous rings, but distinctly separated from setiger 1. All segments similar, with no demarcation between thorax and abdomen. Notopodia with short digitiform postsetal lobes throughout; neuropodia with short postsetal lobes in anterior setigers; absent in posterior setigers.
Notosetae including 3–4 crenulated capillaries (Fig. 56 B), a single flail seta (Fig. 56 C) and a single furcate seta (Fig. 56 D); flail seta with tapering tip and reduced numbers of crenulations; furcate seta with unequal tynes, shorter blunt-tipped, longer thinner and pointed; tynes connected by thin webbing with fine needles. Neurosetae including crenulated capillaries and 1–2 modified crenulated spines in anterior setigers and 0–1 crenulated capillaries and 3– 4 spines in posterior setigers; spines unique, recurved, with broad crenulated blade terminating in pointed tip (Fig. 56 E).
Branchiae absent. Some specimens with large yolky eggs up to 190 µm across widest dimension. Eggs with two nucleoli observed in germinal vesicle (Fig. 56 F).
Pygidium with anus directed posteriorly, surrounded by four cirri; dorsal pair shorter, triangular in shape, ventral pair longer and cirriform (Fig. 56 G).
Etymology. This species is named for Ms. Betty J. Landrum of the former Smithsonian Oceanographic Sorting Center. Ms. Landrum provided support and encouragement during the course of this study and of another project on Antarctic polychaetes.
Remarks. Orbiniella landrumae n. sp. is only provisionally referred to Orbiniella because it differs from related species in having notopodial furcate setae, flail setae, and an unusual type of crenulated neuropodial spine. However, the species does not have distinct body regions, parapodia are reduced, branchiae are absent, two peristomial rings are present, and the posterior parapodia are not elevated as is typical for species of Orbiniella. Further, large ova of 190 µm present in the holotype indicate sexual maturity. Further study is needed to more adequately address the generic placement of this species.
Distribution. Juan Fernandez Islands, intertidal to 29 m.