Flabelligera bicolor
Creators: name: Salazar-Vallejo, Sergio I.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Terebellida
Flabelligeridae
Flabelligera
Flabelligera bicolor

description: Flabelligera bicolor (Schmarda, 1861)   
Figure 2  
 Pherusa bicolor Schmarda 1861:21, Pl. 20, Fig. 169.   
 Flabelligera bicolor: Günther 1912:15 (n. comb.); Benham 1915a:163 (syn.); Benham 1915b:173; Benham 1950:22; Hartman 1966:35, Pl. 10, Figs. 4–6 (syn.).   
 Flabelligera affinis: Monro 1936:164 (partim, non Sars).   
 Siphonostoma antarcticum Baird 1873:95–96.   
 Flabelligera lingulata Ehlers 1905:47–48, Pl. 7, Figs. 1–5; Ehlers 1907:21; Ehlers 1913:535 (383 m, same?); Hartwich 1993:113.   
 Flabelligera semiannulata Ehlers 1905:49–50, Pl. 7, Figs. 6–10; Hartwich 1993:136.   
 Type material. Southwestern Pacific Ocean. Four syntypes of Flabelligera lingulata (three BMNH- 1908.5.9.33; one ZMB- 6773) damaged, Auckland, New Zealand (no further data), W.B. Benham, coll. Additional syntypes of Flabelligera lingulata (BMNH- 1907.5.1.21), damaged, same data (2 anterior and 3 median fragments, in poor shape; largest measured). Three syntypes of Siphonostoma antarcticum (BMNH- 57.1.17.3), off Auckland (?), New Zealand (no further data), A. Sinclair, coll. (body dark or blackish, with a very thick whitish tunic).   
 Additional material. Southwestern Atlantic Ocean. One specimen (BMNH- 1936.2.8:2464), off West side of Falkland Islands, R/ V William Scoresby, Stat. 221 (48°23' S, 65°10' W), 76–91 m, 4 June 1928.   
 Description. Better syntype (F. lingulata BMNH-1908) complete (Fig. 2A); body cylindrical, tapering posteriorly; pale brown in the anterior and posterior ends, paler by the mid-body; 41 mm long, 7 mm wide, cephalic cage 5 mm long, 46 chaetigers. Tunic thick, densely papillated, mostly free from sediment particles; papillae long, clavate, mucronate.   
Cephalic hood exposed. Prostomium not observed; smaller syntype (BMNH-1908) with anterior end exposed (Fig. 2C). Caruncle well developed, extended to the margin of the branchial plate (not beyond it in the better syntype), broken. Palps large, thick, distally rounded; palp bases rounded, elevated. Lateral lips well developed. Ventral lip reduced to thin membrane. Dorsal lip well developed, thick.  
Branchiae separated into two lateral groups; branchial filaments arranged in about five rows, about 60 filaments per group, decreasing in size ventrally. Nephridial lobes in branchial plate very thin, short filaments, placed about the level of prostomium.  
Cephalic cage chaetae as long as 1/8 body length or as 5/7 body width. Chaetigers 1–2 involved in the cephalic cage; chaetiger 1 with about 36 noto- and 22 neurochaetae; chaetiger 2 with about 8–10 chaetae per fascicle (present in all other syntypes). Anterior dorsal margin of first chaetiger papillated. Chaetigers 1–3 of about the same length. Chaetal transition from cephalic cage to body chaetae abrupt; multiarticulated neurohooks from chaetiger 3 (Fig. 2B). Gonopodial lobes not seen.  
Parapodia well developed, lateral, median parapodia lateroventral; median neuropodia ventrolateral. Notopodia long flat lobes; neuropodia long conical lobes; both with long, clavate papillae. Noto- and neuropodia widely separated.  
Median notochaetae arranged in a short oblique row, all multiarticulated capillaries, about 1/4 – 1/5 as long as body width, 8–10 per fascicle, with articulation irregular (Fig. 2D), two with longer articles, 1–2 with mediumsized articles, remainder with very short articles; all with longer articles distally. Neurochaetae multiarticulated capillaries in chaetigers 1–2; multiarticulated neurohooks from chaetiger 3, mostly singly, anterior chaetiger with shorter, thicker hooks (Fig. 2E), than posterior chaetigers (Fig. 2F). Handle articulation basally placed, articles roughly similar or missing; about three medium-sized articles. Other articles anchylosed, small, poorly defined, continued to bending region. Crest wider than handle wider than handle in anterior chaetigers, slightly wider in posterior ones, dark brown, darker distally; width:length ratio 1:4–5.  
Posterior end tapering to short cone; pygidium with anus terminal, rounded, with basal rounded projection; no anal cirri.  
 Remarks. Flabelligera bicolor (Schmarda, 1861) is unique among the species with transparent tunics because its neurohooks are from chaetiger 3 and the body has two distinct colors (hence the name): the anterior region is dark blue and posterior region is reddish brown to gray. However, because the pigmentation fades in ethanol, the start of the neurohooks is a more consistent and useful character to separate it from similar species.   
 Benham (1915a) reestablished Flabelligera bicolor (Schmarda, 1861) to include two species described by Ehlers (1905): F. lingulata and F. semiannulata; he made extensive and conclusive arguments about the synonymy based on morphology and geographical distribution. The only missing piece was the examination of the original type materials, which were already lost by that time. Further, Benham (1915a) and other colleagues before him overlooked the short description by Baird (1873), whose specimens had a dark body wall with a whitish outer cuticle and multiarticulated capillaries in the second neuropodia, and are therefore conspecific with F. bicolor. The syntypes of S. antarcticum however, have a very thick tunic which might be a unique feature, and that might have been removed or eroded in other specimens.   
 Distribution. Originally described from New Zealand rocky bottoms in shallow waters; the record by Ehlers (1913:535) may be a different species since it was collected from almost 400 m depth, but fresh material is needed to clarify this. An apparently disjunct population lives in the Malvinas or Falkland Islands.
description: Published as part of Salazar-Vallejo, Sergio I., 2012, Revision of Flabelligera Sars, 1829 (Polychaeta: Flabelligeridae) 3203, pp. 1-64 in Zootaxa 3203 (1) on pages 12-14, DOI: 10.11646/zootaxa.3203.1.1, http://zenodo.org/record/5248129