Pherusa sibogae ( Caullery, 1944 ) Salazar-Vallejo, 2014

Salazar-Vallejo, Sergio I., 2014, Revision of Pherusa Oken, 1807 (Polychaeta: Flabelligeridae), Zootaxa 3886 (1), pp. 1-61 : 36-38

Pherusa sibogae ( Caullery, 1944) n. comb.

Figure 14

Trophoniella sibogae Caullery, 1944:36–38 , Fig. 28.— Bleeker & van der Spoel, 1992:163.

Type material. Eastern Indian Ocean. Holotype ( ZMA 1599 ), off Western Timor, R.V. Siboga, Stat. 299 (10°52'04" S, 124°01'01" E), 34 m.

Description. Holotype (ZMA 1599) pale, damaged, several parapodia previously removed; anterior and posterior ends better preserved, median region collapsed, narrower than body ends; body cylindrical, slightly tapered posteriorly; 25 mm long, 2 mm wide (chaetiger 7 before constricted region), cephalic cage 4 mm long, 27 chaetigers. Body scarcely papillated; tunic with sediment particles adhered dorsally ( Fig. 14A ) and ventrally ( Fig. 14B ), giving a rough appearance; papillae elongate capitate, apparently arranged in longitudinal series along the body, one row per segment, 3 papillae dorsally, 2 ventrally; largest ones associated with parapodia.

Cephalic hood exposed, short, margin crenulated. Anterior end unknown; not dissected to avoid further damage. Cephalic cage chaetae as long as 1/6 body length, or twice as long as body width. Chaetigers 1–2 forming cephalic cage; chaetae arranged as two lateral series; chaetiger 1 with 8 noto- and 7 neurochaetae, chaetiger 2 with 9 notochaetae and 6 thicker neurochaetae.

Anterior dorsal margin of first chaetiger with rounded anterior projection with small marginal papillae. Chaetigers 1–3 of about the same length. Chaetal transition from cephalic cage to body chaetae abrupt; aristate neurohooks start in chaetiger 4. Gonopodial lobes not seen, probably eroded ( Fig. 14B ).

Parapodia poorly developed; chaetae emerge from body wall. Parapodia lateral; median neuropodia ventrolateral. Notopodia and neuropodia low lobes; chaetal lobes with postchaetal capitate papillae; notopodial papillae very long (at least 5x longer than ventral one). Noto- and neuropodia close to each other.

Median notochaetae arranged in short transverse series; all notochaetae multiarticulated capillaries, articles short basally and medially, distally slightly longer, continued almost to the tip ( Fig. 14D ), 7–8 per fascile (chaetiger 6), as long as 2/3 body width. Neurochaetae multiarticulated capillaries in chaetigers 1–3; aristate neurohooks from chaetiger 4, arranged in transverse series, 4–5 per bundle; anterior neurospines thicker, with aristae broken ( Fig. 14E ), posterior neurospines thinner, aristae delicate, bent ( Fig. 14F ).

Posterior region tapered ( Fig. 14C ); pygidium unknown.

Remarks. Pherusa sibogae ( Caullery, 1944) n. comb., as indicated above, resembles P. rullieri because both have cephalic cages twice as long as body width and aristate neurohooks along the body. These two species differ by the abundance of body papillae and their sediment cover; in P. sibogae body papillae are scarce and there are sand particles over papillae and tunic, whereas in P. rullieri body papillae are abundant, and they do not include sand particles.

Trophoniella Hartman, 1959 has been revised elsewhere ( Salazar-Vallejo 2012b), and it includes species provided with a thick tunic, abundant branchial filaments in a tongue-shaped branchial plate, and with anchylosed neurohooks, at least in posterior chaetigers. Caullery (1944) included three species for Trophoniella and T. sibogae was the only one provided with aristate neurohooks. This species was regarded as belonging to Brada as part of the above generic revision ( Salazar-Vallejo 2012b:459) but that idea was modified once some species of Pherusa were found with aristate neurohooks. Consequently, T. intoshi is transferred to Pherusa and hence the new combination.

Distribution. Only known from the type locality, off Western Timor, in 34 m depth.

Figures

FIGURE 14. Pherusa sibogae (Caullery, 1944) n. comb., holotype (ZMA 1599). A. Anterior end, dorsal view. B. Anterior end, ventral view. C. Posterior region. D. Chaetiger 11, right parapodium, notochaetae (insets: basal and medial regions). E. Chaetiger 11, right parapodium, neurohooks (inset: basal and distal regions). F. Chaetiger 20, right parapodium, neurochaetaae. Scale bars: A, C: 0.5 mm, B: 0.4 mm, D, E: 170 µm, F: 25 µm.