Spirobranchus bakau, Shantti & Kupriyanova & Quek & Yap & Teo, 2021

Shantti, Pavarne, Kupriyanova, Elena K., Quek, Zheng Bin Randolph, Yap, Nicholas Wei Liang & Teo, Serena Lay Ming, 2021, Spirobranchus bakau sp. nov. from Singapore: yet another species of S. kraussii-complex (Polychaeta: Serpulidae), Zootaxa 5040 (1), pp. 33-65 : 39

Spirobranchus bakau sp. nov.

Figs 2–5 ; Table 2

Figures

FIGURE 2. Spirobranchus bakau sp. nov. tubes. A—Cluster of tubes from mangroves at Lim Chu Lang end (photographed ex situ); B, C—Top view of individual tubes; D–F—Cross-sectional views of tubes, showing variation in shapes of tube mouths and lumina: sub-trapezoidal cross-section (D–F), ovoid lumen (D) and circular lumen (E–F); G—Top view of tube with winglike keel structures; inset figure shows cross-sectional view of tube; H—Lateral keels that run along sides of tube of paratype ZRC.ANN.0481 (indicated by red arrows). Scale bars—A: 5 mm, B–H (including inset figure): 0.5 mm.

FIGURE 3. Radiolar crown in Spirobranchus bakau sp. nov. specimens. A—Top view of radiolar crown in paratype (ZRC. ANN.0482), showing circular arrangement of radioles; B, D—Radiolar crown with alternating black and cream-coloured bands at the base. The translucent, free ends of the radioles take on the colouration of underlying golden-brown pinnules. Red pigmented spots are mostly arranged in pairs on each radiole; C, H—Lateral views of complete holotype of S. bakau sp. nov. (ZRC.ANN.0480). Image was taken prior to excision of posterior abdominal segments for molecular studies. Evidence of sperm release in C (white arrow), indicating that the specimen is a male; E—Greyish bands alternating with black bands at base of radioles; F—Pinnules near tips are of brownish colouration; G—Distal end of radiolar base in paratype (ZRC.ANN.0481) with peach colouration (white arrow), which extends into inter-radiolar membrane. Scale bars—A–B, D–G: 0.5 mm, C, H: 1 mm.

FIGURE 4. Structural variation in opercular peduncles and talons in specimens of Spirobranchus bakau sp. nov.. A—Dorsal view of specimen, showing peduncle insertion on the left of median line, with peduncular wings tapering diagonally to the central axis of the operculum; B—Peduncular wings tapering perpendicularly to the central axis of the operculum; C—Wing tips end abruptly as if truncated; D—Top view of opercular endplate showing ovoid concentric layers with shallow depression in innermost layer; E—Opercular talon with bifid terminal region; F—Underside of opercular endplate showing position of talon relative to edges of endplate; G—Opercular talon of holotype (ZRC.ANN.0480) with trifid terminal region; H—Lateral view of talon of holotype (ZRC.ANN.0480); I—Talon of paratype (ZRC.ANN.0486) with protuberances from endplate on each side of peg and wing-shaped protuberance from the peg. Scale bars—A–I: 0.5 mm.

FIGURE 5. SEM photographs of Spirobranchus bakau sp. nov. chaetae. A—Collar chaetae; B—Thoracic chaetae; C—Closeup of abdominal chaetae; inset figure showing top view of abdominal chaetae with central groove in view; D—Thoracic uncini of paratype (ZRC.ANN.0484) showing rasp-shaped teeth above peg; E—Anterior abdominal uncini; F—Posterior abdominal uncini. Scale bars—A: 10 µm, B: 50 µm, C–F: 5 µm, C inset figure: 10 µm.