Spirobranchus kraussii ( Baird, 1865 )

Sun, Yanan, Ten, Harry A. & Qiu, Jian-Wen, 2012, Serpulidae (Annelida: Polychaeta) from Hong Kong, Zootaxa 3424, pp. 1-42 : 28-30

Spirobranchus kraussii ( Baird, 1865)

( Figure 13 A–F)

Placostegus cariniferus var. Kraussii Baird, 1865: 14 .

Pomatoleios kraussii — Day 1967: 800 –801; Morton and Morton 1983: 88 –89; Wang and Huang 1993: 1 –12; Tan and Morton 1998: 392 –401; Fiege and Sun 1999: 130 –131; Sun and Yang 2001b: 213 –214; Ben-Eliahu and ten Hove 2011: 43 –45. Pomatoceros triqueter not ( Linnaeus, 1758), Morton and Morton 1983: 77 (error for Pomatoleios kraussii ).

Material examined. AM W41410, 10 specimens (22°21’N, 114°15’E, Hebe Haven, rocky intertidal, 0–1 m, May 25, 2009).

Description. TUBE: Tube white to blue, triangular in cross-section, with medial keel projecting into flap over the entrance. External tube diameter: from 1.9 mm to 2.4 mm (n=3, µ=2.2±0.3), lumen diameter from 1.5 mm to 2.0 mm (n=3, µ =1.8±0.3).

BRANCHIAE: radioles on each lobe arranged in circles, connected by interradiolar membrane for about one third of their length; numbers ranging from 21 to 26 (n=5, µ=23.4±1.9). Terminal filaments short. Branchial eyes not observed.

PEDUNCLE: subtriangular in cross-section, inserted just below left branchial lobe in all specimens. Pair of lateral wings proximal to opercular ampulla present, constriction not observed. Pseudo-operculum absent.

OPERCULUM: operculum slightly concave, talon absent. Opercular length from 3.8 mm to 4.6 mm (n=5, µ=4.3±0.3), width from 0.9 mm to 1.2 mm (n=5, µ=1.1±0.1).

COLLAR AND THORACIC MEMBRANES: collar high, with entire edge. Thoracic membranes forming apron across anterior abdominal chaetigers.

THORAX: with 6 chaetigers. Collar chaetae absent. Thoracic chaetae of two sizes, largest (limbate) finely serrated ( Figure 13 A). Uncini along entire thorax saw-shaped, with 9 curved teeth and gouged fang ( Figure 13 B). Tori of similar size along thorax, approaching each other posteriorly, leaving ventral depression.

ABDOMEN: total number of abdominal chaetigers varies from 68 to 86 (n=5, µ=78.8±0.2). Uncini sawshaped throughout, with 8 to 9 teeth and gouged peg ( Figure 13 C, E–F). Chaetae true trumpet-shaped, abruptly bent, distally with two rows of denticles separated by a groove forming long pointed tip ( Figure 13 D). Posterior abdominal capillaries absent.

SIZE: total worm length: 7.0 mm to 11.0 mm (n=5, µ=9.1±1.5), thoracic width: 1.5 mm to 1.8 mm (n=5, µ=1.7±0.1). Branchiae and operculum accounting for one fourth of entire length.

COLOUR: in ethanol operculum bluish, peduncle and wings light blue with dark blue pigmentation, branchial radioles banded blue and white, thorax and anterior abdomen blue, posterior abdomen colourless.

Habitat. Depth: 1 to 3 m, on rocks in higher intertidal zone.

Remarks. Spirobranchus kraussii has been reported as one of the dominant species in fouling communities in Hong Kong, forming intertidal aggregations ( Wang and Huang 1993, as Pomatoleios kraussii ).

Distribution. Widely distributed in the Indo-Pacific; South Africa; Lessepsian migrant to the Mediterranean Levant.

Figures

FIGURE 13. Spirobranchus kraussii, AM W 41410. A, limbate and capillary chaetae from chaetiger 4. B, thoracic uncini. C, anterior abdominal uncini. D, serrated edges of trumpet-shaped chaetae from posterior abdomen. E, middle abdominal uncini. F, posterior abdominal uncini. (Scale bars: A – F = 10 μm)