Hydroides longistylaris Chen and Wu, 1980

Sun, Yanan, Ten, Harry A. & Qiu, Jian-Wen, 2012, Serpulidae (Annelida: Polychaeta) from Hong Kong, Zootaxa 3424, pp. 1-42 : 15-17

Hydroides longistylaris Chen and Wu, 1980

( Figure 8 A–I)

Hydroides longistylaris Chen and Wu, 1980: 249 –250; Fiege and Sun 1999: 118 –119; Sun and Yang 2000: 124.? Hydroides cf. fusicola not Mörch, 1863 sensu Mak 1982: 603–604.

?? Hydroides cf. ezoensis not Okuda, 1934 sensu Wang and Huang 1993: 7, 10.

Material examined. AM W40546, 10 specimens (22°21’N, 114°17’E, Sharp Island, on dead coral, 3–6 m, May 21, 2009).

Description. TUBE: white, trapezoidal in cross-section with two longitudinal ridges. Collar-like rings absent. External tube diameter: from 1.0 mm to 1.4 mm (n=3, r: 1.0–1.4, µ=1.2±0.2), lumen diameter from 0.8 mm to 1.0 mm (n=3, µ=0.9±0.1).

BRANCHIAE: radioles on each side arranged in semicircle, numbers ranging from 6 to 13 (n=7, µ=8.4±2.5). Interradiolar membrane absent. Terminal filament long.

PEDUNCLE: long, smooth, with a long yellowish chitinized constriction below funnel, circular in cross-section, inserted below right branchial lobe. Pseudo-operculum club-shaped in six specimens, with an inflated tip in four.

OPERCULUM: Opercular funnel with 16 to 25 radii (n=8, µ=20.5±3.3); distally brown, tips black, pointed and curving outward. Interradial grooves 1/3 of funnel length. Verticil small, strongly chitinized, with 5 to 8 smooth spines (n=8, µ=20.5±3.3), curving outward to almost parallel with funnel radii ( Figure 8 A). Central tooth absent. Opercular length from 0.4 mm to 1.2 mm (n=8, µ=0.7±0.3), width from 0.5 mm to 0.8 mm (n=8, µ=0.6±0.1).

COLLAR AND THORACIC MEMBRANES: collar high, thoracic membranes well-developed, apron present.

THORAX: with 7 chaetigers, 6 uncinigerous. Collar chaetae of two types: bayonet chaetae with two long pointed teeth and smooth distal blade, and capillaries with minute denticles ( Figure 8 B). Subsequent chaetae of two sizes (limbate and capillary, Figure 8 C–D). Uncini along entire thorax saw-shaped with 8 curved teeth including fang ( Figure 8 E). Tori of similar size throughout. Ventral depression present.

ABDOMEN: total number of abdominal chaetigers varies from 52 to 64 (n=3, µ=51±11.5). Uncini saw-shaped with 5 to 6 teeth anteriorly ( Figure 8 F, H), rasp-shaped posteriorly with 3 to 4 rows of teeth and 10 to 12 teeth (incl. fang) in profile view ( Figure 8 I). Chaetae flat trumpet-shaped ( Figure 8 G). Capillary chaetae not observed. Posterior glandular pad absent.

SIZE: total worm length: 8.3 mm to 13.8 mm (n=5, µ=10.8±2.4), thoracic width: 0.4 mm to 1.3 mm (n=7, µ=0.7±0.3). Branchiae and operculum accounting for one fifth of entire length.

COLOUR: in ethanol white.

Habitat. Depth: 3–6 m, on deal corals.

Distribution. South China Sea. Currently reported from Chinese coasts only.

Remarks. Hydroides longistylaris can be distinguished from other Hong Kong species of the genus by the presence of an elongated peduncle with a long chitinized constriction; such a chitinized part is present in H. rectus Straughan, 1967 as well, but this taxon has one enlarged vertical spine. The present specimens agree with the descriptions of Chen and Wu (1980), Fiege and Sun (1999), except for the numbers of radioles in the branchial crown (9 versus 15–23 pairs). Mak´s (1982: 603) statement for his H. cf. fusicola "The proximal half of the peduncle is fleshy and the distal half is transparent with a central chitinous column visible inside", as well as the 7 outward curving verticil spines clearly point to H. longistylaris rather than to the temperate H. fusicola .

Figures

FIGURE 8. Hydroides longistylaris, AM W 40546. A, operculum. B, collar chaetae. C, limbate and capillary chaetae from chaetiger 4. D, details of limbate chaetae from chaetiger 4. E, uncini from chaetiger 4. F, anterior abdominal uncini. G, toothed edge of flat-trumpet chaetae from posterior abdomen. H, middle abdominal uncini. I, posterior abdominal uncini. (Scale bars: A = 200 μm, B – C = 30 μm, D = 2 μm, E, H = 10 μm, F, G, I = 5 μm)