Hydroides sanctaecrucis Krøyer

Sun, Yanan, Ten, Harry A. & Qiu, Jian-Wen, 2012, Serpulidae (Annelida: Polychaeta) from Hong Kong, Zootaxa 3424, pp. 1-42 : 20-21

Hydroides sanctaecrucis Krøyer [in] Mörch, 1863

( Figure 10 A–G)

Hydroides (Eucarphus) sanctae-crucis Krøyer [in] Mörch, 1863: 378 –379.

Hydroides sanctaecrucis —Bastida-Zavala and ten Hove 2002: 146–149; 2003: 101–102; Bastida-Zavala 2008: 29 .

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Material examined. AM W40548, 3 specimens (22°25’N, 114°16’E, Tolo Harbour, on artificial substrate: fouling plates in fish farm, 10 m, April 15, 2009); AM W41408, 1 specimen (22°17’N, 114°11’E, Victoria Harbour, on pier piles, 0–1 m, May 20, 2009).

Description. TUBE: white, circular in cross-section. Peristomes and longitudinal ridges absent. Transversal ridges present. External tube diameter: from 1.5 mm to 1.8 mm (n=2, µ=1.6±0.2), lumen diameter from 1.5 mm to 1.8 mm (n=2, µ =1.6±0.2).

BRANCHIAE: radioles on each side arranged in semicircle, numbers ranging from 12 to 15 (n=3, µ=13.3±1.5). Interradiolar membrane absent. Terminal filament long.

PEDUNCLE: smooth, circular in cross-section, inserted just below left branchial lobe. Constriction hardly defined. Pseudo-operculum club-shaped.

OPERCULUM: numbers of radii ranging from 14 to 24 (n=3, µ=20±5.3), with pointed tip. Interradial grooves almost 1/3 of funnel length. Verticil with 10 to 12 spines (n=3, µ=11±1.0), all spines with pointed tip, dorsal spines slightly larger than ventral ones. Each spine with one external spinule, larger in ventral spines than in dorsal ones, and one basal internal spinule ( Figure 10 A). Lateral spinules absent. Central tooth absent. Opercular length from 0.8 mm to 0.9 mm (n=3, µ =0.9±0.1), width from 0.4 mm to 0.6 mm (n=3, µ=0.5±0.1).

COLLAR AND THORACIC MEMBRANES: collar high, continuous with well-developed thoracic membranes, forming apron across anterior abdominal chaetigers.

THORAX: with 7 chaetigers, 6 uncinigerous. Collar chaetae of two types: bayonet chaetae with two long pointed teeth and smooth distal blade ( Figure 10 B), and capillaries with minute denticles. Subsequent chaetae of two sizes (limbate and capillary, Figure 10 C–D). Uncini along entire thorax saw-shaped with 5 to 6 curved teeth including anterior fang ( Figure 10 E). Tori of similar size throughout, ventral depression present.

ABDOMEN: total number of abdominal chaetigers varies from 70 to 90 (n=3, µ=78.7±10.3). Uncini sawshaped with 4 to 5 teeth including anterior fang in anterior and middle abdominal chaetigers ( Figure 10 F–G), raspshaped with up to 7 teeth in profile view posteriorly. Chaetae flat trumpet-shaped. Capillaries present posteriorly, glandular pad absent.

SIZE: total worm length: 9.2 mm to 15.0 mm (n=3, µ=11.6±3.0), thoracic width: 0.7 mm to 1.0 mm (n=3, µ=1.0±0.5). Branchiae and operculum accounting for one fourth of entire length.

COLOUR: body yellow to light brown, verticil yellow to brown.

Habitat. Depth: 1–3 m, on rock piers or artificial substrate, fouling.

Distribution. Circum(sub)tropical.

Remarks. Hydroides sanctaecrucis is common in the Caribbean (Bastida-Zavala & ten Hove 2003). As a shiptransported species, Hydroides sanctaecrucis is a dominant fouling serpulid in Mexico, Panama and Oaxaca, and has been recorded as an invasive species in Northern Australia and Singapore ( Lewis et al. 2006; Bastida-Zavala 2008; Hutchings 2008). In Hong Kong, Hydroides sanctaecrucis was found in low densities on the pier and the fish farm, where Hydroides elegans dominated the fouling community.

Figures

FIGURE 10. Hydroides sanctaecrucis, AM W 40548. A, operculum. B, bayonet collar chaeta. C, limbate chaetae from chaetiger 4. D, details of limbate chaetae from chaetiger 4. E, uncini from chaetiger 4. F, anterior abdominal uncini. G, middle abdominal uncini. (Scale bars: A = 200 μm, B – D = 20 μm, E – G = 10 μm)