Hydroides elegans ( Haswell, 1883 )

Sun, Yanan, Ten, Harry A. & Qiu, Jian-Wen, 2012, Serpulidae (Annelida: Polychaeta) from Hong Kong, Zootaxa 3424, pp. 1-42 : 11-13

Hydroides elegans ( Haswell, 1883)

( Figure 2 B, Figure 6 A–H)

Eupomatus elegans Haswell, 1883: 633 .

Hydrodies [sic!] multispinosa not Marenzeller, 1885 sensu Lee and Trott 1973: 103.

Hydroides norvegica not Gunnerus sensu Day 1967: 805; Greene and Morton 1977: 231 –232, 235–236.

Hydroides elegans — Imajima 1976b: 237 –238; Huang and Mak 1982: 767–768, 771, 775–780; Mak 1982: 602–603; Mak and Huang 1982: 817–822; Morton and Morton 1983: 77, 88, 90, 121–122; Wang and Huang 1993: 1 –12; Qiu and Qian 1997: 79 –88; 1998: 127–134; Tan and Morton 1998: 392 –401; Bastida-Zavala and ten Hove 2002: 164–165; Ben-Eliahu and ten Hove 2011: 19 –25 [for partial, complicated synonymy].

Hydroides sp.— Thompson et. al. 1982: 748, 756.

Protohydroides elegans — Shin 1982: 170.

Material examined. AM W41405, 4 specimens (22°21’N, 114°17’E, Sharp Island, on dead coral, 3m, May 21, 2009); AM W40540, 20 specimens (22°25’N, 114°16’E, Tolo Harbour, on artificial substrate: fouling plates in the fish farm, 10 m, April 15, 2009)

Description. TUBE: white, circular in cross-section, fragmentary, with numerous transversal ridges, without longitudinal ridges. Collar-like rings absent. External tube diameter from 0.7 mm to 1.3 mm (n=8, µ=1.0±0.2), lumen diameter from 0.5 mm to 1.0 mm (n=8, µ=0.8±0.2).

BRANCHIAE: radioles on each side arranged in semicircle, numbers ranging from 8 to 14 (n=8, µ=1.0±0.2). Interradiolar membrane absent. Terminal filament about 1/5 of whole radiolar length.

PEDUNCLE: long, smooth, circular in cross-section, inserted below left branchial lobe in five specimens, right in eighteen specimens. Constriction absent. Pseudoperculum present in 18 specimens, with an inflated tip or a primary operculum (of the Serpula - type) only.

OPERCULUM: numbers of radii ranging from 22 to 27 (n=8, µ=24.5±2.4), radii with rounded, non-chitinized tips. Interradial grooves 2/3 of funnel length. Verticil with 9 to 16 straight, pointed spines (n=8, µ =10.8±2.0); spines yellowish, similar in shape, with 3 to 4 pointed lateral spinules on both sides and 1 to 3 internal spinules ( Figure 6 A). Central tooth present in fourteen specimens, absent in eight, similar in shape and size to lateral spinules. External spinules absent. Opercular length from 0.4 mm to 0.9 mm (n=8, µ=0.7±0.2), width from 0.4 mm to 0.9 mm (n=8, µ=0.7±0.2).

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

THORAX: with 7 chaetigers, 6 uncinigerous. Collar chaetae of two types: bayonet chaetae with two welldefined denticulate zones delimited by a conspicuous notch, distal one with rows of tiny serrations, proximal zone with four large pointed teeth and many smaller denticles proximally ( Figure 6 B); and finely striated capillaries. Subsequent chaetae of two sizes (limbate and capillary, Figure 6 C–D). Uncini along entire thorax saw-shaped with 6 curved teeth ( Figure 6 E). Tori of similar size throughout.

ABDOMEN: total number of abdominal chaetigers varies from 26 to 68 (n=8, µ=45.4±13.9). Uncini sawshaped with fang and 3 to 4 teeth anteriorly, increasing to 5 to 6 in the middle of the abdomen ( Figure 6 F–G); raspshaped posteriorly with 2 to 3 rows of teeth and 7 to 8 teeth (incl. fang) in profile view. Chaetae flat trumpetshaped. Capillaries present posteriorly ( Figure 6 H), glandular pad absent.

SIZE: total worm length: 8.1 mm to 25.5 mm (n=8, µ=12.7±5.9), thoracic width: 0.6 mm to 1.1 mm (n=8, µ=0.9±0.2). Branchiae and operculum accounting for one fifth of entire length.

COLOUR: in ethanol yellowish.

Habitat. Depth: 3–10 m, on dead coral, artificial substrate of the fish farm. Fouling.

Distribution. Widely distributed in tropical and subtropical waters around the world.

Remarks. Hydroides elegans is an invasive and fouling species ( Zibrowius 1994; Bastida-Zavala & ten Hove 2002). It is the most common serpulid in Hong Kong. Structures submerged in eastern Hong Kong waters for several months during winter and spring can be coated by H. elegans with a thickness up to 3.8 cm and wet-weight reaching 12.5 kg m -2 ( Wang & Huang 1993). Material from Sharp Island seemed to have slightly higher numbers of lateral spinules (4–6) to the verticil spines, the relevance of this occasional observation should be ascertained from further study.

Figures

FIGURE 6. Hydroides elegans, AM W 40540. 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. H, posterior abdominal capillary. (Scale bars: A = 100 μm, B, D – F = 10 μm, C = 20 μm)

FIGURE 2. A, Hydroides diramphus, AM W 40539, lateral view, removed from tube. B, Hydroides elegans, AM W 40540, showing the operculum and branchial crown. C – D, Protula bispiralis, associated with living corals, showing the branchial crown. E, Spirobranchus kraussii, AM W 41410, operculum, lateral view, removed from tube. F. Spirobranchus tetraceros, associated with Porites lutea, showing the opercula and branchial crowns.