Serpula cf. granulosa Marenzeller, 1885

Sun, Yanan, Ten, Harry A. & Qiu, Jian-Wen, 2012, Serpulidae (Annelida: Polychaeta) from Hong Kong, Zootaxa 3424, pp. 1-42 : 26

Serpula cf. granulosa Marenzeller, 1885

( Figure 3 P–Q, Figure 12 A–F)

Serpula granulosa Marenzeller, 1885: 316 –317.

? Serpula vermicularis not Linnaeus, 1767, sensu Mak 1982: 609; Morton and Morton 1983: 278; Wang and Huang 1993: 8.

Material examined. AM W40554, 2 specimens (22°21’N, 114°17’E, Sharp Island, on dead coral, 6 m, May 21, 2009).

Description. TUBE: thick-walled, rough, with a median longitudinal keel, circular in internal cross-section. Median keel violet, grading into pale pink on both sides; tube white inside. Peristomes absent. Up to 6.5 mm wide with lumen up to 4.5 mm diameter.

BRANCHIAE: each lobe with 23 to 25 radioles (n=2, µ=24±1.4), arranged in semicircle. Interradiolar membrane of 1/8th of the radiole. Pinnules short and thin; each radiole ending in thin terminal filament, as long as pinnules.

PEDUNCLE: smooth, circular in cross-section, inserted just below right branchial lobe. Clear constriction just below operculum. Pseudo-operculum evident in one specimen, with globular inflated tip.

OPERCULUM: symmetrical, fleshy funnel with 55–58 radii, with pointed conical tips ( Figure 3 P–Q). Funnel distally shallow, not deeply cupped. Lengths of the operculum from 3.0 mm to 3.4 mm (n=2, µ=3.2±0.2), widths from 3.3 mm to 3.5 mm (n=2, µ=3.4±0.1). External grooves about 1/3rd of opercular length; apical grooves variable in extension, 1/3rd, 2/3rd of width or almost reaching centre. Tubercles on apical radii present.

COLLAR AND THORACIC MEMBRANES: collar high, trilobed, lateral lobes large and continuous with well-developed thoracic membranes, merging with ventrum, not forming an (continuous) apron in the sense of ten Hove (1984: 158), but interrupted above anterior abdominal chaetigers.

THORAX: with 7 chaetigers, 6 uncinigerous. Collar chaetae of two types: bayonet chaetae with two teeth having blunt tips at base of blade, and smooth capillaries ( Figure 12 A–B). Subsequent chaetae of two sizes (limbate and capillary, Figure 12 C). Uncini along entire thorax saw-shaped, with 4–5 teeth, including pointed anterior fang ( Figure 12 D).

ABDOMEN: total number of abdominal chaetigers varies from 110 to 138 (n=2, µ=124±19.8). Achaetous region absent. Uncini saw-shaped, with 3 teeth anteriorly ( Figure 12 E), 5 to 6 teeth in middle and posterior abdomen ( Figure 12 F). Chaetae flat trumpet-shaped. Capillaries present in posterior chaetigers.

SIZE: total worm length: 25.0 mm to 45.0 mm (n=2, µ=35±14.1); thoracic width of both specimens 4.0 mm (n=2, µ=4.0±0). Branchiae and operculum accounting for approximately one fifth of entire length.

COLOUR: Living worm brightly reddish, colour in ethanol pale yellow.

Habitat. Depth: 6 m, on the surface of dead corals.

Remarks. Difficulties in identifying various taxa of Serpula have been discussed by ten Hove and Kupriyanova (2009: 93) and Ben-Eliahu and ten Hove (2011: 78). Six taxa have been recorded from Chinese waters ( Sun & Yang 2001a): Serpula cf. hartmanae Reish, 1968 , S. sinica Wu and Chen, 1979 (in Wu, Sun & Chen 1979), S. tetratropia Imajima and ten Hove, 1984, S. cf. vasifera Haswell, 1885 , S. vermicularis not Linnaeus, sensu auct. (see below), and S. watsoni Willey, 1905 . In narrowing down the identity of the present specimens we can exclude Serpula cf. hartmanae , S. sinica , S. tetratropia and S. cf. vasifera on the basis of fewer opercular radii (11–16, 32, 18–26, respectively 29 as opposed to 55–58), as well by differences in tubes, which have all at least two longitudinal ridges instead of one medial keel. Serpula watsoni is easily recognized by its operculum, a deep funnel with very long radial grooves, almost extending to the peduncle, as well as tube with 2 longitudinal ridges.

Mak (1982) described specimens as S. vermicularis , with a flat operculum bearing 28 to 63 marginal radii, and a thick tube with a medial longitudinal keel. Our material probably is the same, with its high number of opercular radii and triangular tube. However, as amongst others mentioned by ten Hove and Kupriyanova (2009), S. vermicularis has a distribution limited to Western Europe. A number of larger sized taxa, with high numbers of radii have been described for Indo-West Pacific waters (see discussion in Ben-Eliahu & ten Hove 2011: 83–87). Our present material agrees best, but maybe not fully, with the description of S. granulosa . For instance, colour of the tube is missing in the original description and not recorded either when the holotype (Naturhistorisches Museum Wien Evertebrata varia: 1998) was re-examined by one of us (HAtH) a couple of decades ago and the posterior thoracic membranes were damaged. Also because of the confused state of the Serpula jukesi / granulosa -complex (Ben- Eliahu & ten Hove 2011: 84–87), we have given the tentative identification of cf. granulosa to our material. Serpula granulosa Marenzeller is a homonym of the fossil S. granulosa von Hagenow, 1840.

Figures

FIGURE 12. Serpula cf. granulosa, AM W 40554. A, bayonet and capillary collar chaetae. B, bayonet collar chaeta. C, limbate and capillary chaetae from chaetiger 4. D, uncini from chaetiger 4. E, anterior abdominal uncini. F, middle abdominal uncini. (Scale bars: A – C = 100 μm, D – F = 10 μm)

FIGURE 3. A – B: Hydroides albiceps, AM W 40534, operculum, lateral and apical view. C: Hydroides operculatus, AM W 41406, operculum, lateral view. D – J: Hydroides rhombobulus, AM W 41407. D – E, operculum, lateral and apical view. F, G, collar chaetae. H, thoracic limbate chaeta. I, thoracic uncinus. J, abdominal uncinus. K – O: Protula bispiralis, AM W 41409. K, dorsal view; L, limbate collar chaeta. M, limbate chaeta from chaetiger 6. N, abdominal sickle-shaped chaeta. O; abdominal uncinus. P – Q: Serpula cf. granulosa, AM W 40554, operculum, lateral and apical view. (Scale bars: A – E = 0.2 mm, F – G, O = 50 μm, I – J = 10 μm, K = 5 mm, L – N = 100 μm, P – Q = 1 mm)