Pomatostegus actinoceras Mörch, 1863

Sánchez-Ovando, J. Pablo & Bastida-Zavala, J. Rolando, 2021, Redescription of Pomatostegus stellatus (Abildgaard, 1789) and P. kroyeri Mörch 1863 (Polychaeta: Serpulidae) from the Tropical American coasts, Zootaxa 4970 (3), pp. 495-514 : 506-509

Pomatostegus actinoceras Mörch, 1863

( Figures 7A–I , 8C )

Pomatostegus actinoceras Mörch, 1863: 400 , pl. 11, figs 16–17. Type locality: Philippines.

Serpula (Pomatostegus) sanguinea Ehrenberg & Grube in: Grube, 1869: 519–520 (Red Sea); Hartwich 1993: 135 (holotype in the Zoological Museum, Berlin: ZMB Verm. 532).

Pomatostegus actinoceras .— Willey, 1905: 314–316, pl. 8, figs 3–4 ( Sri Lanka; associated to oysters; 14–45 m); Humann & Deloach 2010: 71 (Indo-Western Pacific; in vivo color photograph); Bailey-Brock et al. 2012: 975, fig. 5A–K ( Marshall Islands; on coral rock and mollusk shells; 15–20 m); Kupriyanova et al. 2015: 304, Fig. 14D (Lizard Island, Australia; on coral rubble; 0.5– 10 m).

Pomatostegus actinoceros .— Augener 1914: 152–155 (Shark Bay, Australia; sand and corals bottom; 11–12.5 m); Pillai 2009: 109–112, figs 9A–E & 10A–E (Kimberley, Western Australia; on sand and rocky bottoms; intertidal to 30 m).

Serpula (Pomatostegus) actinoceras .— Treadwell 1920: 601 ( Caguayan Point , Leyte, and Dupon Bay , Point Light, Lauis, Philippines; staghorn coral and rock bottom, 76 m) .

Pomatostegus stellatus not Abildgaard, 1789.— Mesnil & Fauvel 1939: 34 (Aru Island, Rotti (Roti) Island, Indonesia; both samples in ZMA acc. to Bleeker & van der Spoel 1992: 154); Dew 1959: 41–42, fig. 14A–G (Thursday Island, Queensland, Australia and Bougainville Island, Solomon Islands; on oyster spat and the shell of the hammer oyster Malleus vulgaris ); Johanssson 1918: 10–12 (Western Australia); Pillai 1960: 23–25, fig. 9A–D (Pearl Banks, Sri Lanka); Pillai 1971: 94 (Wellawatte, Colombo, Sri Lanka; from reef, on Ostrea sp. ); Straughan 1967a: 38 (Heron Island, Queensland, Australia; coral reef); Straughan 1967b: 238 (Queensland, Australia; on rocks); Straughan 1967c: 224 (Cape Don and Darwin, Northern Territory, Australia); Imajima 1977: 101–102, fig. 7a–k (Ogasawara Islands, Japan; 2 m; on corals); Imajima 1982: 51 ( Palau and Yap Islands, Micronesia; reef); Imajima 1987: 80 (Okinawa and Sesoko Islands, Japan; underside of corals on the reef flat, and dredged on “dead or living corals”; 5–45 m); Mak 1982: 608 ( Hong Kong; on corals); Imajima & ten Hove 1984: 54 ( Truk Islands, Ponape and Majuro Atoll, Micronesia; reef); Imajima & ten Hove 1986: 9 ( Gilbert Islands, Kiribati, and Solomon Islands; intertidal, “chiefly detached from corals”); Stock 1988: 217 (Lizard Island, Queensland, Australia; maybe parasitized by bizarre copepod Octophiophora lacertae Stock, 1988 ); Nishi 1993a: 12, Table 1 (Okinawa Island, Japan; on concrete walls and vinyl plate); Nishi 1993b: 19, Table 1 (Okinawa Island, Japan; internal structure of tube wall); Nishi 1995: 29–31, fig. 1h (Okinawa Island, Japan; on Pavona decussata (Dana, 1846) ; 0.5 m); Nishi 1996: 312 (Okinawa Island, Japan; on living coral; 1–2 m); Fiege & Sun 1999: 131–133, fig. 19a–f (Hainan Island, China; 10–12 m); Sun & Yang 2001: 215, fig. 1B–K (waters off China); Sanfilippo et al. 2010: 7, 9, fig. 6a (Andaman Sea, southwestern Thailand; on cobbles); Bok et al. 2017: 41–42: fig. 2P–S (Lizard Island, Queensland); Pamungkas & Glasby 2019: 619, Table 2 (checklist of Indonesian species); Sivadas & Carvalho 2020: 16687 (checklist of marine annelids from India).

Description. Tube opaque, white with 1–6 longitudinal ridges, the middle with blunt teeth and a horizontal spine protruding from tube aperture; triangular in cross-section ( Pillai 2009: 110, fig. 9, A–B; Bailey-Brock et al. 2012: 975–976, fig. 5, B–D). Body white to yellowish, 8–48 mm long, thorax 2–7 mm wide, with seven chaetigers and abdomen with 77–102 chaetigers ( Imajima 1977: 102; Pillai 2009: 110). Opercular peduncle maculated with brown pigment, wide wings terminating in pointed tips ( Bailey-Brock et al. 2012: 975; Kupriyanova et al. 2015: 304). Operculum chitinous, with successive opercular festooned plates widely separated, shallow dish-shaped (Bailey-Brock et al. 2012: 976, Fig.5A, E ). Distal tip of the hollow column has more “free” circlets of spines (2–4) without accompanying plates, circlets of spines curved downwards on first plates and then becoming straight on the distal whorls ( Fiege & Sun 1999: 132, Fig. 19A–B; Bailey-Brock et al. 2012: 976, Figs 5A–B, E ). Collar chaetae Spirobranchus - type, serrated in subapical section and with a wide proximal boss, twice wider than distal blade ( Imajima 1977: 101, Fig. 7 , c).

Habitat. Littoral to sublittoral (30 m, Pillai 2009). On corals, rocks and mollusk shells ( Imajima 1977; Pillai 2009; Bailey-Brock et al. 2012; Kupriyanova et al. 2015).

Distribution. Indo-Western Pacific: southern Japan, Micronesia and Australia, China and Sri Lanka ( Kupriyanova et al. 2015).

Remarks. Several authors, e.g., Dew (1959), Pillai (1960), Imajima (1977), recorded Pomatostegus specimens from the Indo-Western Pacific more often as P. stellatus than as P. actinoceras (see synonym section). Some authors did not mention the shape of opercular plates and proximal boss of collar chaetae in descriptions of P. actinoceras , but illustrated these structures (e.g., Dew 1959; Imajima 1977): the opercular plates are shallowly dish-shaped and the Spirobranchus - type chaetae have wide proximal bosses. Based on the literature, the main differences between P. actinoceras and P. stellatus is that the former has tubes triangular in cross-section and an operculum with distal tip of the central column hollow and with 2–4 “free” circlets of spines ( Mörch 1863: 400, Fig. 16; Fiege & Sun 1999: 132, Fig. 19A–B; Bailey-Brock et al. 2012: 976, Fig. 5A–B, E ), without accompanying plates ( Fig. 7A–C and Mörch 1863: 396–397, Fig. 14); while the latter has tubes semi-circular to circular in cross-section and an operculum with distal tip of the central column hollow, with only one “free” circlet of spines without accompanying of plates ( Fig. 1A–D ). Unfortunately we could not examine specimens of P. actinoceras , lacking in our collections; a review of material of this nominal species is necessary to verify the differences observed from the literature only herein.

Figures

FIGURE 1. Specimen of Pomatostegus stellatus (Abildgaard, 1789) from Contoy Island, Mexican Caribbean. A. operculum with shallow dish-shaped plates, lateral view; B. opercular peduncle maculated with brown pigment; C. peduncle with wide wings with the wavy edge; D. radiolar crown with bands of brown iridescent pigment.

FIGURE 5. Pomatostegus stellatus: Operculum with shallowly dish-shaped plates. A. specimen from Mahahual, Quintana Roo; B. specimen from Contoy Island, Quintana Roo. P. kroyeri: Operculum with deeply dish-shaped plates. C. specimen from Caleritas Beach, Baja California Sur; D. specimen from Caleta de Chón, Guerrero.

FIGURE 7. Pomatostegus actinoceras Mörch, 1863. A–C. operculum with shallowly dish-shaped plates, distal tip of the column with two “free” circlets of spines without accompanying plates; D. Spirobranchus-type chaetae with a wide proximal boss; E. thoracic capillary chaeta; F. Apomatus-type chaeta; G. abdominal chaeta: flat narrow geniculate; H. thoracic uncinus; I. abdominal uncinus. (A–I. modified after Bailey-Brock et al. 2012).

FIGURE 8. Tubes of species of Pomatostegus. A. Tube of P. stellatus, anterior view; B. Tube of P. kroyeri; C. Tube of P. actinoceras; D. Pomatostegus stellatus, in vivo, between a coral colony, from Chinchorro Bank, Mexican Caribbean (C. modified from Bailey-Brock et al. 2012; D. photo by Humberto Bahena, September 2000).