Placostegus

Kupriyanova, Elena K., Sun, Yanan, Ten Hove, Harry A., Wong, Eunice & Rouse, Greg W., 2015, Serpulidae (Annelida) of Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 275-353 : 303

Placostegus sp.

( Fig. 14 B, C)

? Placostegus tridentatus not ( Fabricius, 1779) Imajima 1978: 67 –69, fig. 9 [Izu Islands, Japan]; 1979: 179 [Kii Peninsula, Japan; see Remarks].

Material examined. SAM E3589, stn.G231, Coconut Beach, 14°41'S, 145°28'E, scuba, G. Rouse & E. Kupriyanova, 26 Oct 2005; ZMA V.Pol. 4649, Carter Reef, reef front, 20–30 m, coll. P. Hutchings, 10 Mar 1986 (tube only).

Diagnosis. Tube transparent, with three longitudinal rows of blunt teeth ( Fig. 14 C); collar region with a band of reddish ocelli, operculum asymetrical, with dark brown distal plate ( Fig. 14 B).

Remarks. We have refrained from giving a list of synonyms for this taxon and the reference to Imajima (1978) is tentative only, mainly meant as an illustration of the genus. Unpublished notes of one of us (HtH) mention two types of opercula for material from all around Australia, one with an almost circular endplate (like figured by Imajima 1978 fig. 9a–c for? P. tridentatus ), the other with a zygomorphic endplate (cf. Hartman 1969: 763 for P. californicus ). The operculum of our present specimen does not entirely fit one of these types, especially with regard to the two ventral bumps of the ampulla, not known from any other Placostegus spec . Placostegus tridentatus (Fabricius, 1799) is listed by ten Hove & Kupriyanova (2009) as a widely distributed species found in the Atlantic, Mediterranean, and Indo-West Pacific, including Zanzibar, Amirantes Islands, Indonesia, Western Australia and Japan (ten Hove 1994: 109). However, Imajima (1978: 69) already doubted whether or not his Japanese material was identical with the Atlantic specimens on a number of differences, a doubt also expressed by ten Hove (1994: 109) for his material from the Seychelles. Such a wide distribution is questionable in itself, and both unpublished morphological and molecular data indicate that Placostegus from Lizard Island is distinct from P. tridentatus from Northern Europe. Placostegus spp. from the Indo-Pacific Region, including Lizard Island, most likely belong to several undescribed species.

Distribution. Currently unknown.

Figures

FIGURE 14. A. Paraprotis dendrova, live animal removed from the tube, with typical brooding appendage bearing developing larvae (arrow), stn. G 243, SAM E 3591; B. Placostegus sp., operculum covered with brown distal plate, stn. G 231, SAM E 3589; C. Same, live animal in transparent tube, radiolar crown and operculum missing, bright orange belt of thoracic eyes (arrow) is seen through tube, stn. G 231, SAM E 3589; D. Pomatostegus actinoceras, live animal in tube, AM W. 44540. Photo: A – C—G. Rouse, D—A. Semenov. Scale bars: A = 0.5 mm, B – D = 1 mm.