Spirobranchus de Blainville, 1818

Ten Hove, Harry A. & Kupriyanova, Elena K., 2009, Taxonomy of Serpulidae (Annelida, Polychaeta): The state of affairs, Zootaxa 2036, pp. 1-126 : 96-98

43. Spirobranchus de Blainville, 1818

( Fig. 47)

Type-species: Serpula gigantea Pallas, 1766

Number of species: 20+

Tube colour white, blue, pink or salmon, inside and/or outside. Tube typically (sub)triangular in cross-section, with median keel, rarely (sub)circular. Granular overlay absent. Operculum with inverse conical to rather shallow ampulla, covered by calcified endplate, with or without group of spines, sometimes branching. Peduncle broad, thickly triangular in cross-section, with distal lateral wings; inserted at base of branchial crown just left of medial line (formed between first and second normal dorsal radiole on left side, see Ontogeny of operculum and peduncle, p. 15). above. Pseudoperculum absent. Operculum rarely lacking. Radioles may be arranged in a clear spiral of up to 8 whorls, but in most small species as well as in Spirobranchus tetraceros arranged in a circle. Up to 50–60 pairs of radioles in larger species. Inter-radiolar membrane present. Branchial eyes may be present; stylodes absent. Mouth palps present. 7 thoracic chaetigerous segments. Collar trilobed (exceptionally pentalobed). Tonguelets present. Thoracic membranes forming ventral apron across anterior abdominal segment. Collar chaetae bayonet-like, with numerous hairlike processes on its basal portion ( Spirobranchus chaetae, Fig. 47A), and limbate. Apomatus chaetae absent. All uncini saw-shaped (9–25 teeth), incidentally with 2 teeth above peg ( Fig. 47B); anterior peg blunt, clearly gouged underneath ( Fig. 47C). Ventral ends of thoracic uncinigerous tori widely separated anteriorly, gradually approaching one another towards the end of thorax, thus leaving a triangular depression. Abdominal chaetae true trumpet-shaped, abruptly bent distally, with two rows of denticles separated by a hollow groove and forming long lateral spine ( Fig. 47D). Achaetous anterior abdominal zone absent. Chaetae becoming increasingly longer posteriorly, but posterior capillary chaetae absent. Posterior glandular pad absent.

Remarks. Species of this genus commonly occur in subtropical and tropical waters, but their taxonomy is confused because of significant variability in the opercular morphology. The major difference between the genera Pomatoceros , Pomatoleios and Spirobranchus is in the collar chaetae that are absent in Pomatoleios , simple limbate in Pomatoceros , and special with a knob consisting of numerous hair-like teeth in Spirobranchus . However, collar chaetae are occasionally absent in Pomatoceros and Spirobranchus and present in juvenile Pomatoleios .

Although Spirobranchus has special collar chaetae, the range of chaetal forms in what traditionally is included in Spirobranchus is quite wide and includes species with almost simple limbate chaetae. Moreover, the sperm morphology of Spirobranchus and Pomatoleios is very similar ( Nishi 1992a). Thus, although it is very likely that the three genera are synonymous, for the purpose of this review we have treated them as separate taxa.

A schematic presentation of the Spirobranchus giganteus -complex in its largest sense is given in Fiege & ten Hove (1999). According to Marsden (1992), the two morphotypes described by ten Hove (1970) as S. polycerus and S. polycerus var. augeneri are reproductively isolated, they thus probably should be regarded as full species.

1. Spirobranchus carinifer ( Gray, 1843) , New Zealand

2. Spirobranchus corniculatus ( Grube, 1862) , Java, Indonesia, Indo-West Pacific; part of a complex of species, often as S. giganteus

3. Spirobranchus coronatus Straughan, 1967b , Queensland, Fiji, Seychelles; compare S. tetraceros

4. Spirobranchus corrugatus Straughan, 1967a , Queensland, widely distributed in Indo-West Pacific

5. Spirobranchus cruciger ( Grube, 1862) , Red Sea, Indo-West Pacific; part of S. corniculatus -complex, often as S. giganteus

6. Spirobranchus decoratus Imajima, 1982 , Palau Islands, widely distributed in Indo-West Pacific

7. Spirobranchus eitzeni Augener, 1918 , Cameroon, tropical East Atlantic

8. Spirobranchus gardineri Pixell, 1913 , North of Madagascar, widely distributed in Indo-West Pacific; maybe complex of 2 species

9. Spirobranchus gaymardi ( Quatrefages, 1866) , unknown type locality, widely distributed in Indo-West Pacific; part of S. corniculatus -complex

10. Spirobranchus giganteus ( Pallas, 1766) , West Indies, widely distributed in tropical Western Atlantic; not in Pacific, where specimens belong to the S. corniculatus -complex

11. Spirobranchus incrassatus Krøyer [in] Mörch, 1863, Puntarenas, Colombia, tropical American Pacific; part of S. giganteus -complex

12. Spirobranchus latiscapus ( Marenzeller, 1885) , South Japan, widely distributed in Indo-West Pacific

13. Spirobranchus lima ( Grube, 1862) , Adriatic Sea, Mediterranean; records from elsewhere are incorrect

14. Spirobranchus maldivensis Pixell, 1913 , Maldive Islands, Indian Ocean, Central Indo-Pacific; compare S. latiscapus

15. Spirobranchus nigranucha ( Fischli, 1903) , Ternate, Indonesia, Indo-West Pacific

16. Spirobranchus paumotanus ( Chamberlin, 1919) , Paumotu Islands, widely distributed in Indo-West Pacific

17. Spirobranchus polycerus ( Schmarda, 1861) , Jamaica, Caribbean; probably “ var. augeneri ten Hove, 1970 ” is a full species

18. Spirobranchus polytrema ( Philippi, 1844) , Mediterranean, Atlantic; records from Indo-West Pacific probably complex of species by themselves

19. Spirobranchus spinosus Moore, 1923 , Sta. Barbara Isl., California; belongs to S. giganteus -complex

20. Spirobranchus tetraceros ( Schmarda, 1861) , New South Wales, circumtropical complex of species; Lessepsian migrant to Eastern Mediterranean and ship-transported to Senegal (Zibrowius, pers. comm.).