Knightjonesia, Pillai, Gottfried, 2009

Pillai, Gottfried, 2009, Knightjonesia, a new genus (Polychaeta: Spirorbidae) with a winged opercular peduncle, and its taxonomy, Zootaxa 2059, pp. 46-50 : 47-49

Knightjonesia , new genus

Diagnosis. Tube sinistrally coiled; opercular peduncle winged; thoracic membranes not joined over thorax. Thorax bears 4 chaetal fascicles, including collar chaetal fascicle, and 3 uncinal tori on concave side left side; two uncinal tori on convex side. Collar chaetae simple blades i.e., lacking a fin at base of blade; remaining thoracic fascicles lack sickle-shaped chaetae ( Apomatus -chaetae); thoracic uncini slender, bearing 1-few rows of teeth; abdominal uncini with several rows of teeth; most anterior uncinal process gouged.

Type species: Knightjonesia platyspira ( Knight-Jones) 1978 = Helicosiphon platyspira Knight-Jones, 1978 .

Material examined: Type Material: Holotype of Helicosiphon platyspira Knight-Jones 1978 : BM (NH) 1976: 883, Marion Island, Prince Edward Islands, southeast of Port Elizabeth, consisting only of an operculum; and its paratypes BM (NH) 1976: 884–899 from the same locality. The latter consist of several individuals of various sizes, from tiny juveniles to adults, the tubes of many of which remain unopened. Some of them were extracted from their tubes in order to study the stages in formation of peduncular wings.

Description. As stated by P. Knight-Jones (1978) the present species is, compared to other spirorbids, a very large species, attaining a coil diameter of 5.0mm when coiled in the same plane. In addition to the generic diagnosis above, see P. Knight-Jones (1978: 233–234) and P. & E. W. Knight-Jones (1994) for further details relating to the tube, worm, chaetae, egg-sac attachment, and other characters. The egg sac and its attachment to the specialized process in the dorsal thoracic groove are shown in Fig. 2E . The brief description which follows is limited to the character of its winged opercular peduncle.

Initially the wings are short and faintly recognizable ( Fig. 2 B ). In a later stage ( Fig. 2C ), they are narrow and elongated. The more fully developed wings are shown in Figs. 2 , A, D & E.

Etymology. The genus is dedicated to both Prof. E. Wyn Knight-Jones & the late Dr. Phyllis Knight- Jones, in appreciation of their numerous contributions to our knowledge of the biology and systematics of serpulimorph and sabellid polychaetes, especially spirorbids, besides other areas.

Taxonomy of genera belonging to the subfamily Romanchellinae P. Knight-Jones, 1978

Among the characters of the subfamily Romanchellinae, included by P. Knight-Jones (1978: 229) and P. & E. W. Knight-Jones (1994: 79), is that the embryos are raised within the tube in an egg sac attached anteriorly by a specialized process to the dorsal thoracic faecal groove. P. & E. W. Knight-Jones (1994: 79) also state that the members of the subfamily are the only spirorbids that possess brush-like abdominal chaetae. P. Knight-Jones (1978: 229–234) included the following genera under the subfamily: Romanchella Caullery & Mesnil (1897) , type species Spirorbi s (Romanchella) perrieri Caullery & Mesnil (1897) and Helicosiphon Gravier (1907) , type species H. biscoensis Gravier, 1907 . On the basis of subsequent studies, P. Knight-Jones & Fordy (1979: 121) include the genus Protolaeospira ( Pixell, 1912) , redefined by Knight-Jones, 1972 and 10 species of the latter under the Romanchellinae. As defined by Knight-Jones & Walker (1972: 35) Protolaeospira is the same as Marsipospira Bailey, 1969 and includes Pixellia Pillai, 1970 . P. Knight-Jones (1978: 233) describes the new species H. platyspira , which is transferred to the new genus Knightjonesia , with K. platyspira P. Knight-Jones, 1978 as its type species in the present paper.

Based on the above and present studies, the differences among those genera may be summarized as follows. Opercular peduncle is winged in Knightjonesia , wingless in Romanchella , Helicosiphon and Protolaeospira . Thoracic membranes of the two sides are not joined over the thorax in Knightjonesia , as seen in Knight-Jones (1978: Fig. 18E) and Figs. 1 E & 2 E of the present paper, Helicosiphon P. Knight-Jones (1978: 232–233) and Fig 1D of the present paper, and in Protolaeospira , whereas it is joined over the thorax in Romanchella (see Knight-Jones, 1978: 229, Figs.16B & 17J). Collar chaetae do not consist of a fin and blade but simple blades in Romanchella , Helicosiphon and Knightjonesia , whereas they consist of a fin and blade in Protolaeospira . Sickle-shaped chaetae ( Apomatus -chaetae) are absent in the thorax of Knightjonesia and Helicosiphon , whereas they are present in Romanchella and Protolaeospira . The most anterior uncinal process is blunt and gouged in Knightjonesia , Romanchella and Helicosiphon , whereas it is bilobed in Protolaeospira .

Figures

FIGURE 2. A – E, Knightjonesia platyspira (P. Knight-Jones, 1978): same scale for all; w— wing. A, Enlarged view of operculum of specimen figured in Fig. 1. B – D, stages in opercular wing development observed in paratypes; B also shows the sub-quadrangular talon. E: whole worm showing the winged opercular peduncle and the egg sac with its specialized attachment stalk to the dorsal thoracic groove.

FIGURE 1. A – D: Helicosiphon biscoensis figured from BM (NH) 1930.10.8.2984, Discovery Expedition, St. 175, South Shetlands, 200 m: A – C: Tubes showing uncoiling. Ontogenetically, however, the earliest formed part of the tube is coiled as shown in Figs. A and C. That part of the tube is missing in the specimen figured in B. Note also the angular sides of the earlier uncoiled parts of the tube. D, Worm, showing the straightened body, which conforms to that of spirorbids (see also description); the attachment stalk for the brood-pouch to the thorax can be seen dorsally (brood pouch missing). E, Knightjonesia platyspira (Knight-Jones) 1978 showing its winged peduncle, figured from among paratypes in BM (NH) 1969.492, Marion Island, Prince Edward Islands, collected by A. F. Villiers, 1973; see Fig. 2 for further details.