Chone letterstedti ( Kinberg, 1867 )

Tovar-Hernández, María Ana, 2007, On some species of Chone Krøyer, 1856 (Polychaeta: Sabellidae) from world-wide localities, Zootaxa 1518, pp. 31-68 : 47-48

Chone letterstedti ( Kinberg, 1867)

Figure 9

Parachonia letterstedti Kinberg, 1867: 73 , Pl. 28, Fig. 6 .— Johansson, 1925: 27, Figs 9–11 . Chone letterstedti .— Day, 1967: 777, Fig. 37.7 g –k.

Material examined. Type material. South Africa [ SMNH 576, holotype], Cap. Coll. Wahlberg.

Additional material. Chone aurantiaca ( Johnson, 1901) [ MCZ 1933, holotype]. Chone gracilis Moore, 1906 [ USNM 5513, holotype]. Chone infundibuliformis Kr ø yer, 1856 [ ZMUC POL –1749, lectotype]. Chone magna ( Moore, 1923) [ USNM 17281, holotype]. Chone mollis Bush in Moore, 1904 [ YPM 2793, holotype]. Chone picta ( Verrill, 1885) [ YPM 30000, topotypes].

Description. Colour, body shape, and size. Body cream coloured. Holotype with histolysis, fragmented in four pieces. Trunk cylindrical ( Fig. 9 C). Body length 21 mm, width 1.5 mm. Tube unknown.

Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar. Branchial crown length: 12 mm. Radioles: 9 pairs. Radioles with median pinnules two times longer than more proximal pinnules. Radiolar tips short ( Fig. 9 D). Palmate membrane extends three quarters the length of branchial crown. Lateral flanges broad ( Fig. 9 D). Dorsal lips two times longer than wide, erect, without a discernable longitudinal ridge. Dorsal pinnular appendages: 1–3 short pairs, united by a palmate membrane. Ventral lips rounded, as long as wide, about one quarter the length of the dorsal lips. Ventral radiolar appendages: 1–3 pairs, the inner one about three quarters of the branchial crown length, the remainder about one quarter the length of the branchial crown.

Peristomium . Anterior peristomial ring lobe not exposed beyond collar, distally entire. Posterior peristomial ring collar: antero-dorsal margin deeply incised (perhaps due to histolysis) ( Fig. 9 A); lateral and ventral margins entire ( Figs 9 B–C), ventral slightly higher than dorsal ( Figs 9 B–C); entire length of mid-dorsal collar margins forms a broad gap. Ventral shield of collar swollen, horseshoe-shaped, two times wider than long ( Fig. 9 B). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 1.5:1.

Thorax. Elongate, narrowly hooded chaetae ( Fig. 9 F); narrowly hooded bayonet chaetae, two posterior rows with symmetrical, paleate chaetae with medium-sized mucro ( Figs 9 G–I). Thoracic uncini ( Fig. 9 J) with five rows of teeth over the main fang, second tooth enlarged and located in midline, dentition covering one quarter of the main fang length. Narrow glandular ridge on chaetiger 2.

Abdomen. Abdominal segments: 41. Elongate, narrowly hooded chaetae, upper row chaetae half as long as lower row ones ( Fig. 9 M); anterior abdominal uncini with the main fang surmounted by four rows of equal in size teeth, occupying one half of the main fang length, main fang not extending beyond breast, breast rectangular ( Fig. 9 K). Posterior segments: 1–2 very elongate, narrowly hooded chaetae, 25% longer than in anterior segments; uncini similar to those in anterior abdominal segments, but smaller ( Fig. 9 L). Pygidium with rounded posterior margin ( Fig. 9 E).

Gametes. Holotype female with oocytes in all thoracic and anterior abdominal segments, diameter undeterminable.

Methyl green staining. Anterior end of ventral collar shield not coloured. Body coloured uniformly dorsal and ventrally.

Remarks. Parachonia Kinberg, 1867 , was regarded as junior synonym of Chone by Johansson (1927). The original description of Chone letterstedti (Kinberg) is brief. Thus, it had to be redescribed to be properly compared with the remaining species in the genus. This redescription points out that in C. letterstedti : a) radiolar tips are short; b) radiolar flanges broad; c) anterior dorsal margins of collar deeply incised; d) entire length of mid-dorsal collar margins forms a broad gap; and e) abdominal uncini with similar shape throughout.

Chone letterstedti , C. infundibuliformis , C. aurantiaca , C. duneri , C. gracilis , C. magna , C. mollis and C. picta have the anterior and posterior abdominal uncini with similar shape: a well developed main fang surmounting by few smaller teeth irregularly arranged, overlapping, not as a uniform set of rows, that occupy less than a half of the main fang lengths; main fang not extending beyond breast, and with rectangular well developed breast, handles absent. However, C. letterstedti is unique among these species because it has the anterodorsal margin of collar deeply incised.

Figures

FIGURE 6. Chone fauveli. (A) Anterior end, dorsal view; (B) same, lateral view; (C) anterior abdominal uncinus; (D) posterior abdominal uncinus; (E) anterior end, ventral view; (F) thoracic uncinus; (G) bayonet chaeta; (H) paleate chaeta; (I) thoracic, elongate, narrowly hooded chaeta; (J) radioles and palmate membrane; (K) dorsal pinnular appendages. (A – B, E) Methyl green staining. (A – B, E, J – K) [ZMO Vaus ủ, Sars 90]; (C – D, F – I) [ZMUB 25488].

FIGURE 9. Chone letterstedti. (A) Anterior end, dorsal view; (B) same, ventral view; (C) same, lateral view; (D) radiolar tip; (E) posterior abdomen, lateral view; (F) thoracic, elongate, narrowly hooded chaeta; (G – I) paleate chaetae; (J) thoracic uncinus; (K) anterior abdominal uncinus; (L) posterior abdominal uncinus; (M) very elongate, posterior abdominal chaeta. (A – M) [SMNH 576, holotype].

FIGURE 10. Chone murmanica. (A) Anterior end, dorsal view; (B – C) same, ventral views; (D – E) paleate chaetae; (F) thoracic uncinus; (G) spermatozoon; (H – J) posterior abdominal uncini; (K – L) thoracic chaetae; (M) anterior abdominal chaeta; (N) posterior abdominal chaeta. (A – C) Methyl green staining. (A) [ZIRAS 38178]; (B – N) [LACM – AHF Carey OSU].

FIGURE 11. Chone normani. (A) Body, ventro-lateral view; (B) anterior end, ventral view; (C) same, dorso-lateral view; (D) posterior abdominal uncinus; (E) paleate chaeta; (F) thoracic uncinus; (G) abdominal elongate, narrowly hooded chaeta. (A – C) Methyl green staining. (A – G) [NMW. Z 1997.078.0062].