Chone

Tovar-Hernández, María Ana, 2007, On some species of Chone Krøyer, 1856 (Polychaeta: Sabellidae) from world-wide localities, Zootaxa 1518, pp. 31-68 : 56-58

Chone sp. Aleutian Islands

Figure 15

Non-type material. Aleutian Islands [ LACM – AHF] Aleutian Cruise, Sta. 86a, 64–30 N, 169–50 W, August 13, 1949, Dredge, 23, Like Beach sand (7). Japan [PC–ZL] Katsuura, Boso Peh, subtidal, 1994, May (1). Additional material. Chone quebecensis Tovar-Hernández (2007) [ CMN, holotype].

Description. Colour, body shape, and size. Holotype complete. Body cream coloured, base of the branchial crown dark brown. Trunk cylindrical. Body length 20 mm (17–29), width 1.5 mm (1.7–3). Tubes unknown.

Branchial lobes and branchial crown. Insertion of the branchial lobes exposed beyond collar ( Fig. 15 A). Branchial crown length 7 mm (5–7). Radioles: 11 pairs (11–13). Anterior margin of the base of the branchial crown festooned ( Figs 15 A–C). Radiolar tips long. Palmate membrane extends three quarters the length of the branchial crown. Lateral flanges broad. Dorsal lips broadly rounded, as long as wide, without mid-rib. Dorsal pinnular appendages: 6 pairs (3–6). Ventral lips short, rounded, one quarter of the dorsal lips length. Ventral radiolar appendages: 6 pairs (4–6).

Peristomium . Anterior peristomial ring lobe (aprl) exposed beyond collar, bilobed ( Fig. 15 B). Posterior peristomial ring collar: antero-dorsal margin swollen; lateral and ventral margins entire ( Figs 15 A–B, D), ventral higher than dorsal ( Fig. 15 D); entire length of mid-dorsal collar margins forms a broad gap, faecal groove broad ( Fig. 15 C). Dorsal pockets well developed. Ventral shield of collar swollen, horseshoe-shaped, twice wider than long ( Fig. 15 B). Collar with rectangular, lateral, swollen spongy cushions (sc) ( Figs 15 A–B, D). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 2:1.

Thorax. Chaetiger 1: two groups of elongate, narrowly hooded chaetae. Chaetigers 2 to 8: Notopodia: two irregular rows of elongate, narrowly hooded chaetae; one row with bayonet chaetae ( Fig. 15 M), two posterior rows with symmetrical chaetae; paleate chaetae with medium-sized mucro ( Figs 15 I–K). Neuropodia: two rows of acicular uncini with three rows of teeth over the main fang ( Fig. 15 L), second tooth enlarged, located in the midline, dentition covering one quarter of the main fang length. Narrow glandular ridge on chaetiger 2.

Abdomen. Abdominal segments 48 (44–48). Anterior segments: two transverse rows of elongate, narrowly hooded chaetae, upper row chaetae half as long as lower row ones; uncini with the main fang surmounted by three rows of equal in size teeth, occupying one half of the main fang length, main fang not extending beyond breast, breast rectangular ( Fig. 15 F). 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 ( Figs 15 G–H). Glandular, longitudinal band (gb) on posterior abdomen ( Fig. 15 E). Pygidium with triangular posterior margin ( Fig. 15 E).

Gametes. Not seen.

Methyl green staining. Thorax and anterior abdomen stains uniformly, dorsal and ventrally ( Figs 15 A–D). The posterior abdomen stains less than anterior abdomen ( Fig. 15 E). The lateral spongy cushions of the collar are dark. The collar segment is darker on lateral sides; the anterior half of the ventral collar shield is unstained ( Figs 15 A–D).

Remarks. Chone sp. Aleutian Islands and C. quebecensis Tovar-Hernández (2007) have the ventral margin of anterior peristomial ring lobe distally bilobed; and a ventral, longitudinal glandular band on the posterior part of abdomen. However, C. sp. Aleutian Islands is easily distinguished from C. quebecensis by lacking the dorsal, oval glandular shields on peristomium (present in C. quebecensis ); glandular ridge on chaetiger 2 narrow (broad ventrally in C. quebecensis ); paleate chaetae with medium-sized mucro (long in C. quebecensis ); lateral flanges broad (narrow in C. quebecensis ), and posterior abdominal uncini not modified (modified in C. quebecensis ). Chone sp. Aleutian Islands has lateral spongy cushions on the collar segment; this is due to a massive glandular epithelium. In C. sp. Aleutian Islands, the base of the branchial crown is very rigid and brown-coloured; and the dorsal antero-lateral margin of collar forms a broad gap.

Figures

FIGURE 15. Chone sp. Aleutian Islands. (A) Anterior end, lateral view; (B) same, ventral view; (C) same, dorsal view; (D) spongy cushions; (E) posterior abdomen; (F) anterior abdominal uncinus; (G – H) posterior abdominal uncini; (I – K) paleate chaetae; (L) thoracic uncinus; (M) bayonet chaeta. (A – E) Methyl green staining. (A – M) [LACM – AHF, Aleutian Cruise].