Chone magna ( Moore, 1923 )

Tovar-Hernández, María Ana, 2007, Revision of Chone Krøyer, 1856 (Polychaeta: Sabellidae) from North America and descriptions of four new species, Journal of Natural History 41 (9 - 12), pp. 511-566 : 536-539

Chone magna ( Moore, 1923)

( Figure 9 )

Euchone magna Moore 1923, p 245 , Plate 18, Figures 45, 46; Hartman 1961, p 42.

Chone magna: Hartman 1969, p 669 ; Banse 1972, p 472 –474, Figure 5 . Material examined

Type material. California [ USNM 17281 (holotype), ANSP AD 3297 (one paratype), ANSP 1-22 , 1-23 (one paratype mounted in slides), San Miguel Island, off Harris, R / V Albatross , Sta. 4436, 271 m, 15 April 1904] .

Non-type material. Washington [ USNM 43636 ], South of Orcas Island, W of Blakeley Island, 48 ° 34.99N, 122 ° 50.89W, 13 August 1964 (1). [ FHL 293 ], Lopez Island , San Juan Archipelago, Upright Head, coll. R . P. Dales and G. John, 2 August 1960 (1). [ LACM- AHF], Point Loma, Westec, LA 5, 430– 480 m, 30 March 1983 (1). [ LACM-AHF], BLM 2296 , BFI (1).

Additional material. Chone aurantiaca ( Johnson, 1901) [ MCZ 1933, holotype]. Chone farringtonae Tovar-Hernández, 2005 [ FSBC I 66733, holotype]. Chone mollis (Bush in Moore, 1904) [ YPM 2793, holotype]. Chone picta ( Verrill, 1885) [ YPM 30000, topotype].

Description (based on holotype, number in parentheses correspond to paratypes and non-type material)

Colour, body shape, and size. Body cream coloured, covered by an iridescent layer of epicuticle. Trunk cylindrical ( Figure 9C, E, F ). Holotype fragmented in three parts (without branchial crown, posterior abdomen damaged as well as a few chaetigers). Body length 8.2 mm (54–71), width 3 mm (2.5–6). Tubes unknown.

Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar (exposed only when anterior margins of collar are reflexed). Branchial crown length (16–18 mm). Radioles: (29) pairs. Radioles with median pinnules two times longer than basal ones. Radiolar tips long (3.5 mm) ( Figure 9D, P ). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges narrow ( Figure 9P ). Dorsal lips (dl) broadly rounded, longer than wide, without mid-rib ( Figure 9I, M ). Dorsal pinnular appendages (dpa): (five to six short and median pairs). Ventral lips small, rounded, as long as wide, about one-half length of dorsal lips. Ventral radiolar appendages: one to three pairs, the inner one about three-quarters the length of branchial crown, the remainder about one-quarter the length of branchial crown.

Peristomium . Anterior peristomial ring lobe not exposed above collar, distally entire, triangular. Posterior peristomial ring collar: antero-dorsal margin entire, entire length of mid-dorsal margins forms a broad gap ( Figure 9A, E ), deep faecal groove, dorsal pockets well developed; lateral and ventral margins entire ( Figure 9E, F ); ventral margin higher than dorsal ( Figure 9B, C, F ). Ventral shield of collar swollen, rounded ( Figure 9B ). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 3:1.

Thorax. Chaetiger 1: two groups of 10 elongate, narrowly hooded chaetae. Chaetigers 2–8: notopodia—two rows of 8–10 elongate, narrowly hooded chaetae ( Figure 9J ); one anterior row with eight to nine bayonet chaetae; two posterior rows with 11 symmetrical, paleate chaetae without mucro (a very short hair-like mucro in additional material) ( Figure 9K ); neuropodia—two irregular rows of 26–46 acicular uncini per torus ( Figure 9G ), facing in the same direction, the oldest upper parts of the tori have only one row (one-quarter the length of tori), main fang surmounted by four rows of teeth, second tooth enlarged, located in the midline, dentition occupying a quarter the length of main fang ( Figure 9L ). Pre- and post-chaetal lobes well developed. Glandular ridge on chaetiger 2: narrow.

Abdomen. Abdominal segments: 42 (62–72). Anterior segments: two rows of 6–10 elongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower row; 10–12 uncini per torus with the main fang surmounted by three rows of teeth, occupying half the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast, breast rectangular with a triangular anterior tip ( Figure 9N ). Posterior segments: one or two very elongate, narrowly hooded chaetae, 50% longer than in anterior segments; five to eight uncini per torus, similar to those in anterior segments, but smaller ( Figure 9O ). Pygidium with rounded posterior margin ( Figure 9H ).

Gametes. Holotype male with sperm in posterior abdomen, spermatozoa nucleus barrelshaped (1.5 times longer than wide), acrosome sub-triangular and two large, rounded mitochondria.

Methyl green staining. Anterior end of the ventral shield of collar not coloured, posterior end dark. Collar coloured only in the basal half. Body coloured uniformly dorsal and ventrally.

Remarks

Euchone magna was transferred to Chone by Hartman (1969), see details in Banse (1972, p 473). Chone magna is included in the Group I (species with anterior and posterior abdominal uncini with similar shape; Table III). Chone magna and C. picta have a long posterior peristomial ring collar, three times longer than second chaetiger; but C. magna has long radiolar tips (short in C. picta ) and narrow radiolar flanges (broad in C. picta ).

Figures

Figure 5. Chone ecaudata. (A–C) Branchial crown, different views; (D) radiolar tip; (E) posterior end; (F) anterior abdominal uncinus; (G) posterior abdominal uncinus; (H) bayonet chaeta; (I) thoracic uncinus; (J) thoracic, elongate, narrowly hooded chaeta; (K, L) paleate chaetae. (A–C) [LACM-AHF 2472-53, 003213]; (D, F, G, K, L) [USNM 17319, holotype C. ecaudata]; (E, H, J) [LACM-AHF 013, paratype C. minuta]; (I) [LACM-AHF, LH02-1205].

Figure 9. Chone magna. (A) Anterior end, dorsal view; (B) same, ventral view; (C) same, lateral view; (D) radiolar tip; (E) anterior end, dorsal view, not reflexed; (F) same, lateral view, not reflexed; (G) thoracic segment, lateral view; (H) posterior abdomen; (I) dorsal lip; (J) thoracic, elongate, narrowly hooded chaeta; (K) paleate chaeta; (L) thoracic uncinus; (M) dorsal most radiole and dorsal lip; (N) anterior abdominal uncinus; (O) posterior abdominal uncinus; (P) radiolar tip. (A–C, L, N, O) [USNM 17281, holotype]; (D, G–I, M) [FHL 293]; (E, F, J, K, P) [USNM 43636].