Chone mollis, : Hartman, 1942

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 : 539-542

Chone mollis (Bush in Moore, 1904)

( Figures 10 , 19B )

Metachone mollis Bush in Moore 1904, p 216, Plate 35, Figures 19 , 20, 28.

Chone mollis: Hartman 1942b, p 87 , Figures 141–143; 1944, p 279; 1969, p 673; Banse 1972, p 469, Figure 3 .

Material examined

Type material. California [ YPM 2793 , holotype], Pacific Grove, Harriman Alaska Expedition , 12, p. 216 W, R. Coe, 1901 .

Non-type material. California [ LACM-AHF], Tomales Bay , 003258, 8 June 1941 (24) . 003240, Sta. 6, coll. G. Jones, August 1958 (78) . 003244, 1610-48 (8). 003245, 211352 (1). 003246, 4938-57 (14). 003247, 5028-57 (9). 003250 (24). 003251, 1958 (15). 003254 (4). [ LACM-AHF], Pitelka, Pelican Point, Sta. 5, 25 June 1941 , sand mud, low tide (3). AB pre 372 P (1). [ LACM-AHF], Monterey Bay , 003256, coll. G. E. MacGinitie, 2 January 1931 (1) . [ LACM-AHF], Central California , 003253 (1). 003255 (5). 003257 (8). [ LACM-AHF], Marina del Rey, MDR 3A, 29 December 1977 (3) . MDR 3A, 16 June 1978 (4). MMS Phase I, Help Collections, MDR 3A, 21 September 1978 (1) . [ LACM- AHF], Newport, 003242, Sta. 11, January 1951 (1) . 003243, Sta. 21, January 1954 (1) . [ LACSD-MBL], Sta. 0194-2D, 30 m (3). Western Mexico [ LACM-AHF], F 3298 , 964-39 (2); M15170-F3311 V-2 (1); N 15184 -F3336, K-116 (1); N 15174 -F3326 K-112 (1); F3345, 1260-41(1); F3330, K-133, M15178 (4). [ ECOSUR], Bahía de Todos Santos, coll. SISV, 18 February 1982 (1) . Panama Pacific [ LACM-AHF], coll. H. Lee: CON-D, Sample A, 28 January 1976 (1) ; 5-F, Sample C, 21 March 1976 (2) ; P-E-2, Sample C, 27 March 1976 (1) ; 5-D, Sample A, 5 April 1976 (3) ; 5-D, Sample B, 5 April 1976 (2) ; T-D, Sample C, 6 April 1976 (2) ; CON-F, Sample B, 14 April 1976 (6) ; CON-D, Sample B, 26 April 1977 (3) ; PE2 Sample B, 16 May 1976 (2) ; 5-F, PF1 Sample B, 23 May 1976 (4) ; PF2 Sample B, 24 May 1976 (1) ; P-E-2, Sample C, 24 May 1976 (2) ; Sample A, 25 May 1975 (3) ; 5-F, Sample C, 26 May 1976 (1) ; P-E-2, Sample C, 27 May 1976 (1) ; 5-F, Sample B, 30 May 1976 (3) ; T-D, Sample A, 1 June 1976 (1) ; CON-D, Sample B, 28 July

1976 (1); Freeser 0/1, 6 July 1977 (1); Freeser 0/2, 6 July 1977 (5); Freeser 0/3, 6 July 1977 (4); Freeser 0/5, 6 July 1977 (10); Freeser 0/6, 6 July 1977 (8); Freeser 0/7, 6 July 1977 (1); Freeser 0/8, 6 July 1977 (6); Freeser 0/9, 6 July 1977 (15); P-E-2, Sample C, 3 September 1976 (2).

Description (in parentheses variation of specimens LACM-AHF 003259)

Colour in preserved material, body shape, and size. Body brown coloured with an iridescent layer of epicuticle (separated from the body wall). Trunk cylindrical. Holotype incomplete (no posterior end, and only the left half of the branchial crown), with histolysis. Body length 25 mm (34–39), width 2 mm (2.5–4).

Colour in life. Body cream coloured, collar yellow, ventral shield of collar and ventral thoracic segments whitish, glandular ridge on chaetiger 2 white, iridescent epicuticle; ventral and dorsal lips red; radioles with six to eight irregular red-brown coloured, narrow bands [ LACM-AHF, Tomales Bay, June 2004, LH 04-286-001].

Branchial lobes and branchial crown. Insertion of the branchial lobes not exposed beyond collar. Branchial crown length 8 mm (8–10). Radioles: 17 pairs (13–16). Pinnules from middle region twice as long as more proximal pinnules. Radiolar tips long, elongate ( Figure 10G ). The palmate membrane extends to three-quarters the length of branchial crown. Lateral flanges broad. Dorsal lips broadly rounded in frontal view, as long as wide, without a mid-rib, resembling the ventral lips. Dorsal pinnular appendages: (five to eight) short pairs united by a palmate membrane. Ventral lips rounded, as long as wide, about one-half of the dorsal lips length. Ventral radiolar appendages (vra): one to five pairs, onequarter to one-half the length of branchial crown ( Figure 19B ).

Peristomium . Base of the peristomium composed of two lateral horns of basal central skeleton (bcs) surrounding the mouth (mo); anterior peristomial ring lobe (lo) exposed beyond collar, distally triangular, elongate ( Figure 10B–D, F ). The base of the posterior peristomial ring collar is supported by basal lateral skeleton (bls). Antero-dorsal, lateral, and ventral margins of the posterior peristomial ring collar entire ( Figure 10A–D ); ventral margin slightly higher than dorsal ( Figure 10C ); entire length of mid-dorsal margins forms a narrow gap; dorsal pockets well developed. Ventral shield of collar swollen, inside and outside of the collar wall ( Figure 10B ), horseshoe-shaped, two times wider than long ( Figure 10B, D ), divided by a median-longitudinal line in large specimens ( Figure 10B ). Ratio of posterior peristomial ring collar length versus chaetiger 2 length, in lateral view: 2:1.

Thorax. Chaetiger 1: elongate, narrowly hooded chaetae. Chaetigers 2–8: notopodia—two rows of elongate, narrowly hooded chaetae; one anterior row with bayonet chaetae ( Figure 10M ), two posterior rows with paleate chaetae with minute mucro, not easily discernible ( Figure 10H–K ); neuropodia—one row of acicular uncini, main fang surmounted by five rows of teeth equal in size, second tooth enlarged, located in the midline, dentition occupying a quarter the length of main fang ( Figure 10L ). Pre- and postchaetal lobes well developed. Broad glandular, columnar epithelium (gce), swollen in first two ventral thoracic segments, narrow in following thoracic segments ( Figure 19B ). Narrow glandular ridge on chaetiger 2, it occupies a quarter of the epithelium in longitudinal section ( Figure 19B ).

Abdomen. Abdominal segments: 42 (41–43), two transverse rows of five to six elongate, narrowly hooded chaetae, chaetae from upper row half as long as chaetae in lower one; uncini with the main fang surmounted by four regular vertical rows of teeth equal in size, occupying one-half the length of main fang, older (dorsalmost) uncini smaller than younger uncini (ventralmost), main fang not extending beyond breast ( Figure 10N ), breast rectangular. Posterior segments: one or two very elongate, narrowly hooded chaetae; uncini similar to those in anterior abdomen ( Figure 10O ). Pygidium with rounded posterior margin ( Figure 10E ).

Gametes. Holotype and specimens from Pacific Panama females with oocytes (oo) in thorax ( Figure 19B ).

Methyl green staining. The epidermis is completely glandular and stains uniformly in thorax and abdomen, dorsally and ventrally ( Figure 10A–C ). The ventral shield of collar is not coloured in the anterior margin ( Figure 10B, D ). Posterior end with granular pattern ( Figure 10E ).

Remarks

Metachone mollis was established as having thoracic paleate chaetae lacking a mucro; however, Fauvel (1927) transferred this species to Chone , arguing that because the size and length of the mucro varies greatly between species it cannot have generic significance. Reexamination of type material confirmed the presence of a very short hair-like mucro in complete chaetae in holotype. Chone aurantiaca , C. magna , C. picta , and C. mollis have paleated chaetae with mucro minute or absent (Table III). In C. mollis , the ratio of posterior peristomial ring collar length versus chaetiger 2 length is 2:1 (2.5: 1 in C. aurantiaca , 3: 1 in C. magna and C. picta ); the ventral margin of the posterior peristomial ring collar is slightly higher than dorsal (very much higher in C. aurantiaca , C. magna , and C. picta ); the radiolar flanges are narrow (broad in C. aurantiaca ); and the entire length of mid-dorsal margins forms a narrow gap (broad C. magna and C. picta ). Like Chone eiffelturris n. sp., C. mollis is distributed in California, Western Mexico, and Pacific coast of Panama.

Figures

Figure 3. Chone bimaculata. (A) Anterior end, dorsal view; (B) same, ventral view; (C) posterior end; (D, E) radiolar tips; (F, G) paleate chaetae; (H) bayonet chaeta; (I) thoracic, elongate, narrowly hooded chaeta; (J) thoracic uncinus; (K) anterior abdominal uncinus; (L) abdominal, elongate, narrowly hooded chaeta; (M–P) posterior abdominal uncini. (A–C, E–P) [USNM 36281, paratype]; (D) [RBCM 973-187-21].

Figure 10. Chone mollis. (A) Anterior end, dorsal view; (B) same, ventral view; (C) same, lateral view; (D) ventral shield of collar without longitudinal division; (E) posterior end; (F) peristomium, frontal view; (G) radiolar tip; (H–K) paleate chaetae; (L) thoracic uncinus; (M) bayonet chaeta; (N, O) anterior abdominal uncini. (A–D) Methyl green staining. (A–C, E–G) [LACM-AHF 003258]; (D) [LACM-AHF 003240]; (H–O) [YPM 2793, holotype].

Figure 19. Thoracic transversal sections. (A) Chone ecaudata; (B) Chone mollis; (C) Chone quebecensis n. sp. (A) [LACM-AHF LH02-1205]; (B) [LACM-AHF, Han Lee]; (C) [CMN 1989-0385].