Chone murmanica Lukasch 1910

Chone murmanica Lukasch, 1910

Figure 10

Chone murmanica Lukasch, 1910: 21 –26.

Material examined. Non-type material. Arctic Ocean [LACM – AHF], Beaufort Sea, Northwest of Cape Halkett, Alaska, Coll. Andrew Carey: 948–04 (3); 835–04 (141); 836–03 (145). [ZIRAS 38178] Franz-Joseph Land, September 29, 1970, 28–30 m, pebble and sand (2).

Diagnosis. Body elongated, cylindrical. Body length 18 mm. Branchial crown length 4 mm. Branchial lobes short. Radiolar tips extra long. Narrow flanges. Anterior peristomial ring lobe exposed beyond collar (aprl), bilobed (Figs 10 B–C). Ventral collar margin higher than dorsal one, bilobed (Figs 10 B–C). Entire length of mid-dorsal collar margins forms a very broad gap (Fig. 10 A). Dorsal pockets well developed (Fig. 10 A). Peristomial eyes present (pe) (Figs 10 B–C). Paleate chaetae with long mucro (Figs 10 D–E); thoracic uncini with four rows of teeth (Fig. 10 F); thoracic narrowly hooded chaetae (Figs 10 K–L). Glandular ridge on chaetiger 2 narrow. Ventral thoracic shields well developed. Abdominal segments: 26. Abdominal chaetae narrowly hooded (Figs 10 M–N); posterior abdominal uncini modified with six rows of teeth (Figs. 10 H–J). Pygidium with triangular posterior margin.

Methyl green staining. Dorsally there is no colour, only lateral spots in the collar, laterally, the following segments have glandular spots (Fig. 10 A). Ventrally: collar segment stained uniformly, except the anterior margin, and the area where the otoliths occurs (Figs 10 B–C).

Gametes. Spermatozoa with barrel-shaped nucleus, triangular, short acrosome, two small, rounded mitochondria (Fig. 10 G).

Remarks. Cochrane (2000) stated that the illustration of the anterior end of C. murmanica, depicted in Lukasch (1910) indeed closely resembles the drawing of C. paucibranchiata by Kr ø yer. Both taxa have three pairs of radioles and a characteristically pronounced dorsal gap in the collar. Chone paucibranchiata has been regarded as a junior synonym of Chone infundibuliformis Kr ø yer, 1856 after Malmgren (1866), but Banse (1972) stated that C. paucibranchiata has well developed ventral glandular shields (absent in C. infundibuliformis); and that its palmate membrane extends at least one-third of the branchial crown length (two thirds in C. infundibuliformis). If C. paucibranchiata is regarded as a valid species, it would have priority over C. murmanica, but examination of topotype material is necessary in order to confirm the synonym. Among species of Chone included in this revision, C. murmanica is unique by having a ventral shield of collar in trapezoidshaped (Table 2).