Ampharete finmarchica can be up to 50 mm long. It can be found along the entire Norwegian coast and Svalbard, but it is more common in the north, at depths between 14 and 2900 meters.

Type locality

Ramfjorden, Troms, Norway, 110–180 m.

Key characters

Measurements: Up to 50 mm long.

Number of thoracic chaetigers, excluding paleae: 14

Number of thoracic uncinigers: 12

Number of abdominal uncinigers: 13

Prostomium: Trilobed; one pair of eyespots.

Mouth tentacles: Papillose.

Branchiae: Four pairs of branchiae in two groups located very close together at mid-dorsum; three branchiae in each group in transverse row, fourth branchia behind middle one of the three; branchial bases on each side fused.

Paleae: Long and stout with curved tips, 12–16 chaetae on each side.

Special features: Abdomen with what under light stereomicroscope appears to be rudimentary notopodia; examination under scanning electron microscope reveals these rudimentary notopodia to be patches of cilia.

Pygidium: With two long lateral cirri and several small rounded papillae.

Tube: Straight and cylindrical; thin layer of organic secretion covered with thick and loose layer of mud and sand.

Distribution

Entire Norwegian coast and Svalbard, more common in the north; 14–2900 m (Jirkov 2001).

Remarks

Ampharete finmarchica is reported both from the North Atlantic and the North Pacific (Holthe 1986a) in a wide depth range: 14 m (Jirkov 2001) to more than 5000 m (Holthe 1986a). With such a wide distribution a species complex can be suspected, and own genetic data indicates that A. finmarchica is represented by two genetic clades in Norwegian waters (unpublished).

Similar species

Ampharete finmarchica is a relatively common species, at least in Northern Norway and Svalbard, but some of its records might be erroneous due to confusing it with Anobothrus gracilis. The first pair of notopodia in A. gracilis is so small that it is easily overlooked, and the worm appears to have 14 instead of 15 thoracic notopodia. Both species have 13 abdominal uncinigers. Ampharete finmarchica has paleae with curved tips while A. gracilis has paleae with filiform tips. 

Sources

Holthe T (1986a). Polychaeta Terebellomorpha. Marine Invertebrates of Scandinavia 7: 1-192.

Jirkov IA (2001). [Polychaeta of the Arctic Ocean] (In Russian). Polikhety severnogo Ledovitogo Okeana. Yanus-K Press. Moscow, 632 pp.

Sars M (1865). Fortsatte Bidrag til Kundskaben om Norges Annelider. Forhandlinger i Videnskabs-Selskabet i Christiania 1864: 5-20. https://biodiversitylibrary.org/page/44007149

Personal observations, Alvestad T.