Amphicteis wesenbergae, Parapar & Helgason & Jirkov & Moreira, 2011

Parapar, Julio, Helgason, Gudmundur V., Jirkov, Igor & Moreira, Juan, 2011, Taxonomy and distribution of the genus Amphicteis (Polychaeta: Ampharetidae) collected by the BIOICE project in Icelandic waters, Journal of Natural History 45 (23 - 24), pp. 1477-1499 : 1493-1496

Amphicteis wesenbergae sp. nov.

( Figures 1 , 9 , 10 )

Type material

Holotype. Zoologisk Museum : ZMUC-POL-1871. “Ingolf” Expedition station 117, east Norwegian Sea (69 ◦ 13 ′ N; 08 ◦ 23 ′ W), 1889 m depth. The specimen was formerly identified as A. gunneri .

Paratypes. Icelandic Museum of Natural History (Reykjavik) : IMNH 24085 (BIOICE sample 2018; 15 paratypes) ; IMNH 24086 (2704; three paratypes) ; IMNH 24087 (2776; 15 paratypes) ; IMNH 24088 (2777; one paratype) ; IMNH 24089 (2844; three paratypes) ; IMNH 24090 (2863; one paratype) ; IMNH 24091 (2903; one paratype) ; IMNH 24092 (3210; one paratype) ; IMNH 24093 (3519; one paratype) ; IMNH 24094 (3595; one paratype) ; IMNH 24095 (3628; three paratypes) ; IMNH 24096 (3629; 10 paratypes) ; IMNH 24097 (3636; one paratype) ; IMNH 24098 (3657; 28 paratypes) .

Additional BIOICE material

Museo Nacional de Ciencias Naturales (Madrid): MNCN 16.01 /13264 (BIOICE sample 3222; 235 specimens). Zoologisk Museum (Copenhagen): ZMUC-POL-2147 (BIOICE sample 3624; 10 specimens) .

Other material examined

East Greenland: R/ V Sevastopol, cruise 10, station 1725 (67 ◦ 32 ′ N; 13 ◦ 15 ′ W), 1730 m, − 0.89 ◦ C (one specimen). R/ V Sevastopol, cruise 15, station 2448 (69 ◦ 20 ′ N; 12 ◦ 00 ′ W), 1940 m, −0.9 ◦ C (one). R/ V Tunetz, cruise 105, station 16 (72 ◦ 50 ′ N; 14 ◦ 00 ′ W), 960 m, −0.96 ◦ C (one). West Norway: R/ V Tunetz, cruise 105, station 6 (68 ◦ 00 ′ N; 10 ◦ 00 ′ W), 260 m, 6.06 ◦ C (one) .

Description based on holotype

Holotype 9 mm long and 1 mm wide at thorax level. Additional material 7–12 mm long and 0.8–2 mm wide. Thorax and abdomen well defined; thorax about 1.5 times the width and length of abdomen ( Figure 9A ); barely tapering towards posterior part. Prostomium of Amphicteis -type ( Figure 10A ) with a pair of dorsal longitudinal ridges, less obvious than in A. gunneri , and a pair of well-marked transverse nuchal grooves. No eyes seen. Four pairs of long, tapering and deciduous branchiae (all missing in holotype) separated in left and right groups and arranged in two pairs, the posterior pair slightly displaced mid-dorsally ( Figure 10A ). Eight to ten long and slender paleae with tapering ends ( Figure 10A, B ). Seventeen thoracic chaetigers with large notopodia provided with long notochaetae ( Figures 9A , 10C ); the posterior 14 also with neuropodia provided with dorsal cirri ( Figure 9B ) and uncini with a single row of teeth. Fifteen abdominal chaetigers provided with large notopodial rudiments, and neuropodia with long dorsal cirri ( Figures 9C , 10D, E ) and uncini with single row of teeth ( Figure 10F ). Pygidium with a pair of long lateral cirri. Colour in alcohol pale yellow. Tubes made of mud with some foraminiferans incrusted.

Occurrence

In all, 330 specimens of A. wesenbergae sp. nov. (18.45% of the total) were collected in 16 BIOICE samples. Amphicteis wesenbergae sp. nov. is present in the warm waters of the deep slope off the southwestern coast of Iceland ( Figure 1C ). Depth range: 916– 2544 m; temperature range: − 0.87 to 5.52 ◦ C. The species was also found further north in east Greenland and in the Norwegian Sea (see above).

Remarks

Hartley (1985:314) noted that “... a range of specimens attributed to A. gunneri from Greenland, Iceland and the deeper North Atlantic... found to consist of several closely related species of Amphicteis ”. In fact, the specimen selected as holotype of A. wesenbergae sp. nov., located in the ZMUC polychaete collection, was originally labelled as A. gunneri . Amphicteis wesenbergae sp. nov. belongs to the group of Amphicteis species with narrow, evenly tapered paleae, which also includes A. gunneri and A. sundevalli . In fact, A. wesenbergae sp. nov. and A. gunneri have the same number of abdominal chaetigers, and look very similar to each other at first sight. Nevertheless, both species can be easily distinguished by the length of the dorsal cirri on the abdominal neuropodia: long in A. wesenbergae sp. nov. and short in A. gunneri (compare Figure 2D with Figure 10E ).

Etymology

The species is dedicated to the Danish Zoologist Elise Wesenberg-Lund (1896–1969) for her remarkable contributions to the taxonomy of polychaetes of Iceland and Greenland.

Key to Arctic-Boreal species of Amphicteis

1. Notopodia of first abdominal chaetiger transformed into a double dorsal fan............................................................. A. vestis 1

Notopodia of first abdominal chaetiger not transformed.................. 2

2. Tips of paleal chaetae evenly tapering.................................... 3

Tips of paleal chaetae blunt............................................. 5

3. Fifteen abdominal uncinigers............................................ 4

Between 18 and 20 abdominal uncinigers (upper shelf, high Arctic distribution)................................................ A. sundevalli 2

4. Abdominal uncinigers with short dorsal cirrus; longitudinal ridges of prostomium well marked (widely distributed)........................ A. gunneri

Abdominal uncinigers with long dorsal cirrus; longitudinal ridges of prostomium inconspicuous............................ A. wesenbergae sp. nov.

5. Paleal chaetae dark brown; usually more than 10 (8–16) on each side (bathyal, Arctic distribution)............................................ A. ninonae

Paleal chaetae light yellow; usually up to eight (10) on each side (shallow waters, low boreal-lusitanian distribution)........................ A. midas 2

Descriptions of A. midas and A. sundevalli can be found in Hartley (1985:309),

Holthe (1986b:58) and Jirkov (2001:473).

Figures

Figure 1. Distribution maps of total Amphicteis material examined (A), Amphicteis vestis (B) and Amphicteis wesenbergae sp. nov. (C).

Figure 2. Amphicteis gunneri (Sars, 1835). Scanning electron micrographs from IMNH 24079. (A) Thoracic chaetigers 1–3, right side, dorsal view; (B) chaetiger 2, ventral clavate papilla; (C) chaetiger 17, notopodium; (D) mid-abdominal chaetiger; (E) mid-abdominal notopodial clavate papilla; (F) detail of ciliature of abdominal notopodial clavate papilla.Abbreviations:cp, clavate papilla.

Figure 9. Amphicteis wesenbergae sp. nov. Holotype (ZMUC-POL-1871). (A) Dorso-lateral view; (B) thorax–abdomen transition, lateral view; (C) abdominal chaetigers, lateral view.

Figure 10. Amphicteis wesenbergae sp. nov. Scanning electron micrograph from paratype (ZMUC-POL-2148). (A) Anterior end, dorsal view; (B) paleae, distal end; (C) thoracic chaetigers 1–4, dorsal view; (D) posterior end, dorsal view; (E) abdominal mid-body chaetiger; (F) abdominal uncini. Abbreviations: cp, clavate papilla; dc, dorsal cirrus.