Ampharete finmarchica ( Sars, 1865 )

Ampharete finmarchica ( Sars, 1865) View in CoL

Figs 12–14 View Fig View Fig View Fig .

Ampharete finmarchica View in CoL (type: Zoologisk Museum, Oslo, two syntypes (Holthe, 1986a); type locality: Ramfjorden, Troms, Norway); Hartmann-Schröder, 1971: 458– 459, Abb. 158; 1996: 493–494, Abb. 240; Holthe, 1986a: 38–39, fig. 11, map 10; Jirkov, 1989: 109, fig. 22. 4, 5; 2001: 465–466; Hilbig, 2000: 182–184, fig. 8.4; Parapar et al., 2011, Fig.2 View Fig , 3 View Fig .

Ampharete arctica Malmgren, 1866: 364–365 View in CoL , fig. 77 (type locality: Spitsbergen, Finmarken, Bahusia (Bohuslen), Sweden); Augener, 1928: 777–778; Annenkova, 1929: 490–491, fig. 36; Zatsepin, 1948: 150, table XXXVII, 11; Uschakov, 1955: 369, fig. 136 З; Chlebovitch, 1964: 175; Tzetlin et al., 1983: 180 (partim) — non Imajima, Hartman, 1964: 331.

non Ampharete arctica var. gagarae Uschakov, 1950: 248 View in CoL , fig. 32, table. II, 7; 1955: 369, fig. 136 И–Л = Anobothrus gracilis View in CoL fide Jirkov, 2001.

non Ampharete brevibranchiata Treadwell, 1926: 6– 7 View in CoL , fig. 11–14.

MATERIAL.361 samples (ca. 2000 specimens). Supplement.

DESCRIPTION. Up to 60 mm long (up to 70 by Augener (1928). The middle lobe of the prostomium anteriorly rounded, about twice as long as the width. Buccal tentacles pinnate. Paleal chaetae ( Fig. 12A– E View Fig ) much longer and thicker than the most developed notochaeta, directed forward they usually reach the level of the front edge of the prostomial middle lobe, if the front part of the body is protruding, then they reach at least the front edge of the prostomial lateral lobes. Each palea with 7–21 paleal chaetae, usually dark cupper colors. Its tops short pointed (the tip often breaks off). The attachment places of the branchostyles ( Fig. 13A View Fig ) located almost in a straight line, the groups of gills close, the gap between them no wider than the diameter of the branchophore or absent. The third branchophore from the edge clearly associated with the notopodia TC2 (= CT6). At the base of the internal branchophores a pair of small nephridial papillae, in few worms, after staining TC3 papillae become visible. Branchostyles cirriform smooth. 14 TC, 12 TU. The notopodia almost hemispherical, the notochaeta slightly protrude from them. 13 AU (as an exception — 14 AU). Rudimentary notopodia small, no neuropodial cirri ( Fig. 13H, M View Fig ). Neuropodia of thorax, TU1 and TU2 tori ( Fig. 13G View Fig ), the rest — pinnuli ( Fig. 13H View Fig ). Pygidium with a pair of lateral cirri and several short papillae ( Fig. 13L View Fig ). Notochaetae ( Fig. 13I, K View Fig ). narrow equally bilimbate. Uncini TU1 ( Fig. 13A View Fig ) in profile are 6–7-toothed, the teeth located in the uncini in two rows ( Fig. 13C View Fig ) from the rostrum itself, the size of the teeth increases apically, the total number of teeth about 12–14; in addition, usually small ones present at the very top. Several uncini in the process of being formed, only their teeth have fully formed, but not the base ( Fig. 13B, E View Fig ). Abdominal uncini ( Fig. 13F–K View Fig ) with fewer teeth in profile, but at the top some teeth arranged in three rows, the number of apical teeth also increases. The tube cylindrical, thick, dense, finely sandy-silty, with a large admixture of detritus, can be encrusted with grains of sand, pebbles, etc., the thickness of the walls several times smaller than the inner diameter, 3–4 times longer than the worm.

VARIABILITY. The number of paleal chaetae of different population slightly varies, but the difference in not valuable ( Fig. 9 View Fig ).

The number of paleal chaetae does not depend on the worm size in diapason 5–50 mm ( Fig. 11 View Fig ). The shape of the bristles also does not change. In the ZIN collection (67/30177) there is one specimen from the Kara Sea with a normally developed right side of the body, whereas there were no fangs on the left, additionally it had 14 AU .

REMARK. Parapar et al. (2011) wrote that presence of “ciliated formation in the dorsal part of abdominal segments after disappearance of notopodial ramus could lead to the erroneous observation of the presence of rudimental notopodia”. However present observation shows that rudimental notopodia really present ( Fig. 13M View Fig ), while ciliated formations are absent. The explanation is probably following: Parapar et al. (2011) have dealt with fresh material, whereas the age of the studied material is about a century, during this time the cilia were lost, exposing rudimental notopodia, which masked the ciliated formation in the Parapar et al. (2011) material.

Hartman (1956, 1959) and, following her, Holthe (1986b) and Read, Fauchald (2022b) accepted Ampharete brevibranchiata Treadwell, 1926 as junior synonym of A. arctica . However, in a very incomplete description of A. brevibranchiata , it is indicat- ed that it has 12 AU not 13 AU as Hartman (1956) wrote with reference to Berkeley, Berkeley (1952). It does not allow to agree with Hartman synonymy. Among species occurring in the type locality A. brevibranchiata (Bering Strait) , A. crassiseta is the most similar species, but for a final conclusion, a study of the holotype is necessary.

RANGE ( Fig. 14 View Fig ). The species is widely distributed in the Northern Pacific: south to the Sea of Japan along Asia, (but absent in the Japan waters) and California along North America. On all the shelves of the Arctic Ocean, but it penetrates into the Atlantic along the American coast only as far as Newfoundland. Along Europe, the species goes as far as the North Sea, including Skagerrak, Kattegat and Öresund (Holthe, 1986a), but probably not further to the south. Despite Holthe (1986a, only data from literature) and Zettler et al. (2018) reported it as widely distributed in the North Sea. The specimens I studied from UK territorial waters, identified previously as A. finmarchica in reality were either Ampharete aff. lindstroemi , or Anobothrus gracilis . Dr. Worsfold (APEM, letter 23/12/2021) wrote me that A. finmarchica is absent in huge collections from this region. Within the North Polar Basin species inhabits exclusively shelf. South to Iceland it can be found as deep as 2708 m. Within Pacific is probably inhabits lower sublittoral.

UNLIKELY REPORTS. Ampharete arctica sensu Imajima and Hartman, 1964 has 7 AU so without any doubt belong to different species.