Ampharete britayevi, Jirkov, 2023

Ampharete britayevi sp.n.

Fig. 3 View Fig , 4 View Fig .

MATERIAL. Holotype 1 ex. ( DGEH), Vitjaz 10.1539 74 m 18.6.1952 62°13′ N 179°30′ E. GoogleMaps

ADDITIONAL MATERIAL: Ampharete seribranchiata Treadwell, 1926: 7–8 , fig. 15–17; type Cat. No. 1634, American Museum Natural History; type locality (according to the type’s label): the Bering Straits Bet., King Id. and the two Diomedes.

DESCRIPTION. The single specimen 35 mm long, but not complete posteriorly. The middle lobe of the prostomium is rounded anteriorly, twice as long as the width. Buccal tentacles have not been preserved. Paleal chaetae much longer and thicker than the most developed notochaeta, directed forward, they go beyond the front edge of the prostomium. There are 42 paleal chaetae and they form 1,5 turns ( Fig. 3B View Fig ). The tip of the bristles pulled into a relatively long tip, much longer than in other species of the genus, this tip does not break off. Branchostyles missing. The attachment points of three pairs of branchostyles arranged in one transverse line, the fourth behind the middle of the three, their branchophores clearly connected to the TC2 notopodia. A very wide gap between the groups of gills, its width greater than the diameter of the branchophore. Nephridial papillae caudal to the inner pair of gills, small ( Fig. 3A View Fig ). 14 TC, 12 TU. The only specimen at hand have incomplete abdomen with 7 AU, but highly likely that species have 13 AU as most species of Ampharete ( finmarchica ). Posterior thoracic neuropodia with additional lobe ( Fig. 3E View Fig ). Rudimentary notopodia small, abdominal neuropodia with short but distinct neuropodial cirri ( Fig. 3F View Fig ). Neuropodia of the thorax, AU1 and AU2 tori, the rest — pinnuli. The ventral surface up to and including TU9 transformed into ñontinuous glandular ventral shields extending from notopodia to notopodia. No ventral shield on TU10, in its place there is a thickening that occupies the entire ventral abdominal surface of the anterior half of the segment. Rudimentary notopodia of the abdomen practically absent. The notochaetae in two rows: the front ones are an order of magnitude thinner and several times shorter than the rear ones, the former narrow equally bilimbate. Uncini ( Fig. 4 View Fig ) with two rows of teeth, usually up to eight in thorax and about six in abdomen. Thoracic and abdominal generally similar. The tube unknown.

REMARKS. Initially I thought that this species is Ampharete seribranchiata Treadwell, 1926 because the original description clearly states “The posterior region has 13 uncinigerous somites without capillary setae” and “On either side of the base of the peristomium is a band of 30 or more goldenyellow paleae arranged in a crescent” ( Treadwell, 1926: 7) and the type locality is closed to our finding. As only species of Ampharete ( finmarchica ) have 13 AU A. seribranchiata as a member of this superspecies should have characteristic paleal chaetae. But when Senior Museum Specialist of AMNH Lily Berneker which I asked to investigate the type took photos and investigated paleal chaetae it turned out that the paleal chaetae taper into a threadlike vertex ( Fig. 5 View Fig ), 33 paleal chaetae on one side and 29 or 30 on the other side. It cannot be at the same time 13 AU and slowly tapering paleal chaetae, because it cannot be never, I asked her to count the number of AU and it turned out that there are only 12 AU, not 13 AU. Both these characters (shape of paleal chaetae and the number of AU) place A. seribranchiata outside Ampharete ( finmarchica ).

Berkeley, Berkeley (1942) considered this species as a junior synonym of A. eupalea . This synonymy was accepted by Hartman (1959) and Holthe (1986b), however, no one gave any argumentation and now it is obvious that it is not correct.

DIFFERENTIAL DIAGNOSIS. Two characters differ the new species from presently know and allow to describe the new species despite only one incomplete specimen is at hand.

1. A. eupalea has the largest number of paleal chaetae among known species of Ampharete ( finmarchica ), but it does not exceed 32 in 170 investigated specimens, while the new species has 42, it is far beyond individual variation of A. eupalea (see below). This number of paleal chaetae exceeds not only those of all other species of the group but probably even the family.

2. Presence of neuropodial cirri. Cirri are absent in other species of Ampharete ( finmarchica ), but it is not seldom character among other Ampharete outside the group.

RANGE. Known only from the type locality. Upper sublittoral. Probably similar to A. eupalea .

ETYMOLOGY. The species is named after my friend Temir Alanovich Britaev Dr. Sci., professor, Head of the Laboratory of Morphology and Ecology of Marine Invertebrates, A.N. Severtzov Institute of Ecology & Evolution RAS ( Fig. 6 View Fig ).