Ophelina sp. (NHM_689) Fig. 20 A–H

Material examined.

NHM_689 NHMUK ANEA 2019.7114, coll. 20 Feb. 2015, 12°32.23N, 116°36.25W, 4425 m http://data.nhm.ac.uk/object/6755d584-a20a-4ce5-a4f1-32ce0965128e.

Description.

This species is represented by a single specimen in poor condition, with anal tube and most of branchiae missing. Posteriorly incomplete specimen 4.7 mm long and 0.35 mm wide for at least 22 chaetigers (exact number of chaetigers is difficult to count in places). Body cylindrical and smooth without distinct annulation (Fig. 20 A–C). Ventral and lateral grooves distinct throughout body. Preserved specimen yellow in ethanol (Fig. 20A); live specimen translucent, pale brown gut (Fig. 20C). Chaetigers crowded in anterior part of the body and posterior part of the body (the last four chaetigers), elongated in the mid-section of the body.

Prostomium of preserved specimen conical, broad (only slightly longer than wide), anteriorly bluntly rounded (but prostomium appears damaged) (Fig. 20D). Proboscis extended, damaged, soft inflated sack-like structure observed.

Branchiae present, but many are likely missing. Branchiae observed in chaetigers 2-4 (Fig. 20D, E) and then in posterior region, where only one branchia remains attached on the fourth before the last chaetiger (Fig. 20F); no branchiae observed in mid-body region.

Parapodia distinct, biramous; embedded in lateral grooves (Fig. 20G). Chaetae are capillaries only (Fig. 20H); all very long but longest on chaetiger 1 where they are nearly twice the length of chaetae of subsequent chaetigers. Anal tube likely missing (damaged).

Genetic data.

GenBank MN217463 for 16S and MN217508 for 18S. COI was unsuccessful for this specimen, no identical GenBank matches for 16S or 18S. In our phylogenetic tree, Ophelina sp. (NHM_689) is sister to Ophelina cylindricaudata (Hansen, 1879) from the Atlantic (New England) (Fig. 23).

Remarks.

Due to the condition of the single specimen representing this morphospecies, important diagnostic characters such as the structure of the anal tube and distribution of the branchiae cannot be determined. See Remarks under Ophelina sp. (NHM_1331) for more details.