Ophelina sp. (NHM_1068)

Wiklund, Helena, Neal, Lenka, Glover, Adrian G., Drennan, Regan, Muriel Rabone, & Dahlgren, Thomas G., 2019, Abyssal fauna of polymetallic nodule exploration areas, eastern Clarion-Clipperton Zone, central Pacific Ocean: Annelida: Capitellidae, Opheliidae, Scalibregmatidae, and Travisiidae, ZooKeys 883, pp. 1-82 : 1

Ophelina sp. (NHM_1068) Fig. 21 A–H

Material examined.

NHM_1068 NHMUK ANEA 2019.7138, coll. 26 Feb. 2015, 12°06.93N, 117°09.87W, 4100 m http://data.nhm.ac.uk/object/b28fd52f-5717-45e3-b0cc-369172a690e5; NHM_1874 NHMUK ANEA 2019.7139, coll. 13 Mar. 2015, 12°02.49N, 117°13.03W, 4094 m, http://data.nhm.ac.uk/object/c3ffe5f4-6ca3-4816-966c-25ec98bbb003.

Description.

This species is represented by two specimens, both in poor condition; specimen NHM_1874 posteriorly incomplete, specimen NHM_1068 mostly complete, but anal tube damaged. Large species 25-30 mm long and 0.8 mm wide, for minimum of 30 chaetigers (exact number of chaetigers cannot be established). Body cylindrical and smooth without distinct annulation ( Fig. 21 A–C ). Preserved specimen yellow in ethanol ( Fig. 21A ); live specimens translucent, yellowish ( Fig. 21C, D ). Ventral and lateral grooves distinct along whole length of the available fragments. Chaetigers somewhat crowded in anterior part of the body, then elongated in the rest of the body, posterior-most chaetigers not observed.

Prostomium of preserved specimen conical (longer than wide), anteriorly pointed and extending into very large and long thick palpode ( Fig. 21D, E ). Branchiae observed in anterior chaetigers only, but many missing (broken off) and the exact distribution cannot be confirmed; mainly observed in chaetigers 4-13; branchiae conspicuous but rather short, straight, distally blunt ( Fig. 21D, F ).

Parapodia biramous, embedded in lateral grooves; parapodia small conical lobes, no distinct pre- or postchaetal lobes observed ( Fig. 21F ). Chaetae are capillaries only; often missing (broken off).

Anal tube missing in specimen NHM_1874; damaged in NHM_1068, but probably scooped-shaped ( Fig. 21G-H ).

Genetic data.

GenBank MN217464 and MN217466 for 16S and MN217509 for 18S. COI was unsuccessful for this specimen, no identical GenBank matches for 16S and 18S.

Remarks.

According to our molecular results, this species forms a clade with Ophelina nunnallyi sp. nov., which is sister to O. acuminata ( Fig. 23 ), but due to specimen damage, meaningful morphological comparison cannot be currently provided. Ophelina sp. (NHM_1068) and O. nunnallyi sp. nov. share a similar prostomium shape and its associated robust palpode, branchiae occurring from chaetiger 4 that are limited to anterior part of the body (ch. 4-9). However, Ophelina sp. (NHM_1068) has a larger body size. See also Remarks under Ophelina nunnallyi sp. nov. above.

Figures

Figure 21. Ophelina sp. NHM _ 1068. A Lab image, whole specimen (specimen NHM _ 1068,) B Lab image, whole specimen (specimen NHM _ 1874, faded stain) C Live image, whole specimen (specimen NHM _ 1874) D Live image, anterior, with branchiae outlined in a fine black line (specimen NHM _ 1068, br = branchiae) E Lab image, detail of palpode (specimen NHM _ 1068) F Lab image, detail of anterior parapodia and branchiae (specimen NHM _ 1874, stained) G Lab image, posterior (specimen NHM _ 1068) H Lab image, detail of anal funnel (specimen NHM _ 1068). Scale bars: 1 mm (A, B); 100 μm (E).

Figure 23. Phylogenetic analysis of Opheliidae. 50 % majority rule tree from the Bayesian analyses using 18 S and 16 S, with posterior probability values on nodes. Twenty-nine taxa from GenBank were included, and Capitellidae and Echiura was chosen as outgroup following the annelid phylogeny of Weigert and Bleidorn (2016).