Ophelina nunnallyi, Wiklund, Helena, Neal, Lenka, Glover, Adrian G., Drennan, Regan, Muriel Rabone, & Dahlgren, Thomas G., 2019

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 nunnallyi sp. nov. Fig. 17 A–I

Material examined.

NHM_683 (holotype) NHMUK ANEA 2019.7133, coll. 20 Feb. 2015, 12°32.23N, 116°36.25W, 4425 m http://data.nhm.ac.uk/object/220fa671-4576-45b7-930d-efde148f223f; NHM_700 (paratype) NHMUK ANEA 2019.7134, coll. 20 Feb. 2015, 12°32.23N, 116°36.25W, 4425 m http://data.nhm.ac.uk/object/63115f48-bcf1-4b3b-9c2e-c339b97845bd; NHM_783F NHMUK ANEA 2019.7135, coll. 20 Feb. 2015, 12°32.23N, 116°36.25W, 4425 m http://data.nhm.ac.uk/object/376a42db-0497-4b4a-851b-c1d5e07bd2b6; NHM_1273 (paratype) NHMUK ANEA 2019.7136, coll. 01 Mar. 2015, 12°15.44N, 117°18.13W, 4302 m http://data.nhm.ac.uk/object/a3540563-8a0c-475b-96b5-12969fb8c2ba; NHM_1309A (SEM specimen) NHMUK ANEA 2019.7137, coll. 01 Mar. 2015, 12°15.44N, 117°18.13W, 4302 m http://data.nhm.ac.uk/object/25066e63-ecc9-439a-9907-eaeaeb72e78c.

Type locality.

Pacific Ocean, CCZ, 12°32.23N, 116°36.25W, depth 4425 m, in mud between polymetallic nodules.

Description.

This species is represented by five complete specimens, none in an excellent condition, anal tube damaged and not clearly observed. However, images of live specimens are available to observe some now missing or damaged features such as anal tube.

Small to medium-sized species 9-14 mm long and 0.25-0.8 mm wide, for 33 chaetigers. Body cylindrical and smooth without distinct annulation. Preserved specimen yellow semi-translucent, iridescent in ethanol ( Fig. 17A ); live specimens translucent ( Fig. 17B ). Ventral and lateral grooves distinct along whole length of the body. Chaetigers elongated, only slightly crowded in first eight anterior chaetigers and towards posterior end.

Prostomium of preserved specimen conical (longer than wide), anteriorly pointed and extending into very long, thick palpode ( Fig. 17C, D ). Rounded, slightly pigmented nuchal organs everted in specimen NHM_683.

Branchiae observed in anterior chaetigers only, some missing (broken off), present from chaetigers 4-9 ( Fig. 17E ). All branchiae cirriform, conspicuous but relatively short, straight, distally blunt.

Parapodia biramous, embedded in lateral grooves; observed as distinct conical lobes throughout the body ( Fig. 17F ). Chaetae are capillaries only ( Fig. 17G ); often missing (broken off), most abundant in anterior eight chaetigers.

Anal tube attached (in holotype, NHM_783F and NHM_1309A), but now poorly preserved and variably damaged, always separated from the rest of the body by a shallow constriction ( Fig. 17H, I ). Anal tube of live specimen well-imaged in Fig. 17H , where anal tube scoop-shaped, ventrally with wide depression; distally with two elongate, slender cirri; no other cirri observed, but may be missing.

Additional morphological observations.

In addition to the material examined here, several more specimens consistent with this species have been found, but no DNA sequencing has been carried out on these and thus they are not included in this manuscript. Where the anal tube was observed, it is scoop-shaped, but the preservation of cirri is variable. In some specimens, short slender cirri can be detected on the lateral margins of the anal tube. Chaetiger counts consistent with 33 chaetigers. Branchiae were consistently observed on chaetigers 4-9. However, in the absence of DNA data we are reluctant to ascribe these specimens formally to O. nunnallyi sp. nov. until further analyses has been done.

Genetic data.

GenBank MN217458-MN217462 for 16S, MN217507 for 18S and MN217532-MN217534 for COI. This species is genetically identical to or very similar to " Ophelina sp. 1" ( Janssen et al. 2015), with K2P values ranging from 0.002-0.006 between O. nunnallyi sp. nov. and the already published sequences with accession numbers KJ736582-KJ736588. Ophelina nunnallyi sp. nov. is sister to Ophelina sp. (NHM_1068) in our phylogenetic analyses ( Fig. 23 ).

Remarks.

Other than sp. NHM_1068 (see Remarks under sp. NHM_1068), the DNA suggest similarity of Ophelina nunnallyi sp. nov. to O. acuminata , originally described from the shallow coast of Denmark, but frequently reported in all oceans (see references in Parapar et al. 2011). These frequent records likely constitute an error as similar, but unrecognized species were likely confused. Deep-sea records of Ophelina aulogaster (Rathke, 1843) by for example Hartman (1965), and Fauchald (1972, may refer to a similar, but unrecognized, species. Hartman (1965) recognized deep Atlantic specimens as a distinct species and later erected Ophelina aulogastrella (Hartman & Fauchald, 1971), which lacks branchiae in posterior region, with most of them present in chaetigers 4-10 (or 13) and anal tube is scoop-shaped with some (easily lost) cirri. Such morphology agrees well with UKSR specimens. However, Hartman (1965) reported variable number of segments (28-36) and wide bathyal distribution (196-5023 m) for O. aulogastrella , which may suggest that more than one species was in fact present in Hartman’s material. The type locality of O. aulogastrella is North Atlantic.

The first occurrence of branchiae from chaetiger 4 is very unusual in Ophelina , where branchiae appear from chaetiger 2. Branchiae are fragile and easily lost structures; therefore, we cannot exclude a possibility that branchiae prior to chaetiger 4 are present but lost in our specimens. Nevertheless, this distribution has been observed in all material examined (including additional specimens, no DNA available) as well as in very similar species Ophelina sp. (NHM_1068).

Ecology.

Found in polymetallic nodule province of the eastern CCZ.

Etymology.

Named in honor of Clifton Nunnally, member of the science party of both the ABYSSLINE cruises.

Figures

Figure 17. Ophelina nunnallyi sp. nov. A Lab image, whole specimen (paratype NHM _ 700) B Live images, whole specimens (holotype [specimen NHM _ 683] [left], paratype NHM _ 700 [right]) C SEM image, anterior and palpode (specimen NHM _ 1309 A, m = mouth) D Lab image, detail of palpode, (paratype NHM _ 1273) E Lab image, anterior and branchiae (paratype NHM _ 1273, br = branchiae) F Lab image, parapodia (holotype, pp = parapodia) G Lab image, capillary chaeta (holotype) H Live image, anal funnel (holotype, c = cirri) I Lab image, detail of anal funnel (holotype, c = cirri). Morphological features in plates E, F, H, I have been outlined with a fine white line to improve clarity of those features. Scale bars: 1 mm (A, E, F); 200 μm (C, D); 100 μm (G, I).

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).