Ophelina meyerae, 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 meyerae sp. nov. Fig. 16 A–G

Material examined.

NHM_1241(holotype) NHMUK ANEA 2019.7130, coll. 01 Mar. 2015, 12°15.44N, 117°18.13W, 4302 m http://data.nhm.ac.uk/object/920d8670-507e-4126-a42b-6e208bbe66d3.

Type locality.

Pacific Ocean, CCZ, 12°15.44N, 117°18.13W, depth 4302 m, in mud between polymetallic nodules.

Description.

This is a medium-sized species represented by a single specimen. Body cylindrical, iridescent, some annulation detectable in first five and few posterior chaetigers, the rest of body smooth, no annulation detectable ( Fig. 16A, B ). Ventral groove distinct throughout the body. Live specimen semi-translucent, with orange gut ( Fig. 16A ). Complete specimen 20 mm long and 1.5 mm wide, with 29 chaetigers; anterior chaetigers not particularly crowded, degree of crowding observable in the posterior-most three to five chaetigers.

Prostomium of preserved specimen oval and broad (about as long as wide) and anteriorly bluntly rounded, somewhat truncated; bearing very distinct oval palpode ( Fig. 16A ). Nuchal organs observed as lightly pigmented slits laterally on posterior part of prostomium.

Branchiae present in all chaetigers, except for first chaetiger; branchiae remain attached in most chaetigers, including ch. 29, but are occasionally missing (lost) in some chaetigers. Branchiae easy to detect, although rather slender, best observed in anterior chaetigers ( Fig. 16C ), then getting progressively thinner and shorter and becoming more difficult to detect ( Fig. 16D ). All branchiae cirriform.

Parapodia distinct, biramous; with a broad lobe in chaetigers 2-10, becoming smaller in subsequent chaetigers; parapodia embedded in distinct lateral grooves ( Fig. 16E ). Chaetae are capillaries ( Fig. 16F ); not particularly numerous in any chaetigers, but most dense and longest in chaetigers 2-8, where of similar length, then becoming shorter, sometimes missing (broken off) entirely.

Anal tube well preserved; relatively short (about the length of two posterior chaetigers) and thick; distally symmetrical; distal opening with circlet of about 20 short, slender cirri with the exception of ventral part of the margin, which is smooth; ventral cirrus not observed ( Fig. 16G ).

Genetic data.

GenBank MN217457 for 16S and MN217506 for 18S. COI was unsuccessful for this specimen, no identical GenBank matches for 16S or 18S. In our phylogenetic analyses this species is sister to Ophelina martinezarbizui sp. nov. ( Fig. 23 ).

Remarks.

Similar to Ophelina martinezarbizui sp. nov. in overall look and form of anal tube, but slender branchiae are present in all chaetigers, midbody and posterior branchiae are smaller than those of the anterior region.

Ecology.

Found in polymetallic nodule province of the eastern CCZ.

Etymology.

Named in honor of Kirstin Meyer-Kaiser, member of the science party onboard RV Thomas G. Thompson on the AB02 ABYSSLINE cruise in 2015.

Figures

Figure 16. Ophelina meyerae sp. nov. holotype (specimen NHM _ 1241). A Live images, whole specimen with detail of anterior (p = palpode) B Lab image, whole specimen, lateral view (faded stain) C Lab image, anterior and branchiae (faded stain) (br = branchiae) D Lab image, mid-body branchiae (faded stain, br = branchiae) E Lab image, anterior parapodia (faded stain, pp = parapodia) F Lab image, detail of capillary chaetae (br = branchiae) G Lab image, detail of capillary chaetae (br = branchiae). Morphological features in plates C-F have been outlined with a fine white line to improve clarity of those features. Scale bars: 1 mm (B-E); 100 μm (F, G).

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).