Ammotrypanella kersteni, 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

Ammotrypanella kersteni sp. nov. Figs 7A, B , 8 A–F

Material examined.

NHM_254 (holotype) NHMUK ANEA 2019.7107, coll. 17 Oct. 2013, 13°45.21N, 116°29.12W, 4128 m http://data.nhm.ac.uk/object/3441cd68-7432-4dee-8415-966b104c3077.

Type locality.

Pacific Ocean, CCZ, 13°45.21N, 116°29.12W, depth 4128 m, in mud between polymetallic nodules.

Description.

This species is represented by a single specimen in very good condition, although now split into two fragments, following tissues sampling for molecular analysis. Specimen (when complete) 31 mm long and 1.5 mm wide for 36 chaetigers. Body cylindrical, iridescent and smooth, no annulation detectable ( Fig. 7 ). Ventral groove along the entire body length. Preserved specimen pale yellow in ethanol ( Fig. 8 ). First seven and posterior (branchial and last six post branchial) chaetigers crowded, chaetigers in midbody elongated.

Prostomium of preserved specimen oval and broad (about as long as wide) and anteriorly blunt, somewhat truncated and bearing very distinct short, button-like palpode ( Fig. 8C ). Nuchal organs observed as narrow slits laterally on posterior part of prostomium.

Branchiae present, but limited to posterior region only, where present in chaetigers 22-28, seven pairs. All branchiae cirriform, of similar length, with red pigment in live specimen ( Fig. 7B ).

Parapodia distinct, biramous; observed as a broad lobe in chaetigers 1-7 ( Fig. 8B ), becoming smaller in subsequent chaetigers; parapodia embedded in distinct lateral grooves. Chaetae are capillaries ( Fig. 8E ), first seven chaetigers with numerous chaetae in bundles, fewer chaetae in following chaetigers; chaetae long, becoming progressively longer over the first seven chaetigers and then getting progressively shorter towards posterior part of the body.

Posterior achateous end (it is unclear if it represents anal tube) the length of two posterior chaetigers, a funnel-shaped structure with broad distal opening, distal margin smooth ( Fig. 8F ).

Reproductive information.

Ovigerous specimen with eggs of 200-250 µm in size clearly observed in mid through to posterior part of the body ( Fig. 7B ).

Genetic data.

GenBank MN217412 for 16S, MN217492 for 18S and MN217515 for COI. No identical matches on GenBank for COI, 16S or 18S. This taxon does not match any previous COI sequences, and we only have one specimen from the current study, which may indicate that this represents a rare species. In our phylogenetic analyses it forms a monophyletic clade with Ammotrypanella keenani sp. nov., Ammotrypanella sp. (NHM_2114) and Ammotrypanella sp. (NHM_1653) ( Fig. 23 ).

Remarks.

Ammotrypanella princessa Schüller, 2008 is most similar to our species because of the shape of prostomium; however, this may be a preservation artefact (see earlier comments), which mimics the shape of a royal crown ( Schüller 2008). However, A. princessa is a much smaller species (5-11 mm long) with fewer body segments (33-35).

The anal tube commonly becomes detached in opheliids and when short anal tubes have been described in the past, it is important to be mindful that the anal tube may in fact be missing. The posterior achateous end in UKSR species is rather short, but it appears to have a distinct form, and therefore we suggest it may possibly represent anal tube rather than damaged posterior end. However, other Ammotrypanella species possess an elongated cylindrical anal tube, which could suggest that the anal tube in A. kersteni sp. nov. is in fact missing. At the same time, the anal tubes of Opheliidae species show a variety of forms, and it is not impossible to speculate that similar variability can be found in Ammotrypanella as more species are discovered. With the current evidence based on single specimen we cannot clarify if the funnel-shaped posterior end represents the anal tube.

Ecology.

Found in the eastern polymetallic nodule province of the CCZ.

Etymology.

Named in honor of Oliver Kersten, member of the science party of both ABYSSLINE cruises.

Figures

Figure 7. Ammotrypanella kersteni sp. nov. holotype (specimen NHM _ 254) live images. A Live image, whole specimen B Live image, detail of anterior (upper) and posterior (lower), with branchiae outlined in a fine black line (e = eggs, br = branchiae).

Figure 8. Ammotrypanella kersteni sp. nov. holotype (specimen NHM _ 254). A Lab images, whole specimens, dorsal (upper) and ventral (lower) B Lab image, anterior C Lab image, detail of palpode D Lab image, mid-body parapodia (p = parapodium) E Lab image, detail of parapodium F Lab image, posterior and anal funnel. Morphological features in plates B, D, F have been outlined with a fine white or black line to improve clarity of those features. Scale bars: 2 mm (A); 1 mm (B, D, F); 100 μm (C, 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).