Ammotrypanella sp. (NHM_1653)

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 sp. (NHM_1653) Fig. 9 A–H

Material examined.

NHM_1653 NHMUK ANEA 2019.7108, coll. 10 Mar. 2015, 12°21.81N, 116°40.86W, 4233 m http://data.nhm.ac.uk/object/a2f7ed04-7275-4a57-a058-bd750cacc715.

Description.

This small species is represented by a single complete specimen in reasonable condition, except for some damage to anal tube ( Fig. 9 ). Complete specimen 7.5 mm long and 0.5 mm wide for 34 chaetigers. Body cylindrical, with slight annulation detectable. Ventral groove along the entire body length. Preserved specimen pale pink in ethanol; live specimen semi-translucent with orange gut ( Fig. 9B ). First seven and posterior (branchial and last six postbranchial) chaetigers crowded, chaetigers in midbody elongated.

Prostomium conical (longer than wide) anteriorly tapering into blunt tip and bearing very distinct, round palpode ( Fig. 9C, D ). Nuchal organs observed as narrow, lightly pigmented 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; large, of similar length except for the last branchial pair, which is reduced ( Fig. 9E ).

Parapodia distinct, biramous; observed as a small lobe in chaetigers 1-7, becoming smaller in subsequent chaetigers; parapodia embedded in distinct lateral grooves ( Fig. 9F ). Chaetae are capillaries ( Fig. 9G ), first seven chaetigers with numerous chaetae in bundles, fewer chaetae in following chaetigers; chaetae long in first seven and last six chaetigers, shorter in midbody.

Anal tube the length of three posterior chaetigers ( Fig. 9H ); cylindrical, distally slightly narrowing; due to some damage, the form of distal end cannot be established with certainty; short thick ventral cirrus attached near the distal end.

Genetic data.

GenBank MN217413 for 16S, MN217493 for 18S and MN217516 for COI. This species is genetically identical or very similar to COI sequences collected in the German and French exploration contract areas and published in Janssen et al. (2015), with K2P values ranging from 0.0-0.002 between Ammotrypanella sp. (NHM_1653) and the already published sequences with accession numbers KJ736387-KJ736392. In our phylogenetic analyses is forms a monophyletic clade with Ammotrypanella keenani sp. nov., A. kersteni sp. nov. and Ammotrypanella sp. (NHM_2114) ( Fig. 23 ).

Remarks.

This is another species with branchiae limited to the posterior end consistent with the genus Ammotrypanella . While this species is similar to Ammotrypanella kersteni sp. nov., it can be clearly distinguished from it by a much smaller body size, shape of prostomium and bearing narrow, elongated, cylindrical anal tube. This form of tube is however similar to other known anal tube-bearing species of Ammotrypanella and due to some damage to this feature in the UKSR specimen, its form cannot be established with certainty.

Ecology.

Found in polymetallic nodule province.

Figures

Figure 9. Ammotrypanella sp. NHM _ 1653 (specimen NHM _ 1653). A Lab image, whole specimen (faded stain B Live image, whole specimen C Lab image, anterior (faded stain) D Lab image, detail of palpode E Lab image, posterior (faded stain, br = branchiae) F Lab image, anterior-midbody (faded stain, pp = parapodia) G Lab image, detail of capillary chaetae H Lab image, detail of posterior and anal tube. Morphological features in plates C, E, F, G have been outlined with a very fine white to improve clarity of those features. Scale bars: 1 mm (A); 100 μm (D, G, H).

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).