Ammotrypanella McIntosh, 1878

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 McIntosh, 1878 Fig. 5 A–C

Notes.

The confused taxonomic history of Ammotrypanella and its type species, Ammotrypanella arctica McIntosh, 1878 has been summarized by Parapar et al. (2011) and attributed to the short description and drawings provided by McIntosh (1878). Støp-Bowitz (1945) proposed that Ammotrypanella should be considered as synonymous with Ophelina , while Fauchald (1977) treated Ammotrypanella as a valid genus characterized by having the branchiae limited to the posterior part of body. Schüller (2008) provided a re-diagnosis of Ammotrypanella , following the examination of the type material of A. arctica , and while she pointed out that the holotype (BMNH.1921.1.2392) is in a poor state, she confirmed the presence of branchiae in the posterior part of the body only. Based on this observation Schüller (2008) then provided descriptions of three new species from abyssal Southern Ocean ( A. cirrosa , A. mcintoshi and A. princessa ), bringing the currently valid number of Ammotrypanella species to four. The holotype of A. arctica has also been examined as part of this study ( Fig. 5 A–C ) but is in too poor condition (now in three fragments) to provide meaningful information.

As a taxonomic revision is beyond the scope of this study, we follow the definition of Ammotrypanella given by Schüller (2008), with one amendment. Schüller (2008) considered that anal tube may be absent, while here we suggest that it was likely missing due to damage.

Diagnosis.

Body long and thin, with ventral groove along whole length of body. Prostomium bluntly rounded to conical with small palpode, peristomium indistinct. Eyes absent. Parapodia embedded into lateral groove in median region, becoming more distinct in posterior region. Parapodia with branchiae in third quarter of body. All chaetae simple. Branchiae flat, wide at base, tapering to top. Anal tube present.

Several morphotypes with branchiae restricted to the posterior part of the body were encountered in the UKSR material, which is consistent with genus Ammotrypanella as discussed above. The UKSR-collected species can be distinguished from four known species assigned to this genus mainly by the form of anal tube:

Ammotrypanella arctica McIntosh, 1878 has an elongated anal tube about same length as posterior abranchiate region and provided with a deciduous anal cirrus and terminal anus (see Schüller et al. 2008; Parapar et al. 2011).

Ammotrypanella cirrosa Schüller, 2008 has an elongated anal tube, its length equals to length of last 5-8 chaetigers, posterior margin with numerous cirri.

Ammotrypanella mcintoshi Schüller, 2008 lacks an anal tube. Although the absence of an anal tube was considered real and a distinguishing feature of this species by Schüller (2008), it is not clear if the anal tube was in fact missing (fallen off) (see comment in Parapar et al. 2011).

Ammotrypanella princessa Schüller, 2008 has a prostomium which mimics the shape of a royal crown ( Schüller 2008).

Additionally, Ophelina opisthobranchiata Wirén, 1901 described from the deep sea of Spitsbergen, also has a posterior distribution of branchiae. In his recent re-description Kongsrud et al. (2011) preferred not to recognize this species as Ammotrypanella due to lack of phylogenetic analysis and variation of morphology in Ophelina .

Our molecular analysis revealed the presence of four distinct CCZ species, forming a well-supported clade. Three of those species ( Ammotrypanella keenani sp. nov., Ammotrypanella kersteni sp. nov. and Ammotrypanella sp. NHM_1653) are represented by reasonably well-preserved specimens. Unfortunately, species NHM_2114 is represented by a single specimen with all branchiae now lost and it is therefore assigned to this genus only based on molecular data.

Figures

Figure 5. Ammotrypanella arctica holotype (BMNH 1921.12392). A Whole specimen (fragmented) B Anterior-most fragment C Posterior-most fragment. Scale bars: 1 mm (A, B, C).