Travisia sp. 1

Gunton, Laetitia M., Kupriyanova, Elena K., Alvestad, Tom, Avery, Lynda, Blake, James A., Biriukova, Olga, Boeggemann, Markus, Borisova, Polina, Budaeva, Nataliya, Burghardt, Ingo, Capa, Maria, Georgieva, Magdalena N., Glasby, Christopher J., Hsueh, Pan-Wen, Hutchings, Pat, Jimi, Naoto, Kongsrud, Jon A., Langeneck, Joachim, Meissner, Karin, Murray, Anna, Nikolic, Mark, Paxton, Hannelore, Ramos, Dino, Schulze, Anja, Sobczyk, Robert, Watson, Charlotte, Wiklund, Helena, Wilson, Robin S., Zhadan, Anna & Zhang, Jinghuai, 2021, Annelids of the eastern Australian abyss collected by the 2017 RV ' Investigator' voyage, ZooKeys 1020, pp. 1-198 : 1

Travisia sp. 1 Fig. 32E

Diagnosis.

Body of 22-25 chaetigers. Prostomium conical, longer than maximum width. Chaetae present from segment 2, one achaetous posterior segment (smallest specimens with chaetae only visible on anterior segments 2-5). Mouth located between chaetigers 1 and 2. Segment 1 uniannulate; anterior and posterior segments, starting at segment 2 triannulate (no obvious differentiation between anterior and posterior regions). Branchiae present, first on chaetiger 3-6, continue for 8-11 chaetigers. Branchiae much shorter than body diameter. Branchiae absent on specimens less than ~ 9.5 mm long, but present on an increasing number of segments on the largest specimens collected. Epidermal papillae are low and sparse at the anterior margin of each segment, becoming larger towards the posterior margin of each segment. Notopodial and neuropodial lobes commencing on chaetiger 3 (in small specimens either absent or difficult to distinguish from adjacent epidermal papillae). Parapodial lobes continuous with an encircling row of papillae, remaining epidermis of each segment low tessellation. Interramal pores first present chaetiger 1, last on chaetiger 20. Pre-pygidial 8-12 segments forming deep lateral grooves within which parapodia and chaetae located (only on the largest specimens). Pygidial tube with six or seven blunt lobes equal in length to the last two chaetigers. The last six dorsal posterior chaetigers crenulated.

Remarks.

Initially the smallest specimens were treated as a distinct OTU (in these the chaetae are sparse, papillae are less distinct and branchiae and parapodial lappets are not observable) but it seems more likely that this represents size-related variation. Other than having branchiae, Travisia sp. 1 is strikingly similar to abranchiate species Travisia glandulosa McIntosh, 1879 (e.g., see Wiklund et al. 2019: fig. 31D) and Travisia gravieri McIntosh, 1908 (see Kirkegaard 1996). As noted above, branchiae are reduced and difficult to observe, or apparently absent in several small specimens of Travisia sp. 1 but branchiae have never been reported in T. glandulosa or T. gravieri . T. glandulosa appears to have a disjunct distribution at abyssal depths, with isolated groups of records at ~ 60°N and 60°S in the Atlantic, plus several isolated records in the Kermadec and Sunda Trenches. Travisia gravieri is also widely reported in the North Atlantic at abyssal and bathyal depths in addition to a single record off Angola in the South Atlantic; however, the Angola specimen was only 4 × 1.5 mm ( Kirkegaard 1996) and we were not able to observe branchiae in specimens of Travisia sp. 1 from this study of similar size. It seems that T. glandulosa , T. gravieri , and Travisia sp. 1 may belong to a single species or species complex but re-evaluation of these taxa is beyond the scope of this study.

Among species with branchiae, only four other species along with Travisia sp. 1 have branchiae commencing at chaetiger 3 ( Travisia carnea Verrill, 1873; Travisia filamentosa León-González, 1998; Travisia hobsonae Santos, 1977 and Travisia profundi Chamberlin, 1919) but none of these have all chaetigers triannulate. T. profundi is similar in having 12 chaetigers with branchiae ( Travisia sp. 1 has 8-11 chaetigers with branchiae), but in T. profundi there is a transition to biannulate and uniannulate posterior chaetigers, and ten or 11 anal lobes compared with six or seven in Travisia sp. 1. This species differs from the two Travisia OTUs reported from 141-375 m in the GAB ( MacIntosh et al. 2018: additional file 2).

Records.

6 specimens. Suppl. material 1: ops. 4, 16, 31, 54, 56 (AM).

Figures

Figure 32. Sternaspidae. Travisiidae A Sternaspis sp., ventral view (op. 40) B Sternaspis sp., dorsal view (op. 40) C Sternaspis cf. annenkovae, ventral view (op. 40) D Sternaspis cf. annenkovae, ventral view (op. 40) E Travisia sp. 1 (AM W. 52547). Scale bars: 1 mm (A, B); 3 mm (C, D); 5 mm (E).