Aricidea cf. simplex Day, 1963b

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

Aricidea cf. simplex Day, 1963b Fig. 19C, D

Diagnosis.

All specimens consist of anterior fragments; most complete with 56 chaetigers, 12.7 mm total length, 1.45 mm maximum width. Prostomium sub-trapezoidal, with large, conspicuous nuchal organs showing dark brown pigmentation. Antenna very short, clavate, reaching the anterior margin of the first chaetiger (absent, likely broken, in one individual). Three pre-branchial chaetigers, 14-17 pairs of acute, relatively short branchiae; last five or six pairs of branchiae gradually decreasing in size. Notopodial lobes tubercular in the first two chaetigers, spindle-shaped in chaetigers 3-15, gradually thinner and thread-like from chaetiger 16 to the end of the fragment. Neuropodial post-chaetal lobes inconspicuous. Notopodial modified chaetae absent. Neuropodial modified chaetae from chaetiger 32, first one or two, then up to five (possibly more in the posterior part of the body, missing in all examined specimens), strong, slightly reddish hooks with bent tip.

Remarks.

The examined specimens are very similar to each other and are clearly similar to ' Aricidea ' Aricidea simplex as described by Blake (1996a) on the basis of shelf specimens. However, molecular data showed that this taxon represents a species complex ( Brasier et al. 2016; Langeneck et al. 2019a) and that interspecific differences are most likely concealed by its extremely simple anatomy and the absence of reliable diagnostic characters. Aricidea neosuecica Hartman, 1965 (with type locality in the West Atlantic) and Aricidea neosuecica nipponica Imajima, 1973 (with type locality off Japan) have been considered synonymous with A. simplex , but may also represent separate species. As A. simplex was described for relatively shallow environments in South Africa ( Day 1963 b), this present deep-sea species most likely does not correspond to the taxon sensu stricto.

Records.

3 specimens. Suppl. material 1: ops. 31, 40, 42 (AM).

Figures

Figure 19. Paraonidae A Aricidea sp., prostomium with median antennae B same, capillary with arista C Aricidea cf. simplex, dorsal view anterior (AM W. 52307) D same, ventral view anterior (AM W. 52307) E Levinsenia uncinata (AM W. 52320), methyl green stained dorsal view F Paraonella sp. 1 (AM W. 52310) G Paraonis cf. quadrilobata chaetae (AM W. 52307). Scale bars: 250 µm (A); 50 µm (B); 1 mm (C, D, E, F); 10 µm (G).