Paraonis cf. quadrilobata (Webster & Benedict, 1887)

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

Paraonis cf. quadrilobata (Webster & Benedict, 1887) Fig. 19G

Diagnosis.

All specimens anterior fragments; most complete specimen with 47 chaetigers (into two pieces), ~ 10 mm length, 1.2 mm maximum width. Prostomium sub-triangular, wider than long, with two large, conspicuous nuchal organs, showing traces of dark pigmentation. Antenna slender, thread-like, reaching chaetiger 3-7 backwards (tip often broken). Three pre-branchial chaetigers, five to 12 pairs of flattened branchiae. Branchial region wider and slightly flattened. Notopodial post-chaetal lobes tubercular in the first three chaetigers, then slender, elongated, with bulbous base in chaetigers 4-15, thread-like from chaetiger 16 to the end of the body. Neuropodial post-chaetal lobes conical, well-developed, in the first 15-17 chaetigers. Notopodial modified chaetae absent. Neuropodial modified chaetae occuring after chaetiger 25 thickened capillaries, with abruptly tapered tips. Remains of thin, dark transverse bars on the dorsal side of the branchial region. The largest specimen showing oocytes (140 × 110 μm) in the coelom of the post-branchial region.

Remarks.

These specimens correspond well to material sampled in the sub-arctic Atlantic Ocean (Norway) in regard to size and number of branchiae. However, P. quadrilobata has been reported from all over the world and from different depths, and most likely represents a species complex (unpublished molecular data point at a separation at least between North Atlantic and Mediterranean specimens, the latter described as Aricidea annae Laubier, 1967 which is now Paraonis annae ). Blake (1996a) suggested that the majority of Pacific specimens should be assigned to Aricidea antennata Annenkova, 1934 (now Paraonis antennata ), but the examined specimens have simple notopodial post-chaetal lobes (instead of branched ones as in A. antennata ).

Records.

8 specimens. Suppl. material 1: ops. 31, 33, 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).