Paraonides nordica Strelzov, 1968

Sikorski, Andrey, 2017, The Paraonidae (Annelida: Sedentaria) from Norway and adjacent seas, with two new species, four new records, and a redescription of Paraonides nordica Strelzov, 1968 based on type material, Zootaxa 4320 (1), pp. 41-67 : 60-61

Paraonides nordica Strelzov, 1968

( Fig. 10 )

Paraonides nordica Strelzov, 1968: 76 , fig. 1A–E.

Paraonella nordica . — Strelzov 1973: 147 –148, fig. 67; Kedra et al. 2011: 430; 2013: 813–814.

Material examined. ZISP 5/38014; Barents Sea; 72.0366°N-51.1133°E; 87 m; muddy sand and pebbles with gravel 06.09.1959; one paratype. ZISP 2/38011; Barents Sea; 72.50°N-46.60°E; 60 m; shells and gravel 09.09.1959; two paratypes.

Description. Longest specimen complete, 9.3 mm long for 56 chaetigers, 0.15 wide at tenth chaetiger level. Prebranchial and branchial regions very slightly flattened, postbranchial region cylindrical. Preserved specimens whitish, without any colour marking. Prostomium distally rounded, nearly twice longer than wide ( Fig. 10A ); antenna, apical sensory organ and eyes absent. Mouth anteriorly oriented, posterior lip extending through first chaetiger only. Nuchal organs straight and oblique, joining to posterior end of prostomium ( Fig. 10A ); secondary ciliary organs absent. Branchiae digitiform, with rounded tips ( Fig. 10A, B ), occurring from chaetiger 5 to chaetiger 10; all similar in length, nearly reaching mid-dorsal line, except the last pair, which is half as long; ciliation not observed. Notopodial postchaetal lobes very short and papilliform in prebranchial region, minute on chaetigers 1 and 2, slightly larger on chaetigers 3 and 4 ( Fig. 10A ); progressively increasing in length through branchial region, becoming digitiform on chaetigers 8 onwards ( Fig. 10B ), about one quarter the length of corresponding branchia, except for chaetiger 10, where the branchiae are shorter; not observed in post-branchial region. Neuropodial postchaetal lobe as low ridge, of even height all along body ( Fig. 10 B, C ); interramal process not observed. Pygidium squared, pygidial cirri not observed. Chaetae arranged in two rows in both noto- and neuropodia, those of posterior row clearly longer; notochaetae thin and slightly curved, numbering 10 on chaetiger 3 and 14 on chaetiger 9, gradually decreasing to seven on chaetigers 32 and 46 ( Fig. 10C ); neurochaetae similar to notochaetae, numbering 15 on chaetiger 3, 14 on chaetigers 9 and 32, and 12 on chaetiger 46 ( Fig. 10C ); modified noto- or neurochaetae absent.

Remarks. The species can be easily distinguished from the remaining species of the genus by a number of characters. Firstly, the presence of branchiae is a useful trait for separating it from the abranchiate species of the genus, namely Paraonides myriamae Katzmann & Laubier, 1975 , from the Mediterranean Sea but also reported from the north-eastern Atlantic Ocean (see above), and P. monilaris Hartman & Fauchald, 1971 , from abyssal depths in the north-western Atlantic Ocean ( Hartman & Fauchald 1971), as well as from the closely related Paraonella abranchiata Fauchald & Hancock, 1981 , from the western coast of the United States ( Fauchald & Hancock, 1981). The branchial arrangement is also very different to that of P. platybranchia ( Hartman, 1961) , from southern California ( Hartman 1961, 1969), which has 21 to 25 pairs of branchiae, many more than the six pairs of P. nordica . The most similar species are P. rubriceps Hartman & Fauchald, 1971 , from abyssal depths off New England ( Hartman & Fauchald 1971), and P. cedroensis Fauchald, 1972 , from western Mexico ( Fauchald 1972). Both species can present a similar number of branchiae (five to 11 pairs in P. rubriceps , five pairs in P. cedroensis ), but they have three instead of four prebranchial chaetigers. Moreover, notopodial postchaetal lobes of postbranchial region in P. cedroensis and P. rubriceps are longer than those in prebranchial one, whereas in P. nordica they are very short and almost unnoticeable.

Distribution. Barents Sea ( Strelzov 1973, Kedra et al. 2013). Spitsbergen ( Kedra et al., 2011). Canadian Arctic ( Goldsmit et al. 2014).

Figures

FIGURE 10. Paraonides nordica Strelzov, 1968. A. Anterior end, dorsal view; B. Left parapodium of chaetiger 8, anterior view; C. Right parapodium of chaetiger 46, anterior view. Scale bar: A: 0.2 mm; B, C: 50 µm.