Laonice (Norgensia) rasmusseni, Sikorski & Pavlova, 2018

Sikorski, Andrey & Pavlova, Lyudmila, 2018, Two new species of Laonice (Norgensia) (Spionidae, Polychaeta) from subtropical Atlantic and subequatorial Pacific coasts of North America, Zootaxa 4418 (2), pp. 171-178 : 175-176

Laonice (Norgensia) rasmusseni sp. nov.

( Figure 3 )

Holotype: Sapelo Island , Biological Collection Sapelo Island Research Foundation, Sta. 359, 30°48'05"N 80°00'W, 843 m, 0 9.12.1963, coll. Erik Rasmussen (NHMD-157378).

Description. Holotype: specimen of 0.7 mm wide is complete, having 75 chaetigers for 17 mm length. No additional material available.

Prostomium bell-shaped, rounded anteriorly and not fused with peristomium. Two pairs of small brownish eyespots in posterior part of prostomium, posterior eye-spots larger, anterior eye-spots moved onto the lateral surface of the middle part of the prostomium. Occipital tentacle long. Palps absent ( Fig. 3A, D ).

Nuchal organ extending to chaetiger 14 (or maybe 17—difficult to see due to damaged surface).

Branchiae appear on chaetiger 2, present along more than ½ of the body except the 19 most posterior chaetigers. Branchiae long, on chaetiger 2 as high as notopodial postchaetal lobes and higher posteriorly. Branchiae ¼ of their length over lobes already on chaetiger 3 and ½ over in the middle part of body ( Fig. 3E, F ). In the posterior part of body branchiae very thin, on the last branchial segments branchiae as high as the notopodial postchaetal lobes. Long cilia on the branchial margin opposite the margin of notopodial postchaetal lobes in the anterior and the middle part of body.

Notopodial postchaetal lobes gradually narrow into acute tips on the anterior chaetigers bearing capillaries in more than two rows ( Fig. 3E ), upper part of notopodial postchaetal lobes nearly twice as narrow as the lower ones in more posterior chaetigers ( Fig. 3F ). Here the lobes without acute tips, but become acute in the posterior part of body ( Fig. 3G ). Neuropodial postchaetal lobes acute, nearly triangular, in most anterior chaetigers ( Fig. 3E ), becoming low and nearly rectangular, in caudal region ( Fig. 3F–G ). Lobes become comparatively large, oval, and bulbous in 18 most posterior chaetigers ( Fig. 3C ) moreover the neuropodial lobes set below the fascicle of chaetae.

Capillaries arranged in three vertical rows between chaetiger 2 and 12. Sabre chaetae first appear in neuropodia on chaetiger 15, 1 per neuropodium. Hooded hooks accompany capillaries in neuropodia from chaetiger 18, up to 8–9 per fascicle. No hooks in notopodia. Hooks are bifid in side and frontal view ( Fig. 3H–I ).

Low transversal dorsal membranes connecting the notopodial postchaetal lobes present from about chaetiger 22 and present on 34 subsequent segments ( Fig. 3B ).

Genital pouches appearing after the fourth neuropodium, present along body, except 18 most posterior chaetigers.

Pygidial papillae not distinct, but two ventral papillae recognisable. Two thin dorsal cirri present ( Fig. 3C ). Pygidium with diffuse dark pigmentation mostly concentrated in folds of pygidium.

Methyl green. No special staining pattern detected.

Distribution. Sapelo Island, 30°48'05"N 80°00'W, 461 FT.

Etymology. The name is dedicated to Dr Erik Rasmussen who collected at Sapelo Island for the collection of the Natural History Museum of Denmark in the 1960’s.

Remarks. This species definitely belongs to the subgenus Norgensia due to the prostomium and peristomium not being completely fused, branchiae existing along nearly all the segments, and capillaries are arranged in more than two vertical rows. Neuropodial hook have one unpaired apical tooth. Genital pouches starting more anteriorly than in other species of this subgenus. The hooded hooks in L. rasmusseni sp. nov. appear more anteriorly compared to L. vieitezi —from chaetiger 18 instead of chaetiger 34. The branchiae surpass the notopodial postchaetal lobes in height on chaetiger 3 in L. rasmusseni sp. nov. but on chaetiger 6 in L. norgensis . The transversal dorsal membranes connecting the notopodial postchaetal lobes (one per segment) are low and are present on 34 chaetigers in L. rasmusseni sp. nov. while the membranes (two per chaetiger) in L. norgensis are comparatively high, up to the most posterior chaetigers. Complete specimens belonging to L. norgensis of ~ 0,7 mm width have 95–104 chaetigers while the specimen of L. rasmusseni sp. nov. of comparable width has only 75 chaetigers.

Figures

FIGURE 3. Laonice (Norgensia) rasmusseni sp. nov. Holotype. A. Anterior end with six chaetigers, dorsal view; B. Transdorsal membranes on chaetigers 41–43; C. Posterior end with pygidium, dorsal view; D. Anterior end with seven chaetigers, lateral view; E–G. Parapodia of chaetigers 5, 42 and 57; H–I. Hooded hook of chaetiger 40, side and frontal view. Scale:A–D—1 mm; E–G—0.5 mm; H–I—0.02 mm.