Pygospio elegans Claparede 1863

Pygospio elegans Claparède, 1863

(Fig. 3)

Pygospio elegans Claparède 1863: 37 –38, pl. XIV, figs 27–31. Söderström 1920: 267 –271, figs 113, 114a, 117–120. Fauvel 1927: 46 –47, fig. 16 a–h. Ditlevsen 1929: 30. Thorson 1946: 83 –88, figs 40–41 (larvae). Hannerz 1956: 91 –100, figs 32– 34 (larvae). Hartmann-Schröder 1971: 320 –322, fig. 109; 1996: 330–332, fig. 150. Light 1978: 125 –127, textfig. 126. Rasmussen 1973: 96 –104, figs 29–32 (larvae). Morgan et al. 1999: 125 –130. Gibson & Harvey 2000: 42 –46, figs 1–6. Sikorski 2001: 310 –311, textfigs 1–7. Kesäniemi et al. 2012: 998 –1005. Radashevsky 2012: figs 7C, D, 9B.

N Sample Sample, location 1 2 3 4 5 6

16S (296 bp)

1. P. elegans, White Sea, Russia 6 0.00

2. P. elegans, California, USA 5 0.68 0.00

3. P. elegans, Oregon, USA 2 0.68 0.00 0.00

4. P. elegans, Scotland, UK 1 0.34 1.01 1.01 -

5. Pygospio sp. 1, Sea of Okhotsk, Russia 6 3.43 2.76 2.76 3.77 0.11

6. Pygospio sp. 2, Oregon, USA 5 7.36 6.69 6.69 7.70 7.22 0.68

18S (1667 bp)

1. P. elegans, White Sea, Russia 6 0.04

2. P. elegans, California, USA 5 0.09 0.00

3. P. elegans, Oregon, USA 2 0.03 0.06 0.00

4. P. elegans, Scotland, UK 1 0.03 0.06 0.00 -

5. Pygospio sp. 1, Sea of Okhotsk, Russia 7 0.39 0.42 0.36 0.36 0.00

6. Pygospio sp. 2, Oregon, USA 5 1.92 1.98 1.92 1.92 1.80 0.00

28S (295 bp)

1. P. elegans, White Sea, Russia 6 0.10

2. P. elegans, California, USA 5 0.06 0.00

3. P. elegans, Oregon, USA 2 0.06 0.00 0.00

4. P. elegans, Scotland, UK 1 0.06 0.00 0.00 -

5. Pygospio sp. 1, Sea of Okhotsk, Russia 6 1.07 1.02 1.02 1.02 0.00

6. Pygospio sp. 2, Oregon, USA 5 1.14 1.08 1.08 1.08 2.10 0.14

H3 (318 bp)

1. P. elegans, White Sea, Russia 6 0.17

2. P. elegans, California, USA 5 0.10 0.00

3. P. elegans, Oregon, USA 2 0.10 0.00 0.00

4. P. elegans, Scotland, UK 1 0.10 0.00 0.00 -

5. Pygospio sp. 1, Sea of Okhotsk, Russia 12 2.83 2.73 2.73 2.73 0.00

6. Pygospio sp. 2, Oregon, USA 4 7.60 7.49 7.49 7.49 8.50 0.16

Combined data (2576 bp)

1. P. elegans, White Sea, Russia 6 0.06

2. P. elegans, California, USA 5 0.16 0.00

3. P. elegans, Oregon, USA 2 0.12 0.04 0.00

4. P. elegans, Scotland, UK 1 0.08 0.16 0.12 -

5. Pygospio sp. 1, Sea of Okhotsk, Russia 6 1.11 1.04 1.00 1.11 0.01

6. Pygospio sp. 2, Oregon, USA 4 3.16 3.10 3.06 3.18 3.26 0.10 Synopsis. Adults up to 25 mm long, 0.75 mm wide for 75 chaetigers. Prostomium anteriorly incised. Caruncle to end of chaetiger 1. Occipital antenna absent. Nuchal organs ciliary bands on lateral sides of caruncle (Fig. 3B). Hooks in neuropodia from chaetiger 8; in juveniles, spoon-like hooks present in chaetigers 8–9 and bidentate hooks present in succeeding chaetigers; in adults, spoon-like hooks present from chaetiger 8 through chaetigers 11–12 and bidentate hooks present in succeeding chaetigers (Fig. 3A, E, F). Males with a pair of dorsal horns on chaetiger 2. Branchiae from chaetigers 11–13, flattened, with surfaces oriented parallel to body axis, fused to notopodial postchaetal lamellae, with ciliation along inner surface (Fig. 3A, C). Nototrochs from chaetiger 2 to last branchiate chaetiger; in females, nototrochs composed of single transverse row of ciliated cells extending onto branchia; in males, nototrochs double, with anterior row extending onto branchia (Fig. 3B, C). Pygidium with one pair of dorsal cirri and one pair of slightly thicker and longer ventral cirri (Fig. 3D). Glandular pouches in neuropodia from chaetiger 3. Digestive tract without gizzard-like structure. Nephridia from chaetiger 4 onward posteriorly. Reproducing asexually by architomy. Gonochoristic. Spermatids in octads. Spermatozoa elongated introsperm. Mature oocytes about 100 µm in diameter. Females laying up to 250 eggs in 34 capsules joined in a string and each attached by one stalk to inside wall of tube. Broods of three kinds: mainly planktotrophic, with larvae developing three chaetigers inside capsules before hatching, developing in plankton until 14–19-chaetiger stage, and then settling; entirely lecithotrophic, with larvae developing inside capsules 14–19 chaetigers, hatching and settling soon thereafter; and intermediate, with larvae developing 6–10 chaetigers inside capsules, hatching, developing in plankton until 14–19-chaetiger stage, and then settling. Larvae with nototrochs from chaetiger 3 onwards, neurotroch terminated by ciliated pit on chaetiger 2, and gastrotrochs on chaetigers 3, 5, 7, and 11; dorso-lateral grasping cilia absent. Living in silty tubes intertidally and in shallow water. Occurring in Arctic and in boreal waters in Atlantic and Pacific oceans.

Remarks. The synopsis is based on the descriptions of P. elegans cited above and also on the material recognized in the present study as a monophyletic P. elegans group (Table 1, Fig. 2). The Figure 3 is based on individuals from Broad Bay, Nahant, Massachusetts, U.S.A. (USNM 177011–177016). These individuals were not examined in the present molecular analysis but appeared identical to P. elegans from European waters. Kesäniemi et al. (2012) compared partial sequences of the mitochondrial COI of worms identified as P. elegans from Europe and the United States (comprising two sites from Maine) and did not find evidence for cryptic speciation in this taxon. We suggest that our worms from Massachusetts belong to the same population as worms from Maine, and, thus, also belong to P. elegans.

Adults of Pygospio sp. 2 differentiated in the present molecular analysis co-occurred with P. elegans in Oregon, appeared similar to the latter but differed from them in the absence of spoon-like hooks in neuropodia. Their morphology will be described elsewhere. Adults of Pygospio sp. 1 were collected in two sites in the Sea of Okhotsk and were the only Pygospio worms in the area. No morphological character to discriminate them from adults of P. elegans has been revealed so far.