Polycirridae Malmgren 1866

Family Polycirridae Malmgren, 1866

Figs 1B, 2

Diagnosis (after Hutchings et al. 2021a; most important diagnostic characters highlighted in bold)

Transverse prostomium attached to dorsal surface of upper lip; basal part usually as thick horse-shoe shaped crest, eye spots absent; distal part either as another thick crest, with flaring distal lobes, with or without mid-dorsal process, or extending along upper lip until near anterior margin of lip; prostomium

frequently extending ventrally, terminating laterally to mouth (Fig. 2A–D). Buccal tentacles of two types at least, short ones thin, uniformly cylindrical, long tentacles stouter, expanded at tips to variable degrees, distally spatulate (Fig. 2B, D) or more specialised. Peristomium forming lips; lips expanded, upper lip large, frequently circular and convoluted, folded into three lobes; swollen lower lip, only midventral or cushion-like across ventrum, sometimes extending posteriorly for a few segments (Fig. 2A– D). Segment I reduced, frequently only visible ventrally, sometimes completely hidden. Segment II distinctly narrower than following segments, constricting body posteriorly to “lips head”; SG II usually with rectangular or pentagonal mid-ventral shield at beginning of mid-ventral groove, sometimes extending anteriorly through SG I until near posterior margin of lower lip (Fig. 2C). Anterior segments highly glandular ventrally, frequently papillose or tessellated, with paired ventro-lateral pads separated from each other within pairs by mid-ventral groove extending from SG II–IV to posterior body (Fig. 2A–D). Branchiae absent. Notopodia, if present, from SG III (Fig. 2A–D), extending for variable number of segments, usually few; bilobed, elongate notopodia, post-chaetal lobes sometimes longer, notochaetae originating between lobes along all extension of notopodia, separating lobes from base on ventral side of notopodia (Fig. 2A–D); notochaetae winged (Fig. 2E) and/or pinnate, wings of variable width. Neuropodia, if present, located posteriorly to notopodia, frequently from posterior thoracic segments or only on abdomen; neurochaetae as acicular spines or avicular uncini, of two types, and arranged in a single row (Figs 1C, 2F–G). Nephridial and genital papillae usually present, at anterior bases of all notopodia, or only at anteriormost notopodia (Fig. 2A). Pygidium smooth or with rounded ventral papilla.

Remarks

This family was previously considered as a subfamily of Terebellidae (Polycirrinae Malmgren, 1866), but was recently raised to familial level after a comprehensive phylogenetic analysis showed the monophyly of this group (Nogueira et al. 2013). Polycirridae is represented by six genera (Amaeana Hartman, 1959; Biremis Polloni, Rowe & Teal, 1973; Enoplobranchus Verrill, 1879; Hauchiella Levinsen, 1893; Lysilla Malmgren, 1866 and Polycirrus Grube, 1850), distinguished from each other by the presence/ absence of noto- and neuropodia, and if present, the type of neurochaetae. Only Amaeana (Fig. 2A, C), Hauchiella, Lysilla and Polycirrus (Fig. 2B, D–G) are represented in European waters (Lavesque et al. 2020b) (Table 1).

Main morphological characters of European species

PARAPODIA. The parapodia of the members of this family are extremely important to separate the different genera. The genus Hauchiella is characterised by the absence of parapodia and Lysilla by the absence of neuropodia only. The neuropodia of members of Amaeana are characterised by the presence of spines, while those of Polycirrus bear avicular uncini (Figs 1B, 2F–G). Within the genus Polycirrus, the number and location of segments with notopodia and/or neuropodia are of important taxonomic value. Particularly, some species have uncini present only on abdominal segments, i.e., on segments without notopodia, and others have uncini starting before the end of the thorax, on segments bearing also notopodia.

SHAPE OF THE LIPS. As for other terebellids, polycirrids have a peristomium with well-defined upper and lower lips. The upper lip is large and can be trilobed (Fig. 2B) or with a single medial lobe (Fig. 2D). Generally, the upper lip is trilobed but the lobes differ in size and shape and lateral lobes can be reduced or well developed. The shape and the size of the lower lip is also highly variable between species. This lip can be rectangular, squared, rounded or subtriangular, swollen or not, longer than wide or wider than long (Fig. 2B–D).

.

NOTOCHAETAE. Two types of notochaetae can be present: winged chaetae as for P. glasbyi (Fig. 2E) and/ or pinnate as for P. plumosus. The winged notochaetae have wings of different width which are often conspicuous under light microscope but appear hirsute under SEM (Fig. 2E).

UNCINI SHAPE AND DENTICULATION. In Polycirrus two types of uncini are present: Type 1 with a short occipitum (back) and a straight to slightly convex base (Fig. 1B); and Type 2 with a long occipitum and a concave base (Glasby & Hutchings 2014). To date, all described European species have Type 1 uncini. The denticulation of uncini is also helpful in separating species, with the presence (as for P. catalanensis) (Fig. 2F) or the absence (as for P. arenivorus) of a main tooth above the main fang, and the number of rows of secondary teeth.

Key to European species of Polycirridae (after Lavesque et al. 2020b)

1. Parapodia absent (no chaetae)............................................. Hauchiella tribullata (McIntosh, 1869)

– Parapodia present.............................................................................................................................. 2

2. Only notopodia present....................................................................................................... 3 (Lysilla)

– Notopodia and neuropodia present................................................................................................... 4

3. Notochaetae with smooth tips, 6 pairs of thoracic papillae............... Lysilla loveni Malmgren, 1866

– Notochaetae with plumose tips, 9 pairs of thoracic papillae............ Lysilla nivea Langerhans, 1884

4. Neuropodia with spines..................................................................................................5 (Amaeana)

– Neuropodia with avicular uncini..................................................................................6 (Polycirrus)

5. Upper lip without lobe, lower lip rounded, long achaetous region.......................................................................................................... A. gremarei Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020

– Upper lip with trilobed, lower lip rectangular, short achaetous region......................................................................................................................................................... Amaeana trilobata (Sars, 1863)

6. With 28 or more segments with notochaetae.................................................................................... 7

– With 22 or fewer segments with notochaetae................................................................................... 8

7. With 29 segments with notopodia, neuropodia from SG XII, lower lip longer than wide, uncini without a main tooth above the main fang........................... Polycirrus arenivorus (Caullery, 1915)

– With 46 segments with notopodia, neuropodia from SG XIV, lower lip longer than wide, uncini with a main tooth above the main fang............................................. Polycirrus aurantiacus Grube, 1860

– With 28 segments with notopodia, neuropodia from SG XV, lower lip wider than long, uncini with a main tooth above the main fang........................................................................................................................................... Polycirrus gujanensis Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020

8. Neuropodia beginning before SG VIII............................................................................................. 9

– Neuropodia beginning between SG IX and SG XII....................................................................... 10

– Neuropodia beginning after SG XIII.............................................................................................. 14

9. Upper lip trilobed, lower lip wider than long, uncini with 2 rows of teeth above the main tooth.......................................................................................... Polycirrus asturiensis Cepeda & Lattig, 2016

– Upper lip with single medial lobe, lower lip longer than wide, uncini with 1 row of teeth above the main tooth........................... Polycirrus idex Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020b

10. Uncini without a main tooth about the main fang.............. Polycirrus norvegicus Wollebaek, 1912

– Uncini with a main tooth about the main fang................................................................................11

11. Lower lip subtriangular, pointed towards mouth............................................................................ 12

– Lower lip oval or oblong................................................................................................................ 13

12. With 12 or 13 segments with notopodia, lower lip longer than wide......................................................................................................................................... Polycirrus denticulatus Saint-Joseph, 1894

– With 16 segments with notopodia, lower lip wider than long........................................................................................................................................................... Polycirrus elisabethae McIntosh, 1915

13. With 18 or more segments with notopodia, lower lip oval, ventro-lateral pads not separated by a large mid-ventral groove............................................................................................................................................................... Polycirrus glasbyi Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020

– Fewer than 18 segments with notopodia, lower lip oblong, ventro-lateral pads separated by a large midventral groove................ Polycirrus readi Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020

14. With 16 or more segments with notopodia..................................................................................... 15

– Fewer than 16 segments with notopodia........................................................................................ 17

15. Neuropodia beginning from SG XIV–XVI.................................................................................... 16

– Neuropodia beginning from SG XVIII–XX....................... Polycirrus plumosus (Wollebaek, 1912)

16. Upper lip elongated, uncini with a main tooth above the main fang, ventro-lateral pads well developed..................... Polycirrus nogueirai Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020

– Upper lip semicircular, uncini without a main tooth above the main fang, ventro-lateral pads poorly defined................................................................................................ Polycirrus arcticus Sars, 1865

17. Neuropodia beginning from SG XIV, uncini with four teeth above the main fang arranged in single vertical series; lower lip large, shield-like, wider than long......... Polycirrus latidens Eliason, 1962

– Neuropodia beginning from SG XV or after, secondary teeth of uncini not as above................... 18

18. Upper lip trilobed, lower lip subtriangular pointed toward mouth............................................................................................................................................................... Polycirrus medusa Grube, 1850

– Upper lip with a single median lobe, lower lip not subtriangular.................................................. 19

19. Upper lip with thick medial lobe, uncini with two small lateral teeth above the main tooth, lower lip rectangular longer than wide................................................................................................................................................ Polycirrus catalanensis Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020

– Upper lip with elongated triangular medial lobe, uncini with two rows of teeth above the main tooth, lower lip oval and wider than long.................................................................................................................................................... P. pennarbedae Lavesque, Hutchings, Daffe & Londoño-Mesa, 2020