Petta pusilla Malmgren, 1866,

Zhang, Jinghuai, Hutchings, Pat & Kupriyanova, Elena, 2019, A revision of the genus Petta Malmgren, 1866 (Annelida: Pectinariidae), with two new species from deep waters of southeastern Australia, and comments on phylogeny of the family, Zootaxa 4614 (2), pp. 303-330: 306-309

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Petta pusilla Malmgren, 1866


Petta pusilla Malmgren, 1866 

Figs 2–5View FIGURE 2View FIGURE 3View FIGURE 4View FIGURE 5, Table 2

Petta pusilla Malmgren, 1866: 361  , Tab. XVIII fig. 43 (Gullmarsfjord, west coast of Sweden, type locality).

Pectinaria pusilla — Levinsen 1883: 155  (Northern Europe); Wollebaek 1912: 35, pl. III, fig. 1–8 (Western Norway); Crawshay 1912: 346 (description, English Channel); Dauvin et al. 2003: 85 (name only, English Channel).

Petta  pusilla— LoBianco 1893: 48 (Naples, Italy); Nilsson 1912: pl. III, fig. 3–4 (anatomy of nervous system, Kristineberg, Sweden); Fauvel 1914: 279, pl. XXV, fig. 22–26 (Azores, Portugal); Hessle 1917: 83–84 (West coast of Sweden); Fauvel 1927: 224 (description, Plymouth, Ireland, Azores, Irish Sea, Marseille, Naples, North Sea, Arctic Ocean); Nilsson 1928: 83–85, Fig. 30 (Arctic Ocean, Atlantic Ocean and Mediterranean Sea); Holthe 1977 (zoogeography, Atlantic-boreal); Holthe 1986: 27–28, Fig. 7View FIGURE 7, map 6 (description, Norway); Castelli & Valentini 1995: 52–53 (name only, Italy); Méndez & Cardell 1996: 138 (name only, Catalonia, Spain); Arvanitidis 2000: 95 (name in checklist only, Greece); Orrhage 2001 (anatomy of nervous system, west coast of Sweden); Simboura & Zenetos 2002: 100 (name only, Mediterranean Sea); García-Diez et al. 2005 (name only, Azores); Zaâbi et al. 2010: 11 (name only, north-east coast of Tunisia), Jirkov & Leontovich 2013: 220 (name in key, Arctic Ocean); Çinar et al. 2014: 751 (name in checklist, Turkey).

Material examined. Holotype, with tube, SMNH T361View Materials,Bohuslän,Gullmarsfjord, Sweden, 58º16.002´N 11º28.002´E, depth not stated, but apparently subtidal, coll. L. S. Lovén; AM W.50333 (donated by Gothenburg Natural History Museum ( GNM) Polychaeta 749)GoogleMaps  , 2 specimens, Gullmarsfjord, Sweden, coll. July 1878; AM W.50334 (donated by GNM Polychaeta 14334), 1 specimen plus tube, Kattegatt , 56º52.65´N 12º13.422´E, 20 m, coll. Sep 2005.GoogleMaps 

Description. Based on holotype and two specimens from Gullmarsfjord. Preserved specimens pale in colour. Body cylindrical, curved dorsally ( Fig. 3B, CView FIGURE 3). Body length 14.5–16.7 mm (15.2 mm), including paleae and scaphe, width at cephalic regions 2.8–3.2 mm (3.2 mm).

Cephalic veil leaf-shaped, free from operculum, with smooth lateral margins, distal margins smooth, except for a free and crenulated median extension with 3–4 (4) slightly distorted lappets (raised mounds) with crenulated margins ( Figs 2View FIGURE 2 A–B; 4A, C–D; 5A–C). Pair of ventro-lateral ear-shaped lobes adjacent to dorsal side of cephalic veil ( Figs 2AView FIGURE 2; 4View FIGURE 4 D–E; 5A). Buccal tentacles with deep longitudinal grooves, arising from around buccal cavity, posterior to cephalic veil ( Figs 2AView FIGURE 2; 4AView FIGURE 4, C–D; 5A). Distinct broad ventral lobe (lower lip) between buccal cavity and segment 1 ( Figs 2AView FIGURE 2; 4AView FIGURE 4, C–D; 5A).

Operculum semicircular; dorsal and lateral margins short and smooth; ventral margin (opercular ridge) with 10–11 (11) pairs of amber-coloured, stout notopodial paleae, curved dorsally, and ending in blunt tips ( Figs 2BView FIGURE 2; 3DView FIGURE 3; 5BView FIGURE 5).

First pair of tentacular cirri not extending beyond tips of paleae, slightly annulated with rounded cirri arising from inflated base between opercular margin and paleal ridge ( Figs 2View FIGURE 2 A–B; 3D; 4A, C; 5B). Pair of sharp-tipped triangular ventral lappets present behind tentacular cirri, on segment 1, not covered by ventral lobes of segment 2 ( Figs 2View FIGURE 2 A–B; 4A, C; 5A–B). Ventral region visible on segment 1 ( Figs 2AView FIGURE 2; 4AView FIGURE 4; 5AView FIGURE 5).

Second pair of tentacular cirri almost same length as first, but thinner and slightly annulated, its base more bulbous than that of 1 st pair  of tentacular cirri, and slightly placed dorsally, on mid-lateral connecting ridge of segment 2 ( Figs 2View FIGURE 2 A–B; 4C; 5A–B). Segment 2 with pair of broad and elongated ventro-lateral lobes separated from each other by a broad and deep mid-ventral groove; each lobe with 3–5 (left 5, right 4) continuous rows of triangular lappets ( Figs 2View FIGURE 2 A–B; 4A, C; 5A–B).

Segments 3–4 with two pairs of almost equal sized comb-like branchiae, consisting of large basal hump and series of loose flat lamellae ( Figs 2BView FIGURE 2; 4BView FIGURE 4; 5BView FIGURE 5). First pair of branchiae on segment 3 inserted more ventrally than 2 nd pair on segment 4. Pair of dorso-lateral pads small and smooth, arising from dorsal side of notopodia on segment 5 ( Figs 2BView FIGURE 2; 3DView FIGURE 3; 5BView FIGURE 5).

Distinct ventral glandular lobes (pads) present on segments 2–7, becoming progressively more lateral and broader on segments 3–5 ( Figs 2AView FIGURE 2; 3CView FIGURE 3; 5View FIGURE 5 A–B). Humps near branchiae absent ( Figs 2BView FIGURE 2; 4CView FIGURE 4; 5BView FIGURE 5). Segment 3 with a pair of smooth broad ventro-lateral lobes and a pair of mid-ventral lappets, separated by deep notches; ventro-lateral lobes without projection on ventral margin; mid-ventral lappets rounded, narrow about 1/4 width of ventro-lateral lobes, and more anterior than ventro-lateral lobes ( Figs 2AView FIGURE 2; 3CView FIGURE 3; 4AView FIGURE 4; 5AView FIGURE 5). Segments 4–6 with a pair of broad ventrolateral lobes separated from each other by a shallow median groove becoming progressively broader on segments 4–6. Segment 7 with a pair of broad ventro-lateral lobes separated from each other by a median swelling about 1/4 width of ventro-lateral lobes.

Notopodia of segment 1 with paleae, from segment 5 to 21 (17 pairs) notopodia with two rows of different chaetae. Anterior row bearing shorter chaetae with distal serrated wings, covered with numerous minute spines from below wing to about mid-basal portion of chaeta; posterior row with about 1.3 times longer capillary chaetae, straight and stout, tapering to acute tip, anterior surface covered with numerous spines from mid-length to tip ( Figs 2View FIGURE 2 D–E; 3B–C; 5D–G). Neuropodia on segments 8–21 (14 pairs in total) with slightly raised torus bearing a transverse row of uncini; uncinus with a rounded anterior peg with a blunt tip embedded into torus, followed by several rows of minor teeth on a swelling and one longitudinal row of two major teeth, each covered with many small teeth basally ( Figs 2FView FIGURE 2; 5View FIGURE 5 H–I). Neuropodia of segment 21 with enlarged posterior lobe ( Fig. 4View FIGURE 4 H–I).

Scaphe long, ovoid, flattened dorsally, slightly separated from posterior segments. Lateral margins dorsally rolled, with six pairs of lobes; first pair largest and elongated, connected to dorsal margin of scaphe; posterior lobes narrow, triangular, almost same size; dorsal margin of scaphe smooth with two shallow notches on holotype ( Figs 2CView FIGURE 2; 3View FIGURE 3 B–C; 4G–I). Anal flap vestigial with oblong swollen area distally bearing long anal cirrus ( Figs 2CView FIGURE 2; 4GView FIGURE 4). Anus located behind anal cirrus, between last pair of lateral lobes on scaphe. Scaphal hooks amber-coloured, 7–8 (8) pairs arising from both sides of dorsal margin of scaphe, with blunt tips slightly curved dorsally ( Figs 2GView FIGURE 2; 4View FIGURE 4 F–G).

Tube slightly curved, robust, made of small gastropod shells ( Fig. 3AView FIGURE 3).

Distribution. Type locality Gullmarsfjord, Sweden ( Fig. 1View FIGURE 1), Arctic Ocean: along Norwegian coast from Lofoten Islands to Swedish West Coast to northern part of Oresund, North Eastern Atlantic Ocean ( Faroe Islands, Irish Sea, Azores, the UK coasts) and Mediterranean Sea (coasts of France, Italy, Turkey, Greece, Tunisia, Spain). According to Jirkov & Leontovich (2013), this is a low boreal species, although only a few available records from northern areas suggest that this species is restricted to more southern regions.

Habitat. According to Holthe (1986), the species is found in Norwegian waters in sandy or mixed sediments, 15–200 m deep, while the record from 800 m in the Azores seems questionable.

Remarks. Considerable discrepancies in some morphological characters exist between our description of the holotype and the description of Malmgren (1866). For example, he reports smooth anterior tip of cephalic veil, while it actually bears 3–4 lappets. We also expanded the description with additional characters not mentioned in the original description, such as presence of broad ventral lobe (lower lip) between buccal cavity and segment 1, pair of pointed ventral lappets on segment 1, ventral region visible on segment 1, large basal hump on branchiae, a pair of dorso-lateral pads on segment 5, and uncini with a longitudinal row of two major teeth. Petta pusilla  is distinguished from other species of this genus by having 3–4 lappets on anterior margin of cephalic veil, broad ventral lobe (lower lip) between buccal cavity and segment 1 and a pair of rounded mid-ventral lappets on segment 3 ( Table 2). Petta pusilla  is similar to P. pellucida  , P. tenuis  and P. williamsonae  n. sp. as all have smooth ventro-lateral lobes on segment 3 and a long anal cirrus. Petta pusilla  differs from P. assimilis  and P. investigatoris  n. sp. because the last two species have a continuous row of lappets on ventro-lateral lobes of segment 3. Petta pusilla  also differs from P. pellucida  which has neurochaetae on segments 7–21, whereas P. pusilla  has neurochaetae on segments 8–21.

Nilsson (1928) illustrated specimens of P. pusilla  with three minute lappets on the anterior margin of cephalic veil and also a pair of dorso-lateral pads on segment 5, however the locality where his illustrated specimens came from is unclear, he reports a distribution in the Arctic Ocean, Atlantic Ocean and Mediterranean Sea. Nilsson (1928) believed that P. pusilla  and P. pellucida  from the Caribbean were synonymous, and the material from Mediterranean Sea, which has 12 pairs of paleae, and more spinose capillary chaetae, could be another species, but his material needs to be examined to confirm this. All records of this species from outside the type locality should be carefully checked against the expanded here re-description of the type as they may represent additional undescribed species.


Department of Paleozoology, Swedish Museum of Natural History


Australian Museum


Gothenburg Museum of Natural History (Goteborgs Naturhistoriska Museum)














Petta pusilla Malmgren, 1866

Zhang, Jinghuai, Hutchings, Pat & Kupriyanova, Elena 2019

Pectinaria pusilla —

Dauvin, J. - C. & Dewarumez, J. - M. & Gentil, F. 2003: 85
Wollebaek, A. 1912: 35
Crawshay, L. R. 1912: 346
Levinsen, G. M. R. 1883: 155

Petta pusilla

Malmgren, A. J. 1866: 361