Petta pellucida
Creators: name: Zhang, Jinghuai
name: Hutchings, Pat
name: Kupriyanova, Elena
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Terebellida
Pectinariidae
Petta
Petta pellucida

description: Petta pellucida (Ehlers, 1887)
Fig. 6, Table 2
Pectinaria (Petta) pellucida Ehlers, 1887: 194–199, Taf. 44, Fig. 1–9.
Material examined. Syntypes, MCZ ANNc-2559, 1 specimen in tube and 1 empty tube, Santarem Channel between Cay Sal Bank and Bahamas, Caribbean Sea, 270 m, coll. S. Bibb & L. F. Pourtales in 1868–1869.
Description. Two complete tubes, one with specimen, broken, dried and twisted, yellow (Fig. 6 A–C).
Based on damaged type. Operculum with 11 pairs of amber-coloured, long stout paleae curved dorsally, ending in blunt tips (Fig. 6A).
Notopodia of segment 1 with paleae, other notopodia with two rows of different chaetae; anterior row with shorter chaetae with distal serrated wings, anterior surface below wing to about mid-basal portion of chaeta covered with numerous minute spines; posterior row with longer capillary chaetae, straight and stout, tapering to acute tips, anterior surface covered with numerous spines from mid-length to tip (Fig. 6 F–H). Neuropodia each with a transverse row of uncini on torus; each uncinus with one rounded anterior peg with blunt tip embedded into torus, followed by several rows of minor teeth on a swelling, one longitudinal row of two major teeth, both covered by many small teeth basally (Fig. 6 I–G). Last segment with notochaetae and neurochaetae (Fig. 6D).
Scaphe contorted, 7 pairs of amber-coloured scaphal hooks arising from both sides of dorsal margin of scaphe, with blunt tips weakly curved dorsally (Fig. 6 D–E).
Tubes slightly curved, almost straight, robust, made of large sand grains (Fig. 6B).
Distribution. Santarem Channel between Cay Sal Bank and Bahamas, Caribbean (Fig. 1). Known only from the type locality.
Habitat. 270 m, no information on sediments available.
Remarks. The syntypes of P. pellucida are in poor condition and the label indicates that the material has dried out at some stage. This means that characters such as shape of cephalic veil and scaphe, number of segments with neurochaetae, presence of dorso-lateral pads in segment 5, and the shape of anal flap could not be examined. According to the description of Ehlers (1887), P. pellucida differs from P. pusilla in having a smooth anterior acute tip of the cephalic veil, a pair of ventral lobes on segment 1, and a narrow deep notch between ventral lobes of segment 2.
We disagree with Nilsson (1928) ’s suggestion that P. pusilla and P. pellucida are synonymous as they were collected from very different biogeographical areas and we list characters distinguishing these species in Table 2. Petta pellucida is easily distinguished from P. assimilis that has continuous row of lappets on the ventro-lateral lobes of segment 3, whereas P. pellucida has smooth ventro-lateral lobes on segment 3. Petta pellucida has neurochaetae from segments 7 onwards according to Ehlers (1887), whereas in other all pectinariid species neurochaetae occur from segment 8. However, this cannot be confirmed on the type and perhaps Ehlers misinterpreted the segment numbering.
Petta tenuis Caullery, 1944
Figs 7–8, Table 2
Petta tenuis Caullery, 1944: 75, Fig. 61.
Material examined. Syntypes 2 specimens and 1 empty tube: NBC ZMA V.Pol. 1516, Sulu, Philippines 6º07.998´N 121º19.002´E, 275 m depth.
Description. Based on both syntypes, although one has been dried and become twisted (Fig. 7 B–C). Preserved specimens pale in colour. Body cylindrical, curved dorsally (Fig. 7 B–D). Body length 16.6 and 18.9 mm including paleae and scaphe, width 2.2 and 2.3 mm at cephalic regions.
Cephalic veil heart-shaped with pointed median extension, free from operculum, with smooth margins (Fig. 7 E–F). Pair of ventro-lateral ear-shaped lobes (palps) adjacent to dorsal base of cephalic veil. Buccal tentacles short, with longitudinal grooves, arising from around buccal cavity, posterior to cephalic veil (Fig. 7F). Ventral lower lip not visible between buccal cavity and segment 1 (Fig. 7F).
Operculum semicircular; dorsal and lateral margins short and smooth; ventral margin (opercular ridge) with 11 pairs of amber-coloured, stout paleae, curved dorsally, and with long pointed tips (Fig. 7C).
First pair of tentacular cirri annulated, arising from connection of opercular margin and paleal ridge, not extending beyond tips of paleae, cirri elongated with rounded tips arising from triangular base (Fig. 7E, G). Pair of long narrow ventral lappets present on segment 1, arising under ventral lobes of segment 2 (Fig. 7 E–F). Ventral region of segment 1 covered by ventral lobes of segment 2 (Fig. 7 E–F).
Second pair of tentacular cirri almost same length as first, weakly annulated, and slightly displaced dorsally, inserted on latero-median connecting ridge of segment 2 (Fig. 7E, G) more elongated than 1 st pair arising from triangular base. Segment 2 with pair of broad ventro-lateral lobes separated from each other by narrow deep mid-ventral groove, left ventro-lateral lobe with 5 triangular lappets and right ventro-lateral lobe with 4 triangular lappets on one type (Fig. 7E, G), but not possible to count on the other type.
Two pairs of similar sized comb-like branchiae on segments 3–4, consisting of large basal hump and series of loose flat lamellae (Fig. 7H). First pair of branchiae on segment 3 inserted more ventrally than 2 nd pair.
Pair of dorso-lateral pads small and smooth, arising from dorsal side of notopodia on segment 5 (Fig. 7 G–H).
Distinct ventral glandular lobes (pads) present on segments 2–7, becoming progressively more lateral and broader on segments 3–5 (Fig. 7 D–E). Hump near branchiae absent on ventral lobes of segment 4 (Fig. 7G). Segment 3 with a pair of smooth broad ventro-lateral lobes and a pair of mid-ventral lappets, separated from those by deep notches; ventro-lateral lobes with a triangular projection on ventral margin; mid-ventral lappets narrow about 1/6 length of ventro-lateral lobes, and more posterior than ventro-lateral lobes (Fig. 7E). Segments 4–6 with a pair of long ventro-lateral lobes separated 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 median swelling about 1/4 width of ventro-lateral lobes.
Notopodia of segment 1 with paleae, segments 5–21 (17 pairs) with two rows of different chaetae; anterior row of shorter chaetae with distal serrated wings, anterior surface below wing to about mid-basal portion of chaeta covered with numerous minute spines; posterior row with longer capillary chaetae, straight and stout, tapering to acute tip, anterior surface covered with numerous spines from mid-length to tip (Fig. 8 C–F). Neuropodia 14 pairs on segments 8–21, each with slightly raised torus bearing a transverse row of uncini. Each uncinus with one rounded anterior peg with blunt tip embedded into torus, followed by several rows of minor teeth on a swelling, a longitudinal row of two major teeth, both covered with many small teeth basally (Fig. 8 G–H). Neuropodia on segment 21 with enlarged posterior lobe (Fig. 8B).
Scaphe ovoid, flattened dorsally, not separated by a constriction from abdomen. Lateral margins dorsally rolled with six pairs of lobes; first pair of lobes largest and elongated, connecting with dorsal margin of scaphe; posterior lobes narrow triangular, almost same size; dorsal margin of scaphe smooth (Fig. 8 A–B). Anal flap vestigial with oblong swollen area distally bearing long anal cirrus (Fig. 8 A–B). Anus located behind anal cirrus, between last pair of lateral lobes on scaphe. Eight pairs of scaphal hooks, arising from both sides of dorsal margin of scaphe, ambercoloured, slightly curved dorsally, ending with blunt tips (Fig. 8I).
Tube slightly curved, robust, made of sand grains and shells (Fig. 7A).
Distribution. Sulu Sea, Philippines (Fig. 1). Known only from the type locality.
Habitat. 275 m, no information on sediments available.
Remarks. No holotype was designated by Caullery (1944) and the original description is based on two specimens (syntypes). The two syntype specimens of P. tenuis are twisted, and only one type could be examined for the morphological characters of the anterior and posterior ends. We have expanded the description to give details of a pair of lateral ear-shaped lobes (palps) adjacent to dorsal base of cephalic veil, pair of ventral lappets on segment 1, pair of dorso-lateral pads in segment 5, basal hump of branchia and details of uncini. Petta tenuis can be distinguished from other species of Petta by ventro-lateral lobes on segment 2 with 4–5 triangular lappets and ventrolateral lobes on segment 3 with a triangular projection on ventral margin (Table 2).
description: Published as part of 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, pp. 303-330 in Zootaxa 4614 (2) on pages 312-315, DOI: 10.11646/zootaxa.4614.2.3, http://zenodo.org/record/3242403