Petta investigatoris, Zhang & Hutchings & Kupriyanova, 2019

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 : 316-320

Petta investigatoris n. sp.

Figs 9–11 , Table 2

Material examined: Holotype AM W.50672, Jervis Commonwealth Marine Reserve ( CMR), Australia, 35º19.98´S 151º15.48´E, 2650– 2636 m, R/V “ Investigator ”, Voyage 3 St. 56, Beam trawl, May 2017.

Paratypes: AM W.50671, 1 specimen, Jervis CMR, Australia, 35º19.98´S 151º15.48´E, 2650– 2636 m, R/V “ Investigator ”, Voyage 3 St. 056, Beam Trawl, May 2017; AM W.50668, 1 specimen, Freycinet CMR, Australia, 36º21.042´S 150º54.858´E, 2793 m, R/V “ Investigator ”, Voyage 3 St. 11, biological box corer, May 2017; AM W.50670, 1 specimen, East Gippsland CMR, Australia, 37º47.52´S 150º22.92´E, 2338–2581 m, R/V “ Investigator ” Voyage 3 St. 035, Beam Trawl, May 2017; AM W.50669, 1 specimen, Bass Strait, Australia, 39º27.72´S 149º16.56´E, 2760– 2692 m, R/V “ Investigator ” Voyage 3 St. 22, Beam Trawl, May 2017; AM W.50666, 1 specimen, Freycinet CMR, Australia, 41º43.83´S 149º7.182´E, 2820– 2751 m, coll. R/V “ Investigator ” Voyage 3 St. 4, Beam Trawl, May 2017.

Description. Preserved specimens pale reddish in colour, cylindrical in shape ( Figs 9A ; 10 B–C). Body length of holotype 20.1 mm including paleae and scaphe, width 2.7 mm at cephalic regions.

Cephalic veil heart-shaped, free from operculum, with narrow triangular anterior end and smooth margin ( Figs 9C ; 10D ). Pairs of lateral ear-shape lobes (palps) adjacent to dorsal base of cephalic veil ( Fig. 9F ). Buccal tentacles with broad longitudinal deep grooves, arising from around buccal cavity, posterior to cephalic veil ( Figs 9C ; 10D ). Lower lip not visible between buccal cavity and segment 1.

Operculum semicircular; dorsal and lateral margins well developed, smooth; ventral margin (opercular ridge) with 13 pairs (holotype) of amber-coloured, stout long notopodial paleae, curved dorsally, with blunt tips ( Figs 9B ; 10E ).

First pair of tentacular cirri not extending beyond tips of paleae, not distinctly annulated, arising from connection of opercular margin and paleal ridge ( Figs 9C ; 10D ). Pair of narrow triangular ventral lappets present behind tentacular cirri, on both sides of segment 1, partly covered by ventral lobes of segment 2 ( Figs 9C ; 10D ). Ventral region of segment 1 covered by ventral lobes of segment 2 ( Figs 9C ; 10D ).

First and 2 nd pairs of tentacular cirri almost same length, annuli not distinct, 2 nd pair inserted more dorsally than 1 st pair , on almost mid-laterally connecting ridge of segment 2 ( Figs 9 A–B; 10D–E). Segment 2 with pair of broad ventro-lateral lobes, each with 7–8 triangular lappets, separated from each other by a narrow and deep mid-ventral groove ( Figs 9C ; 10D ).

Two pairs of similar sized comb-like branchiae on segments 3–4, each consisting of large basal hump and series of loose, flat lamellae ( Figs 9G ; 10F ). First pair of branchiae on segment 3 inserted more ventrally than those on segment 4.

Pair of dorso-lateral pads small and smooth, arising from dorsal side of notopodia on segment 5 ( Figs 9B ; 10E ).

Distinct ventral glandular lobes (pads) present on segments 2–7, becoming progressively more dorsal and broader on segments 3–5 ( Figs 9A, C ; 10 D–E). Segment 3 with a pair of broad ventro-lateral lobes and a pair of short mid-ventral lappets, separated from those lobes by deep notches; ventro-lateral lobes with continuous row of papillae; mid-ventral lappets square rounded and narrow about 1/6 width of ventro-lateral lobes, and more posterior than ventro-lateral lobes ( Figs 9C ; 10D ). Segments 4–6 with a pair of broad ventro-lateral lobes separated from each other by a shallow median groove becoming progressively broader on segments 4–6. Segment 7 with a pair of ventro-lateral lobes separated from each other by a median swelling about 1/3 width of ventro-lateral lobes.

Notopodia of segment 1 with paleae, segments 5–21 (17 pairs) with two rows of chaetae; anterior row of shorter chaetae with distal serrated wings, anterior surface from below wing to about mid-basal portion of chaeta covered with numerous minute spines; posterior row with about 1.5 times longer capillary chaetae, straight and stout, tapering to acute tips, anterior surface covered with numerous spines from mid-length to tip ( Figs 9 I–J; 11A–C). Neuropodia on segments 8–21 (14 pairs), 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, one longitudinal row of two major teeth, both covered by many small teeth basally ( Figs 9H ; 11 D–E). Neuropodia on segment 21 with elongated posterior lobe ( Figs 9A, E ; 10I ).

Scaphe long ovoid, flattened dorsally, not distinctly separated by a constriction from posterior segments. Lateral margins dorsally rolled, with six pairs of lobes; first pair of lobes largest, connected to dorsal margin of scaphe; posterior lobes triangular, almost same size; dorsal margin of scaphe smooth with shallow median notch ( Figs 9 D–E; 10F–H). Anal flap vestigial with oblong swollen area distally bearing long anal cirrus ( Figs 9E ; 10F ). Anus located behind anal cirrus, between last pair of lateral lobes of scaphe. Nine pairs of scaphal hooks in the holotype, straight, amber-coloured, with blunt tips, on both sides of dorsal margin of scaphe ( Figs 9E ; 10I ).

Tube slightly curved, made of coagulations and shells ( Fig. 10A ).

Variability. The paratypes vary in length from 14.5 to 21.8 mm, including paleae and scaphe, width 2.3–3.1 mm at cephalic regions. Paleae 12–13 pairs. Scaphal hooks 9–12 pairs. Paratypes (AM W.50668 and AM W.50669) only with 3–4 papillae on ventro-lateral of segment 3. Some specimens with deep median notch on dorsal margin of scaphe.

Distribution. Jervis CMR to Freycinet CMR along south-eastern coasts of Australia ( Fig. 1 ).

Habitat. 2338–2820 m. No substrate data available.

Etymology. The species is named “ investigatoris ” after the Australian Marine National Facility R/V “ Investigator ” because these specimens were collected during the 2017 “Sampling the Abyss” cruise on board this ship.

Remarks. Petta investigatoris n. sp. can be distinguished from other species of Petta by the following characters: ventral lappets on segment 1 partly covered by ventral lobes of segment 2; short ventro-lateral lobes on segment 2 separated from each other by a narrow mid-ventral groove, and with 7–8 triangular lappets per lobe; ventrolateral lobes with continuous rows of papillae on segment 3; straight scaphal hooks ( Table 2 ). Petta investigatoris n. sp. is similar to P. assimilis as they both share continuous row of papillae on ventro-lateral lobes of segment 3. However, P. assimilis has a scale-like anal flap without anal cirrus and 4–5 lappets (fimbriae) on ventro-lateral lobes of segment 2, while P. investigatoris n. sp. has a vestigial anal flap with long anal cirrus and 7–8 lappets on the ventro-lateral lobes of segment 2.

Figures

FIGURE 1. Type localities of all Petta species.

FIGURE 9. Line drawings of Petta investigatoris n. sp. Holotype (AM W.50672): A. Lateral view of entire body; B. Dorsolateral view of anterior end; C. Ventral view of anterior end; D. Ventral view of posterior end; E. Dorso-lateral view of posterior end, showing lobes on lateral margin of scaphe; F. Lateral ear-shaped lobe adjacent to the dorsal base of cephalic veil, ventral view; G. Close-up view of branchia; H. Uncinus; I. Notochaeta from anterior row; J. Notochaeta from posterior row. Abbreviations: ac, anal cirrus; an, anus; ap, anterior peg; br, branchiae; bt, buccal tentacles; cv, cephalic veil; dlp, dorso-lateral pad; dms, dorsal margin of scaphe; hb, hump of branchia; lb, lamellae of branchia; lel, lateral ear-shaped lobe; mat, major teeth; mit, minor teeth; nec, neurochaetae; noc, notochaetae; op, operculum; or, opercular rim; p, paleae; s, segment; sc, scaphe; tc, tentacular cirri; sh, scaphal hooks; vl, ventral lappet.

FIGURE 10. Petta investigatoris n. sp. Methyl green stained body and tube of the holotype (AM W.50672):A. Tube; B. Ventral view of entire body; C. Dorso-lateral view of entire body; D. Ventral view of anterior end; E. Dorso-lateral view of anterior end; F. Close-up view of left branchiae, in lateral view; G. Dorsal view of posterior end; H. Ventral view of posterior end; I. Lateral view of posterior end, showing lobes on lateral margin of scaphe; J. Scaphal hooks. Abbreviations: ac, anal cirrus; an, anus; br, branchiae; bt, buccal tentacles; cv, cephalic veil; dms, dorsal margin of scaphe; hb, hump of branchia; lb, lamellae of branchia; dlp, dorso-lateral pad; nec, neurochaetae; noc, notochaetae; nop, notopodium; op, operculum; or, opercular rim; p, paleae; s, segment; sc, scaphe; tc, tentacular cirri; sh, scaphal hooks; vl, ventral lappet.

FIGURE 11. Chaetae of Petta investigatoris n. sp. Holotype (AM W.50672) A–C. Close-up view of notochaetae, segment 12; B. Tip of notochaeta from posterior row; C. Tips of notochaetae from anterior row; D–E. Uncini, segment 12.