Phyllodoce concava, Oliveira & Magalhães & Lana, 2021

Oliveira, Verônica Maria De, Magalhães, Wagner F. & Lana, Paulo Da Cunha, 2021, Ten new species of Phyllodoce Lamarck, 1818 (Phyllodocidae, Annelida) from Brazil, Zootaxa 4924 (1), pp. 1-61 : 21-24

Phyllodoce concava sp. nov.

urn:lsid:zoobank.org:act:C181979A-B8EC-4E19-828B-90C3C4DC0AA4

Figures 15–17

Holotype. Margin of continental shelf in Campos Basin, Rio de Janeiro, Brazil, Hab6 C07 R3 , 22º59’52.2”S 40º47’45.3”W, 686.1 m, 24 Jun 2008 ( ZUEC– POL 16322).

Paratypes. A total of 4 paratypes length 5.5 ± 3.1 mm for 41.8 ± 12.9 segments. Continental slope of Campos Basin: Hab 10 D12 R2 , 23º18’34.5”S 49º35’55.6”W, 3016.4 m, 11 Jan 2009 (1 paratype, ZUEC–POL 16475 ) ; Hab3 C10 R1 , 23º8’22.0”S 40º36’43.1”W, 1891.2 m, 9 May 2008 (1 paratype, ZUEC–POL 16584 ) ; AMBES11 E08 R3 , 20º15’55.63”S 38º40’45.57”W, 1892 m, 15 Jun 2013 (1 paratype, ZUEC–POL 18584 ) ; AMBES11 C5 R3 , 20º14’17.9”S 39º48’34.3”W, 395 m, 19 Jun 2013 (1 paratype, ZUEC–POL 18582 ) , Brazil.

Diagnosis. Conspicuous concavity in posterior margin of prostomium with one central nuchal papilla with lateral bars. U-shaped lateral bars clearly connected with a nuchal papilla and reaching half the margin in anterior prostomium. Parapodial dorsal cirri oval to rectangular in shape.

Description. Holotype incomplete, lacking pygidial cirri, 3.0 mm elongate, 0.5 mm wide median part of body including parapodia and excluding chaetae for 29 segments. Body long, dorso-ventrally flattened and tapered posteriorly. Prostomium cordiform, longer than wide, with protuberance anteriorly ( Fig. 15 A–B). Posterior prostomial margin with constriction, one central nuchal papilla and a nuchal bar on each side. U–shaped bars, extending from base of nuchal papilla to anterior median margin of prostomium ( Fig. 15 A–B). Paired frontal antennae and palps cylindrical, slender and of similar lengths.Antennae and palps with half the length of prostomium. Eyes absent. Proboscis dissected and divided into two parts: proximal, with oblique rows of sclerotized cusps-shape papillae ( Fig. 15 C–D); distal with longitudinal rows of tubercles. Terminal ring not observed. Segment 1 not visible dorsally. Four pairs of cylindrical and biarticulated tentacular cirri, with short cirrophores and long cirrostyles, situated on first three segments. Tentacular cirri of segment 1, reaching segment 5. Dorsal and ventral tentacular cirri of segment 2 reaching segments 9 and 4, respectively. Dorsal tentacular cirri of segment 3, reaching segment 5. Neuropodia with chaetae from segment 2 ( Fig. 16A ). Dorsal cirri with well-developed cirrophores without dorsal extensions and from segment 4. Dorsal cirri symmetrical, oval to quadrangular and with rounded edges anteriorly, cirri from median segments with tapered edges, and elongated posteriorly. Parapodial lobes shorter than dorsal and ventral cirri, with median light-brown aciculae and bundles of chaetae. Prechaetal lobes bilobate, symmetrical and rounded. Prostchaetal lobes rounded. Ventral cirri horizontally oriented in relation to lobes, dorso-ventrally flattened, present from segment 3. Ventral cirri asymmetrical, cordiform to conical anteriorly and on median and posterior segments slender and elongated ( Figs 16 B–D; 17A–C). Compound spinigerous chaetae uniform from segment 2. Rostrum of chaetal shaft with three main teeth, surrounded of denticles; articles with serrated outer edges ( Fig. 17D ) and simple capillary chaetae at median bundle of chaetae ( Fig. 16B ). Pygidial cirri not observed.

Colour. Preserved specimens with dark brown pigmentation in the prostomium and parapodial cirri ( Fig. 15 ). A median dorsal black stripe is present in the first five segments ( Fig. 15A, B ).

Habitat. Collected in well-sorted fine silt sediments at 1,865 m.

Geographical Distribution. Atlantic Ocean, Brazil: Margin continental of continental slope in Campos Basin.

Etymology. The name species is derived from the Latin concavus (arched, curved), referring to the shape of the posterior part of the prostomium.

Remarks. Phyllodoce concava sp. nov. has the U–shaped structure in the posterior part of the prostomium unique among the known species of the genus. Phyllodoce concava sp. nov. shares the presence of capillary chaetae with P. micrognatha sp. nov., which is a commonly observed characteristic in Protomystides and Pseudomystides (Pleijel, 1993) . Phyllodoce concava sp. nov. and P. micrognatha sp. nov. are readily distinguishable by the characteristics of the proboscis. The cuspidate chitinous proboscidial papillae in P. concava sp. nov. are different from the chitinous hard structures observed in P. micrognatha sp. nov. In addition, the two species differ in the shape of the prostomium because P. concava sp. nov. has a protuberance at the anterior margin where antennae and palps are located and this is not observed in P. micrognatha sp. nov. Another characteristic that sets it apart is the morphology of the parapodial cirri, which in P. concava sp. nov. are oval to quadrangular, whereas in P. micrognatha sp. nov. they are oval to sub-rectangular.

Phyllodoce concava sp. nov. differs from P. colorata sp. nov. and P. rosea by the absence of eyes. Phyllodoce concava sp. nov., P. colorata sp. nov., P. rosea , P. lamella sp. nov., and Phyllodoce sp. B differ in the morphology of the prostomium (cordiform in P. concava sp. nov. and P. lamella sp. nov., oval with an anterior depression in P. colorata sp. nov., and rounded to oval in P. rosea and Phyllodoce sp. B.). P. ovalis sp. nov. also lacks eyes and has long and slender tentacular cirri, unlike the other species of Phyllodoce described here. It differs from P. concava sp. nov. because it presents antennae and palps with inflated bases, short tentacular cirri, and rounded dorsal cirri. Phyllodoce concava sp. nov. differs from P. medipapillata , P. williamsi , and P. hiatti because these present dorsal-foliaceous cirri ( Pettibone 1963; Blake 2001). In addition, it differs from P. lamella sp. nov. because the latter presents ventral cylindrical tentacular cirri with lateral lamella.

Figures

FIGURE 15. Phyllodoce concava sp. nov. A, prostomium and tentacular cirri, dorsal view; B, nuchal lateral bars and U-shaped bars (black arrows); C, dissected proboscis; D, cuspidate papillae, ventral view. A–D, holotype. Abbreviations: US, U-shaped; Lb, lateral bar. Scale bars: A, 0.05 mm; B, 0.04 mm; C–D, 0.05 mm.

FIGURE 16. Phyllodoce concava sp. nov. A, chaeta from segment 2 shown in black arrow. Anterior view of parapodia. B, parapodium 5. C, parapodium14; D, parapodium 27; A–D, holotype. Scale bars: A, 0.03 mm; B–D, 0.02 mm.

FIGURE 17. Phyllodoce concava sp. nov. Anterior view of parapodia.A, parapodium 5. B, parapodium 14; C, parapodium 27; D, Compound spinigerous chaetae from holotype. Scale bars: A–C, 0.02 mm; D, 0.004 mm.