Phyllodoce micrognatha, 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 : 34-36

Phyllodoce micrognatha sp. nov.

urn:lsid:zoobank.org:act:6849E76F-3D11-4BB8-8FE9-9EC85D002C46

Figures 25–26

Holotype. Campos Basin , Rio de Janeiro, Brazil, continental slope, Hab 7 F07 R2 , 22º20’50.7”S 40º2’58.1”W, 705.3 m, 7 Jul 2008 ( ZUEC–POL 16326 ).

Paratypes. A total 6 of paratypes, length 15.4± 21.2 mm for 67.1± 38.8 segments. Continental slope in Campos Basin : Hab 8 A06 R1 , 23º37’57.4”S 41º19’41.9”W, 390.7 m, 1 Feb 2009 (1 paratype, NHMD–2378); Hab 9 I07 R1 , 21º11’12.1”S 40º12’51.8”W, 682 m, 4 Feb 2009 (3 paratypes, ZUEC–POL 16343 ); Hab 7 A06 R3 , 23º37’57.3”S 41º19’42.9”W, 388.9 m, 3 Jul 2008 (1 paratype, ZUEC–POL 16426 ); Hab 17 I05 R3 , 21º23’2.9”S, 40º15’9.5”W, 140 m, 21 Jul 2009 (1 paratype, NHMD–865951), Brazil .

Diagnosis. Proximal part of proboscis with chitinous structures irregularly distributed in median-dorsal area. Proboscis with large area of small multi-pronged structures with posteriorly directed teeth on ventral half and single dorsal row of overlapping plates in dorsal groove; teeth with 3–4 prongs and single anchoring rod; plates, curved, smooth, and with delicate striations across the surface. Biramous parapodium with dorsal cirri having well-developed cirrophores.

Description. Holotype incomplete with 6 mm long for 51 segments. Body long, dorso-ventrally flattened and tapered posteriorly. Prostomium anteriorly rounded, posteriorly truncate, longer than wide, with nuchal papilla visible dorsally ( Fig. 25A ). Paired frontal antennae and palps cylindrical and slender, subequal in length. Antennae and palps 1/3 of prostomium length ( Fig. 25 A–B). A pair of oval black eyes present, clearly with lenses and situated medially on prostomium. Proboscis basally with chitinous structures irregularly distributed in median-dorsal area; large area of small multi-pronged structures with posteriorly directed teeth on ventral half, and two dorsal row of overlapping plates in dorsal groove; teeth with 3–4 prongs and single anchoring rod; plates curved, smooth, with cusp-like papillae at base of last plate ( Fig. 25 C–E). Distal part of proboscis with six rows of tubercles. Terminal ring not observed ( Fig. 25B ). Segment 1 not visible dorsally. Four pairs of cylindrical tentacular cirri, biarticulated, with short cirrophores and long cirrostyles, located on first three segments. Tentacular cirri of segment 1 reaching segment 4. Dorsal and ventral tentacular cirri of segment 2 reaching segments 7 and 6, respectively. Dorsal tentacular cirri of segment 3 extending to segment 9. Neuropodia and ventral cirri from segment 3. Biramous parapodium with noto- and neuro-acicular from segment 4. Dorsal cirri with well-developed cirrophores and dorsal extensions from segment 4. Dorsal cirri of anterior and median segments symmetrical and subrectangular with rounded edges, dorsal cirri rounded posteriorly ( Fig. 26 A–E). Parapodial lobes shorter than dorsal and ventral cirri with light brown aciculae and bundles of chaetae ( Fig. 26 A–B). Prechaetal lobes bilobate, symmetrical on anterior and median segments and asymmetrical posteriorly with supra-aciculars longer than sub-aciculars. Postchaetal lobes rounded. Ventral cirri horizontally oriented in relation to lobes, from segment 3, asymmetrical, elongated and dorso-ventrally flattened. Chaetae compound spinigerous from segment 2. Rostrum of chaetal shaft with pronounced anterior depression and with numerous conical teeth posteriorly; articles with serrated outer edges and simple capillary chaetae in the posterior segments ( Fig. 26 F–G). Anal cirri not observed.

Colour. Preserved animals showing orange-brown pigmentation throughout the body ( Fig. 25A, B ). Tentacular cirri and parapodium presenting dark brown pigmentation ( Fig. 26A, B ).

Habitat. Muddy substrates, 701 to 3,889 m.

Geographical distribution. Atlantic Ocean, Brazil: Margin of continental shelf in Campos Basin and Paranaguá Bay in Paraná State.

Etymology. The species name is derived from the combination of the latin words micro (short) and gnathia (jaw) referring to the chitinous structures that are similar to the micrognaths of goniadids of the genus Glycinde M̹ller, 1858. These structures are irregularly distributed in the median-dorsal area of the proboscis.

Remarks. Phyllodoce micrognatha sp. nov. shares the presence of oval eyes, proboscis containing an armature, presence of numerous teeth, and biramous parapodium with chaetae from segment 2 with Phyllodoce armigera ( Blake 1988) . It differs from P. armigera by the presence of two rows of overlapping rectangular chitinous plates in the dorsal groove of the proboscis instead of one and colour and shape of parapodial cirri. According to Blake (1988), the teeth and plates on the proboscis probably support active burrowing and these teeth could actually be an advantage in prey capture and retention.

In a revision of the genus, Pleijel (1991) referred to Phyllouschakovius Blake, 1988 as junior synonym of Phyllodoce by the presence of chitinous teeth, biramous parapodium, and chaetae from segment 2. The presence of a biramous parapodium seems to be a character that evolved independently within Phyllodoce and phyllodocids, and has also been recorded in P. bulbosa and P. monroi and shared with the genera Austrophyllum Bergstr ̂m, 1914 and Notophyllum Örsted, 1843 ( Averintsev 1972; Pleijel 1990, 1993a).

Phyllodoce bulbosa Wesenberg-Lund, 1962 and Phyllodoce monroi ( Hartman, 1964) differ from P. micrognatha sp. nov. by the absence of chitinous proboscidial structures. Phyllodoce micrognatha sp. nov. differs from P. medipapillata by the presence in the latter of papillated probocis, dorsal cirri foliaceous, and anal cirri clavate. It differs from P. concava sp. nov., P. ovalis sp. nov., and Phyllodoce sp. B. by the presence of chitinous structures in the proboscis and dorsal cirri being subrectangular.

Figures

FIGURE 25. Phyllodoce micrognatha sp. nov. A, anterior end, dorsal view; B, anterior end, showing prosboscis; C, dorsal view of row of chitinous plates; D, rectangular chitinous rows. E, detail of denticles from the proximal part of proboscis. Scale bars: A–B, 0.5 mm; C, 0.02 mm; D–E, 0.06 mm.

FIGURE 26. Phyllodoce micrognatha sp. nov. Anterior view of parapodia. A, parapodium 10; B, parapodium 100; C, parapodium 8 with dorsal extension of cirrophores; D, parapodium 10; E, parapodium 100; F–G, compound spinigerous chaetae. Abbreviations: deCir, dorsal extension of cirrophore. Scale bars: A, 0.06 mm; B, 0.09 mm; C, D, 0.06 mm; E, 0.09 mm; 0.05 mm, F–G, 0.01 mm.