Paucibranchia kinbergi ( McIntosh, 1910 ) Molina-Acevedo, 2018

Molina-Acevedo, Isabel C., 2018, Morphological revision of the Subgroup 1 Fauchald, 1970 of Marphysa de Quatrefages, 1865 (Eunicidae: Polychaeta), Zootaxa 4480 (1), pp. 1-125 : 67-71

Paucibranchia kinbergi ( McIntosh, 1910) n. comb.

Figures 46–49 , Tables 1, 4

Marphysa kinbergi McIntosh, 1910:451 –452, Pl. LXXIV Figs. 9–9a , Pl. LXXXIII, Fig. 6–6a–b ; Rullier 1965:32, Fig. 4 ; Kurt- Sahin 2014:10 –12, Figs. 6 , 7 .

Material examined. Type material: Lectotype BNHM 1921.5.1.2021 and paralectotypes BNHM 2018.25374 (1), BNHM 2018.25375 (1), off Cape Finisterre, Spain, Atlantic Ocean , Porcupine Expedition, coll. W. McIntosh , 148 m. Additional material: MNHN-A432 (1), sta. AZ 767, Benin, Africa, Atlantic Ocean, 1963 , 55 m. MNHN-A432 (1), sta. AZ 770, Benin, Africa , Atlantic Ocean, 19 Oct 1963, 27 – 48m. MNCN 16,01 /4601 (1), Sancti-Petri Islet, Chiclana de la Frontera, Cadiz, Spain, Atlantic Ocean.

Description. Lectotype incomplete, with 53 chaetigers, L10= 7.8 mm, W10= 2.3 mm, with TL= 81 mm. Anterior region of body with dorsum convex and flat ventrum, without groove; body depressed from chaetiger 8, widest at chaetiger 50, tapering not observed.

Prostomium entire, 0.9 mm long, 1.6 mm wide, frontally rounded, without median sulcus ( Fig. 46A–C ), ventral sulcus deep ( Fig. 46B ). Prostomial appendages in a semicircle, equidistant. Palps reaching second peristomial ring; lateral antennae reaching the middle of first chaetiger; median reaching second chaetiger. Palpophores and ceratophores ring-shaped, short, slender; palpostyles and ceratostyles tapering, with base thick, without articulation. Eyes absent.

Peristomium wider than prostomium (1.5 mm long, 2.8 mm wide), first ring two times longer than second ring, separation between rings distinct on all sides ( Fig. 46A–C ). Inferior lip without central depression ( Fig. 46B ).

Maxillary apparatus lost, described from paralectotype, with MF= 1+1, 6+6, 6+0, 4+7, 1+1 ( Fig. 47A–B ). Maxillary carriers 1.9 times shorter than length of MI. MI forceps-like; closing system 7 times shorter than length of MI; ligament between MI and MII, rectangular, slightly sclerotized ( Fig. 47A–D ) . MII wide ; with teeth recurved, cavity opening oval 4 times shorter than length of MII ; ligament between MII and MIII, and right MIV, slightly sclerotized ( Fig. 47A–D ) . MIII short; with triangular teeth; with attachment lamella not sclerotized ( Fig. 47A–D ). Left MIV with smaller basal tooth; attachment lamella triangular, slender, situated in a small portion of edge of maxilla, sclerotized. Right MIV with teeth of similar size; attachment lamella slender, circular, situated in a small portion of edge of maxilla ( Fig. 47A–D ). MV rectangular, longer than wide, with a short rounded tooth ( Fig. 47A–D ). Mandibles dark; cutting plates translucent, with 12 growth rings ( Fig. 47E ).

Branchiae pectinate with up to 23 filaments, in chaetigers 15R–17L–33R–31L ( Figs. 46A ; 48B ). Number of branchial filaments per chaetiger in order anterior-posterior: 5?, 8?, 5?, 14, 14,?, 16, 17, 19, 19, 20, 22, 26, 22, 24, 22, 12, 7, 3. Basal branchial filaments longer and slender than dorsal cirri.

First parapodia smallest; most developed in chaetigers 4–36, following ones becoming gradually smaller. Notopodial cirri conical, increasing in size from chaetiger 4 (Ldc3: 0.64 mm; Ldc25: 0.8 mm), from chaetiger 30, gradually decreasing in width and increasing in length, in posterior region filiform, 2.7 times longer than prebranchial region ones (Ldc83: 1.7 mm); Hayashi & Yamane’s organ present ( Fig. 48A–D ). Prechaetal lobes as transverse fold in all chaetigers ( Fig. 48A–D ). Chaetal lobes in chaetigers 1–34, rectangular, shorter than postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 35, triangular, longer than other lobes, with acicula emerging dorsally to midline ( Fig. 48A–D ). Postchaetal lobes well developed, in second paralectotype developed in chaetigers 1–64, tongue-shaped in pre-branchial chaetigers; conical, thinner, elongated in branchial chaetigers; decreasing in size in chaetigers 45–64. Ventral cirri digitiform in chaetigers 1–3; in second paralectotype chaetigers 4–52 with oval swollen base and digitiform tip; from chaetiger 53, digitiform, gradually reducing in size posteriorly ( Fig. 48A–D ).

Aciculae blunt; with reddish basal end, distally amber ( Fig. 48A–D ). First three chaetigers with one acicula; in chaetigers 4–13 with 3 aciculae; in chaetigers 14–33 with 2 aciculae; from chaetiger 34, with only one acicula.

Limbate chaetae of two sizes in same chaetiger, larger in anterior region, in second syntype reduced in number around chaetiger 15. Two types of pectinate chaetae; in anterior chaetigers isodonts narrow with long and slender teeth, with 1–2 pectinate, with up to 7 teeth, with oblique distal edge ( Fig. 49A ); in median-posterior chaetigers isodonts narrow with short and slender teeth, with 3–4 pectinate, with up to 7 teeth, with oblique distal edge ( Fig. 49B ). Compound spinigers present in all chaetigers; in anterior, media and posterior region with blades of similar size (200 µm, Fig. 49C ). Subacicular hooks unidentate, with reddish basal end, distally amber, starting in chaetiger 48, with one hook per chaetiger ( Fig. 49D ).

Variation. Material examined varied in the following features: L10= 1.9–7.8 mm, W10= 0.6–3 mm. Palps reaching second peristomial ring or middle of the first chaetiger; lateral antennae reaching the middle of the first chaetiger or fourth chaetiger; median antenna reaching second chaetiger or firth chaetiger. Maxillary formula varies as follows: MII 6+6–7, MIII 6–7, MIV 4 +7–10. The proportion of maxillary apparatus varies as follows: maxillary carriers shorter with respect to the MI varies 1.9–2.1 times; closing system shorter with respect to the MI varies 6– 7 times; cavity opening shorter with respect to MII varies 4–4.6 times. Branchiae from chaetigers 9–16 to 17–33 . Maximum number of branchial filament varied from 8 to 23. Well developed postchaetal lobe in first 29–64 chaetigers. Ventral cirri with swollen base from chaetigers 4–5 to 22–52. Start of subacicular hooks in chaetigers 23–48.

Distribution. Spain (Atlantic Ocean), Benin and Togo.

Remarks. According to the online catalog of the Natural History Museum, London (BNHM), the lot BNHM 1921.5.1.2021 holds the holotype of P. kinbergi n. comb.; however, three specimens were found inside this cataloged vial. The longer specimen fits well with the original description; thus, it was designated as the lectotype and the other two as paralectotypes.

Paucibranchia kinbergi n. comb. has been recorded from distant regions of its type locality (Cape Finisterre, Spain). For instance, Rullier (1965) reported some specimens from Benin (formerly Dahomey) and Togo, and Orensanz (1975) from Uruguay. Rullier’s specimens match well with the type materials herein studied. Regarding Orensanz’s record, some critical differences were found in his description. The subacicular hooks are unidentate in the median region and bidentates in the posterior chaetigers, and the postchaetal lobes are always conical. Whereas in P. kinbergi n. comb., subacicular hooks are unidentante in all chaetigers, and the postchaetal lobes are tongueshaped in pre-branchial chaetigers and conical in branchial region. Furthermore, the specimens from Uruguay have spinigers with blades of four sizes; whereas in P. kinbergi n. comb. spinigers have all blades of similar size. It would be necessary to review in detail the material from Uruguay to corroborate that its taxonomic status, since it is likely that it belongs to a new species. The comparison with other Paucibranchia n. gen. species having only compound spinigers present is provided in Remarks section of P. gilberti n. sp. or in Table 4.

Figures

FIGURE 4. Paucibranchia adenensis (Gravier, 1900) n. comb., non-type MNHN-A148. A. Maxillary apparatus, dorsal view; B. Mandibles; C. Left MII-III-IV-V, dorsal view; D. Maxilla I, dorsal view. Apparatus stained with methyl green. Scale bars: A, C, 50 µm; B, 150 µm; D, 130 µm. al-MIV= attachment lamellae in MIV, LMI-MII= ligament between MI and MII.

FIGURE 6. Paucibranchia adenensis (Gravier, 1900) n. comb., non-type MNHN-A148. A. Compound falciger, long blade, chaetiger, 11; B. Compound falciger, median blade, chaetiger, 11; C. Compound falciger, short blade, chaetiger, 216; D. Isodonts pectinate narrow with long and slender teeth, chaetiger 3; E. Isodonts pectinate narrow with short and slender teeth, chaetiger 216; F. Subacicular hook, distal end, chaetiger 158. Scale bars: A, 12.5 µm; B, 20 µm; C, F, 9.8 µm; D, 14 µm, E, 4.9 µm.

FIGURE 7. Paucibranchia andresi n. sp., holotype USNM 28955. A. Anterior end with branchiae, dorsal view; B. Anterior end, dorsal view; C. Anterior end, ventral view; D. Pygidium, ventral view. Scale bars: A, B, 1.1 mm; C, 0.8 mm; D. 0.55 mm.

FIGURE 9. Paucibranchia andresi n. sp., holotype USNM 28955. A. Parapodium 3; B. Parapodium 8; C. Parapodium 14; D. Parapodium 55; E. Parapodium 213. All in anterior view. Scale bars: A, 0.17 mm; B, D, E, 0.2 mm; C, 0.4 mm.

FIGURE 46. Paucibranchia kinbergi (McIntosh, 1910) n. comb., lectotype BNHM 1921.5.1.2021. A. Anterior end, dorsal view; B. Anterior end, ventral view; C. Anterior end, lateral view; D. Anterior end with branchiae, dorsal view. Scale bars: A– D, 2 mm.

FIGURE 47. Paucibranchia kinbergi (McIntosh, 1910) n. comb. A. Maxillary apparatus, dorsal view; B. Maxillary apparatus, dorsal view; C, Left MI-II-III-IV-V, lateral view; D. Right MI-II-IV-V, lateral view; E. Mandibles. A, from paralectotype BNHM 2018.25374; B-E, from non-type MNHN-A432. Scale bars: A–D, 0.75 mm; E 0.48 mm.

FIGURE 48. Paucibranchia kinbergi (McIntosh, 1910) n. comb. A. Parapodium 3; B. Parapodium 25; C. Parapodium 67; D. Parapodium 74. All in anterior view. A, D, C from non-type MNHN-A432; B, from lectotype BNHM 1921.5.1.2021. Scale bars: A, 0.16, mm; B, 0.19 mm; C, 0.26 mm; D, 0.43 mm.

FIGURE 49. Paucibranchia kinbergi (McIntosh, 1910) n. comb. A. Isodonts pectinate narrow with long and slender teeth, chaetiger 25; B. Isodonts pectinate narrow with short and slender teeth, chaetiger 59; C. Compound spiniger, chaetiger 18; D. Subacicular hook unidentate, chaetiger 59. A, from lectotype BNHM 1921.5.1.2021; B–D, from paralectotype BNHM 2018.25374. Scale bars: A, 21 µm; B, 17.5 µm; C, 10.5 µm; D, 25 µm.