Paucibranchia disjuncta ( Hartman, 1961 ) 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 : 40-47

Paucibranchia disjuncta ( Hartman, 1961) n. comb.

Figures 26–30 , Tables 1, 3

Marphysa disjuncta Hartman, 1961:81 –83, Pl. 10, Figs. 1–3 ; Kurt-Sahin 2014:12 –15, Figs. 6–7 .

Material examined. Type material: Holotype LACM-AHF POLY 724 , R/V VELERO IV sta. 2107–52, 2.2 miles ESE (bearing 114° T) from Los Angeles Light, Los Angeles County, California, USA, North Pacific, 33°41'36'' N 118°12'37'' W, 20 Apr 1952, in sand and mud, Hayward orange peel grab, 23.77 m . Additional material: LACM- AHF POLY 10195 (4) R/V VELERO IV sta. 5594–58, 6.7 miles from Ventura Pier Light bearing 270° true north, Ventura , Ventura County, Southern California Bight, California, USA, 34°16'15'' N 119°25'40'' W, 30 Jan 1958, green mud, grab, 22 m, coll. Allan Hancock Foundation . LACM-AHF POLY 10196 (1), Laguna Beach , Orange County, Southern California Bight , California, USA, North Pacific, 11 Jun 1933, in kelp holdfast, coll. O. Hartman . LACM-AHF POLY 6946 (5), R/V VELERO IV Sta. 6107–59, 1.8 miles bearing 062° true north from Point Fermin Light, Los Angeles County, California, USA, 33°43'05'' N 118°15'43'' W, 19 Feb 1959, black silt, Hayward orange peel grab, 13 m, coll . Allan Hancock Foundation. LACM-AHF POLY 6947 (1), R/V VELERO IV sta. 4855–57, 3.8 miles from Point Vicente Light bearing 319° true north, Los Angeles County, California, USA, 33°47'30'' N 118°27'45'' W, 0 8 Feb 1957, in grab, 71 m, coll . Allan Hancock Foundation. LACM-AHF POLY 6948 (1), R/V OCEAN SENTINEL sta. 0101–1C, off Palos Verdes, Los Angeles County, California, USA, 33.75730° N 118.44100° W, 0 4 Jan 2001, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6951 (1) R/V OCEAN SENTINEL sta. 0106–0D, off Palos Verdes , Los Angeles County, California, USA, 33.80280° N 118.42270° W, 10 Jan 2006, 30 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6953 (3), R/V OCEAN SENTINEL sta. 0106–3D, off Palos Verdes , Los Angeles County, California, USA, 33.73320° N 118.40050°W, 10 Jan 2006, 30 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6954 (1), R/V OCEAN SENTINEL sta. 0106–7C, off Palos Verdes , Los Angeles County, California, USA, 33.70520° N 118.34870° W, 10 Jan 2006, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6955 (1), R/V OCEAN SENTINEL sta. 0191–0B, Los Angeles County, California, USA, 33.81170° N 118.44170° W, 16 Jan 1991, 152 m, coll . Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6956 (1), R/V OCEAN SENTINEL sta. 0191–1C, off Palos Verdes , Los Angeles County, California, USA, 33.75730° N 118.44100° W, 16 Jan 1991, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6957 (1), R/V OCEAN SENTINEL sta. 0192–2C, off Palos Verdes , Los Angeles County, California, USA, 33.73770° N 118.42320° W, 22 Jan 1992, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6958 (1), R/V OCEAN SENTINEL sta. 0193–10C, off Palos Verdes , Los Angeles County, California, USA, 33.66850° N 118.29680° W, 14 Jan 1993, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6959 (2), R/V OCEAN SENTINEL sta. 0194–4C, off Palos Verdes , Los Angeles County, California, USA, 33.72330° N 118.38470° W, 12 Jan 1994, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6960 (1), R/V OCEAN SENTINEL sta. 0196–0C, 33.80720° N 118.43050° W, 24 Jan 1996, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory. LACM-AHF POLY 6961 (1), R/V OCEAN SENTINEL sta. 0197–3C, off Palos Verdes , Los Angeles County, California, USA, 33.73000° N 118.40250° W, 15 Jan 1997, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6962 (1), R/V OCEAN SENTINEL sta. 0701–1C5, off Palos Verdes , Los Angeles County, California, USA, 33.75730° N 118.44100° W, 19 Jul 2001, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6963 (1), R/V OCEAN SENTINEL sta. 0792–0C1, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, Jul 1993, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6964 (1), R/V OCEAN SENTINEL sta. 0702–0C2, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 17 Jul 2002, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6965 (3), R/V OCEAN SENTINEL sta. 0790– 0C1, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 18 Jul 1990, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6966 (1), R/V OCEAN SENTINEL sta. 0790–2C, off Palos Verdes , Los Angeles County, California, USA, 33.73770° N 118.42320° W, 19 Jul 1990, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6967 (1), R/V OCEAN SENTINEL sta. 0793–0C1, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 14 Jul 1993, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6968 (1), R/V OCEAN SENTINEL sta. 0794–0C, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 21 Jul 1994, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6969 (1), R/V OCEAN SENTINEL sta. 0795–0C1, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 14 Jul 1995, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6970 (1), R/V OCEAN SENTINEL sta. 0796–0C1, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 11 Jul 1996, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6971 (1), R/V OCEAN SENTINEL sta. 0797–0C, off Palos Verdes , Los Angeles County, California, USA, 33.80720° N 118.43050° W, 0 9 Jul 1997, 61 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6972 (1), R/V OCEAN SENTINEL sta. 0798–3D, off Palos Verdes , Los Angeles County, California, USA, 33.73320° N 118.40050° W, 15 Jul 1998, 30 m, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6973 (1), R/V OCEAN SENTINEL sta. PSCBE 0 6210, off Palos Verdes , Los Angeles County, California, USA, 16 Aug 1994, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 6974 (1), R/V OCEAN SENTINEL sta. W30, off Palos Verdes , Los Angeles County, California, USA, 10 Nov 1997, coll. Los Angeles County Sanitation District, Marine Biology Laboratory . LACM-AHF POLY 10197 (1), sta. 1210–40, reefs just north of caves, La Jolla , San Diego County, Southern California Bight, California, USA, 32°51'02''N 117°16'17'' W, 28 Nov 1940, intertidal, coll. Allan Hancock Foundation . LACM-AHF POLY 10198 (1), R/V VELERO III sta. 1142–40, bearing 165° true north, off Point Vicente Light House , Palos Verdes Peninsula, Los Angeles County, California, USA, 33°44'10' N 118°24'20'' W to 33°43'45''N 118°24'16''W, 0 6 May 1940, coarse sand, mud, dredge, 31–75 m, coll. Allan Hancock Pacific Expeditions .

Description. Holotype incomplete, broken into three parts (first one with 111) with 117 chaetigers, L10= 5.2 mm, W10= 2 mm, TL= 52 mm. Anterior region of body with convex dorsum, and flat ventrum, with a shallow groove between chaetigers 4–13; body depressed from chaetiger 6, widest at chaetiger 8, tapering after chaetiger 13.

Prostomium entire, 1 mm long, 1.2 mm wide, frontally rounded, without median sulcus ( Fig. 26A–E ), ventral sulcus deep ( Fig. 26C ). Prostomial appendages in a semicircle, median antenna isolated by a gap. Palps reaching first chaetiger; lateral antennae reaching second chaetiger; median antenna reaching third chaetiger. Palpophores and ceratophores ring-shaped, short, thick; palpostyles and ceratostyles tapering, thick, without articulation. Eyes absent (see Remarks section).

Peristomium wider than prostomium (1.1 mm long, 1.8 mm wide), first ring two times longer than second ring, separation between rings distinct on all sides ( Fig. 26A–C ). Inferior lip without central depression ( Fig. 26C ).

Maxillary apparatus with FM= 1+1, 6+7, 7+0, 4+9, 1+1. Specimen LACM-AHF POLY 10195 with MF= 1+1, 6+7, 7+0, 5+9, 1+1 ( Fig. 27A ). Maxillary carriers 2.5 times shorter than length of MI. MI forceps-like; closing system 6.3 times shorter than length of MI; ligament between MI and MII, slightly sclerotized ( Fig. 27A–C ). MII wide; with teeth recurved; cavity opening oval, 4.7 times shorter than length of MII; ligament between MII and MIII and right MIV slightly sclerotized ( Fig. 27A–C ). MIII short; with triangular teeth; with attachment lamella not sclerotized ( Fig. 27A–C ). Left MIV with three distal teeth bigger; attachment lamella rectangular, narrow, situated in the central edge of maxilla. Right MIV with blunt teeth; attachment lamella narrow, circular, situated in the central edge of maxilla ( Fig. 27A–C ). MV rectangular, longer than wide, with a short triangular tooth ( Fig. 27A–C ). Mandibles dark; with whitish cutting plates, rectangular, with around 10 growth rings ( Fig. 27D ).

Branchiae pectinate with up to 21 filaments, in chaetigers 12–27 ( Figs. 26B, D ; 28B ). Number of branchial filaments per chaetiger in order anterior-posterior: 13, 13, 13, 15, 15, 16, 16, 16, 20, 21, 21, 20, 19, 19, 15, 10. Branchial filaments longer than dorsal cirri.

First three parapodia smallest; most developed in chaetigers 7–30, following ones becoming gradually smaller. Notopodial cirri conical, increasing in size from chaetiger 4 (Lcd3: 0.46 mm; Lcd23: 0.96 mm), from chaetiger 25, gradually decreasing in width and increasing in length, in posterior region filiform, 2.7 times longer than prebranchial region ones (Lcd111: 1.3 mm); Hayashi & Yamane’s organ present ( Fig. 28A–E ). Prechaetal lobes as a transverse fold in all chaetigers ( Fig. 28A–E ). Chaetal lobes in chaetigers 1–46, rectangular, shorter than postchaetal lobes, with aciculae emerging dorsal to midline; from chaetiger 47, triangular, longer than other lobes, with acicula emerging dorsally to midline ( Fig. 28A–E ). Postchaetal lobes well developed in chaetigers 1–52, conical; thicker and longer in branchial region; decreasing in size in chaetigers 31–52, following ones inconspicuous ( Fig. 28A–E ). Ventral cirri conical in chaetigers 1–4; in chaetigers 5–39 with oval swollen base and digitiform tip, from chaetiger 40, conical, gradually reducing in size posteriorly ( Fig. 28A–E ).

Aciculae blunt, with reddish basal end, distally amber ( Fig. 28A–E ). First 29 chaetigers with 2 aciculae; from chaetiger 30, with only one acicula.

Limbate chaetae of two sizes in the same chaetiger, larger in anterior region, reduced in number around chaetiger 12. Two types of pectinate chaetae; in anterior chaetigers isodonts narrow with long and slender teeth, with 1–2 pectinate with up to 5–6 teeth, with oblique distal edge ( Fig. 29C–D ); in median-posterior chaetigers isodonts narrow with short and slender teeth, with 2–4 pectinate, with up to 10–11 teeth, with oblique distal edge ( Fig. 29E ). Compound spinigers in all chaetigers, with blade of two sizes, reduced in number in median-posterior region ( Fig. 29A ). Compound falcigers present only in posterior region, from chaetiger 112, one or two per chaetiger, with short blade ( Fig. 29B ), with triangular teeth, of similar size, distal tooth directed upward, proximal tooth directed laterally. In organisms with short size, falcigers present from first chaetigers (see notes on the development). Subacicular hooks with seeming unidentate (see notes on the development), with reddish basal end, distally translucent, starting in chaetiger 29 ( Fig. 29G ). In some of the additional material with short size, subacicular hook bidentate ( Fig. 29F ).

In specimen LACM-AHF POLY 6972, anal cirri without articulation; dorsal pair as long as last four chaetigers; ventral pair short, as long as last chaetiger.

Variation. Material examined varied in the following features: L10= 1.2–6.4 mm, W10= 0.3–4 mm. Thirtynine organisms were examined, of which the smallest ones had not developed the palps (n= 6, L10= 1.3–2 mm), a single specimen possessed only the median antenna (L10= 1.2 mm) and in six adults the eyes were not observed. Palps reaching the middle of first peristomial ring or middle of the first chaetiger; lateral antennae reaching second peristomial ring or the middle of second chaetiger; median antenna reaching first peristomial ring or third chaetiger. Maxillary formula varies as follows: MII 5–7+6–7, MIII 6–8, MIV 3–5+6–9. The proportion of maxillary apparatus varies as follows: maxillary carriers with respect to the MI varies 1.5–2.7 times; closing system with respect to the MI varies 4.5–8 times; cavity opening with respect to MII varies 2–4 times. Branchiae from chaetigers 6–15 (R2= 0.7412, n=39; Fig. 30B ) to 9–33 (R2= 0.8319, n=39; Fig. 30C ). Maximum number of branchial filaments varied from 4 to 26 (R2= 0.8736, n=39; Fig. 30A ). Well developed postchaetal lobe in first 7–74 chaetigers (R2= 0.60, n=36; Fig. 30D ). Ventral cirri with a swollen base from chaetigers 1–6 to 9–71 (R2= 0.807, n=37; Fig. 30E ). Start of compound falcigers in chaetigers 1–102 (R2= 0.867, n=29; Fig. 30F ). Start of subacicular hooks in chaetigers 9–39 (R2= 0.8118, n= 39; Fig. 30G ).

It was observed that in specimens with L10Ẽ 2 mm the compound spinigers were distributed from the first chaetiger to chaetigers 7–26; whereas in specimens with L10> 2 mm, the spinigers were present in all chaetigers. Also, specimens with L10Ẽ 2.5 mm only have bidentate subacicular hooks; whereas, in specimens with L10= 2.6– 3.8 mm the subacicular hooks are bidentate in first chaetigers, and hooks unidentate in the median and posterior regions, excepting in posterior chaetigers where the hooks are again bidentate. Specimens with L10> 3.8 mm have all hooks unidentate, except the most posterior chaetigers (growth zone).

Distribution. Southern California, USA.

Remarks. Paucibranchia disjuncta n. comb. has been recorded in Baja California, Mexico ( Fauchald 1970), New Zealand ( Knox & Green 1972) and Japan ( Miura 1977). The specimens observed by Fauchald (1970) and Knox & Green (1972) match in terms of their branchial distribution, and shape and color of subacicular hooks. Due to geographical distance and ecological differences, the material reviewed by Knox & Green (1972) may be suspected to belong to a different species. It is also necessary to review these New Zealand specimens to compare other features such as length of the dorsal cirri, the shape of postchaetal lobe, and maxillary apparatus, as well as, some size-dependent characters; this will allow for determination if these specimens belong to P. disjuncta n. comb. or if they are an undescribed species.

The specimens observed by Miura (1977) from Japan differ from P. disjuncta n. comb. because the former have dorsal cirri shorter than branchial filaments, and the shape of the chaetal lobe is rounded and short; whereas in P. disjuncta n. comb., the dorsal cirri are as long as the branchial filaments, and the chaetal lobe is rectangular and elongated. Furthermore, the specimens from Japan have pectinate chaetae with transverse distal edge, whereas in P. disjuncta n. comb. pectinate chaetae have an oblique distal edge. It is necessary to review those specimens to confirm the differences; however, herein, the presence of P. disjuncta n. comb. in Japan is considered questionable.

Paucibranchia disjuncta n. comb. resembles P. cinari n. comb. by the presence of the spinigers in all chaetigers, falcigers only in posterior region in adult specimens, and unidentate subacicular hooks, reddish basally. However, as noted in the Remarks section of the P. cinari n. comb., the main differences between both species lie in the length of dorsal cirri in the posterior region, the shape of the chaetal lobe, and presence of eyes. The comparison with other Paucibranchia n. gen. species having the compound spinigers and falcigers present is provided in Table 3.

Figures

FIGURE 1. Maxillary apparatus. A. Paucibranchia disjuncta n. comb. (Hartman, 1961), LACM-AHF POLY 6447, dorsal view; B. Marphysa viridis Treadwell, 1917, ECOSUR-P2678, dorsal view; C. Treadwellphysa yucatanensis Molina-Acevedo & Carrera-Parra, 2017, ECOSUR-P2811, dorsal view; D. Left MI-II-III-IV-V of P. disjuncta n. comb., dorsal view; E. Left MI- II-III-IV-V of M. viridis, dorsal view; F. Left MI-II-III-IV-V of T. yucatanensis, dorsal view. Scale bars: A, D, 0.4 mm; B, E, 0.45 mm; C, F, 0.25 mm. Dark and thin lines in D, E and F indicate the different forms in the MI of the apparatus of each species. fa= falcal arch, boe= basal outer edge, bie= basal inner edge, rp= rounded projection in base of MII.

FIGURE 2. Marphysa bonhardi McIntosh, 1885, holotype BMNH 1885.12.1.210. A. Anterior end, dorsal view; B. Anterior end, ventral view; C. Aciculae, anterior chaetigers. Scale bars: A, 0.8 mm; B, C, 0.67 mm.

FIGURE 3. Paucibranchia adenensis (Gravier, 1900) n. comb. A. Anterior end with branchiae, dorsal view; B. Anterior end, dorsal view; C. Anterior end, ventral view; D. Anterior end, dorsal view; E. Anterior end with branchiae, dorsal view; F. Anterior end, ventral view. A, B, C from holotype MNHN-531; D, E, F from non-type MNHN-A148. Scale bars: A, 2 mm; B, 1 mm, C, 2.6 mm, D, F, 0.7 mm; E, 1.3 mm.

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 26. Paucibranchia disjuncta (Hartman, 1961) n. comb. A. Anterior end, dorsal view; B. Anterior end with branchiae, dorsal view; C. Anterior end, ventral view; D. Juvenile, dorsal view; E. Juvenile anterior end, dorsal view. A, B, C. from holotype LACM-AHF POLY 724; D, E, from non-type LACM-AHF POLY 6954. Scale bars: A, C, 1.3 mm; B, 2.6 mm; D, 0.6 mm; E, 3.5 mm. Red arrow points to the inset with the prostomium larva. The black lines indicate the location of the larval eyes and adult eyes.

FIGURE 27. Paucibranchia disjuncta (Hartman, 1961) n. comb., non-type LACM-AHF POLY 10195. A. Maxillary apparatus, dorsal view; B. Left MI-II-III-IV-V, dorsal view; C. Right MI-II-IV-V; D. Mandibles. Scale bars: A, B, C, 0.75 mm; D, 0.9 mm. LMI-MII= ligament between MI and MII; LMII-MIII= ligament between MII and MIII.

FIGURE 28. Paucibranchia disjuncta (Hartman, 1961) n. comb. A. Parapodium 3; B. Parapodium 25; C. Parapodium 47; D. Parapodium 65; E. Parapodium 111. A–D from non-type LACM-AHF POLY 6947, E from holotype LACM-AHF POLY 724. All in anterior view. Scale bars: A, 0.23 mm; B, 0.48 mm; C, 0.26 mm; D, 0.32 mm; E, 0.25 mm. White arrow in C point the Hayashi & Yamane’s organ.

FIGURE 29. Paucibranchia disjuncta (Hartman, 1961) n. comb. A. Compound spinigers, chaetiger 55; B. Compound falciger, chaetiger 115; C. Isodonts pectinate narrow with long and slender teeth, chaetiger 3; D. Isodonts pectinate narrow with long and slender teeth, chaetiger 6; E. Isodonts pectinate narrow with short and slender teeth, chaetiger 65; F. Subacicular hook bidentante, chaetiger 55; G. Subacicular unidentate with hood, chaetiger 47. A, D, E, G, from non-type LACM-AHF POLY 10195; B from holotype LACM-AHF POLY 724; C from non-type LACM-AHF POLY 10196; F from non-type LACM-AHF POLY6948. Scale bars: A, B, 20 µm; C, 14 µm; D, E, G, 10 µm; F, 20 µm.

FIGURE 30. Length-dependent variation of some morphological features in Paucibranchia disjuncta (Hartman, 1961) n. comb. A. Maximum number of branchial filaments (n= 39); B. First chaetiger with branchia (n=39); C. Last chaetiger with branchia (n=39); D. Last chaetiger with well developed postchaetal lobe (DPL) (n=36); E. Last chaetiger with ventral cirri with swollen base (VCSB) (n=37); F. First chaetiger with falciger (n=29); G. Start of subacicular hook (n=39).