Anguillosyllis blakei, Maciolek, 2020

Maciolek, Nancy J., 2020, Anguillosyllis (Annelida: Syllidae) from multiple deep-water locations in the northern and southern hemispheres, Zootaxa 4793 (1), pp. 1-73 : 48-51

Anguillosyllis blakei n. sp.

Figures 22–23

urn:lsid:zoobank.org:act:DB1D9215-3368-405B-88A6-37AAE08EEF8C

Braniella sp. 1: Hilbig & Blake 2006: 269.

Material examined. (51 specimens from 8 samples, 8 stations) Gulf of the Farallones , California continental slope. EPA 102 Site Survey, south of Pioneer Canyon , R/V Point Sur, coll. J.A. Blake. Sta. 3-7 , 14 Sep 1991, 37 o 27.44ʹN, 123 o 19.50’W, 1675 m, 1 specimen ( LACM-AHF Poly 10446 ) ; Sta. 3-12 , 15 Sep 1991, 37 o 25.03ʹN, 123 o 18.00ʹW, 1745 m, 1 specimen ( LACM-AHF Poly 10447 ) ; Sta. 4- 2, 18 Sep 1991, 37 o 15.29ʹN, 123 o 07.13ʹW, 995 m, 1 specimen ( LACM-AHF Poly 10448 ) ; Sta. 4-5 , 17 Sep 1991, 37 o 13.54ʹN, 123 o 16.26ʹW, 1820 m, 6 specimens ( LACM-AHF Poly 10449 ) ; Sta. 4-10 , 17 Sep 1991, 37 o 11.26ʹN, 123 o 15.26ʹW, 1760 m, holotype ( LACM-AHF Poly 10443 ), 6 paratypes ( LACM-AHF Poly 10444 ), 11 paratypes ( LACM-AHF Poly 10445 ) ; Sta. 4-12 , 17 Sep 1991, 37 10.78ʹN, 123 09.87ʹW, 1480 m, paratype ( LACM-AHF Poly 10450 ) ; Sta. 4-13 , 17 Sep 1991, 37 o 10.34ʹN, 123 o 10.78ʹW, 1730 m, 9 specimens ( LACM-AHF Poly 10451 ) ; Sta. 4-15 , 19 Sep 1991, 37 o 12.42ʹN, 123 o 15.81ʹW, 1730 m, 14 paratypes ( LACM-AHF Poly 10452 )

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Description. Body with 10 setigers ( Figs. 22A , 23A ), colorless; holotype complete, 1.4 mm long without anal cirri, 0.2 mm wide without parapodia, 0.6 mm wide with parapodia but excluding setae; other specimens maximum length 2 mm, maximum width with parapodia 0.75 mm. Palps elongated, completely fused, slightly wider at base, narrowing to weakly pointed anterior margin( Fig. 22A ), indication of median furrow reaching to base on some specimens ( Fig. 23B ); prostomium oval, with three antennae in transverse row, eyes lacking; peristomium shorter than either prostomium or setiger 1, with two short oval tentacular cirri. Nuchal cilia present as small patch between prostomium and peristomium. Eversible pharynx distally surrounded by 10–12 soft papillae, tooth absent. Proventricle in 2.5–4 setigers, bluntly barrel-shaped anteriorly, tapered posteriorly ( Figs. 22A , 23C ); ca. 20–25 rows of muscle cells; post-ventricle caeca with dorsal circlet of cells retaining faint MG stain.

Dorsum biannulate on setiger 1 and sometimes setiger 2, anterior ring shorter. Parapodia uniramous, shortest on setiger 1, becoming elongated, rectangular over next few setigers, then slightly shorter again on setigers 9–10; very small anterior lobe present ( Fig. 22 B–C); dorsal lobe obvious, largest on several anterior and middle setigers ( Fig. 22 B–C), smaller posteriorly; posterior lobes absent; pad of cells that retain MG stain on posterior portion of parapodia ( Fig. 22 B–C). Single large golden tubular gland in all setigers, largest and most obvious in middle and posterior parapodia (setigers 5–9) ( Figs. 22D , 23D ), gland with elongated nipple-like structure at distal end ( Fig. 22D inset). Dorsal cirri long, filiform, observed on setigers 1, 6, 7, 8, and sometimes 9; with basal cirrophores ( Fig. 22 D–E). Ventral parapodial cirri triangular to digitiform, inserted in middle of parapodium.

All setae compound with heterogomph shafts; number of setae per parapodium increasing through setiger 6 then decreasing in posterior setigers: setiger 1 with 14–20 setae, setiger 2 with 20–22, setiger 6 with 24–25, setigers 9–10 with up to 15 setae. Several setae emerging from distal tip of parapodium, remaining setae emerging from ventral face of parapodium between insertion of ventral cirrus and distal tip ( Fig. 23G ). Ventral falcigers with blunttipped blades measuring 12–25 µm, blades of distal spiniger-like setae long, thin, with finely tapered tips, measuring ca. 70 µm long in setiger 1, becoming longer in subsequent setigers, up to ca. 130 µm. All blades with fine proximal serrations. Parapodia each with two aciculae, not protruding but forming anterior and posterior bumps at distal end of parapodia; anterior acicula heavy, golden; posterior acicula less obvious.

Pygidium with two ventromedial, long, thin, filiform cirri and two lateral oval cirri; these often lost, but seen in various combinations, holotype with two filiform ventromedial cirri remaining (one lost during reexamination).

Reproductive specimens with oocytes in coelom of setigers 6–9 ( Fig. 23 E–F), oocytes measuring 50–115 µm greatest diameter (largest one is outlier, ave.=75.7 ± 14.6 µm, median diameter = 70 µm, n=18);some oocytes entering or within parapodia ( Figs. 22E , 23 E–F).

Remarks. Of the 51 specimens of A. blakei n. sp. examined in this study, all retained dorsal cirri on the first setiger and the majority had cirri on setigers 6–8 and sometimes setigers 5 and/or 9. Basal cirrophores were noted on the dorsal cirri and were seen on those setigers where the cirri had broken off; however, cirrophores were not seen on setigers 2–4 or 10, suggesting that cirri may be entirely absent from those setigers. A few specimens had fewer than 10 setigers and these are thought to be juveniles of the species. The smallest of these (Sta. 4-10, 7 setigers, 0.6 mm long) had palps that were somewhat softly rounded rather than the narrow and pointed palps of the larger specimens; also, the proventricle occupied only two setigers.

The single tubular gland in the posterior portion of middle and posterior parapodia is distinctively large and clear, often appearing golden in color; it appears to open externally through a nipple-like structure. A similar gland is seen in A. sepula n. sp., described below, but in that species the gland is deep in the parapodium and obscured by a sheath of cells that stain with MG; whereas, in A. blakei n. sp., the pad of cells is posterior to the gland and does not obscure it.

Other Anguillosyllis species with ten setigers include four from the South China Sea: A. taleola n. sp. and A. denaria n. sp., which have large posterior lobes rather than lacking then as in A. blakei n. sp.; A. elegantissima n. sp., which has unique heterogomph setal shafts that differ from those in A. blakei n. sp.; and A. sepula n. sp., which lacks biannulation on setigers 1 and 2, has much larger eggs, and is generally a more robust species with palps that are wider anteriorly and have a defined medial notch. Anguillosyllis lanai from Brazil also has 10 setigers, but lacks the biannulation of setigers 1 and 2, has fewer setae that reach a greater length, lacks anterior lobes on the parapodia, has a smaller proventricle with half the number of muscle rows (1.5–2 setigers with ca. 12 rows in A. lanai vs. 2.5–4 setigers with ca. 20–22 rows in A. blakei n. sp.), and lacks the large internal tubular glands of A. blakei n. sp.

Etymology. This species is named in honor of Dr. James A. Blake, who collected the specimens and recognized them as an undescribed species.

Records. California continental slope, 995–1820 m .

Figures

FIGURE 22. Anguillosyllis blakei n. sp. Holotype (LACM-AHF 10443): A, entire specimen, dorsal view. Paratype (LACM- AHF 10444): B, setiger 1, dorsal view, dorsal lobe folded back; C, setiger 2, dorsal view, dorsal lobe extended laterally. Holotype (LACM-AHF 10443): D, setiger 6, dorsal view, inset not to scale. Paratype (LACM-AHF 10444): E, setigers 7 and 8, dorsal view. Abbreviations: aL—anterior lobe, dC—dorsal cirrus, dCscar— dorsal cirrus scar, dL—dorsal lobe, InGl—internal gland, MGst—cells stained with Methyl Green.

FIGURE 23. Anguillosyllis blakei n. sp. Holotype (LACM-AHF 10443): A, entire specimen, ventral view. Paratype (LACM- AHF 10452): B, anterior end, dorsal view. Paratype (LACM-AHF 10450): C, proventricle, dorsal view. Holotype (LACM-AHF 10443): D, large gland in setiger 8. Paratype (LACM-AHF 10452): E, entire specimen with eggs, dorsal view, damaged; F, eggs in setigers 6–8; Paratype (LACM-AHF 10450): G, setigers 3–5.