Myxicola sulcata Ehlers, 1912

Tovar-Hernández, María Ana, León-González, Jesús Ángel De & Bybee, David R., 2017, Sabellid worms from the Patagonian Shelf and Humboldt Current System (Annelida, Sabellidae): Phyllis Knight-Jones’ and José María Orensanz’s collections, Zootaxa 4283 (1), pp. 1-64 : 17-21

Myxicola sulcata Ehlers, 1912 , redescription

( Figs 6–8 , 32 A)

Myxicola sulcata Ehlers, 1912: 29 –30, pl. 3, figs 5–12.— Hartman 1966: 122, pl. 40, figs 4–7 (redrawn from Ehlers 1912).— Tovar-Hernández 2010: 17.

Material examined. ARGENTINA, UANL 8046 : Puerto Ingeniero White , Bahía Blanca, 38°46′S, 62°16′W, 28 October 1968, intertidal, on dock pilings, coll. S. Valentinuzzi, 5 specimens . Campana SAO I: UANL 8047 : Golfo de San Matías , St. 9a, 41°01’30”S, 64°11’W, 18 m depth, sedimentary rock, 14 February 1971, coll. J.M. Orensanz, 1 specimen ; UANL 8048: St. 53, 41°00’S, 65°06’W, 38 m depth, gravel & shell, 17 February 1971, coll. J.M. Orensanz, 1 specimen. Campaña SAO II, UANL 8049 : Golfo de San Matías , St. 103, 40°59’S, 64°23’W, 64 m depth , 4 May 1971, 1 fragment undergoing hystolisis. Campaña SAO V, UANL 8050 : Golfo de San Matías, St. 230, off Bajo Oliveira , 18.2 m depth, sand, 5 March 1973, coll. J.M. Orensanz, 1 specimen . Campaña, 1, UANL 8051 : Golfo de San José, off El Riacho , subtidal, 42°24’S, 64°35’W, May 1976, coll. J.M. Orensanz, 2 specimens, one female with oocytes in abdomen ; UANL 8052 : Golfo de San José, dredge haul 5, E of Tehuelche , 3 miles offshore, 42°22’S, 64°16’W, 47,5 m depth, coll. J.M. Orensanz, 11 May 1976, 1 specimen . Campaña Goyena II, UANL 8053 : Mar del Plata , St. 12, 38°03.9’S, 57°22’W, coarse sand, shell, 12 specimens ; UANL 8054 : Bahía San Blas, 40°33’S, 62°14’W, February 1982, intertidal, coll. A. Moguilevsky, 1 specimen complete but with histolysis in branchial crown . URUGUAY, Campaña Akademik Knipovich, UANL 8055: St. 250, 34°51’S, 52°35’W, 83 m depth, 1965, 1 specimen. Campaña Atlantis II, UANL 8056: St. 284, 36°08.3’S, 53°42.3’W, 98 m depth, 1971, 1 specimen.

Redescription. Trunk length 9–35 mm, width 2.5– 4 mm, cylindrical in cross section ( Fig. 7 D). Branchial crown length 6–12 mm, with semicircular radiolar lobes fused dorsally, bearing 12–17 pairs of radioles ( Fig. 7 C). Eight thoracic and 35–72 abdominal segments. Dorsal and ventral basal flanges absent. Palmate membrane between radioles along 3/4 of their length; radioles with broad radiolar flanges, and long, filiform bare tips ( Fig. 6 I); radioles with longest pinnules distally ( Figs 6 I, 7F). Dorsal lips small, with radiolar appendages located in inner margin of each dorsal lip ( Fig. 8 B, C), adjacent to mouth. Ventral lips well developed, broadly rounded, extending from dorsal-most edges of inner branchial lobe margins to ventral-most edges ( Figs 8 A–C); dorsal pinnular appendages absent and ventral radiolar appendages all absent. Parallel lamellae and ventral sacs absent. Posterior peristomial ring collar absent ( Figs 6 A, B, D, E; 7A, B). Anterior peristomial ring with triangular ventral lobe, distally entire ( Fig. 6 B); laterally with shallow notch ( Fig. 6 D, E). Narrow glandular ridge on chaetiger 2 ( Fig. 7 A, B). Ventral shields absent throughout. Interramal eyespots absent but perhaps they fade. First notopodia with thin elongate-narrowly hooded chaetae. Following thoracic chaetigers with almost inconspicuous notopodia, with 10–20 thin, elongate narrowly-hooded chaetae arranged in transverse rows anterior to uncini ( Fig. 7 G). Thoracic neuropodia with acicular uncini with curved tips as hooks, each equipped with narrow tooth above main fang (unidentate), hood absent ( Fig. 7 G–I), handle broad medially, then thickened to basal end. Companion chaetae absent. Abdominal neurochaetae narrowly-hooded, on almost inconspicuous neuropodia. Abdominal notopodial tori forming almost complete cinctures around body, except for faecal groove ( Fig. 6 G, H), with avicular uncini with one row of two teeth above main fang, breast well developed and handle minute ( Fig. 7 J). Pygidium triangular ( Fig. 6 C, F), pygidial cirrus absent. Tubes not preserved.

Type locality. Antarctic, Ross Sea, Winter Quarters.

Remarks. Rullier & Amoreux (1979) reported Myxicola aesthetica , a species described from Italy, near Cabo Polonio ( Uruguay), 25 m depth, but in that contribution neither figures nor description were provided.

Orrhage (1980) and Fitzhugh (1989) reported the genus Myxicola as lacking ventral lips but in later studies this was modified. Fitzhugh (2003) and Capa et al. (2011) corroborated the presence of ventral lips extending dorsoventrally along the entire interior margin of the branchial lobes (wrap around dorsal lips), as opposed to only adjacent to the ventral half of radioles, as in all other sabellid genera.

When branchial lobes were opened dorsally using forceps to describe dorsal lips morphology in M. sulcata , a pair of broadly rounded lips were visible ( Fig. 8 A, also see Giangrande et al. 2012: fig. 11F for M. infundibulum ). Each lip presented a finger-like radiolar appendage on its inner margin, which is surrounded partially by the ventral lip ( Fig. 8 B, C). This appendage would represent the dorsal lip. According to Fitzhugh (2003) and Capa et al. (2011), these enveloping lips are ventral, instead of the dorsal lips. The digitiform processes of dorsal lips were interpreted by Fitzhugh (2003) as a combination of dorsal lips and radiolar appendages, and the overall structures that essentially surround the dorsal lips were therefore considered as the ventral lips.

Figures

FIGURE 6. Myxicola sulcata Ehlers, 1912. A) Thorax and base of branchial crown, dorsal view, B) same, ventral view, C) posterior end, ventro-lateral view, D, E) thorax and base of branchial crown, lateral view, F) posterior end, dorso-lateral view, G) cinctures of abdominal uncini (white arrows), ventral view showing the faecal groove (black arrow), H) same, dorsal view, I) pinnules and radiolar tip. Scale bars: A, B 2.2 mm, C, F, I 1 mm, D, E 1.5 mm, G, H 0. 5 mm. Abbreviation: fg faecal groove. Stain: A – H Shirla. Specimen: A – I UANL 8053.

FIGURE 7. Myxicola sulcata Ehlers, 1912. A, B) Thorax, dorsal view, C) branchial crown, D) peristomium, apical view, branchial crown removed, E) ventral lip, F) radiole and pinnules, G) thoracic noto- and neuropodial fascicles, H) thoracic uncini, I) same, detail, J) abdominal uncini. Arrows in A and B point to glandular ridge on chaetiger 2. Scale bars: A, B, F 2 mm, C 4 mm, D 0.8 mm, E 0.6 mm, G, H 40 µm, I, J 10 µm. Abbreviations: d dorsum, v ventrum, sl surrounding lip. Stain: A methyl green, C – F Shirla. Specimen: A – J UANL 8054.

FIGURE 8. Myxicola sulcata Ehlers, 1912. A – C) Ventral lips and radiolar appendages (arrows). Scale bars: A 0.8 mm, B, C 0.6 mm. Abbreviation: sl surrounding lip. Stain: A – C Shirla. Specimens: A – C UANL 8054.

FIGURE 32. Distribution of some sabellid species in South America. A) Myxicola sulcata Ehlers, 1912, B) Notaulax tilosaula (Schmarda, 1861) (star) and Notaulax salazari sp. nov. (circle), C) Parasabella columbi (Kinberg, 1867) (circles) and Parasabella yonowae sp. nov. (star denotes type locality and triangle indicates additional records).