Leodamas tribulosus ( Ehlers, 1897 )

Blake, James A., 2017, Polychaeta Orbiniidae from Antarctica, the Southern Ocean, the Abyssal Pacific Ocean, and off South America, Zootaxa 4218 (1), pp. 1-145 : 78-80

Leodamas tribulosus ( Ehlers, 1897)

Figures 36–37

Aricia tribulosa Ehlers, 1897: 91 , pl. 6, figs. 141–147; 1901: 166; Fauvel 1907: 19.

Scoloplos (Scoloplos) tribulosus: Mesnil & Caullery 1898: 142 .

Scoloplos tribulosus: Fauvel 1941: 286 .

Scoloplos (Leodamas) tribulosus: Hartman 1957: 290 ; 1966: 13, pl. 3, figs. 1–2; Hartmann-Schröder 1962b: 129 –130, figs. 151–153; 1965: 192; Rozbaczylo, 1985: 132.

Scoloplos armiger trioculata Hartmann-Schröder, 1962b: 134 –135, figs. 88–89. New Synonymy.

Protoariciella uncinata: Elias, Vallarino & Bremec 2000: 181 –184. Not Hartmann-Schröder 1962b.

Leodamas tribulosus: Bleidorn et al. 2009: 57 –69 (molecular phylogeny).

Material examined. Argentina, Mar del Plata , intertidal, Feb 1970, coll. J.M. Orensanz (1 juvenile, JAB); Santa Clara, mussel beds, coll. R. Elias, 12 Jan 2001, (3, MCZ 135298 ) ; Golfo San Matías, Las Chañares , intertidal, Feb 1972, Coll. J.M. Orensanz (2, USNM 1013664 ) ; South of Isla Colorado, intertidal, Jan 1973, coll. J.M. Orensanz (7, USNM 1013667 ) ; Puerto Lobos Beach , intertidal, 21 Jan 1973, coll. J.M. Orensanz (1, USNM 1013666 ) ; IBM Sta. SAO-IV-1133, intertidal (5, 1013665).— Tierra del Fuego, Hero Sta. 71-2-8, intertidal (1, USNM 69384 ) ; Staten Island, off Tierra del Fuego, Hero Sta. 71-2-21, intertidal (1, USNM 60686 ) .— Chile, Valparaiso Province, Viña del Mar, Montemar , next to Estacion de Biologia Marina, Universidad de Chile, 32°57′25″S, 71°33′W, sheltered beach, intertidal sand, coll. Eric Guiler, Feb 1955 (10, LACM-AHF Poly 5022); Puerto Montt , 19 Dec 2003, coll. I. Kruse,(3, SEM, JAB) ; Isla Santa Maria, Dec 2003, coll. I. Kruse, 1 specimen ( MCZ 135297 ) . — Straits of Magellan, Punta Arenas , in sand, Sep 1892, Coll. W. Michaelsen, syntype of Aricia tribulosa ( ZMB 6767 ) .— Peru, Punta Chira, ca. 30 km north of Camana , 9 Aug 1955, intertidal, coll. G. Hartmann, holotype of Scoloplos armiger trioculata ( ZMH P-14965).

Description. A single complete specimen from Staten Island 8 mm long, 1 mm wide for 80 setigerous segments; larger specimens from Chile up to 40 mm long, 2.5 mm wide for about 185 segments. Anterior segments dorsoventrally flattened, abdominal segments cylindrical in cross section. Thoracic region with 22–25 segments; Peruvian specimen with 16. Color in alcohol brown with lighter areas between segments and on prostomium.

Prostomium pear-shaped, acutely pointed on anterior margin ( Fig. 36 A, D) or narrowing to rounded tip ( Fig. 37 A); juveniles with short, rounded prostomium; with 0–3 pairs of eyespots, usually only present in smallest or juvenile specimens; nuchal organs narrow vertical slits at posterior margin of prostomium ( Fig. 37 A); two indistinct achaetous rings preceding first setiger on smaller specimens ( Figs. 36 A, 37A), forming smooth circular rings, ventrally forming lateral lips of mouth; larger specimens with less distinct rings, sometimes appearing to be single achaetous segment. Specimens from Montemar with multi-lobed proboscis everted ( Fig. 36 D).

Thoracic notopodia simple, with fascicles of long, tapering crenulated capillaries ( Fig. 37 B–C); long, thin, cirriform postsetal lobe from setiger 1 ( Fig. 36 A, D), gradually becoming longer and thicker in last 10 thoracic setigers. Abdominal notopodia elongated with swollen, medial expansion directed laterally ( Fig. 36 E). Thoracic neuropodia expanded, with short, thick postsetal lobe from setiger 1 ( Fig. 37 B–C). Abdominal notopodia with elongate postsetal lobe, thickened basally, tapering to narrow tip ( Fig. 36 E). Abdominal neuropodia elongate divided apically producing short presetal lobe and elongate postsetal fingerlike lobe, between which setae emerge ( Figs. 36 E, 37I).

Thoracic notosetae including 10 or more long crenulated capillaries; abdominal notosetae with five or more capillaries and 2–5 furcate setae; each furcate seta with two unequal blunt-tipped tynes joined by thin membranous web composed of fine needles ( Fig. 37 F–G). Thoracic neurosetae including dense fascicles of uncini in 5–6 long vertical rows and one short posterior row and crenulated capillaries in 1–2 rows posterior to uncini ( Fig. 37 A–C); first row of uncini longest, curving ventrally below other uncini and continuing dorsally as posterior short row ( Fig. 37 B–C). Uncini strongly bent in a posterior direction, convex side of shaft with transverse rows of minute barbs or teeth, curving into dorsal groove terminating apically in two pointed teeth ( Fig. 37 D), with thin hyaline sheath observed in light microscope surrounding end of uncini ( Fig. 36 C), with SEM sheath a flange, extending along lateral sides of shaft to point of emergence from neuropodium ( Fig. 37 D); abdominal neurosetae with 2–5 crenulated capillaries and 1–2 protruding acicular spines with curved, blunt tips ( Figs. 36 E, 37H–J).

Cirriform branchiae from setiger 5 ( Fig. 36 A–B). Pygidium with several large and small lobes, anal cirri absent ( Fig. 36 B).

Remarks. Leodamas tribulosus is readily distinguished from other species by the unusual thoracic neuropodial uncini with a dorsal groove that terminates in two apical teeth and with a prominent lateral sheath. The species is common along the Chilean coast and in Patagonia where it occurs in the intertidal zone ( Hartman, 1966; Hartmann- Schröder, 1962b; 1965). The holotype of Scoloplos armiger trioculata agrees in all particulars with L. tribulosus , and is herein synonymized with this species.

As part of a study of Orbiniidae phylogeny by Bleidorn et al. (2009), specimens identified as Protoariciella uncinata from Mar del Plata, Argentina were found to have the same genetic structure as Leodamas tribulosus from Chile and these authors concluded that the Argentinian specimens were juveniles of L. tribulosus . Elias et al. (2000) had earlier reported P. uncinata from Mar del Plata and noted that its morphology was variable including having a prostomium that was often pointed instead of rounded, thus further supporting the concept that juveniles of L. tribulosus have a rounded prostomium, two achaetous peristomial rings, and eyespots sometimes present. The same features are present in several of the smaller specimens examined in the present study. Three of the specimens given to C. Bleidorn were provided to me and were carefully examined; in addition to the characters mentioned, the thoracic neuropodial uncini have a distinct apical curvature, lateral sheath, and are bifid on the tips as in L. tribulosus . This does not confirm, however, that P. uncinata of Hartmann-Schröder (1962a) is the same species and in fact, it shares characters with Naineris grubei .

Distribution. Peru; Chile; Argentina; Patagonia; intertidal to low water.

Figures

FIGURE 36. Leodamas tribulosus (Ehlers, 1897). Holotype of Scoloplos armiger trioculata (ZMH P- 14965). A, anterior end, dorsal view; B, posterior end, dorsal view; C, thoracic neuropodial uncinus. — Specimen of L. tribulosus from Montemar, Chile (AHF Poly 5022). D, Anterior end, dorsal view; E, abdominal parapodium, anterior view.

FIGURE 37. Leodamas tribulosus (Ehlers, 1897). SEMs, specimen from Chile, Puerto Montt (JAB). A, anterior end, right lateral view; B, thoracic region, right lateral view; C, detail of thoracic neuropodia; D, thoracic neuropodial uncini; E, abdominal parapodia. — Phase Contrast Images, specimen from Chile, Isla Santa Maria (MCZ 135297): F, abdominal furcate setae; G, detail of furcate setae; H, abdominal neuropodial spine, isolated; I, abdominal neuropodium with two spines emerging from neuropodium; J, same, detail of spines.