Opisthodonta morena Langerhans, 1879

Fukuda, Marcelo V., Nogueira, João M. M. & Martín, Guillermo San, 2015, Eusyllinae and “ Incertae sedis ” syllids (Annelida: Syllidae) from South America, with a new species from Brazil and a new combination for a Peruvian species, Zootaxa 3936 (4), pp. 507-537 : 526-530

Opisthodonta morena Langerhans, 1879

Figures 11–13

Opisthodonta morena Langerhans, 1879: 547 , fig. 12; San Martín 2003: 54 –57, figs 15–16; San Martín & Hutchings 2006: 306 –308, figs 40–42A-B; Fukuda 2010: 61 –63, fig. 16.

Material examined. Project‘ REVIZEE ’. State of Rio de Janeiro— 23º08´S 41º00´W, 105 m: 1 spec. ( MZUSP 1010), 1 Mar 1998; 23º26´S 41º15´W, 145 m: 1 spec., 28 Feb 1998; 23º29´S 41º09´W, 266 m: 1 spec. ( MZUSP 1009), 28 Feb 1998; 23º36´S 42º09´W, 187 m: 3 specs, 16 Feb 1998; 23º40´S 42º31´W, 162 m: 1 spec. ( MZUSP 1008), 16 Feb 1998; 23º49´S 43º14´W, 138 m: 5 specs, 15 Feb 1998; 24º02´S 43º30´W, 147 m: 3 specs, 14 Feb 1998. State of São Paulo— 24º07´S 44º42´W, 101 m: 3 specs, 11 Jan 1998; 24º07´S 45º51´W, 147 m: 18 specs ( MZUSP 1006), 9 Jan 1998; 24º20´S 44º09´W, 258 m: 1 spec., 10 Jan 1998; 25º18´S 44º52´W, 808 m: 1 spec., 12 Jan 1998; 26º27´S 44º30´W, 165 m: 1 spec. ( MZUSP 1007), 11 Jan 1998.

Project ' Habitats '. 21°9'9"S 40°16'5"W, 101 m: 2 specs ( MZUSP 2396), 7 Mar 2009, and 2 specs ( MZUSP 2405), 21 Jul 2009; 21°22'58"S 40°19'41"W, 52 m: 1 spec. (ZUEC-POL 16127), 5 Mar 2009, and 1 spec. (ZUEC- POL 16136), 21 Jul 2009; 21°23'38"S 40°15'37"W, 88 m: 1 spec. (ZUEC-POL 16137), 21 Jul 2009; 21°24'43"S 40°25'18"W, 33 m: 1 spec. ( MZUSP 2386), 7 Mar 2009; 21°42'53"S 40°10'16"W, 98 m: 2 specs ( MZUSP 2398; ZUEC-POL 16144), 9 Mar 2009; 21°43'10"S 40°11'30"W, 71 m: 1 spec. ( MZUSP 2404), 7 Jul 2009; 21°45'13"S 40°14'7"W, 67 m: 1 spec. ( MZUSP 2387), 14 Mar 2009; 22°3'38"S 40°6'59"W, 90 m: 3 specs ( MZUSP 2403; ZUEC-POL 16145), 7 Jul 2009; 22°3'45"S 40°9'59"W, 75 m: 4 specs ( MZUSP 2394; ZUEC-POL 16125), 25 Feb 2009, and 4 specs ( MZUSP 2402; ZUEC-POL 16133), 6 Jul 2009; 22°6'12"S 40°3'5"W, 150 m: 1 spec. (ZUEC- POL 16134), 7 Jul 2009; 22°13'42"S 40°32'39"W, 70 m: 1 spec. (ZUEC-POL 16117), 24 Jul 2009; 22°17'42"S 40°26'59"W, 104 m: 1 spec. ( MZUSP 2395), 23 Feb 2009, and 9 specs ( MZUSP 2401; ZUEC-POL 16131, 16143), 4 Jul 2009; 22°19'3"S 40°5'28"W, 386 m: 1 spec. ( MZUSP 2385), 30 Jan 2009; 22°19'32"S 40°37'18"W, 75 m: 12 specs ( MZUSP 2393; ZUEC-POL 16126), 15 Mar 2009, and 8 specs ( MZUSP 2400; ZUEC-POL 16129), 4 Jul 2009; 22°23'21"S 40°34'57"W, 110 m: 1 spec. (ZUEC-POL 16135), 25 Jul 2009; 22°23'39"S 40°20'40"W, 153 m: 1 spec. (ZUEC-POL 16124), 23 Feb 2009, and 2 specs (ZUEC-POL 16132), 4 Jul 2009; 22°31'7"S 40°31'32"W, 139 m: 1 spec. (ZUEC-POL 16123), 23 Feb 2009, and 2 specs (ZUEC-POL 16130), 3 Jul 2009; 22°46'54"S 41°3'33"W, 77 m: 3 specs ( MZUSP 2392; ZUEC-POL 16122), 22 Feb 2009, and 3 specs ( MZUSP 2399; ZUEC- POL 16128), 2 Jul 2009; 23°10'4"S 41°3'6"W, 105 m: 4 specs ( MZUSP 2388; ZUEC-POL 16118), 21 Feb 2009, and 3 specs ( MZUSP 2389; ZUEC-POL 16119), 2 Jul 2009; 23°11'28"S 41°0'49"W, 117 m: 8 specs ( MZUSP 2391; ZUEC-POL 16121), 21 Feb 2009; 23°12'8"S 40°59'35"W, 142 m: 2 specs ( MZUSP 2390; ZUEC-POL 16120), 2 Jul 2009.

Additional material examined. Opisthodonta morena —Atlantic Ocean, Josephine Bank (36°40.7'N 14°15.5'W): 17 specs ( ZMH P- 17193), coll. 'Meteor 9c', station 120, 0 1 Jul 1967, det. G. Hartmann-Schröder, 1979. Opisthodonta mitchelli Kudenov & Harris, 1995 — USA, California, Santa Maria Basin, off Point Arguello (34°30'15"N 120°35'34"W), 54–63 m: 1 spec. (holotype, USNM 170919), coll. SAIC / Mbc BLM / MMS, R/V Diaphus DS, 11 Jul 1984, det. Kudenov & Harris, 1995; off Purisima Point (34°46'14"N 120°49'58"W), 91.5–123 m: 1 spec. (paratype, USNM 170920), coll. SAIC / Mbc BLM / MMS, R/V Diaphus DS, 23 Jul 1984, det. Kudenov & Harris, 1995.

Description. Medium-sized, fragile body, specimens examined mostly anterior fragments, with few chaetigers after proventricle segments; largest fragment 2.6 mm long, 0.52 mm wide, with 26 chaetigers; body without pigmentation patterns, dorsally with transverse rows of tufts of cilia, at least on midbody ( Fig. 13 B, D). Palps foliaceous, broader than prostomium, frequently ventrally folded ( Figs 11 A; 12A–B; 13A). Prostomium oval to pentagonal, with 2 pairs of eyes in trapezoidal arrangement and 1 pair of anterior eyespots ( Fig. 11 A); lateral antennae inserted in front of anterior pair of eyes, near anterior margin of prostomium, up to twice as long as combined length of prostomium and palps; median antenna inserted centrally, almost twice as long as lateral antennae ( Figs 11 A; 12A–B); nuchal organs as paired, transverse, dorso-lateral rows of cilia at posterior margin of prostomium ( Fig. 12 A–B). Peristomium dorsally short, frequently covered by prostomium and chaetiger 1; dorsal peristomial cirri of approximately same size as median antenna, ventral peristomial cirri with approximately same size as lateral antennae or slightly longer ( Figs 11 A; 12A–B). Dorsal cirri of anterior chaetigers, specially of chaetiger 1, long and slender, sometimes conspicuously longer than median antenna ( Fig. 11 A); dorsal cirri alternating long, almost twice as long as body width, and short, slightly longer than half body width at corresponding chaetiger ( Figs 11 A; 12A; 13B); ventral cirri large, ovate, partially fused to parapodial lobes on anterior segments ( Fig. 13 A, C); from proventricle segments onwards, ventral cirri short, conical, shorter than parapodial lobes and free from them ( Fig. 12 C). Antennae, peristomial and dorsal cirri throughout similar, long and slender, with short cirrophores ( Figs 11 A; 12C; 13B). Anterior body parapodia with ~20–25 falcigers each, decreasing to ~5–10 falcigers per parapodium from midbody onwards; falcigers with shafts and blades spinulated, blades with spines slightly distally directed, bidentate; on anterior body, 2–4 dorsalmost falcigers with longer blades, ~30–22 µm long, teeth of even size or distal tooth slightly larger, rounded space between teeth; blades of remaining falcigers of anterior parapodia ~17–13 µm long, subdistal tooth of same size or slightly larger than distal tooth ( Figs 11 B; 12D); on midbody parapodia, 1–2 dorsalmost falcigers with blades 22–20 µm long, blades of remaining falcigers ~15 µm long, subdistal tooth progressively larger and more hooked towards posterior body ( Fig. 11 C). Dorsal simple chaetae only present on posteriormost parapodia, thin, slightly spinulated subdistally, bidentate, teeth minute, of even size, with rounded space between teeth ( Fig. 11 D); ventral simple chaetae only present on posteriormost parapodia, sigmoid, bidentate, subdistal tooth larger ( Fig. 11 E); dorsal and ventral simple chaetae sometimes present from anterior body, in juveniles. Anterior body parapodia with up to 4 aciculae each ( Fig. 11 F), aciculae per parapodium diminishing towards posterior body, from midbody onwards only 1 acicula per parapodium ( Fig. 11 G); aciculae progressively thinner towards posterior body, distally tapering, with rounded tips protruding from parapodial lobes ( Fig. 12 D), more evidently on posterior body. Pharynx long and wide, through 8–12 segments, with large, conical to pyriform tooth near midlength or slightly anteriorly; proventricle through 7–8 segments, with ~23 muscle cell rows ( Fig. 11 A).

Remarks. Opisthodonta morena closely resembles O. mitchelli , from California ( USA), but both can be differentiated mostly by posterior body features: in O. mitchelli aciculae have tips slightly bent, and falciger blades have a finer spinulation and the subdistal tooth conspicuously larger than the distal tooth, which resembles an enlarged spine in some chaetae; on the other hand, in O. morena all aciculae are straight ( Fig 11 F–G), and the falciger blades have coarser spinulation and less pronounced difference in sizes between the teeth.

Brazilian specimens of O. morena are virtually indistinguishible from those from close to the type locality (Josephine Banks, Atlantic Ocean). As the species is reported from nearly all over the world (see below), it is a possible case of a complex of sibling-species.

Type locality. Atlantic Ocean: Portugal—Madeira Island

Distribution. Pacific Ocean: Australia (New South Wales). Indic Ocean: Australia (Western Australia), Red Sea. Mediterranean Sea. Atlantic Ocean: Madeira Island. First occurrence for the Brazilian coast.

Figures

FIGURE 11. Opisthodonta morena. (A) anterior body, dorsal view; (B) falcigers, anterior body; (C) falcigers, mid- and posterior body; (D) dorsal simple chaeta; (E) ventral simple chaeta; (F) aciculae, anterior body; (G) acicula, posterior body. Scale bars: A = 200 µm; B – G = 10 µm.

FIGURE 12. Opisthodonta morena, SEM. (A) Anterior body, dorsal view; (B) prostomium, dorsal view; (C) posterior body, ventral view; (D) anterior body parapodia, dorsal view. Scale bars: A, C = 100 µm; B = 50 µm; D = 20 µm.

FIGURE 13. Opisthodonta morena, SEM. (A) Anterior body, fronto-ventral view; (B) midbody, dorsal view; (C) anterior body, ventro-lateral view; (D) tufts of cilia on dorsum, midboy. Scale bars: A – B = 100 µm; C = 50 µm; D = 20 µm.