Sphaerephesia sibuetae ( Desbruyeres , 1980) Desbruyeres, 1980

Capa, Maria, Nygren, Arne, Parapar, Julio, Bakken, Torkild, Meissner, Karin & Moreira, Juan, 2019, Systematic re-structure and new species of Sphaerodoridae (Annelida) after morphological revision and molecular phylogenetic analyses of the North East Atlantic fauna, ZooKeys 845, pp. 1-97 : 56-58

Sphaerephesia sibuetae ( Desbruyeres, 1980) comb. n. Figs 5Q, 15O, P, 22

Sphaerodoropsis sibuetae Desbruyères, 1980: 226-229, Figs 9-10; Moreira et al. 2011: 26-28, Fig. 1.

Type locality.

Banc le Danois, Bay of Biscay, 44°5.2'N, 05°19.4'W, 1913 m.

Examined material.

Holotype: MNHN TYPE1284, Banc Le Danois, Bay of Biscay, 44°05.2'N, 5°19.4'W, 1913 m. Paratypes: same sample (6 specs, 2 on SEM stub).

Additional material.

(28 specs) Iceland, SMF 25297, (16 specs), Irminger Basin, 63°00.46'N, 028°04.09'W, 1593m, 8 Sep 2011; SMF 23906 (1 spec. used for DNA sequencing, SPH273), Irminger Basin, 63°00.46'N, 028°04.09'W, 1593m, 8 Sep 2011; SMF 23906 (1 spec. used for DNA sequencing, SPH 044), Irminger Basin, 63°00.46'N, 028°04.09'W, 1593m, 8 Sep 2011; SMF25298 (22 specs), Irminger Basin, 63°00.46'N, 028°04.09'W, 1593 m, 8 Sep 2011; SMF24855 (1 spec. used for DNA sequencing, SPH273), Irminger Basin, 63°00.46'N, 028°04.09'W, 1593 m, 8 Sep 2011; ZMBN 127325 (8 specs) South Iceland, 61°38.2'N, 16°27.7'W, 2355 m, 5 Jun 1983. NW Iberian Peninsula, MNCN 16.01/13268 (1 spec.), 42°31.66'N, 09°40.06'W, 1974-2034 m, 29 Sep 2008.

Diagnosis.

Body ellipsoid, flattened dorsoventrally, up to 5 mm long. Head appendages smooth, lacking spurs or basal papillae. Antenniform papillae present. Four longitudinal rows of macrotubercles, in a single transverse row per segment, from segment two. Macrotubercles sessile, pear-shaped or with terminal papilla. Small spherical papillae scattered on dorsal (four irregular transverse rows with ca. 30 papillae per segment) and on ventral surfaces (four irregular transverse rows per segment). Parapodia with acicular lobe from segment 1, with 16-19 rounded sub-equal papillae, apparently randomly arranged. Approximately 20-25 compound chaetae with long blades (9-13 times as long as wide).

Re-description of holotype.

Measurements and general morphology. Holotype 2.82 mm long, 0.5 mm wide and with 19 segments. Body with rounded anterior end, tapering from segment 6 to pygidium, circular in transverse section. Segmentation not conspicuous and pigmentation absent (Fig. 22A).

Head. Head fused to first segment (Fig. 22A, B). Prostomial appendages, palps, lateral antennae, and median antenna conical (Fig. 22 B–D). Palps and lateral antennae three times longer than wide, smooth, and lacking spurs or basal papillae (Fig. 22 B–D). Median antenna almost one third of the length of lateral antennae, digitiform (Fig. 22B, C). Antenniform papillae present (Fig. 22C). Head papillae rounded, numerous and randomly arranged (over 20 papillae enclosed by prostomial appendages). Tentacular cirri digitiform, shorter than lateral antennae and longer than median antenna (Fig. 22B, C).

Tubercles. Four longitudinal rows of dorsal macrotubercles, in one transverse row per segment, from segment 2 (Figs 15O, 22A). Macrotubercles, sessile, large pear-shaped or with a terminal papilla (Fig. 22A, E–H, L). Additional papillae, rounded, arranged in three or four irregular transverse rows along dorsal and ventral surfaces (Figs 15O, P, 22E, M).

Parapodia. Parapodial conical or cylindrical, three or four times longer than wide at mid-body (Fig. 22 G–I). Ventral cirri digitiform, as long as maximum wide of parapodia, reaching the tip of the acicular lobe (Fig. 22H, I). Acicular lobe from chaetiger 1. Parapodial papillae (16-19) rounded, hemispherical and randomly distributed over their surface, being one, dorsal to acicular lobe, slightly larger than the rest. Three papillae on dorsal surface, 6-7 anterior, 3-4 ventral and 4-5 posterior (Figs 5Q, 22 G–I).

Chaetae. All chaetae compound, ca. 15-25 in mid-body chaetigers, with long, unidentate compound chaetae with long blades (ca. 9-13 times their width showing some variation within parapodia) and with finely serrated edge (Fig. 22J, K). One straight acicula per parapodia.

Pygidium. A pair of globular anal cirri, similar to dorsal macrotubercles but smaller and digitiform medio-ventral anal papilla similar in length to lateral cirri (Fig. 22L, M).

Internal features. Muscular pharynx present through segments 1-4. Nuchal organs openings behind lateral antennae.

Reproductive features. Sexual structures or genital pores not observed in holotype.

Variation.

Size range of material examined: 2-5 mm long; 0.8-1.5 mm wide; with 17-31 chaetigers. Sexual dimorphism or reproductive features not observed in paratypes or additional material examined. Everted pharynx bare (Fig. 22D).

Remarks.

The species was originally considered as belonging to Sphaerodoropsis ( Desbruyères 1980) even though the original description and iconography revealed that specimens have pear-shaped macrotubercles or with distal papilla; this was corroborated with the new scanning electron micrographs of paratypes provided herein (e.g., Fig. 22A).

Sphaerephesia sibuetae comb. n. differs from other species reported as presenting dorsal pear-shaped macrotubercles or with terminal papilla in the following combination of features: ellipsoid in shape, flattened dorsoventrally; head appendages smooth, without spurs or basal papillae; four irregular transverse rows of rounded papillae in both dorsum and ventrum, with ca. 30 papillae per segment; parapodia with ca. 16-19 papilllae and 15-25 compound chaetae with blades up to 13 times longer than wide in mid chaetigers. Other NEA similar congeners include Sphaerephesia multichaeta sp. n., distinguished from S. sibuetae in the chaetal morphology (with shorter blades, up to seven times longer than wide) while S. sibuetae have longer blades (7-13 times as long as wide).

Distribution.

Newly recorded in southern Iceland (present study). Previously reported in Bay of Biscay and NW Iberian Peninsula ( Moreira et al. 2011).

Habitat.

Sediments at 1400-2000 m ( Desbruyères 1980, Moreira et al. 2011, present study).