Euritmia carolensis, Capa, Maria, Osborn, Karen J. & Bakken, Torkild, 2016

Capa, Maria, Osborn, Karen J. & Bakken, Torkild, 2016, Sphaerodoridae (Annelida) of the deep Northwestern Atlantic, including remarkable new species of Euritmia and Sphaerephesia, ZooKeys 615, pp. 1-32 : 7-11

Taxon classification Animalia Phyllodocida Sphaerodoridae

Euritmia carolensis sp. n. Figs 3, 4

Material examined.

Holotype: USNM 1001792, Off Charleston Bump South Carolina United States 32.3944N, 77.0181W, 799 m, coll. Battelle/Woods Hole Oceano graphic Institute for BLM/ MMS, Atlantic Slope and Rise Program, ASLAR, 18 Nov 1985. Paratypes: USNM 1001791 (1 ind.), off Cape Fear, North Carolina, 33.0806N, 76.4194W, 896 m, 23 Sep 1985; USNM 1001793 (1 ind.), off New Jersey, 38.5944N, 72.8953W, 2024 m, 13 Nov 1985.

Type locality.

Off Charleston Bump, South Carolina, 799 m.

Diagnosis.

Body short and ellipsoid. Dorsum with approximately 20 sessile spherical papillae arranged in three transverse rows per segment. Ventrum with 4-6 larger papillae near the parapodial bases. Prostomial and peristomial appendages short and ellipsoidal. Parapodia without papillae; with 4-5 simple chaetae with serrated cutting edges, enlarged sub-distally.

Description.

Measurements and general morphology. Holotype 0.5 mm long, 0.2 mm wide, with 12 chaetigers; gravid female. Body ellipsoid, with strongly convex dorsum and flattened ventrum. Epithelium with transversal wrinkles, segmentation not noticeable (Fig. 4A, B). Pigmentation absent on preserved material.

Head. Head fused to first chaetiger (Figs 3A, 4A, B). Prostomial appendages ellipsoid, slightly longer than wide (Figs 3A, 4A). Pair of palps and pair of lateral antennae similar in size, median antenna smaller (Fig. 4B). Dorsal antenniform papillae absent or not conspicuous. Few small hemispherical papillae scattered on head surface, approximately four arranged among palps and antennae. Tentacular cirri, ellipsoid, smaller than palps, similar in size and shape to median antenna (Fig. 4A). Eyes not observed.

Tubercles. Dorsum with three transverse rows of papillae per segment (Figs 3A, 4A, B). Papillae sessile, spherical but some larger and ellipsoid papillae over dorsum (Figs 3 C–E, 4A), over 20 per segment on mid-body chaetigers. Ventrum with fewer and larger spherical papillae, arranged near parapodial bases in two transverse rows, about 4-6 papillae per segment (Fig. 4B).

Parapodia. Parapodia conical, as long as wide in all chaetigers (Fig. 4D), small in anterior chaetigers. Acicular lobe hemispherical; ventral cirri ellipsoid longer than acicular lobe (Fig. 4D). No additional papillae or parapodial appendages.

Chaetae. Large, recurved hooks in first chaetiger absent. All parapodia with 4-5 simple chaetae; blades seemingly smooth on cutting edge and slight curved distal tip (Figs 3D, E, 4D, E). One straight acicula per parapodium.

Pygidium. Pygidium with two dorsolateral pear-shaped tubercles and single midventral digitiform cirrus, longer than lateral cirri (Fig. 4C).

Internal features. Muscular pharynx visible though body wall from chaetiger 2-5.

Reproductive features. Copulatory organs not observed. Ovoid eggs measuring 100 µm diameter occupy most of the coelomic cavity.

Variation.

The two paratypes lack eggs, other features are very similar.

Remarks.

Euritmia carolensis sp. n. is distinguished from other congeners by the presence of dorsal papillae arranged in three transverse rows per segment. Most of these are spherical and similar in size but some in a dorsal-most position are elliptical and larger, without a clear distribution pattern. Euritmia hamulisetosa is provided with spherical papillae, all similar in size, in four transverse rows per segment; Euritmia capense bears two different sizes of spherical papillae each on a single transversal row per segment; and Euritmia bipapillatum bears both hemispherical and elliptical papillae in three transversal rows per segment and with a particular zig-zag arrangement ( Day 1963, 1967, Sardá-Borroy 1987, Kudenov 1987a) (Table 2). The number and arrangement of ventral papillae are also distinct in the new species, with two transverse rows of 4-6 papillae, mainly arranged near the parapodial bases, while the other species (unknown for Euritmia capense ) bear numerous papillae with similar arrangement to the dorsum. The parapodia are in all cases conical and small, but only Euritmia carolensis sp. n. lacks parapodial papillae; the only appendices present on parapodia being acicular lobe and the ventral cirrus.

Etymology.

The epithet of this species refers to the type locality North Carolina.

Distribution.

North Carolina to New Jersey (US), from 799 to 2014 m.