Sphaerephesia ponsi Capa, Parapar & Moreira

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 : 54-56

Sphaerephesia ponsi Capa, Parapar & Moreira sp. n. Figs 5P, 15M, N, 21

Type locality.

Irminger Basin, SW of Iceland, North Atlantic Ocean, 63° 0.46'N, 28° 4'W, 1593 m.

Examined material.

Holotype: SMF 25295, Irminger Basin, SW of Iceland, 63°00.46'N, 28°04.09'W, 1593 m, 8 Sep 2011. Paratypes SMF 24841 (1 spec. used for DNA sequencing and SEM, SPH047), Irminger Basin, SW of Iceland, 63°00.46'N, 28°04.09'W, 1593 m, 8 Sep 2011; SMF 25296 (1 spec., on SEM stub), Irminger Basin, SW of Iceland, 63°00.46'N, 28°04.09'W, 1593 m, 8 Sep 2011.

Diagnosis.

Body ellipsoid, flattened dorsoventrally. Body unpigmented (fixed specimen). Head appendages smooth and digitiform. Tentacular cirri smaller than prostomial appendages. Dorsum with four longitudinal rows of large, sessile and pear-shaped macrotubercles in a single transverse row per segment, from segment 2. Additional papillae on dorsum and ventrum. Acicular lobe from segment 1. Parapodia with four papillae. Ventral cirri digitiform reaching tip of acicular lobe. Approximately eight compound chaetae with medium length blades (7-9 times as long as wide); unidentate.

Description.

Measurements and general morphology. Holotype 1.8 mm long, 0.5 mm wide; with 12 chaetigers (Fig. 21A). Body ellipsoid. Segmentation not conspicuous.

Head. Head fused to first segment (Fig. 21 A–C). Head appendages digitiform (Fig. 21C). Palps and lateral antennae three times longer than wide, smooth, and lacking spurs or basal papillae (Fig. 21C). Median antenna two-thirds the length of lateral antennae, slightly wider (Fig. 21C). Antenniform papillae absent (Fig. 21C). Head papillae elliptical, ca. 20 papillae enclosed by prostomial appendages. Tentacular cirri digitiform, similar in shape and size to lateral antennae (Fig. 21C).

Tubercles. Four longitudinal rows of dorsal macrotubercles, in one transverse row per segment, from segment 2 (Fig. 21 A–E). Macrotubercles, sessile, large, pear-shaped or with a terminal papilla (Fig. 21 A–E). Distance between mid-dorsal rows larger than between these and lateral longitudinal rows of macrotubercles. Additional papillae, rounded, arranged in three or four irregular transverse rows along dorsal and ventral surfaces (Figs 15M, N, 21A). Ventrum with few papillae in holotype.

Parapodia. Parapodial conical, as long as wide (Fig. 21 F–J). Ventral cirri conical, as long as maximum wide of parapodia, reaching the tip of the acicular lobe, or shorter (Fig. 21G, H, K). Acicular lobe from chaetiger 1. Anterior segments with two parapodial papillae, one ventral, near the base of parapodium and one posterior (Fig. 21 F–H). Three or four parapodial papillae in mid-body segments, sub-equal, rounded (one dorsal, one or two anterior, one ventral near base of parapodium) (Figs 5P, 21G, J).

Chaetae. All chaetae compound, ca. eight in mid-body parapodia, with medium size blades (7-9 times as long as wide), unidentate, with finely serrated edge (Fig. 21L, M). One straight acicula per parapodia.

Pygidium. A pair globular anal cirri, similar to dorsal macrotubercles but smaller and digitiform medio-ventral anal papilla similar in length to lateral cirri (Fig. 21I).

Internal features. Holotype with everted proboscis, as long as 5-6 segments. Eyes not observed.

Reproductive features. No gametes, sexual structures, or genital pores observed.

Variation.

Paratypes 1-2 mm long, 0.3 mm wide, 15-17 segments. Epithelial parapodial papillae are more evident in paratypes, and ventral papillae include of ca. 20 rounded and sub-equal papillae, arranged in four irregular transverse rows per segment (Fig. 15N). Acicular lobe and ventral cirri are almost spherical in holotype while in the paratypes show longer and digitiform parapodial appendages. The rest of features are consistent among specimens studied.

Remarks.

Sphaerephesia ponsi sp. n. is distinguished from other congeners by the unique combination of following features: head appendages smooth and without spurs or basal papillae, antenniform papillae absent, macrotubercles in four longitudinal rows, pear-shaped and with terminal papillae, parapodial papillae with four spherical papillae, chaetae with blades up to nine times as long as wide. Other Sphaerephesia with ca. four parapodial papillae are S. artabrensis comb. n., S. mamalaensis , S. longisetis comb. n., and S. amphorata . Sphaerephesia amphorata is clearly distinguished from S.  ponsi  sp. n. in the shape of the macrotubercles, with a long terminal papilla. Sphaerephesia ponsi sp. n. is distinguished from S. artabrensis comb. n. and S. longisetis in the length of chaetal blades, over ten times as long as wide in the former two species and shorter in the new species; and shorter in S. mamalaensis (up to six times as long as wide).

Etymology.

This new species is dedicated to Joan Pons, a researcher from the Mediterranean Institute of Advanced Studies (IMEDEA), Balearic Islands, colleague, and friend.

Distribution.

Only known from type locality, the Irminger Basin in the North East Atlantic.

Habitat.

Sediments at ca. 1600 m.