Sphaerodoridium celiae Moreira, Capa & Parapar

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 : 66-71

Sphaerodoridium celiae Moreira, Capa & Parapar sp. n. Figs 5U, 23E, F, 25, 26, 27A

Type locality.

NW Iceland, 67°30.76'N, 24°10.03'W, 1012 m.

Material examined.

Type series: Holotype: IINH 38817, Iceland, 67°30.72'N, 24°10.03'W, 1012 m, 25 Aug 1999. Paratypes (535 specs).: IINH 38795 (6 specs on SEM stub), 63°08.60'N, 22°14.80'W, 248 m, 30 June 1996; IINH 38796 (1 spec.), 67°0.25'N, 17°25.01'W, 248 m, 10 July 1994; IINH 38797 (1 spec.), 67°55.91'N, 15°21.29'W, 1098 m, 13 July 1994; IINH 38798 (3 specs), 66°50.20'N, 16°15.74'W, 227 m, 15 July 1994; IINH 38799 (2 specs), 66°43.92'N, 16°50.54'W, 150 m, 15 July 1994; IINH 38800 (1 spec.), 68°01.13'N, 20°39.28'W, 970 m, 31 July 1995; IINH 38801 (34 specs), 63°15.00'N, 17°59.40'W, 175 m, 24 Aug 1995; IINH 38802 (26 specs), 63°30.12'N, 17°42.07'W, 120 m, 25 Aug 1995; IINH 38803 (20 specs), 63°25.06'N, 16°50.40'W, 272 m, 25 Aug 1995; IINH 38804 (22 specs), 62°20.17'N, 16°59.40'W, 2074 m, 28 Aug 1995; IINH 38805 (6 specs), 65°21.22'N, 27°25.43'W, 513 m, 24 Aug 1996; IINH 38806 (19 specs), 65°31.14'N, 26°13.11'W, 157 m, 28 Aug 1996; IINH 38807 (25 specs), 65°39.90'N, 26°11.33'W, 166 m, 28 Aug 1996; IINH 38808 (5 specs), 65°42.18'N, 25°16.99'W, 160 m, 29 Aug 1996; IINH 38809 (31 specs), 65°08.01'N, 23°36.17'W, 120 m, 30 Aug 1996; IINH 38810 (207 specs), 63°45.60'N, 14°50.60'W, 216 m, 5 July 1997; IINH 38811 (33 specs), 67°11.02'N, 21°45.68'W, 230 m, 21 Aug 1999; IINH 38812 (42 specs); IINH 38813 (9 specs), 66°10.23'N, 12°00.94'W, 243 m, 14 July 2001; IINH 38814 (11 specs), 65°50.34'N, 12°01.27'W, 192 m, 14 July 2001; IINH 38815 (1 spec.), 68°00.92'N, 009°14.78'W, 1727 m, 16 July 2004; IINH 38816 (30 specs), 66°31.42'N, 20°56.69'W, 200 m, 27 July 2004.

Additional material.

(17 specs) Barents Sea: ZMBN 127338 (1 spec.), Finnmark 71°16.53'N, 27°0.94'E, 278 m, 16 Apr 2011; ZMBN 127336, (1 spec. used for DNA sequencing, SPH 279), Finnmark, 71°20.262'N, 25°13.17'E, 297 m, 23 Apr 2011. ZMBN 127337 (1 spec. used for DNA sequencing, SPH013), Finnmark 71°16.53'N, 27°0.94'E, 278 m, 16 Apr 2011; Skagerrak: ZMBN 127335 (4 spec.), 58°35.254'N, 10°19.395'E, 274 m, 14 May 2009; ZMBN 127334 (3 spec.), 58°33.795'N, 10°23.725'E, 254 m, 14 May 2009; ZMBN 103136 (1 spec. used for DNA sequencing, SPH008), 58°35.254'N, 10°19.395'E, 274 m, 14 May 2009; ZMBN 127333 (1 spec. used for DNA sequencing, SPH014.), Skagerrak 58°33.795'N, 10°23.725'E, 254 m, 14 May 2009; ZMBN 125434 (1 spec. used for DNA sequencing, SPH316 photographed alive, Fig. 27A), 58°30.733'N, 10°25.109'E, 275 m, 14 May 2009; ZMBN 127339 (1 spec. used for DNA sequencing, SPH317), 58°30.733'N, 10°25.109'E, 275 m, 14 May 2009; ZMBN 127340 (1 spec. used for DNA sequencing, SPH318), 58°30.733'N, 10°25.109'E, 275 m, 14 May 2009; ZMBN 127341 (1 spec. used for DNA sequencing, SPH319), 58°30.733'N, 10°25.109'E, 275 m, 14 May 2009.

Diagnosis.

Body ellipsoid with strongly convex dorsum and flat ventrum, up to 6 mm long. Median antenna and head appendages digitiform, elongated. Median antenna smooth, shorter than other head appendages. Lateral antennae and palps similar, with 4-10 papillae (spurs) on proximal half. Antenniform papillae absent. Tentacular cirri digitiform, with 2-3 elongated papillae on proximal third. Dorsal macrotubercles stalked, without terminal papilla, arranged in 10-12 longitudinal rows in mid-body chaetigers; stalk half as long as tubercle, with 0-1 small papilla on proximal half. Dorsum with up to additional 50-60 spherical-oval papillae with short stalk, in front of each row of macrotubercles, somewhat arranged in 3-4 irregular transverse rows roughly following a zig-zag pattern. Ventrum with ca. 20 papillae per segment in mid-body, arranged in at least four more or less defined transverse rows in a zig-zag pattern. Parapodia with digitiform acicular lobe from chaetiger 3; large ventral cirri, not surpassing the length of acicular lobe; mid-body parapodia with 7-8 papillae. Chaetae blades showing slight gradation in length between chaetigers, slightly shorter in posterior chaetigers; ca. 8-9 times longer than maximum width.

Description.

Measurements and general morphology. Holotype 5.5 mm long, 0.8 mm wide; with 29 segments (Figs 25A, 27A). Body ellipsoid with strongly convex dorsum and flat ventrum. Segmentation not distinct. Pigmentation absent (Fig. 27A).

Head. Prostomium with five digitiform elongated appendages, including a pair of palps and lateral antennae, similar in size and shape, and a shorter median antenna (Fig. 25C, D). Lateral antennae and palps with ca. 8-10 papillae (spurs) on proximal half. Tentacular cirri shorter than lateral antennae and palps, with three papillae on proximal third. Many rounded to digitiform small papillae scattered around head appendages (Fig. 25C, D).

Tubercles. First chaetiger with 12 dorsal macrotubercles (Fig. 25A); following chaetigers each with one transverse row of 12 (sometimes 11 or 13) dorsal macrotubercles, last chaetiger with ten macrotubercles. Macrotubercles spherical to club-shaped with a stalk near half-length of macrotubercle; first six chaetigers with smooth stalk, from chaetiger 7 backwards stalk provided with small basal papilla (Figs 25B, 26B); all macrotubercles mostly similar in shape and size (Fig. 23E). Additional spherical-oval papillae in different sizes over dorsum, with short stalk, somewhat arranged in 3-4 irregular transverse rows per chaetiger roughly following a zig-zag pattern; ranging from 40 to 60 papillae on each mid-body chaetiger (Fig. 23E). Ventral surface with spherical papillae with short stalk, arranged in four transverse rows in a zig-zag pattern, with ca. 20 papillae per segment in mid-body; numbers decreasing towards posterior end (Figs 23F, 26C).

Parapodia. Parapodia sub-conical, increasing in size towards chaetiger 3-4 (Fig. 25 E–G), ca. 2-2.5 times longer than wide, some with wrinkled appearance (Figs 25E, 26 D–G). Acicular lobe anterior to chaetae, digitiform, longer than parapodial papillae and projecting distally (Figs 25 G–J, 26G). Ventral cirri digitiform projecting 1/2 to 2/3 as long as acicular lobe on anterior mid-body segments, almost as long as in posterior segments (Figs 25I, J, 26 D–G). First three chaetigers with parapodia provided with 3-5 spherical to clavate papillae: one on antero-dorsal surface, one on antero-lateral surface, one on medio-ventral surface, and two on posterior surface opposite to acicular lobe (Fig. 25E, F); following chaetigers through mid-body with up to three additional papillae: one on posterior surface opposite to acicular lobe, one on antero-lateral/lateral surface and one on ventro-basal position (Fig. 5U); last 3-4 chaetigers lacking some of aforementioned papillae.

Chaetae. All parapodia with 8-10 compound chaetae, arranged in a curved transverse row around acicular lobe (Figs 5U, 26G, H). Shaft distal end with thin spinulation (Fig. 26I). Serrated, long blades, 8-9 times longer than maximum width, with a curved tip (Fig. 26H, J), blades slightly shorter in posterior chaetigers.

Pygidium. Pygidium terminal, with one mid-ventral digitiform anal cirrus projecting beyond last parapodia, flanked by four spherical papillae (2+2) and one pair of clavate anal cirri at base (Fig. 25K).

Internal features. Eyes not discernible in holotype. Pharynx extending over three chaetigers.

Reproductive features. Sexual structures or genital pores not observed in holotype. Several oblong eggs visible by transparency ca. 170 µm in length.

Variation.

Paratypes measuring 1.1-6.0 mm long, 0.4-0.9 mm wide, with 16-30 chaetigers. Most specimens measuring ca. 2-4 mm in length, 0.4-0.7 mm in width with 20-25 chaetigers. Two dark dorsal eyes behind lateral antennae observed in many paratypes. Some variation occurring in number of papillae and spurs on head appendages: lateral antennae and palps with at least four spurs and tentacular cirri with two short papillae near base. Macrotubercles numbering 7-11 on first chaetiger and usually 10-12 in mid-body. Small papilla at base of macrotubercle stalk not distinguished in all specimens, not related to size or degree of contraction of stalks or body. Short stalk of body papillae (dorsum and ventrum) not always distinguished. Variation in number and distribution of body, ventrum, and parapodial papillae similar to holotype. Pharynx extending over 3-4 chaetigers. Sexual dimorphism not observed in paratypes or additional material examined; several females with oocytes observed.

Remarks.

Sphaerodoridium celiae sp. n. is characterized by the unique combination of following features: head appendages with up to ten spurs or basal papillae, 10-12 stalked macrotubercles per mid-body chaetiger, many body papillae among rows of macrotubercles (up to 50 per chaetiger), ventrum of each mid-body chaetiger with at least 20 papillae, and chaetae with blades up to 8-9 times as long as wide.

Sphaerodoridium cf. minutum , from European waters (see below), also presents a similar range of variation in the number of macrotubercles, many dorsal additional papillae between consecutive rows of macrotubercles and ca. 20 papillae per chaetiger on ventrum. However, Sphaerodoridium celiae sp. n. bears more dorsal papillae per chaetiger showing a more “crowded” appearance (up to 50-60) and parapodial papillae are more numerous (7-8 vs. 3). Sphaerodoridium guerritai is also similar to Sphaerodoridium celiae sp. n. in general body appearance and size but dorsal body papillae are less numerous being dorsal side of chaetigers more “smooth”; stalk of macrotubercles are usually provided with at least a small papilla (sometimes up to three) while in Sphaerodoridium celiae sp. n. the presence of the only papilla is more variable across specimens or at least harder to distinguish. The number of parapodial papillae is similar between both species but they differ in their distribution, mostly in the presence in S. guerritai of one papilla on the anterior lateral surface that is lacking in Sphaerodoridium celiae sp. n.; the former presents, in turn, one anterior papilla that is present instead on the dorsal surface (cf. Fig. 5U).

The three species recently described from Arctic waters ( S. evgenovi Gagaev, 2015; S. kolchaki Gagaev, 2015; S. kupetskii Gagaev, 2015) also present up to 10-14 macrotubercles per chaetiger and dorsal body papillae. However, the original description does not mention explicitly how many papillae are between two consecutive rows of macrotubercles. Furthermore, the drawings of the stalk of the macrotubercles of the three species show a small basal papilla that is not mentioned in the description, and is similar to that present in S. guerritai and Sphaerodorodium celiae sp. n. The aforementioned species differ, however, from Sphaerodoridium celiae sp. n. in the number and distribution of parapodial papillae (only 2-3). On the other hand, Gagaev (2015) characterizes S. evgenovi , S. kolchaki and S. kupetskii according to the relative length of anal cirri, macrotubercle stalk and body length but these characters may show variation according to the state of contraction of specimens. Otherwise, they are morphologically close to S. guerritai and a comparative review of the four species would be desirable ( Capa et al. 2016b).

Etymology.

This new species is dedicated to Celia Moreira, in regard of her support and friendship to her brother, JM.

Distribution.

Around Iceland and coastal Norwegian waters from the Skagerrak in the south to Finnmark in the north.

Habitat.

Soft bottoms, from gravelly sand to silt, at depths of 120-2074 m.