Sphaerodoropsis corrugata Hartman & Fauchald, 1971

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 : 19-22

Taxon classification Animalia Phyllodocida Sphaerodoridae

Sphaerodoropsis corrugata Hartman & Fauchald, 1971 Figs 8, 9

Sphaerodoropsis Hartman & Fauchald, 1971: 69-71, pl 34, figs a, b.

Sphaerodoridium sp. A. - Hartman 1965: 94, Pl. 14, fig. f.

Material examined.

Holotype: LACM- AHF POLY 950, west of Atlantis Canyon, New England continental slope, North Atlantic, 39°56.5'N, 70°39.9'W, 400 m, 28 Aug 1962. Additional material. USNM 1002203 (1 ind.), off Massachusetts, United States, North Atlantic Ocean, 40°01.284'N, 70°55.032'W, 255 m, 8 Dec 1984; USNM 1002207 (6 ind., 3 for SEM) Lydonia Canyon, Georges Bank, United States, 40°21.114'N, 67°32.232'W, 590 m, 28 Apr 1985; USNM 1002209 (4 ind.) ff Massachusetts, United States, 40°01.248'N, 70°55.086'W, 250 m, 4 May 1985; USNM 1002193 (2 ind., 1 for SEM), Off Cape Hatteras, North Carolina, United States, 35°26.268'N, 74°41.436'W, 2003 m, 24 May 1985; USNM 1002212 (1 ind.) off Massachusetts, United States, 39°50.382'N, 70°01.65'W, 1239 m, 27 Nov 1985; USNM 1001989 (2 juvenile ind.) off New Jersey, United States, 38°40.068'N, - 072°56.418'W, 1519 m, 13 Nov 1985; USNM 1001830 (1 ind.), Baltimore Canyon, United States, 37°53.286'N, 73°45.264'W, 1619 m, 7 Aug 1984; USNM 1002032 (1 ind.), off Massachusetts, 39°48.36'N, 70°54.93'W, 1249 m, coll. Battelle-New England Marine Research Lab For BLM/ MMS, 30 Nov 1985; USNM 1002033 (1 ind.), Georges Bank, 41°01.35'N, 66°20.23'W, 1345 m, coll. Battelle-New England Marine Lab For BLM/ MMS, 25 Jul 1986; USNM 1002035 (1 ind.), Georges Bank, 41°01.54'N, 66°20.11'W, 1345 m, coll. Battelle-New England Marine Lab For BLM/ MMS, 25 Jul 1986.

Comparative material.

Sphaerephesia fauchaldi Kudenov, 1987b, holotype NMNH 102785; Sphaerephesia longisetis Fauchald, 1972, holotype AHF POLY 0964; Sphaerephesia regularis Böggemann, 2009, holotype ZMH P25498, paratypes ZMH P25497 (4 ind.), ZMH P25499 (4 ind.); Sphaerephesia similisetis Fauchald, 1972, paratype AHF POLY 0967 (2 ind.). Sphaerephesia hutchingsae Capa & Bakken, 2015, holotype East of Malabar, Sydney, New South Wales, Australia, AM W.42748, 33°58.71667'S, 70°39.9'E, 82 m, 22 Aug 1995; paratypes from nearby collecting sites (see Capa and Bakken 2015).

Diagnosis.

Body ellipsoid, with four longitudinal rows of sessile, rounded to pear-shaped macrotubercles without terminal papillae, per segment. Distance between dorsal-most macrotubercles exceeds distance between those and lateral ones. Parapodia with ventral cirri as long as acicular lobe or slightly shorter and 4-6 rounded, small papillae, sometimes a dorsal one slightly larger. Parapodia with 10-16 compound chaetae, with thin shafts and blades 12-16 times as long as wide.

Re-description.

Measurements and general morphology. Gravid female, 2 mm long, 0.5 mm wide, with 17 chaetigers. Body ellipsoid, slightly flattened dorso-ventrally (wider than high). Tegument with transverse wrinkles and segmentation only barely discernible. Preserved specimen lacking pigmentation.

Head. Anterior end bluntly rounded (Fig. 8 A–F). Prostomium with seven longer appendages, including a pair of palps, in ventral-most position near the mouth, conical, wrinkled and about 4-5 times longer than wide at base; a pair of lateral antennae, similar in shape and size to palps; a median antenna, shorter (two thirds) than lateral antennae and with a rounded distal end; and a pair of antenniform papillae behind lateral antennae, similar in shape and size to median antenna, or smaller (Fig. 8 C–F). Around 20 digitiform smaller papillae confined by prostomial appendages and mouth, in frontal view (Fig. 8F). One pair of tentacular cirri similar in shape and size to lateral antennae and palps.

Tubercles. First chaetiger with two macrotubercles; rest of chaetigers with four macrotubercles, each arranged in four longitudinal rows along dorsum (Fig. 8 A–D, G). Distance between mid-rows larger than between these and lateral rows of macrotubercles (Fig. 8G). Size of all macrotubercles similar, with base as large as base of parapodia or smaller, or slightly increasing in size in first four chaetigers (Fig. 8 A–B), also slightly reducing in size in posterior chaetigers towards pygidium. Macrotubercles spherical or pear shaped, with some pores (Fig. 8 G–J). Spherical papillae present over dorsum and ventrum, with arrangement hard to determine in holotype.

Parapodia. Parapodia sub-conical, 1-2 times longer than wide (shorter in anterior and posterior most chaetigers), wrinkled (Fig. 9 A–E). Acicular lobe projecting distally anterior to chaetae (Fig. 9 A–E). Ventral cirri sub-conical, similar in length to acicular lobe but not projecting over the tip of acicular lobe (Fig. 9A). Mid-body parapodia with 4-5 spherical papillae: 1-2 on dorsal surface, 1 on anterior surface, 2 on ventral surface and 0-1 on posterior surface (Fig. 9 A–F); all similar in size or a dorsal slightly larger.

Chaetae. Compound chaetae present in all chaetigers, arranged in a curved transverse row around acicular lobe and numbering 8-12 per fascicle in mid-body chaetigers (Fig. 9 A–E). Blades similar in length along fascicles (12-16 times longer than maximum width), only slightly longer than those from mid-fascicle, with fine and short spinulation along superior edge, slightly curved (Fig. 9G).

Pygidium. Pygidium terminal, with mid-ventral digitiform anal cirrus and a pair of dorsal anal cirri, similar in shape to macrotubercles but slightly smaller.

Internal features. Eyes not observed in any specimen; holotype with a pair of reddish anterior spots that may not be eyes, but the nuchal organs. Muscular pharynx runs along chaetigers 3-6.

Reproductive features. Holotype and a few of the additional specimens examined are gravid females carrying large discoid eggs, 200 µm in diameter that occupy most of the body coelom, from the anterior to the posterior segments. "Copulatory organs" not observed.

Variation.

Specimens measured from 0.6 mm to 3.5 mm. Specimens assigned to this species show some variation in the number and arrangement of the epithelial papillae, probably because there are not easily ascertained in the holotype and were not described in detail in the original description. Larger specimens with approximately 30 papillae present between mid-macrotubercles and 10 between these and the lateral ones in mid-segments (Fig. 8G). Smaller specimens with less epithelial papillae (Fig. 8B). About five papillae between lateral macrotubercles and parapodia. Ventral surface with small papillae, arranged in about five transversal rows in mid-body. Body epithelium with ellipsoid granules (Fig. 8H). Chaetae numbering up to 16 per fascicle in mid-body chaetigers. Shaft with slightly widened distal end with delicate, almost inconspicuous spinulation (Fig. 9G), length of blades up to 15-16 times longer than wide.

Remarks.

Sphaerodoropsis corrugata has not been reported since its original description. Records of this species include off New York state, from 400 to 1500 m ( Hartman and Fauchald 1971). The type is not in excellent conditions to examine the number and arrangement of papilla. Nevertheless, some features observed on this specimen do not match the original description or are somehow imprecise. Antenniform papillae are present, unlike indicated in original and later descriptions by Hartman and Fauchald (1971) and Fauchald (1974). The parapodial papillae are all spherical or hemispherical, there is no truncate forms ( Hartman and Fauchald 1971: Fig. 34B, Fauchald 1974) and if they were observed with that shape it could have been due to a collapse of the structure that has recovered its original shape after years of preservation (see Capa and Bakken 2015 for other examples). The chaetae drawn ( Hartman 1965) may be ones with shorter blades in the fascicle, and some of the additional chaetae observed in the type and additional material are provided with longer and slender blades. As originally described, the acicular lobe is well developed and there is no additional parapodial lobes, only epithelial papillae, what seems to be the common pattern from all members in the family ( Capa et al. 2014), and not characteristic of this particular species. The different terminology for papillae used by different authors creates confusion.

Sphaerodoropsis elegans Hartman & Fauchald, 1971 originally described from Brazil but also reported from New England, resembles Sphaerodoropsis corrugata . It also belongs to the Sphaerodoropsis Group 1 sensu Borowski (1994) and is provided with long blade chaetae. Review of the types of this species reveal that the macrotubercles are pear-shaped, almost possessing a terminal papilla, indicating they could formally be considered as Sphaerephesia . Other Sphaerephesia species with ellipsoid body, four rows of macrotubercles with a terminal rounded papilla, several additional papillae on dorsal surface, and falcigers with long blades are Sphaerephesia similisetis Fauchald, 1972, Sphaerephesia longisetis Fauchald, 1972, Sphaerephesia chilensis Fauchald, 1974, Sphaerephesia fauchaldi Kudenov, 1987b, and Sphaerephesia hutchingsae Capa & Bakken, 2015. Sphaerodopsis corrugata differs from all of these in the number of parapodial papillae since the other have one or two ( Sphaerodopsis chilensis ) or more than seven ( Fauchald 1972, 1974, Kudenov 1987b, Capa and Bakken 2015) while Sphaerodopsis corrugata has four or five in mid-body chaetigers.

Distribution.

New England, United States, 250-2000 m.