Sphaerephesia amphorata, 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 : 11-14

Taxon classification Animalia Phyllodocida Sphaerodoridae

Sphaerephesia amphorata sp. n. Figs 5, 6

Material examined.

Holotype: USNM 1001815, East of Cape Lookout, North Carolina, United States, north Atlantic, 34°16.32'N, 75°45.498'W, 640 m, 11 Nov 1983, MMS Collections, Atlantic Slope and Rise Program, ASLAR (CRSAP 1 st.1 rep. 2 core 6 sec 0.2). Paratypes: USNM USNM 1407168, same sample, different cores (7 ind.). Additional material. USNM 1001801 (4 ind.), East of Cape Lookout, North Carolina, United States, North Atlantic, 34°16.002'N, 75°45.967'W, 580 m, 11 Nov 1983; USNM 1001802 (5 ind.), East of Cape Lookout, North Carolina, 34°15.936'N, 75°46.164'W, 583 m, 26 Mar 1984; USNM 1002041 (9 ind., 3 for SEM), East of Cape Lookout, North Carolina, 34°15.816'N, 75°45.786'W, 593 m, 27 Mar 1984; USNM 1002196 (1 ind.), East of Cape Lookout, North Carolina, 34°49.8'N, 75°13.5'W, 2003 m, 20 Jul 1985.

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 and Bakken, 2015, holotype: AM W.42748, East of Malabar, Sydney, New South Wales, Australia, 33° 58.717 S’, 151°18.00'E, 82 m, 22 Aug 1995; paratypes: east of Malabar, Sydney, New South Wales, 80-28 m. AM W.42717 (1 ind.), AM W.42721 (1 ind.), AM W.42731 (2 ind.), AM W.42749 (1 ind.), AM W.42751 (1 ind.), AM W.42752 (2 ind.), AM W.42758 (1 ind.).

Diagnosis.

Four longitudinal rows of sessile, bottle-shaped macrotubercles with long digitiform terminal papilla and 3-4 transverse rows of small spherical papillae per segment. Microtubercles absent. Distance between dorsal-most macrotubercles similar to distance between those and lateral ones. Parapodia with ventral cirri nor surpassing length of acicular lobe and four rounded and small papillae. Parapodia with 4-7 compound chaetae, with thin shafts and blades 7-11 times as long as wide.

Description.

Measurements and general morphology. Gravid female, 1.5 mm long, 0.2 mm wide, with17 chaetigers. Body elongated, tapering at both ends, slightly flattened dorso-ventrally (wider than high). Dorsum convex and ventrum flattened (Fig. 5A, B). Tegument with transverse wrinkles and segmentation not obvious (Fig. 5A). Preserved specimen lacking pigmentation.

Head. Anterior end bluntly rounded (Fig. 5A, C–F). Prostomium with seven longer appendages including a pair of palps, in ventral-most position near the mouth, a pair of lateral antennae and a median antenna; and a pair of antenniform papillae behind lateral antennae, all digitiform, slightly wrinkled and similar in size except for the antenniform papillae, slightly shorter than lateral antennae (Fig. 5 C–F). Approximately 10 digitiform papillae confined by prostomial appendages and mouth, in frontal view (Fig. 5D, F). A pair of tentacular cirri, similar in shape and size to lateral antennae and palps, and several scattered papillae similar to prostomial in head surroundings. Nuchal organ pits located between lateral antennae and tentacular cirri (Fig. 5E).

Tubercles. First and last chaetigers with two macrotubercles, sessile, bottle-shaped and provided with a long terminal papilla (Figs 5A, C, D, 6E). Rest of chaetigers with four macrotubercles each, arranged in four longitudinal rows along dorsum (Figs 5C, 6A, B). Distance between mid rows and lateral rows similar (Fig. 5 A–B). Shape and size of all macrotubercles similar, slightly decreasing in size in last chaetigers (Fig. 5A). Spherical or ellipsoid papillae present over dorsum, arranged in 3-4 transversal rows per segment (Fig. 5A, D, G), around 10 papillae present between mid-macrotubercles and five between these and lateral ones in mid-body segments (Fig. 5A, G). Microtubercles absent. Ventral surface with small ellipsoid papillae, arranged in 3-4 irregular transversal rows (Fig. 5H), with a total of around 12 papillae per segment in mid-body; numbers decreasing towards posterior end (Fig. 6D). Body epithelium with ellipsoid granules (e.g. Fig. 6A).

Parapodia. Parapodia elongated, sub-conical, increasing in size towards chaetiger 4 and around 2-3 times longer than wide (Figs 5B, H, 6 A–D). Acicular lobe projecting distally anterior to chaetae (Fig. 6 A–D). Ventral cirri sub-conical, pear-shaped, as long as acicular lobe in posterior chaetigers, and shorter in anterior (Figs 5B, H, 6 A–E). Mid-body parapodia with about four small spherical papillae, all similar in size: one distal, on dorsal surface, one anterio-dorsal and one anterio-ventral and another ventral, all in proximal half of parapodia (Figs 5H, 6 A–E).

Chaetae. Compound chaetae present in all chaetigers, arranged in a curved transverse row (C-shaped) behind acicular lobe and numbering 4-7 per fascicle (Fig. 6 A–D). Shaft with slightly widened distal end with delicate, almost inconspicuous spinulation (Fig. 6G, H). Blades decreasing in size from mid-fascicle to dorsal and ventral ends (7-11 times longer than maximum width), with fine and short spinulation along cutting edge and a slightly curved tip (Fig. 6G, H).

Pygidium. Pygidium terminal, with mid-ventral digitiform anal cirrus and a pair of dorsal anal cirri, similar in shape to macrotubercles (Fig. 6E).

Internal features. Eyes not observed in any specimen. Muscular pharynx runs along three anterior chaetigers.

Reproductive features. Some paratypes and 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; other specimens seem to be filled with sperm. However, 'copulatory organs’ were not observed in either females or males.

Variation.

Paratypes varying in size from 0.8 to 1.5 mm and seven to 17 chaetigers. Most features are conserved in this species and all specimens examined regardless the size bear the dorsal macrotubercles with the unusual elongated terminal papillae as long as the macrotubercle. Length of blades vary within fascicles and also along the chaetigers, generally between 7-11 times longer than maximum width.

Remarks.

The most conspicuous and distinct morphological attribute of Sphaerephesia amphorata sp. n. is the presence of dorsal macrotubercles with elongated papillae providing them the characteristic amphora shape, while other described species in the genus have a rounded terminal papilla. Six of the nine nominal Sphaerephesia species share with Sphaerephesia amphorata sp. n. the presence of four rows of macrotubercles with a terminal rounded papilla, several additional papillae on dorsal surface, and falcigers with long blades. These are Sphaerephesia similisetis Fauchald, 1972, Sphaerephesia longisetis Fauchald, 1972, Sphaerephesia chilensis Fauchald, 1974, Sphaerephesia fauchaldi Kudenov, 1987b, Sphaerephesia regularis Böggemann, 2009 and Sphaerephesia hutchingsae Capa & Bakken, 2015. None of the species mentioned share with the new species the number of parapodial papillae; Sphaerephesia fauchaldi , Sphaerephesia hutchingsae , Sphaerephesia longisetis and Sphaerephesia similisetis bear over six parapodial papillae while Sphaerephesia regularis and Sphaerephesia chilensis are provided with one or two parapodial papillae ( Fauchald 1972, 1974, Kudenov 1987b, Capa and Bakken 2015). Other differences between Sphaerephesia longisetis , Sphaerephesia fauchaldi and Sphaerephesia amphorata sp. n. are the presence of microtubercles in the former two species, absent in the latter.

Distribution.

Only known from type locality, East of Cape Lookout, North Carolina, United States, North Atlantic, ranging from 580 to 2003 m.

Etymology.

Amphora, is a Greek word that refers to the pottery vases used since the Bronze Age by the Greco-Romans to transport liquids. The shape of these containers resembles the characteristic shape of the dorsal macrotubercles of this species.