Paratherochaeta orensanzi Salazar-Vallejo 2013, n. sp.

Paratherochaeta orensanzi n. sp.

(Fig. 12)

TYPE MATERIAL. — Southwestern Atlantic Ocean. Holotype (MACN 39031) and paratypes (two in MACN 39032; one in ECOSUR; one in MNHN), stomach contents of reticulated raja, Psammobatis bergi Marini, 1932, female, 35 cm long (L18 N3), R/V Chiarpesca 59, Cruise REDE 04, 105 m, X-XI.2006 (paratypes anterior fragments 28-34 mm long, 3-4 mm wide, cephalic cage chaetae broken, 18-23 chaetigers; sediment grains small; chaetiger 2 displaced anteriorly; falcate dark neurohooks from chaetiger 5; gonopodial pores in chaetiger 5).

ETYMOLOGY. — This species is named as a modest homage to Dr. José M. (Lobo) Orensanz, in recognition of his fine publications on South Atlantic and Antarctic polychaetes and as a means to thank him for providing materials from his collections.

TYPE LOCALITY. — Off Central Argentina, Southwestern Atlantic Ocean.

DISTRIBUTION. — Only known from the type locality, found in the stomach contents of a ray (P. bergi) caught in 105 m.

DESCRIPTION

Holotype broken posteriorly, body wall damaged (Fig. 12A), whitish anteriorly, darker in median and posterior chaetigers. Body medially swollen, tapered anteriorly, posteriorly widening; 29 mm long, 3 mm wide, cephalic cage chaetae 8 mm long, broken, 20 chaetigers. Tunic thin, most sediment particles lost; anterior body papillae long, tapered, median papillae shorter, posterior papillae larger, medially swollen.

Cephalic hood exposed, cylindrical, made by two similar sized rings. Cephalic hood margin smooth.

Anterior end exposed, partly damaged. Prosomium projected cone, eyes not seen (Fig. 12D). Caruncle not reaching branchial plate margin. Palps and branchiae lost. Branchiae arranged into two marginal dorsolateral groups, about 36 filaments per side. Nephridial lobes placed between branchial rows.

Cephalic cage partly damaged, remaining chaetae three times as long as body width. Chaetigers 1-2 involved in cephalic cage, chaetiger 2 displaced anteriorly; chaetiger 3 with chaetae shorter, not contributing to cage. Cephalic cage chaetae arranged in short series; chaetiger 1 with seven-eight notochaetae, seven-eight neurochaetae; chaetiger 2 with seven notochaetae and five neurochaetae.

Anterior dorsal margin of first chaetiger with a short truncate lobe (papillae eroded). Anterior chaetigers with long papillae in chaetal lobes, not arranged in transverse series. Chaetiger 2 longer than chaetigers 1 or 3; constriction between chaetigers 2-3 indistinct.

Sand cemented anterior shield surrounding chaetigers 1-5, interrupted posteriorly (Fig. 12A, B), stiff, ventrally discontinuous (Fig. 12C). Chaetal transition from cephalic cage to body chaetae abrupt, chaetigers 1-4 with multiarticulate capillary neurochaetae (Fig. 12E); anchylosed neurohooks from chaetiger 5. Gonopodial lobes reduced to dark pores, in chaetiger 5, placed slightly ahead of neurohooks (or their scars).

Parapodia better developed in anterior chaetigers; remaining parapodia reduced, chaetae emerging from body wall. Parapodia lateral; median neuropodia ventrolaeral. Noto- and neurochaetae low lobes, barely noticeable; without long chaetal lobe papillae, or interramal papillae, probably eroded. Noto- and neuropodia distant to each other.

Median notochaetae arranged in short longitudinal series; all multiarticulated capillaries, most broken, two per bundle, relative length to body width unknown, in median chaetigers each with short articles basally, medium sized medially, longer towards tip. Neurochaetae multiarticulated capillaries in chaetigers 1-4, falcate dark anchylosed hooks in remaining chaetigers, one-two in median chaetigers (Fig. 12F), three-four in posterior chaetigers (Fig. 12G), arranged in transverse series.

Posterior end unknown.

REMARKS

Paratherochaeta orensanzi n. sp. is unique among the species provided with a thin sediment shield and falcate neurohooks, because its sediment cover is reduced to a thin crust along chaetigers 1-5 and it is midventrally discontinuous.