Paratherochaeta ehlersi, Salazar-Vallejo, 2013

Salazar-Vallejo, Sergio I., 2013, Revision of Therochaeta Chamberlin, 1919 (Polychaeta: Flabelligeridae), Zoosystema 35 (2), pp. 227-263 : 253-255

Paratherochaeta ehlersi n. sp.

( Fig. 11 )

Stylarioides coronatus Ehlers, 1908: 121-123 , pl. 16, figs 3-8 (partim). — Hartwich 1993: 93.

TYPE MATERIAL. — Southwestern Indian Ocean, Madagascar. Holotype ( SMF 15365 ), Stat. 11 B1, 2.V.1967, R. Plante coll . One paratype ( SMF 15362 ), juvenile, without posterior end, 8 km off Canyon du Banc, Stat. E, 70-80 m, 29.IV.1970, R. Plante coll. (3 mm long, 1 mm wide, cephalic cage 2 mm long, 14 chaetigers; tunic thin with few sediment particles; multiarticulated neurospines in chaetigers 4-6, following chaetigers with neurospines) . Two paratypes ( SMF 15373 ), adults, Banc du Pracel , Chesterfield Island, Stat. BP9 (16°21’45”S, 43°45’00”E), grab, 32 m, 9.IV.1970, R. Plante coll. (10.0- 12.5 mm long, 1.0- 2.5 mm wide, cephalic cage 5-8 mm long, 44-53 chaetigers).

ETYMOLOGY. — The species name is formed after Ernst Ehlers in recognition of his many publications on polychaetes.

TYPE LOCALITY. — Off Madagascar, Western Indian Ocean.

DISTRIBUTION. — Indian Ocean, in shallow water (32-141 m).

DESCRIPTION

Holotype (SMF 15365) markedly bicolor, covered with whitish, large sediment particles anteriorly, fine rust-colored particles posteriorly ( Fig. 11A ). Body anteriorly swollen, posteriorly tapered; 10 mm long, 1.5 mm wide, cephalic cage 2 mm long, 52 chaetigers. Tunic thin, with large sediment particles over anterior chaetigers, posterior chaetigers with tunic poorly developed, papillae can be recognized individually.

Cephalic tube exposed, made by two muscular rings ( Fig. 11 A-C); basal ring wider, about as long as distal one; margin smooth. Anterior end exposed, palps and branchiae lost. Prostomium low, eyes brownish, fading. Caruncle thick, not separating branchial filaments into lateral groups. Dorsal lip short, lateral lips thicker, bent ventrally; ventral lip expanded ( Fig. 11D ). Branchiae sessile on branchial plate, dorsally connected, 10-11 filaments per side. Nephridial lobes lost, bases placed off upper caruncle margin.

Cephalic cage partly damaged, chaetae 1/5 as long as body length, or slightly longer than body width. Chaetigers 1-2 involved in cephalic cage; chaetiger 3 with chaetae twice as long as those in chaetiger 4, but not contributing to cage. Cephalic cage chaetae arranged in short series, surrounding anterior end. Chaetiger 1 with three notochaetae, two larger, broken, and two-three neurochaetae; chaetiger 2 with five-six notochaetae and two-three neurochaetae.

Anterior dorsal margin of first chaetiger with a short rounded lobe (ventrally rounded with two long papillae). Anterior chaetigers with long papillae in chaetal lobes; in chaetigers 3-5 papillae arranged in single transverse bands; each papillae making a large tubercle, fused laterally forming collar. Chaetiger 2 longer; constriction in chaetigers 2 and 3.

Sand cemented anterior shield surrounding chaetigers 1-6, fading posteriorly, stiff, extended dorsally and ventrally. Chaetal transition from cephalic cage to body chaetae gradual, chaetigers 1-6 with multiarticulate capillary neurochaetae; anchylosed neurohooks from chaetiger 7. Gonopodial lobes not seen.

Parapodia better developed in anterior chaetigers; remaining parapodia reduced, chaetae emerge from the body wall. Parapodia lateral; median neuropodia ventrolateral. Noto- and neurochaetae low lobes, barely noticeable; without long chaetal lobe papillae, one-two interramal papillae. Noto- and neuropodia distant to each other.

Median notochaetae arranged in short longitudinal series; all multiarticulated capillaries, two-three per bundle, about as long as 1/5 body width, in median chaetigers each with long articles throughout the chaetae, posterior chaetigers with small articles basally, medium-sized medially and longest distally. Neurochaetae multiarticulated capillaries in chaetigers 1-6 ( Fig. 11E ), thin falcate anchylosed hooks in remaining chaetigers, three-four in median chaetigers, each with thick hooks ( Fig. 11F , insert), becoming thinner in posterior chaetigers ( Fig.11G ).

Posterior end without sediment particles, tapered into rounded pygidium, anus terminal, no anal cirri.

REMARKS

As stated above, there were two different species included as syntypes of S. coronatus . The shallow water form having its chaetiger 3 wider than chaetigers 1-2, and provided with larger papillae is herein regarded as a different species and described as P. ehlersi n. sp. The species is unique among those species provided with falcate neurohooks because its body has two different colors, being anteriorly whitish, due to the presence of sediment grains, and posteriorly dirty orange or pale brown, without whitish sediment particles.

Further, P. ehlersi n. sp. resembles P. scutigera n. comb. but they differ in two features: P. ehlersi n. sp. has a bicolored body and neurohooks start from chaetiger 7, whereas P. scutigera n. comb. has a single color body and neurohooks from chaetiger 9. Further, if the drawings are accurate, then neurohooks would also differ in their relative curvature, because in P. ehlersi n. sp. they are not curved, whereas in P. scutigera n. comb. they are clearly sigmoid.

Figures

FIG. 11. — Paratherochaeta ehlersi n. sp.: A-D, holotype (SMF 15365); A, lateral view, anterior end exposed; B, anterior end, dorsal view; C, anterior end, ventral view; D, head, frontal view; E-G, paratype (SMF 15373), chaetiger 6, right parapodium, neurochaetae; F, chaetiger 11, complete, right parapodium; G, posterior chaetiger, right parapodium, neurochaetae. Abbreviations: BS, branchial scars; LL, lateral lip; PS. palp scar. Scale bars: A, C, 0.68 mm; B, 0.56 mm; D, 130 µm; E, 140 µm; F, 125 µm; G, 90 µm.