Paratherochaeta scutigera ( Ehlers, 1887 ), 2013

Salazar-Vallejo, Sergio I., 2013, Revision of Therochaeta Chamberlin, 1919 (Polychaeta: Flabelligeridae), Zoosystema 35 (2), pp. 227-263 : 256-258

Paratherochaeta scutigera ( Ehlers, 1887) n. comb.

( Fig. 13 )

Stylarioides scutiger Ehlers, 1887: 165-168 , pl. 42, figs 1-5.

Pherusa scutigera – Nonato & Luna 1970: 91, 92, figs 79-83.

Therochaeta scutigera – Fauchald 1972: 416 (n. comb.).

TYPE MATERIAL. — Grand Caribbean Sea. The holotype and single specimen, off La Habana, Cuba, 180 m, was supposed to be deposited in Harvard, but it has not been found (A. Johnston, 2003, pers. com.). Because Ehlers indicated it was dissected, it might have been destroyed .

DISTRIBUTION. — Only known from the type locality, off Northwestern Cuba, in moderate depths.

DESCRIPTION

Based on the original description and illustrations. Holotype posteriorly incomplete ( Fig. 13A ); body dark-cinnamon, clavate, wider posteriorly; 18 mm long, 3 mm wide, cephalic cage chaetae 7 mm long, 28 chaetigers.Tunic thick, forming large sediment tubercles anteriorly, with less sediment in median and posterior chaetigers.

Cephalic hood not exposed. Anterior end details unknown.

Cephalic cage chaetae about as long as half the length of the fragment (the illustration shows that chaetae are as long as body length) or five times longer than body width. Chaetigers 1-2 involved in the cephalic cage; chaetiger 3 with long chaetae but not reaching the anterior margin of chaetiger 1. Cephalic cage chaetae arranged in short series, about five-six chaetae per bundle.

Anterior dorsal margin of first chaetiger with papillae, but no median projections. Chaetigers 1-2 with long papillae restricted to base of chaetal lobes. Chaetiger 1 very short, chaetiger 2 markedly longer, slightly constricted towards its posterior margin, chaetiger 3 shorter than 2, about as long as chaetiger 1. Sand cemented anterior shield surrounding chaetigers 1-2, depressed, smoother dorsally ( Fig. 13B ), swollen, rougher ventrally ( Fig. 13C ). Chaetal transition from cephalic cage to body chaetae gradual; falcate neurohooks start in chaetiger 9. Gonopodial lobes unknown.

Parapodia well-developed in chaetigers 1-3, flat lobes with long papillae; remaining parapodia poorly developed, chaetae emerge from body wall. Parapodia lateral, median neuropodia ventrolateral. Noto- and neuropodia details unknown. Noto- and neuropodia distant to each other.

Median notochaetae probably arranged in longitudinal series; all notochaetae multiarticulated capillaries, articles long throughout the chaetae ( Fig. 13D ), three-four per bundle. Neurochaetae multiarticulate capillaries in chaetigers 1-8; falcate neurohooks from chaetiger 9 to the end of the fragment, four per bundle in median chaetigers ( Fig. 13E ); each neurohook blunt, anchylosed.

Posterior end unknown.

REMARKS

Paratherochaeta scutigera n. comb. has not been found since its original description. Because the presence of pseudocompound neurohooks along anterior chaetigers was not indicated, they are probably missing and consequently the species should be transferred to Paratherochaeta n. gen.

Because the dorsal tubercles of chaetiger 3 are larger than those present in following chaetigers, P. scutigera n. comb. resembles P. ehlersi n. sp. They differ in three attributes: the general body color, the start of neurohooks, and their relative curvature. In P. scutigera n. comb. the body has a single color, neurohooks start from chaetiger 9, and they are markedly sigmoid, whereas in P. ehlersi n. sp. the body is whitish anteriorly and dark orange or pale brownish posteriorly, neurohooks start from chaetiger 7, and the neurohooks are barely falcate and delicate.

Paratherochaeta scutigera n. comb. is similar to P. africana n. comb., n. stat. because both have sediment tubercles present beyond chaetiger 5. As stated above, their main difference lies in the relative curvature of neurohooks because they are markedly sigmoid in P. scutigera n. comb., whereas they are almost straight, distally curved in P. africana n. comb., n. stat. There might be some other differences but because P. scutigera n. comb. has not been found again, some additional materials are needed to clarify their distinction.

On the other hand, the material examined by Nonato & Luna (1970) might belong to this same species but some differences were found by the authors. First, their illustrations and description were apparently based upon a specimen without anterior shield because the chaetal lobes are well-defined, and even the larger papillae, often forming sediment tubercles, were depicted without sediment at all. Second, in the Brazilian specimen falcate neurohooks start by chaetiger 6, whereas Ehlers indicated that they start by chaetiger 9, and although these chaetae are brittle, the difference is enough for distinguishing two similar species. Other body features are similar but more specimens are needed to clarify this potential wide distribution from Cuba to northern Brazil.

The size measurements in the original description do not fit Ehlers’ whole specimen illustration. The artist may have exaggerated the length for the cephalic cage chaetae because they were described as being half as long as body length, but the illustration shows chaetae at least as long as the body.

Figures

FIG. 13. — Paratherochaeta scutigera (Ehlers, 1887) n. comb.; A, lateral view; B, anterior end, dorsal view; C, anterior end, ventral view; D, notochaeta and companion chaeta; E, neurochaetae and companion chaetae from posterior chaetiger (modif. Ehlers 1887). Scale bars: A, 2.1 mm; B, C, 1.3 mm.