Paratherochaeta africana ( Rullier, 1965 ), 2013

Salazar-Vallejo, Sergio I., 2013, Revision of Therochaeta Chamberlin, 1919 (Polychaeta: Flabelligeridae), Zoosystema 35 (2), pp. 227-263 : 248-250

Paratherochaeta africana ( Rullier, 1965) n. comb., n. stat.

( Fig. 8 )

Stylarioides plumosa africana Rullier, 1965: 47 , 48, fig. 9a–e. — Fauchald 1972: 413.

Stylarioides scutigerioides – Tebble 1955: 127, 128, fig. 28 (partim, Stat. 55, not fig. 28; non Augener, 1918).

TYPE MATERIAL. — Equatorial Eastern Atlantic Ocean. Holotype of Stylarioides plumosa africana ( MNHN 1443) , off Cotonou, Benin, Stat. 33 (06°10’N, 02°08’E), 45 m, muddy sand, 3.X.1963, A. Crosnier coll. Paratype of S. p. africana ( MNHN 1444) , off Cotonou, Benin, Stat. 38 (06°07’N, 02°4.5’E), 91 m, gray mud, 3.X.1963, A. Crosnier coll. (16 mm long, 3 mm wide, cephalic cage 6 mm long, 38 chaetigers; some parapodia removed previously) .

ADDITIONAL MATERIAL. — Eastern Tropical Atlantic Ocean.One anterior fragment ( BMNH 1953.3.1.901), damaged, anteriorly depressed, dissected midventrally, off Accra, Ghana, Stat. 55, 7 km WSW Accra Lighthouse , 12 m, 15.I.1951, R. Bassindale coll. (6 mm long, 1.5 mm wide, cephalic cage 3 mm long, 13 chaetigers) .

DISTRIBUTION. — Western Africa, from Senegal to Angola, in 20-91 m depth.

DESCRIPTION

Holotype of Stylarioides plumosa africana (MNHN 1443) complete, swollen anteriorly, tapered caudally ( Fig. 8A ); 22 mm long, 3 mm wide, cephalic cage 8 mm long, 68 chaetigers. Body with cemented sand grains on anterior end forming sediment tubercles, smoother along chaetigers 1-2, constriction before chaetiger 3, large tubercles in chaetigers 3-8, reducing in size posteriorly. Median and posterior chaetigers with globular tubercles made with fine sediment particles; prepygidial region with papillae almost without adherent sediment. Tunic thin, with adherent sediment grains. Body papillae long, capitate, from chaetiger 3 making large tubercles, larger in chaetigers 3-8 with sand grains, posteriorly papillae forming individual tubercles with fine sediment particles; posterior end with almost naked papillae.

Anterior end not exposed.No dissection attempted to avoid further damage.

Cephalic cage chaetae as long as 1/3 body length, or almost three times longer than body width ( Fig. 8A ). Chaetigers 1-2 involved in cephalic cage; chaetiger 3 with long chaetae but not reaching anterior end, directed laterally ( Fig. 8B, C ). Cephalic cage chaetae arranged in short series, five-six chaetae per bundle. Anterior dorsal margin of first chaetiger with a median, long papillae making a triangular lobe, projected anteriorly, with two(-three) papillae on its tip. Chaetigers 1-2 with long papillae restricted to base of chaetal lobes. Chaetiger 1 very short, chaetiger 2 markedly longer, constricted on its posterior margin, chaetiger 3 shorter than 2, about as long as chaetiger 1. Sand cemented anterior shield surrounding chaetigers 1-2. Chaetal transition from cephalic cage to body chaetae abrupt; neurohooks start in chaetiger 8. Gonopodial lobes not seen.

Parapodia poorly developed, except along chaetigers 1-4, flat lobes making large tubercles, projected anteriorly, carrying five-six basal papillae in chaetigers 1-2, only two in chaetiger 3; subsequently chaetae emerge from the body wall. Parapodia lateral, median neuropodia ventrolateral. Notopodia and neuropodia without chaetal lobes, or associated papillae. Noto- and neuropodia distant to each other.

Median notochaetae arranged in short longitudinal series; all notochaetae multiarticulated capillaries, articles long, becoming shorter and less defined distally; three notochaetae per fascicle, about 1/6 as long as body width. Neurochaetae multiarticulated capillaries in chaetigers 1-7 ( Fig. 8E ), becoming progressively smaller, with long articles; falcate blunt neurohooks from chaetiger 8, arranged in transverse series, three-four per fascicle ( Fig. 8F ).

Posterior region tapered, more or less cylindrical; pygidium with anus terminal, hemispherical, no anal cirri ( Fig. 8D ).

REMARKS

Rullier (1965) described S.p. africana as a variety and as such, would not be regulated by the International Code of Zoological Nomenclature ( ICZN 1999, Art. 15.2). However, because it was listed as a subspecies by Fauchald (1972) the name became available ( ICZN 1999, Art. 45.6.4.1) with the original author and year.

Despite listing four main differences, Rullier decided to retain his variety under S. plumosa africana , resting on a previous record for this northern species (p. 48): “… a été signalé jusqu’à la latitude du Maroc ” (Transl.: … has been recorded up to the Morocco latitude). This record was not cited by Rullier but corresponds to Fauvel (1936: 76). The holotype has a clear constriction after chaetiger 2, large dorsal tubercles with sand particles, but does not have pseudocompound neurohooks and consequently it does not belong in Therochaeta but has to be transferred to Paratherochaeta n. gen.

Paratherochaeta africana n. comb., n. stat., resembles P. scutigera n. comb. because both species have sediment tubercles continued beyond chaetiger 5. They differ mainly on the relative curvature of neurohooks because they are almost straight, but distally curved in P. africana n. comb., n. stat., whereas they are markedly sigmoid in P.scutigera n. comb. Other differences must be sought once some specimens of P. scutigera n. comb. become available.

Figures

FIG. 8. — Paratherochaeta africana (Rullier, 1965) n. comb., n. stat.: A-D, holotype (MNHN 1443); A, lateral view; B, anterior end, oblique dorsal view; C, anterior end, lateral view; D, posterior region, oblique lateral view; E, F, paratype (MNHN 1444); E, chaetiger 6, right parapodium, neurochaeta; F, chaetiger 10, left parapodium neurochaetae. Scale bars: A, 2.5 mm; B, 0.7 mm; C, D, 1 mm; E, 120 µm; F, 60 µm.