Therochaeta fauchaldi, Salazar-Vallejo, 2013

Salazar-Vallejo, Sergio I., 2013, Revision of Therochaeta Chamberlin, 1919 (Polychaeta: Flabelligeridae), Zoosystema 35 (2), pp. 227-263 : 236-239

Therochaeta fauchaldi n. sp.

( Fig. 3 )

Therochaeta sp. - A Milligan 1984: 47.19-20, figs 47.13, 47.14 (diagnosis).

TYPE MATERIAL. — Northern Gulf of Mexico. – Holotype ( USNM 117637 ) and three paratypes (USNM 1206495), off Florida,R/V Sofla , Stat.14 (25°46’01”N, 82°23’49”W), 26 m, 28.VII.1981 (paratypes 1-2 mm long, 0.5-0.7 mm wide, cephalic cage 1.0- 2.5 mm long, 15-18 chaetigers; papillae less abundant).

ADDITIONAL MATERIAL. — Norhtern Gulf of Mexico. Three specimens ( USNM 255041 ), off Panama City, Florida, R/V Lash-up, Stat. 4, 19 km offshore, 32 m, 9.IX.1959, M.L. Jones, N. Hulings & R. Waller coll. (2.0- 4.5 mm long, 0.8-1.0 mm wide, cephalic cage 2.3-4.0 mm long, 15-21 chaetigers) .

ETYMOLOGY. — This species is named after Kristian Fauchald, in recognition of his many studies on polychaetes, and especially because of his insight about flabelligerid taxonomy and his significant support for all of my research activities.

DISTRIBUTION. — Northeastern Gulf of Mexico, off Florida, in sublittoral soft bottoms, about 30 m depth.

DESCRIPTION

Holotype (USNM 117637) without posterior region ( Fig.3A ).Body anteriorly swollen, tapered posteriorly, cross-section oval, slightly compressed laterally; 4.5 mm long, 1 mm wide, cephalic cage 3.5 mm long, 16 chaetigers. Tunic thin with fine sediment particles adherent over papillae.Body papillae filiform, capitate, with large amount of sediment towards its base, slightly larger dorsally, decreasing gradually in size ventrally ( Fig. 3B, C ), five-six rows per segment.

Cephalic hood exposed in three paratypes, narrow, apparently made by two rings, rugose; basal ring about four times longer than distal ring. Cephalic hood margin crenulated, with small papillae.

Anterior end observed in paratypes. Prostomium low, with four large black eyes. Caruncle short, not reaching the branchial plate posterior margin. Palps thick, pale, smooth (only one left in one paratype); palp keels not seen.

Branchiae cirriform, sessile on branchial plate, arranged as two concentric rows, posterior row continuous with about 12 branchial scars, anterior row separated in two lateral groups, each with four branchial scars, making 20 total filaments. Size relationships between palps and branchiae unknown.

Cephalic cage chaetae about as long as body length, or four times longer than body width. Cephalic cage made only by chaetigers 1-2, with chaetiger 2 slightly displaced dorsally. Chaetiger 3 with chaetae long but less than half those present in chaetiger 2. Cephalic cage chaetae arranged in short series, lateral, four-five chaetae per chaetal lobe.

Anterior dorsal margin of first chaetiger papillated. Chaetigers 1-2 with long papillae over their chaetal lobes, longer than following chaetigers. Post-cephalic cage chaetigers not elongated; only chaetiger 3 longer. No constriction behind those chaetigers forming the cephalic cage; parapodia of chaetigers 1-2 better developed than posterior ones. A crescentic glandular pad with a smaller portion on chaetiger 1. Chaetal transition from cephalic cage to body chaetae abrupt; pseudocompound neurohooks from chaetiger 4. Gonopodial lobes not seen. Parapodia better developed in chaetigers 1-2; following ones poorly developed; chaetae emerging from the body wall. Notopodia with longer papillae than neuropodia ( Fig. 3C ). Noto- and neuropodia close to each other. Median notochaetae arranged as lateral tufts. All notochaetae multiarticulated capillaries, articles long throughout the chaetae or becoming shorter distally; longest chaetae as long as about 1/3 body width. Median neuropodia ventrolateral. Neurochaetae multiarticulated capillaries in chaetigers 1-3, one-two pseudocompound hooks in chaetigers 4-8 ( Fig. 3E, D ), from chaetiger 9 two or three falcate anchylosed hooks ( Fig. 3E ) to the end of the fragment.

Posterior end present in paratypes, tapered to a blunt cone; pygidium with anus terminal, without anal cirri.

REMARKS

Therochaeta fauchaldi n. sp. is similar to T. caudata n. comb. as both lack a marked constriction in anterior chaetigers; but they differ because in T. fauchaldi n. sp. body papillae are abundant and of about the same size, whereas in T. caudata n. comb. they are less abundant and dorsal ones are larger.

Figures

FIG. 3. — Therochaeta fauchaldi n. sp.; A, holotype (USNM 117637), lateral view; B, same,anterior end,lateral view; C, non-type specimen (USNM 255041), chaetiger 5, cross section; D, same, chaetiger 6, anchylosed neurohooks; E, same, chaetiger 12, neurohooks. Scale bars: A, 0.4 mm; B, C, 0.25 mm; D, 20 µm; E, 35 µm.