Therochaeta collarifera
Creators: name: Salazar-Vallejo, Sergio I.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Terebellida
Flabelligeridae
Therochaeta
Therochaeta collarifera

description: Therochaeta collarifera (Ehlers, 1887)
(Fig. 1)
Stylarioides collarifer Ehlers, 1887: 161-164, pl. 43, figs 2-7. — Hartman 1938: 14.
Therochaeta collarifera – Hartman 1965: 180, pl. 40 (n. comb.). — Hartman & Fauchald 1971: 121.
TYPE MATERIAL. — Grand Caribbean, Eastern Gulf of Mexico. One syntype (MCZ 775) dried-out, anterior end damaged, off SW Sand Key, Florida, Bibb Stat. 137 (24°13’30”N, 81°59’00”W), 586-595 m, 17.II.1869, L.F. de Pourtalès coll. One syntype (MCZ 778), off Boca Grande, Florida, Bibb Stat. 132 (24°11’00”N, 89°09’45”W), 673 m, 16.II.1869, L.F. de Pourtalès coll. One syntype (MCZ 784), many pieces, completely dried-out, off Carysfort Reef, Florida, Bibb Stat. 160 (25°06’30”N, 80°01’00”W), 377 m, 31.III.1869, L.F. de Pourtalès coll.
ADDITIONAL MATERIAL. — Northeastern Atlantic Ocean. 24 specimens (LACM-AHF), R/V Atlantis, Stat. D1 (39°54’30”N, 70°35’00”W), 466.7-508.7 m, 23.V.1962 (complete specimens 7-15 mm long, 1.5-2.0 mm wide, cephalic cage 4-6 mm long, 23-24 chaetigers). 20 specimens (LACM-AHF), R/V Chain, Stat. 105B (39°56.6’N, 71°03.6’W), 530 m, 5.V.1966 (complete specimens 3.5-10.5 mm long, 1.0- 2.5 mm wide, cephalic cage 3.5-7.5 mm long, 17-26 chaetigers). One specimen (USNM 57061), off Delaware, R/V Pierce, Stat. H1 (39°12.1’N, 72°23.6’W), 390 m, 28.VIII.1976, G.R. Gaston, (7.5 mm long, 2 mm wide, cephalic cage 6.5 mm long, 27 chaetigers). Three specimens, one damaged (USNM 57060), off Delaware, R/V Pierce, Stat. H-1, 350- 400 m, 16.III.1976, G.R. Gaston (11/10/ 6 mm long, 2/2.5/ 2 mm wide, only one has most cephalic cage chaetae left, 5.5 mm long, 24(8 in tail)/ 24(8 in tail)/ 16 chaetigers [cauda lost]). One specimen (USNM 1073350), collected in Stat. 7 (39°54.134’N, 70°35.054’W), 503 m (11 mm long, 2.3 mm wide, cephalic cage damaged, remaining chaetae 1 mm long, 26 chaetigers). Grand Caribbean, Off Cuba. One specimen (UMML unumb.), without cephalic cage nor posterior end, R/V Gerda, Cruise 6813, Stat. 1015 (23°34’N, 79°16’W), N off Central Cuba, 520 m, 15.VI.1968. One specimen (UMML unnumb.), R/V Pillsbury, Cruise 6809, Stat. 810 (26°04’N, 78°58’W), 183 m, 11.X.1968 (13 mm long, 2 mm wide, cephalic cage 4 mm long, 23 chaetigers). Guadeloupe. One specimen (UMML unnumb.), R/V Pillsbury, Cruise 6907, Stat. 943 (16°26’N, 61°36’W), W off Point-Louis, Grand Terre, 274 m, 17.VII.1969 (9.5 mm long, 2 mm wide, cephalic cage 9 mm long, 23 chaetigers).
DISTRIBUTION. — Western Atlantic Ocean, from Delaware to Florida to Guadeloupe, in soft bottoms in 274-600 m water depth.
DESCRIPTION
Syntype (MCZ 778) slightly dehydrated, whitish, depressed, anteriorly swollen, posteriorly tapered into a thin cauda (Fig. 1A); 10 mm long, 2 mm wide, cephalic cage 6 mm long, 28 chaetigers.Tunic thick, with small whitish sediment particles, including forams. Body papillae long, capitate, making large stiff tubercles, laterally continuous in chaetiger 3, discontinuous in following chaetigers, one-two transverse rows in median chaetigers (Fig. 1B), slightly smaller ventrally (Fig. 1C), decreasing in size posteriorly; cauda without large tubercles, finely covered by sediment (Fig. 1E).
Anterior end modifications observed in two nontype specimens (LACM-AHF Atlantis, Stat. D1). Cephalic tube exposed (1 mm long), rugose, made of a single ring, margin papillated. Oral siphon long (1.5 mm long), pale. Prostomium low; eyes not seen. Caruncle short, not separating branchiae into two lateral groups. Palps thick, slightly longer than branchiae; palp keels reduced. Lateral and dorsal lips fused, well developed; ventral lip reduced.
Branchiae cirriform, sessile on branchial plate, arranged in two rows, distal row with eight filaments of similar thickness, proximal row with two filaments per side (Fig. 1D). Longest branchiae slightly shorter than palps. Nephridial lobes placed more or less between branchial rows.
Cephalic cage with many chaetae broken, chaetae as long as 3/5 body length or three times longer than body width.Chaetigers 1-2 involved in cephalic cage; chaetae arranged in short lateral groups; chaetigers 1 and 2 with two-three chaetae per bundle. Anterior dorsal margin of first chaetiger pentagonal, papillated. Anterior chaetigers probably with long papillae, eroded in syntype. Chaetiger 1-2 increasing in length posteriorly, chaetiger 2 longer, about as wide as chaetiger 1, constricted posteriorly; chaetiger 3 shorter, enhanced with sediment tubercles. Chaetal transition from cephalic cage to body chaetae gradual; pseudocompound neurochaetae in chaetigers 5-7 (those in chaetiger 4 broken), falcate neurohooks from chaetiger 8. Gonopodial lobes not seen.
Parapodia poorly-developed, lateral, chaetae emerge from the body wall; median neuropodia ventrolateral. Noto- and neuropodia with large rounded tubercles, widely separated from each other. Median notochaetae arranged in a tuft; all notochaetae multiarticulated capillaries, articles medium-sized, becoming longer medial- and distally, notochaetae as long as 1/3-1/4 body width, one-two per bundle. Neurochaetae annulated capillaries in chaetigers 1-4, two pseudocompound neurohooks per bundle in chaetigers 5-7 (Fig. 1F), decreasing in size posteriorly, each with handle slightly expanded distally, with medium-sized poorly defined articles, and blade hyaline (many lost in syntype); falcate neurohooks from chaetiger 8, arranged in transverse series, three per bundle along trunk (Fig. 1G), decreasing to two in posterior chaetigers. Falcate neurohooks with medium-sized anchylosed articles, tips hyaline.
Posterior end tapered into a blunt cone; pygidium with anus terminal, without anal cirri.
REMARKS
Therochaeta collarifera resembles T. pacifica; however they differ in the relative development of the first two chaetigers and of the sediment tubercles. Thus, T. collarifera has the first two chaetigers in a thinner and more swollen pattern, whereas in T. pacifica this region is wider and less swollen. Further, in T. collarifera the sediment tubercles in chaetigers 3 and 4 are more elevated than the corresponding ones in T. pacifica and these projected tubercles are even present in the smallest specimens examined (LACM-AHF, Stat. Ch 105B; 3.5 mm long). The record for the Northeastern Atlantic Ocean (Amoureux 1982: 192) should be assigned to the Mediterranean form of T. flabellata (see below). Hartman (1965: pl. 40, fig. d) provided a schematic illustration for the anterior end, but it was based on a dissected specimen and although the relative size of palp and branchiae are correct, the branchial filaments were illustrated as arranged in a single row with only eight filaments, which correspond to the distal row, but the proximal filaments as well as the nephridial lobes were not illustrated.
description: Published as part of Salazar-Vallejo, Sergio I., 2013, Revision of Therochaeta Chamberlin, 1919 (Polychaeta: Flabelligeridae), pp. 227-263 in Zoosystema 35 (2) on pages 233-234, DOI: 10.5252/z2013n2a7, http://zenodo.org/record/5165233