Therochaeta collarifera ( Ehlers, 1887 )

Salazar-Vallejo, Sergio I., 2013, Revision of Therochaeta Chamberlin, 1919 (Polychaeta: Flabelligeridae), Zoosystema 35 (2), pp. 227-263 : 233-234

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.

Figures

FIG. 1. ― Therochaeta collarifera (Ehlers, 1887): A, syntype (MCZ 778), oblique dorsal view; B, same, anterior end; C, same, ventral view;D, non-type specimen (LACM-AHF,R/V Atlantis, Stat.D1), head,frontal view;E, syntype (MCZ 778),posterior region,lateral view; F, non-type specimen (USNM 57060), chaetiger 7, right parapodium (insert tip of pseudocompound hooks); G, same, chaetiger 16, right parapodium (insert neurohooks).Abbreviations:BS, branchial scars,LL, lateral lip, PS, palp scar.Scale bars:A, 1 mm; B, 0.7 mm; C, 0.6 mm; D, 75 µm; E, 0.5 mm; F, 350 µm; G, 450 µm.