Thelepus pascua (Fauchald, 1977)

Londoño-Mesa, Mario H., 2009, Terebellidae (Polychaeta: Terebellida) from the Grand Caribbean region 2320, Zootaxa 2320 (1), pp. 1-93 : 83-85

Thelepus pascua (Fauchald, 1977)

Figures 25 A-K

Euthelepus pascua, Fauchald, 1977b:57–58 , Figs 12 D-H.

Thelepus pascua, Hutchings & Glasby, 1986:114 (comb. nov.).

Type material: Holotype: USNM 53093 (1) Galeta Reef , Panama, 17.III.1972. Coll. K. Fauchald.

Description: Holotype incomplete, 35 segments, 4.5mm long, 0.5mm wide ( Figs 25A, B ). Upper lip short, semicircular. Lower lip short, wide ( Figs 25C,D ). Tentacular membrane short; eyespots absent. No tentacles remaining. Twelve ventral shields; anterior most shields wider and swollen, and decreasing in width. Two single pairs of branchiae on segments 2–3 ( Figs 25E,F ); each branchia with a long, stout filament on each side, as long as 7 thoracic segments. First pair arising more laterally than second pair (second pair incomplete, missing left filament); each branchiae near anterior margin of segments. Nephridial papillae not seen. Notopodial glandular tissue not developed. Notopodia from segment 3; 32 pairs of notopodia; oar-like chaetae on two lengths ( Figs 25 G-I). Pairs of neuropodia small on segment 6, then more visible and distinguishable, but low and flattened. Thoracic uncini ( Figs 25J from Fauchald, 1977b; 25K) with dental formula MF:2–4:4–5:7; PP developed as a heel; PF absent; Oc slightly convex; Cp with three series of accessory teeth decreasing in size; Sr narrow; SrP as square button close to rounded AP; SrA absent; AF absent; Bs strongly curved. Pygidium missing.

Staining pattern: Only ventral shields stain deeply. Other structures do no stain.

Discussion: The holotype is the only specimen known so far. Hutchings and Glasby (1986) transferred the species from Euthelepus to Thelepus because of the lack of lateral lappets. After their revision, they stated that the specimen has 29 segments with notochaetae, which was missing in the original description. Nevertheless, there are 32 segments with notochaetae, with the last ones not easily visible. Further, the holotype includes an anterior fragment, without the abdominal portion; thus, the abdominal neuropodia reported in the original description might belong to a lost abdominal fragment lost. No other species in the genus has been described with a single pair of branchial filaments. On the other hand, chaetae were never drawn in the original and subsequent descriptions. Oar-like chaetae have not been reported in this subfamily. Thus, the number of single branchial filaments and the presence of paleate chaetae confirm the validity of the species.

Type locality: Galeta Reef , Laurencia Zone, Panama, Atlantic Ocean .

Figures

FIGURE 12. Neoleprea sp. 1., (ZMA V.Pol. 7571B): A. Thoracic region in ventral view. B. Anterior end in ventral view. C. Mid-thoracic region in lateral view. D. Fascicles of notochaetae on notopodium from segment 5. E. Long chaetae from segment 5. F. Short chaetae from segment 5. G. Uncini from segment 10. H. Double rows of uncini from mid-thoracic region. I. Pygidium. Scale bars: A: 1.1mm; B: 0.4mm; C: 0.3mm; D: 0.1mm; E,F: 0.05mm; G: 0.03mm; H: 0.03mm.

FIGURE 25. Thelepus pascua (Holotype USNM 53093): A-B. Lateral view. C. Anterior end in ventral view (from Fauchald, 1977b). D. Anterior end in lateral view. E. Anterior end in lateral view (from Fauchald, 1977b). F. Anterior end in dorsal view (from Fauchald, 1977b). G. Fascicle of notochaetae from anterior thoracic region. H. Long notochaetae from anterior thoracic segment. I. Short notochaetae from anterior thoracic segment. J. Anterior uncini (from Fauchald, 1977b). K. Uncini from anterior thoracic segment. A,B: 0.7mm; C,E,F,J: no original scale; D: 1.3mm; G: 0.05mm; H,I: 0.02mm; K: 0.008mm.