Thelepus crassibranchiatus Treadwell, 1901

Londoño-Mesa, Mario H., 2009, Terebellidae (Polychaeta: Terebellida) from the Grand Caribbean region 2320, Zootaxa 2320 (1), pp. 1-93 : 79

Thelepus crassibranchiatus Treadwell, 1901 reinstated

Figures 23 A-H

Thelepus crassibranchiatus, Treadwell, 1901:206 , Figs 69–71.

Thelepus cincinnatus, Hartman, 1959:530 .— Holthe, 1986b:164 (non Fabricius, 1780).

Type material: Holotype USNM 16114 (1) Mayaguez Harbor , Off Custom Harbor, Puerto Rico, 21.VI.1899. Sta. (142) 6070; 402–411m.

Description: Holotype incomplete, 40 segments, 27mm long, thorax 22mm long, 2mm wide (seg. 5), 2.7mm wide (seg. 12) ( Figs 23A,B ). Thoracic dorsum with numerous aligned tubercles of similar size. Upper lip short, rounded, slightly projecting forwards. Lower lip swollen, wide, projecting ventrally. Tentacular membrane short, with rounded edge ( Fig. 23C ); eyespots small, in single line, extending along entire tentacular membrane. Few tentacles, short, without pigmentation. First segments equal-sized. About 14 ventral shields ( Fig. 23D ); anterior most shorter, becoming wider and longer through 10 segments; then decreasing in size. No ventral groove, but with middle whitish line up to end of fragment. Last shields poorly developed. Two pairs of branchiae, the first longer, composed of thick filaments, but thinner than tentacles ( Figs 23E,F ). Filaments not completely sessile, emerging from small shared base. First pair of branchiae with 4 filaments on each side, and second pair with 2 filaments on each side. Nephridial papillae on segments 4–8, small, rounded, between noto- and neuropodium towards posterior margin of segment. Notopodial glandular tissue whitish, thin, dorsal to notopodium and along the first half of thorax. Twenty-nine pairs of notopodia equal-sized; notochaetae mostly broken; those complete in two intercalated lengths ( Fig. 23G ), smooth, bilimbate asymmetrically, with longitudinal striations. First 6 pairs of neuropodia flattened, then increasingly swollen but short and narrow up to end of fragment. Thoracic and abdominal uncini ( Fig. 23H ) with dental formula MF:2; PP and PF absent; Oc slightly convex; Cp with two teeth, as long as one half MF; Sr narrow; SrP as square button close to a rounded AP; SrA absent; AF absent; Bs curved. Pygidium missing.

Staining pattern: Ventral shields stain deeply on anterior thoracic region; then, staining decreasing in intensity toward the last shield. Notopodial glandular tissue stains lighter. Other structures do not stain.

Discussion: Thelepus crassibranchiatus was synonymized by Hartman (1959) with Thelepus cincinnatus . Holthe (1986b) followed this. Nevertheless, after the revision of material of T. cincinnatus from Sweden ( USNM 79669 (5) North Atlantic Ocean, Sweden, Loken, Skagerrak, 14.VI.1967; 37m. USNM 79670 (7) North Atlantic Ocean, Sweden, Smörkullen, Gullmar Fjord, 15.VI.1967; 40m), near the type locality ( Greenland), there are important differences, which justify considering T. crassibranchiatus as a valid species. Thelepus cincinnatus has nephridial papillae on segments 4–7, the first pair of branchiae with 14–20 filaments at each side, the second pair with 10–15 filaments at each side, notochaetae with narrower but longer symmetrical limbation, and uncini with dental formula MF:2:1–2. Also, T. cincinnatus has large and small dorsal tubercles, transversally aligned in number of 4–11 tubercles, on both the thoracic and abdominal dorsum. These large tubercles are lighter without stain, but deeply colored when stained. Tubercles of T. crassibranchiatus are similar in size but without any staining pattern. The presence of dorsal tubercles in T. cincinnatus , with an irregular arrangement, has been commented on by Fauvel (1927), as well as the characters mentioned and was seen in the specimens from Sweden by Holthe (1986a).

Thelepus crassibranchiatus differs from other species described in the Grand Caribbean , mainly in terms of the number of pairs of branchiae present. Also, it differs from Thelepus tenuis ( Verrill, 1900) comb. nov., with regards to the type of chaetae and the uncinal dental formula (see below) present

Type locality and distribution: Mayaguez Harbor , Puerto Rico .

Figures

FIGURE 23. Thelepus crassibranchiatus (Holotype USNM 16114): A. Dorso-lateral view. B. Ventro-lateral view. C. Anterior end in dorsal view. D. Anterior end in ventro-lateral view. E. Anterior end in dorso-lateral view. F. Anterior end in dorsal view. G. Fascicle of notochaetae from segment 18. H. Uncini from segment 18. Scale bars: A,B: 3.1mm; C: 0.7mm; D,E,F: 1.4mm; G: 0.1; H: 0.03mm.