Pycnoderma glabra ( Treadwell, 1901 ) Treadwell, 1901

Salazar-Vallejo, Sergio I., 2011, Revision of Piromis Kinberg, 1867 and Pycnoderma Grube, 1877 (Polychaeta: Flabelligeridae), Zootaxa 2819, pp. 1-50 : 38-39

Pycnoderma glabra ( Treadwell, 1901) n. comb.

Figure 17

Stylarioides glabra Treadwell, 1901:208 , Figs. 73–75; Treadwell, 1939:279 –280, Fig. 95.

Type material. Caribbean Sea. Holotype of Stylariodes glabra Treadwell, 1901 ( USNM 16162), Mayaguez Harbor, Punta del Algarrobo, R/V Fish Hawk 1898–99 Sta. (138) 6066, 16–17 fathoms.

Description. Holotype (USNM 16162) damaged, almost without chaetae; anterior end dissected ( Fig. 17 A). Body cylindrical, tapering posteriorly; individual papillae small, of about same size dorsally and ventrally, each with fine brown-red sediment making brown spherules, arranged in about ten transverse rows in median segments ( Fig. 17 B). Tunic in posterior chaetigers forming a crust ( Fig. 17 C). Below the tunic, dorsal surface with two large papillae per segment. Holotype 26 mm long, 1 mm wide, cephalic cage 2 mm long, 43 chaetigers.

Anterior end not exposed, torn away when the outer cover was removed, as stated in the original description (a label indicates the anterior end was loose in the bottle; now lost).

Cephalic cage chaetae twice as long as body width. Chaetigers 1–2 involved in the cephalic cage; notochaetae of chaetigers 3–4 directed forward, but chaetal size relationships unknown due to being broken. Cephalic chaetae in short row, about five per ramus.

Anterior dorsal margin of chaetiger 1 with median triangular projection; other details probably damaged or lost during the original tunic removal. First two chaetigers without long papillae (probably lost); one pair of larger papillae per segment, arranged in two longitudinal rows along body. Post-cephalic cage chaetigers not elongated. Chaetal transition from cephalic cage to body chaetae abrupt; large ventral hooks from chaetiger 2. Gonopodial lobes not seen.

Parapodia better developed on chaetigers 1–5(6). Noto- and neuropodia positioned on body corners. Notopodia provided with three long postchaetal papillae and about five long multiarticulated capillaries.

Median notochaetae arranged in short transverse row; 3–4 per ramus, as long as ½ body width, longer in posterior chaetigers; all notochaetae multiarticulated capillaries, articles small basally, longer medially and distally ( Fig. 17 D). Median neuropodia ventrolateral. Neuropodia less developed than notopodia; with no papillae observed. Neurochaetae broken, multiarticulated (bidentate?) hooks from chaetiger 2, arranged in transverse row, 4–5 per bundle, each with shorter articles basally, larger ones medially and distally ( Fig. 17 E). All neurohooks broken, start, number, extension of short articles and tips unknown.

Posterior end lost, terminal part regenerating.

Remarks. The specimen is severely damaged; the anterior end was eroded by the removal of the outer cover and the dissection that permitted the observation of the anterior end (now lost). Despite its preservation state, the median chaetigers show the bases of multiarticulate neurochaetae but the lack of the posterior region does not allow for a precise indication of the start of the anchylosed neurohooks. Consequently, its placement in Pycnoderma is provisional based on its general resemblance to two other species, rather than anything diagnostic. The anterior end was illustrated by Treadwell (1901, Fig. 74), but was confused with the pharynx; later ( Treadwell 1939), the structure was correctly regarded as a palp.

Pycnoderma glabra ( Treadwell, 1901) n. comb., is closely allied with P. talehsapensis ( Fauvel, 1932) n. comb., since both have cephalic cage chaetae as long as the first 7–8 chaetigers. They differ basically in the relative length of median notochaetae, being about as long as body width in P. gl a br a while they are about 1/3 body width in P. talehsapensis .

Distribution. Restricted to the type locality, Mayaguez, Puerto Rico, in 16–17 fathoms.

Figures

FIGURE 17. Pycnoderma glabra (Treadwell, 1901) n. comb. Holotype (USNM- 16162). A. Complete specimen, dorsal view (insert: anterior end, dorsal view). B. Same, anterior chaetigers, close up of tunic. C. Same, median chaetigers, close up of tunic. D. Notochaetae of anterior chaetiger, showing basal, medial and distal regions. E. Neurochaetae of anterior chaetiger (insert: close up showing articulation pattern). Scale bars: A: 1 mm, B, C: 0.4 mm, D: 40 µm, E: 65 µm.