Pycnoderma escobarae, Salazar-Vallejo, Sergio I., 2011

Salazar-Vallejo, Sergio I., 2011, Revision of Piromis Kinberg, 1867 and Pycnoderma Grube, 1877 (Polychaeta: Flabelligeridae), Zootaxa 2819, pp. 1-50 : 35-36

Pycnoderma escobarae n. sp.

Figure 15

Type material. Western Gulf of Mexico. Holotype (ECOSUR-103), R/V Justo Sierra Cruise Sigsbee 2, Sta. 22 (21°12.110ʹ N, 96°56.029ʹ W), off Tuxpan, Veracruz, Mexico, 246 m, muddy sand, 30 Jun. 1999, E. Escobar, coll.

Description. Holotype incomplete, without posterior end, anteriorly blunt, cylindrical, with some irregular constrictions towards anterior end, several chaetae broken ( Fig. 15 A); anterior third of body golden, yellowish, with some tiny dark particles, rest of body pale; tunic finely papillated. Body papillae small, thin, cirriform, covering body, mostly eroded, arranged along body in several transverse rows; larger papillae subchaetal in notopodial and neuropodia. Holotype 28 mm long, 1 mm wide, cephalic cage 1.3 mm long, 67 chaetigers.

Details of anterior end unknown. Cephalic cage chaetae broken ( Fig. 15 B), one left slightly longer than body width. Only chaetiger 1 involved in cephalic cage, notochaetae in chaetiger 2 not more than twice as long as those in following chaetigers. Cephalic cage notochaetae in short dorsolateral row; neurochaetae in short lateral row; 1–2 noto- and 3–4 neurochaetae per bundle, longest neurochaetae about 1/3 as long as notochaetae. Anterior dorsal margin of first chaetiger short, papillae eroded. Anterior chaetigers without especially long papillae. Chaetigers 1– 3 of similar length, second parapodia displaced dorsally. Chaetal transition from cephalic cage to body chaetae abrupt; multiarticulate neurohooks from chaetiger 2; oligo-articulate neurohooks beginning from chaetiger 16, mostly broken. Gonopodial lobes not seen.

Parapodia poorly developed, lateral. Median neuropodia ventrolateral. Notopodia long, thin lobes, each usually with two long, capitates, infrachaetal papillae, superior one larger. Neuropodia long lobes, each with single infrachaetal papilla, smaller than notochaetal papillae.

Median notochaetae in transverse row, 1–2 per bundle (3–4 in posterior chaetigers), 1/2–1/3 as long as body width (posterior notochaetae 1.5 times as long as body width); all notochaetae multiarticulated capillaries with very long articles basally, slightly decreasing in size medially and distally ( Fig. 15 E, F). Neurochaetae multiarticulate in chaetigers 2–15 ( Fig. 15 D), oligo-articulate in following chaetigers, arranged in a transverse row. Neurohooks from chaetiger 16, 3–4 per bundle, each with anchylosed, short articles, and two longer articles ( Fig. 15 E); blade long, lanceolate, aristate ( Fig. 15 G).

Posterior region tapering ( Fig. 15 C); pygidium unknown.

Etymology. This species is named after Dr. Elva Escobar, a Mexican deep-sea biologist who has coordinated several scientific cruises in the Gulf of Mexico, and because during one of those studies, this interesting specimen was found.

Remarks. Pycnoderma escobarae n. sp. resembles P. ferruginea ( Gallardo, 1968) n. comb. (see below). Both species have an opaque tunic with papillae and notochaetae with very long articles. They differ mainly because in P. escobarae n. sp., papillae are shorter and less abundant, while they are longer and more abundant in P. ferruginea ; further, P. escobarae n. sp. has less notochaetae per bundle (3–4), while P. ferruginea has twice as many notochaetae per bundle; the two species also differ in the relative number of articles per neurospine. Thus, P. e s c o - barae n. sp. has three articles and a smaller median one while P. ferruginea has only two articles.

Type locality. Off Tuxpan, Veracruz, Mexico, in muddy sands at about 250 m depth.

Distribution. Only known from the type locality in the Southwestern Gulf of Mexico, in muddy sands at moderate depths (246 m).

Figures

FIGURE 15. Pycnoderma escobarae n. sp. Holotype (ECOSUR 0000). A. Lateral view. B. Same, anterior end, dorsolateral view. C. Same, terminal part, dorsal view. D. Parapodium from chaetiger 9, notochaetae detached. E. Parapodium of chaetiger 29. F. Same, notochaetae with long articles. G. Same, oligoarticulate neurohooks (insert: close-up of longest neurohook tip). Scale bars: A: 2 mm, B: 0.5 mm, C: 0.5 mm, D: 80 µm, E: 170 µm, F: 30 µm, G: 100 µm.