Bradabyssa ilyvestis (Hartman, 1960) Salazar-Vallejo, 2017

Salazar-Vallejo, Sergio I., 2017, Revision of Brada Stimpson, 1853, and Bradabyssa Hartman, 1967 (Annelida, Flabelligeridae), Zootaxa 4343 (1), pp. 1-98 : 68-69

Bradabyssa ilyvestis (Hartman, 1960) n. comb.

Figure 34

Ilyphagus ilyvestis Hartman, 1960: 130 –133, Pl. 13, Figs 1–3 .—Hartman 1969: 293–294, 3 textfigs.

Type material. Eastern Pacific Ocean. Holotype ( LACM 538), and 1 paratype ( LACM 539), Long Basin, 109 km off China Point, San Clemente Island, California, R.V. Velero IV, Sta. 6351 (32°01'00" N, 119°23'00" W), 1782 m, gray, stiff, silty-clay, 17 Aug. 1959.

Description. Holotype (LACM 538) truncate anteriorly. Body globose, depressed, 13 mm long, 5 mm wide, 16 chaetigers (paratype with ventral longitudinal dissection towards truncate end, 12 mm long, 6 mm wide, 16 chaetigers); tunic papillated; papillae abundant, elongate, tapered, densely covered by very fine sediment particles forming thick, tapered projections ( Fig. 34A ).

Anterior end missing in type specimens; details unknown. Parapodia lateral ( Fig. 34B ), completely covered by papillae. Median neuropodia ventrolateral. Notopodia and neuropodia close to each other.

Median notochaetae arranged in transverse series; all multiarticulate capillaries, articles short basally, mediumsized medially, alternating several short articles with one long distally ( Fig. 34C ), 8–9 chaetae per bundle, longest chaetae as long as 1/3 body width. Neurochaetae about twice as wide as notochaetae, arranged in transverse series, 4–5 per bundle, each with short articles thoroughly except subdistally, slightly widened, mucronate ( Fig. 34D ).

Posterior end rounded, pygidium with anus terminal, cirri absent.

Remarks. The original description indicates that the cephalic cage chaetae are missing but this is explained by the fact that the anterior end is missing, which is confirmed also by the lack of the dorsally displaced first chaetiger. So far, this species is unique in having a large number of notochaetae, which unlike other species, are less markedly thinner than neurochaetae, and by the thick sediment cover of body papillae. However, another species also possesses more than the usual number of notochaetae (1–3), B. mezianei n. sp. (see below). This was originally identified as I. cf ilyvestis by Amoureux (1982) because of the resemblance to the known species, but no further explanation was provided about any difference. As indicated below, this latter material includes specimens with anterior ends and showing different degrees of abrasion, such that a better understanding of both species is now possible. Their cephalic cage, as can be seen in one of the species, has very few, thin chaetae and consequently they cannot belong in Ilyphagus Chamberlin, 1919 , but rather in Bradabyssa .

Consequently, B. ilyvestis (Hartman, 1960) n. comb. resembles B. mezianei n. sp. because they both have elongate papillae forming fusiform sediment tubercles and many notochaetae per bundle. They differ because in B. ilyvestis there are more notochaetae per bundle (8–9), and the neurochaetae are subdistally swollen, whereas in B. mezianei there are only 3–5 notochaetae, and neurochaetae taper distally with a very slight subdistal swelling.

Distribution. Off San Clemente Island, California, in 2000 m.

Figures

FIGURE 1. Morphological features of Brada Stimpson, 1853, and Bradabyssa Hartman, 1967. A. Brada granulosa Hansen, 1880, lateral view. B. neurochaeta. C. Bradabyssa (olim Trophonia) rugosa (Hansen, 1880) n. comb., lateral view. D. Median parapodium. E. Notochaeta. F. Neurochaeta (modif. after Hansen 1880).

FIGURE 2. Brada granosa Stimpson, 1853. A. Neotype (USNM 1422407), lateral view, anterior end to the right (inset: small paratype, lower right in Fig. 3 A). B. Same, anterior end, ventral view (arrows point to gonopodial lobes). C. Non-type specimen (USNM 22851), head dissected, branchiae and palps removed (Br: branchial scar, PS: palp scar). Scale bars: A: 1.7 mm, B: 1.3 mm, C: 0.4 mm.

FIGURE 3. Brada granosa Stimpson, 1853. A. Juveniles (USNM 453). B. Non-type specimens (USNM 22851), chaetiger 2, right parapodium, anterior view. C. Same, notochaetal basal, medial and distal regions. D. Same, neurochaetal tips. E. Chaetiger 17, right parapodium, anterior view. F. Same, neurochaetal tips. Scale bars: A: 0.8 mm, B, E: 0.3 mm, C: 80 µm, D, F: 20 µm.

FIGURE 34. Bradabyssa ilyvestis (Hartman, 1960) n. comb.: A. Holotype (LACM 538), dorsal view, after a few seconds immersion in methyl green stain. Paratype (LACM 539), B. Median chaetiger, right parapodium, anterior view. C. Same, notochaetal basal, medial and distal regions. D. Same, neurochaetal basal, medial and distal regions. Scale bars. A: 0.9 mm, B: 0.1 mm, C – D: 30 µm.