Saphobranchia ilys, Salazar-Vallejo, 2020

Salazar-Vallejo, Sergio I., 2020, Four new deep-water flabelligerid species from Pacific Costa Rica (Annelida Sedentaria, Flabelligeridae), Zootaxa 4885 (4), pp. 560-578 : 570-571

Saphobranchia ilys n. sp.

urn:lsid:zoobank.org:act:2D7FC8D5-5368-4CCC-B5A6-909FBB2B0C2F

Figures 5 , 8F, G

Diagnosis. Saphobranchia with tunic without sand particles; median chaetigers with notochaetae longer than body width; neurochaetae with tips falcate, basal anchylosed region ½-1/3 chaetal length, articles 4–5 times longer than wide; no gonopodial lobes.

Type material. Holotype ( SIO A9605 ), CR18-0028, Alvin dive 4973 slurp, Jaco Scar (09°07’04.80” N, 84°50’24.00” W), 1795 m, 19 Oct. 2018, V. Orphan & N. Gallo, coll. [ MW 172262 ] . Paratypes: Two fragments ( SIO A9725 ), one anterior, one posterior, probably from same specimen, Alvin dive 4977, mussel pot 2, Jaco Scar (09°07’04.80” N, 84°50’24.00” W), 1783 m, 23 Oct. 2018, E. Cordes & J. Klein, coll.

Description. Holotype (SIO A9605) mature female, without pygidium, greenish. Body anteriorly swollen, slightly bent laterally, tapered posteriorly ( Figs 5A ; 8F ); 31 mm long, 2.5 mm wide (widest by chaetigers 5–6, 4 mm), cephalic cage 8 mm long, 31 chaetigers.

Tunic papillated, sediment particles mostly fine, adherent along body, and few larger sand particles, especially dorsally, and some dorsal papillae basally swollen ( Fig. 5B ). Venter with digitate to conical papillae, 3–4 times longer than wide. Papillae short, about 1/5–1/10 as long as notochaetae, about five rows per chaetiger, especially visible in median and posterior chaetigers, anterior dorsal surface slightly eroded. Venter with smaller papillae, digitate, about five rows per chaetiger ( Fig. 8G ).

Anterior end features not visible; not dissected to avoid further damage.

Cephalic cage chaetae 2–3 times longer than body width. Chaetigers 1–2 forming cephalic cage, chaetae direct-ed anteriorly; chaetiger 3 with less chaetae, notochaetae about half as long as those of chaetiger 2. Chaetae arranged in short rows, dorsolateral thin fascicles along chaetigers 4–7, in fan-shaped fascicles posteriorly.

Chaetiger 1 with 7–8 notochaetae, 3–4 neurochaetae, longest ones basally anchylosed, medially and distally articulated, shorter ones completely articulated, articles 3–4 times longer than wide medially, progressively longer distally. Chaetiger 2 with three thinner notochaetae, 2/3 as long as those of chaetiger 1, anchylosed section progressively shorter in smaller chaetae; neurochaetae shorter, 1/3 as long as those of chaetiger 1, articles 3–4 times longer than wide medially, progressively longer distally. Chaetigers 3–7 damaged, most chaetae broken.

Anterior dorsal margin of chaetiger 1 with 2 larger, conical papillae. Chaetigers 1–4 progressively longer. No chaetal transition from cephalic cage to body chaetae; all neurochaetae multiarticulate. Gonopodial lobes not seen ( Fig. 5C ). Oocytes seen in an ovary fragment, with oil droplets between them, each about 80–100 μm in diameter.

Parapodia poorly developed, chaetae emerge from body wall. Parapodia lateral; median neuropodia ventrolateral. Notopodia with a larger, digitate postchaetal conical to digitate papillae along chaetigers 3–8; other notopodia and neuropodia with a few short papillae, each about as long as 1/5–1/10 notochaetal length ( Fig. 5D ).

Median notochaetae arranged in short transverse rows, chaetal fascicles fan-shaped, directed dorsally, up to twice longer than body width. All notochaetae multiarticulate capillaries; 9–10 per bundle, central notochaetae with basally anchylosed region up to half total length, basal chaetae fully articulated; articles 4–5 times longer than wide, becoming longer distally; tips straight ( Fig. 5E ). Neurochaetae about as long as body width; 7–8 per bundle, anchylosed region 1/2–2/5 total length, medially with articles 3–4 times longer than wide, progressively shorter distally; tips falcate ( Fig. 5F , inset).

Posterior region cylindrical ( Fig. 5G ), posterior end unknown.

Etymology. The specific name is the Greek word for mud, feminine, is because of the presence of fine sediment particles in the tunic and covering papillae, as opposed to having sand particles on them. The specific name is regarded as a noun in apposition ( ICZN 1999, Art. 31.2).

Variation. A paratype ( SIO A 9725 ) is 8 mm long, 2.8 mm wide, 10 chaetigers; anteriormost left chaetigers removed, integument with fine sediment particles making dorsal papillae look digitate to conical; epizoic organisms on chaetae making them look pilose. Cephalic cage chaetae 6 mm long; chaetiger 1 with eight notochaetae and seven neurochaetae; chaetiger 2 with eight notochaetae, 4/5 as long as those of chaetiger 1, and seven neurochaetae, half as long as those of chaetiger 1. Chaetiger 3 with smaller chaetae, neurochaetae directed laterally. Posterior fragment with seven chaetigers, 4 mm long, 1.4 mm wide .

Remarks. Saphobranchia ilys n. sp. resembles S. micans ( Fauchald, 1972) n. comb. from Western Mexico because they have long papillae, giving integument an hirsute appearance, by having a few sand particles along body, notochaetae far longer than body width in median chaetigers, and neurochaetae with articles longer than wide. They differ in neurochaetal features in median chaetigers. In S. ilys n. sp. articles are 4–5 times longer than wide, with a very slight reduction distally, and the anchylosed region is ½–1/3 chaetal length, whereas in S. micans they are progressively smaller, about twice longer than wide, and the anchylosed region is 1/5–1/6 chaetal length.

On the other hand, S. ilys n. sp. resembles S. omorpha n. sp. especially because both have pale body wall and brownish chaetae. They differ in the development of tunic papillae, associated sediment particles, parapodial development, and chaetal size in median chaetigers. In S. ilys n. sp. body wall is rugose because the dorsal papillae are short, blunt mainly with fine sediment and a few sand particles, parapodia are barely projected from the body wall, and chaetae are as long as body width. On the contrary, in S. omorpha n. sp. body wall is pilose because the fewer dorsal papillae are without sediment particles, or fine particles adhering forming a thin cover, parapodia are markedly projected laterally, and chaetae are up to 4 times longer than body width.

Distribution. Off Pacific Costa Rica, in 996–1784 m depth.

Figures

FIGURE 5. Saphobranchia ilys n. sp., holotype (SIO A9605). A. Dorsal view. B. Anterior region, dorsal view. C. Anterior region, ventral view. D. Chaetiger 14, right parapodium, posterior view. E. Same, notochaetal basal, medial and distal sections. F. Same, neurochaetal basal and distal sections (inset: neurochaetal tip). G. Posterior region, ventral view. Scale bars.- A: 2.1 mm, B: 1.1 mm, C: 1.5 mm, D: 0.65 mm, E, F: 17 μm, G: 0.7 mm.

FIGURE 8. Living specimens. A. Lamispina polycerata n. sp., holotype (SIO A9842), anterior fragment, left lateral view. B. Same, posterior fragment, dorsal view. C. Saphobranchia canela n. sp., holotype (SIO A1332), dorsal view. D. Same, ventral view. E. Same, anterior end, frontal view (Br: branchia, Pa: palp). F. S. ilys n. sp., holotype (SIO A 9605), dorsal view. G. Same, ventral view. H. S. omorpha n. sp., holotype (SIO A9595), dorsal view. I. Same, ventral view. Scale bars: A, B: 1.0 mm; C, D: 2.2 mm; E: 0.4 mm; F, G: 3.5 mm; H, I: 3.7 mm (Photos: Greg Rouse).