Lamispina polycerata Salazar-Vallejo 2020, n. sp.

Lamispina polycerata n. sp.

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Figures 2; 3; 8A, B

Diagnosis. Lamispina with few sand particles along dorsum; cephalic cage chaetae barely longer than body width; anterior margin of chaetiger 1 with 5–6 long, horn-shaped papillae; lamispines longer than body width, tips falcate, tapered.

Type material. Holotype (SIO A9842), AD 4987, Mound 12 West (08°55’51.60” N, 84°18’46.80” W), 999 m, 2 Nov. 2018, E. Cordes & E Cowell, coll. [MW 172256].

Description. Holotype (SIO A9842), an anterior fragment, bent dorsally, now broken into two pieces; anterior region bent dorsally, ventrolaterally expanded medially, 6.5 mm long, 1.3 mm wide, cephalic cage chaetae 2 mm long, 16 chaetigers (Figs 2A; 8A, B); posterior region 5 mm long, 1 mm wide, 11 chaetigers. Body pale, truncate anteriorly, tapered posteriorly. Tunic with a few sand particles adhering to papillae; papillae conical, mucronate, stiff; sand particles on median to posterior regions, not on anterior region. Dorsum with two transverse series of large papillae, four larger, forming longitudinal rows, at least along anterior chaetigers, posterior chaetigers with only two larger middorsal papillae rows. Venter with smaller conical papillae, 2–3 transverse rows per segment along a few anterior chaetigers, up to five rows per segment in median, and up to eight rows per segment in posterior chaetigers.

Cephalic cage chaetae slightly longer than body width; chaetigers 1–2 involved in cephalic cage with longer chaetae. Chaetiger 1 apparently damaged, with three notochaetae and one neurochaetae per side; chaetiger 2 with two notochaetae and seven neurochaetae. Chaetiger 3 with shorter chaetae, two notochaetae and seven neurochaetae, directed laterally.

Anterior end not observed in holotype; not dissected to avoid further damage. Living specimen (Fig. 8A) with palps pale, branchiae brownish, blunt or slightly tapered. Palps twice wider than branchiae and slightly longer than them. Other features unknown.

Anterior dorsal margin of chaetiger 1 papillose, papillae conical, middorsally with 5–6 larger ones (Figs 2B, C; 3A), middorsal papillae longest. Chaetigers 1–3 progressively longer. Chaetal transition from cephalic cage neurochaetae to body neurochaetae abrupt; lamispines present from chaetiger 4. Gonopodial lobes not seen (Fig. 2C).

Parapodia low transverse folds (Fig. 3B), more projected along posterior chaetigers. Notopodia dorsolateral, neuropodia ventrolateral. Notopodia with a longer basal papilla. Neuropodia with 2–3 longer papillae per segment.

Median notochaetae multiarticulated capillaries in fan-shaped bundles, up to 14 per side, longest ones twice longer than body width; articles anchylosed basally, medially 2–3 times longer than wide, progressively longer distally; tips straight (Fig. 3C). Neurochaetae in transverse rows, six per bundle, longest ones longer than body width; subdistally widened, tips falcate, acute (Fig. 3D).

Posterior region with parapodia slightly more projected laterally (Fig. 3E). Notochaetae and neurochaetae in fan-shaped bundles.

Posterior end processed for molecular studies; living specimen with posterior region tapered, chaetae progressively smaller (Fig. 8B); pygidium with anus terminal.

Etymology. The epithet is made by combining the Greek words for many (polýs) and horns (kérata), becoming latinised to polycerata. This indicates the 5–6 horn-like larger papillae positioned over the anterior margin of first chaetiger. The specific name is regarded as a noun in apposition (ICZN 1999, Art. 31.2).

Remarks. Lamispina polycerata n. sp. belongs in the species group having sand or other foreign particles on their tunic, together with L. ammophila Jimi & Kajihara, 2018 from Japan, L. amoureuxi Salazar-Vallejo, 2014 from the northeastern Atlantic, and L. keeli Salazar-Vallejo, 2014 from the Gulf of Mexico. The latter differs by having sediment particles concentrated mid-dorsally, and lamispines with bifid tips, whereas L. polycerata and the other two species have sediment particles throughout their dorsum, and lamispines with entire tips. In L. ammophila, the cephalic cage chaetae are 1.5–2.0 times longer than body width, whereas in L. amoureuxi and L. polycerata they are shorter, slightly longer than body width. The main differences are that in L. polycerata sand particles are few and concentrated along median and posterior chaetigers, and median chaetigers have lamispines longer than body width, whereas sand particles are abundant, and lamispines are shorter than body width in L. ammophila and L. amoureuxi.

On the other hand, if L. polycerata would be regarded as without sand particles, especially after finding only the anterior region, it would be joined with other three species having papillae stiff or conical and lamispines falcate, subdistally widened: L. carrerai Salazar-Vallejo, 2014 from the NE Pacific, L. gymnopapillata (Hartmann-Schr̂der, 1965) from the SE Pacific, and L. horsti (Haswell, 1892) from southern Australia. The main difference would be that in L. polycerata the cephalic cage chaetae are slightly longer than body width, whereas the other species have them 2–6 times longer.

Distribution. Only known from the type locality, off Pacific Costa Rica.