Sigambra ligneroi, Salazar-Vallejo, Sergio I., Rizzo, Alexandra E., Leon-Gonzalez, J. Angel de & Brauko, Kalina M., 2019

Salazar-Vallejo, Sergio I., Rizzo, Alexandra E., Leon-Gonzalez, J. Angel de & Brauko, Kalina M., 2019, Four new Caribbean Sigambra species (Annelida, Pilargidae), and clarifications of three other Sigambra species, ZooKeys 893, pp. 21-50 : 21

Sigambra ligneroi sp. nov. Fig. 8

Sigambra wassi : Liñero-Arana and Díaz-Díaz 2005: 69-70, fig. 3 (non Pettibone 1966).

Type material.

Holotype (ECOSUR 218), southern Caribbean, Venezuela. 15 km west off Barcelona (10°06'50"N, 64°51'20"W), dredge, 22 m, 30 May 2000, I. Liñero-Arana & O. Díaz-Díaz, coll.

Diagnosis.

Sigambra with median antenna twice as long as laterals, reaching chaetiger 1-2; dorsal cirri larger than ventral cirri; chaetiger 2 with ventral cirri; dorsal hooks from chaetiger 26-28, without capillaries; pharynx with 8 marginal papillae.

Description.

Holotype (ECOSUR 218), anterior fragment, bent dorsally, slightly damaged ( Fig. 8A ). Body contracted, cylindrical anteriorly, depressed medially and posteriorly, 17 mm long, 4 mm wide (excluding chaetae), 49 chaetigers. Dorsal integument rugose, segment margins better defined along first 8 chaetigers, then crenulated along medial and posterior segments. Left parapodia of chaetigers 1-9, 13, 14, and right parapodia of chaetigers 45-49 previously removed. Right parapodia of chaetigers 16 and 36 removed for observing parapodial features.

Prostomium blunt, three times wider than long ( Fig. 8B ). Palps with palpophores massive, as long as wide, palpostyles tiny, directed laterally; interpalpal area distinct, truncate anteriorly, expanded posteriorly. Antennae digitate, median antenna twice as long as laterals, laterals not reaching tips of palps, median antenna reaching chaetiger 1-2. Lateral antennal depressions indistinct.

Pharynx exposed with two rings ( Fig. 8D ). Basal ring rugose, with ca. 22 globular projections, better defined dorsally and laterally, basally shorter. Distal ring with 8 short, wide, conical papillae, arranged as 4 per side.

Tentacular segment five or six times wider than long; dorsal tentacular cirri slightly longer than ventral ones, approx. half as long as dorsal cirri of chaetiger 1.

Parapodial cirri tapered along chaetigers 1-4 (5), foliose, longer than wide thereafter; dorsal cirri longer than ventral ones, triangular along anterior chaetigers ( Fig. 8E, F ), basally wider in posterior ones ( Fig. 8G, H ), tips long, with globular brownish glands concentrated subdistally, especially along posterior chaetigers. Ventral cirri longer than neurochaetal lobes. Chaetiger 1 with dorsal cirri at least twice as long as ventral ones ( Fig. 8C, D ). Chaetiger 2 with dorsal cirri slightly longer than ventral ones. Prechaetal lobes rounded, more projected along its upper margin; postchaetal lobes long, acute.

Notochaetae include dorsal hooks from chaetiger 27, barely exposed, without accessory capillaries. Neurochaetae of two types: smaller and medium-sized fine denticulates and long smooth capillaries. No pectinate chaetae present.

Posterior region features unknown. Oocytes not seen.

Variation.

A larger specimen was recorded by Liñero-Arana and Díaz-Díaz (2005), and they also provided several illustrations, probably combining some features of both specimens. Their largest specimen was also an anterior fragment but twice as large and with more chaetigers (33 mm long, 5 mm wide, ca. 90 chaetigers). All body features match and they also included an illustration of the far posterior chaetigers; parapodial cirri are tapered, about twice as long as wide, dorsal hooks become more exposed and there is an additional chaeta, thick, slightly falcate, which might correspond to an acicula, instead of a capillary.

Etymology.

The species name is after Dr. Ildefonso (Mikel) Liñero-Arana, polychaete specialist from the Universidad de Oriente, Instituto Oceanográfico de Venezuela, Cumaná, in recognition of his many publications about Venezuelan polychaetes. The specific epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Remarks.

Sigambra ligneroi sp. nov. resembles S. wassi Pettibone, 1966 in having similar body, parapodia and prostomial shapes, such that the holotype plus another specimen were identified as the latter species. They differ, however, in several features, the most important ones being the relative size of antennae, the length of parapodial cirri on chaetiger 1, and the number of marginal pharyngeal papillae, or at least their shape. In S. ligneroi the median antenna is twice as long as laterals, dorsal cirri are three times longer than ventral one on chaetiger 1, and there are eight regular papillae on the pharynx. By comparison, in S. wassi antennae are subequal, dorsal cirri are twice as long as the ventral ones (cf. Wolf 1984: 29.7, fig. 29.4c), and there are ca. eight irregularly-defined papillae on the pharynx.

As indicated in the key below, S. ligneroi also resembles S. healyae Gagaev, 2008 because both have ventral cirri on chaetiger 2, and their pharynx has 8 papillae. They differ by the relative size of antennae, and in the start of dorsal hooks; in S. ligneroi median antenna is twice as long as laterals, and dorsal hooks start on chaetiger 26-28, whereas in S. healyae antennae are subequal and dorsal hooks start on chaetiger 4.

Distribution.

Only known from the type locality, off Barcelona, Venezuela, in sediments of water depths of 22 m.

Figures

Figure 8. Sigambra ligneroi sp. nov., holotype (ECOSUR 218) A dorsal view B anterior region, dorsal view, after Shirlastain-A staining C same, ventral view D same, right lateral view E chaetiger 16, right parapodium, anterior view F same, dorsal cirrus and chaetal lobes G chaetiger 36, right parapodium, anterior view (inset: notohook) H same, dorsal cirrus and chaetal lobes. Scale bars: 1.4 mm (A), 1 mm (B), 1.7 mm (C), 1.6 mm (D), 0.3 mm (E, G), 180 µm (F), 250 µm (H).