Sigambra diazi, 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 diazi sp. nov. Fig. 2

Sigambra tentaculata : Liñero-Arana and Díaz-Díaz 2005: 68-69, fig. 2 (non Treadwell 1941).

Type material.

Holotype (ECOSUR 214) and paratype (ECOSUR 215), southern Caribbean, Venezuela, Laguna de Chacopata (10°39'50"N, 63°48'30"W), 1.5 m, sediments, 15 May 2000, O. Díaz-Díaz, coll.

Diagnosis.

Sigambra with median antenna reaching chaetiger 5-7, twice as long as laterals; tentacular segment four times wider than long, anterior margin smooth; dorsal cirri larger than ventral ones; chaetiger 2 without ventral cirri; notopodia with dorsal hooks and capillaries from chaetiger 4-5; median and posterior chaetigers with ventral cirri reaching neuropodial lobes tips; pharynx with 13-16 marginal papillae.

Description.

Holotype (ECOSUR 214) an anterior fragment, 7.5 mm long, 1.5 mm wide, 41 chaetigers, right parapodia of chaetigers 16 and 40 removed for observing parapodial features. Body obconic, cylindrical along chaetigers 1-22, depressed thereafter. Dorsal integument rugose, weakly areolate, especially along chaetigers 4-16 ( Fig. 2A ).

Prostomium blunt, three times wider than long. Palps with palpophores massive, directed ventrally, palpostyles digitate, with a basal oblique mark; interpalpal area distinct, right longitudinal depression better defined than left one, expanded posteriorly. Antennae tapered, median antenna twice as long as laterals, laterals barely surpassing palp tips, median antenna reaching chaetiger 2-3. Lateral antennal depressions distinct, more or less parallel to anterior margin of tentacular segment.

Pharynx barely exposed ( Fig. 2B ). Basal ring not exposed. Distal margin with 14 papillae, four centrolateral ones twice larger than others, each papilla prismatic, tips globular, variably developed.

Tentacular segment three times wider than long; dorsal tentacular cirri slightly longer than ventral ones, approximately half as long as dorsal cirri of chaetiger 1.

Parapodial cirri tapered throughout body. Dorsal cirri tapered, not basally expanded, longer than ventral ones ( Fig. 2C, D ). Ventral cirri shorter than neurochaetal lobes in anterior chaetigers, as long as neurochaetal lobes in median and posterior chaetigers, missing on chaetiger 2. Prechaetal lobe truncate, not projected along its upper margin, postchaetal lobes long, acute. Anterior and median parapodia with hypertrophied gonopores, some showing abundant sperm ( Fig. 2D , inset).

Notochaetae include dorsal hooks from chaetiger 4, heads of hooks fully exposed initially, progressively larger and exposing handles; one accessory capillary present from chaetiger 13. Neurochaetae include three or four short wide pectinates, approximately ten large thin pectinates, and many long finely denticulate capillaries.

Posterior region missing. In paratype tapered to a blunt cone ( Fig. 2E ). Pygidium laterally expanded, anus terminal, anal cirri ventrolateral, as long as last five or six chaetigers.

Oocytes not seen in parapodial spaces.

Etymology.

This species is named after Oscar Díaz-Díaz, Venezuelan polychaete specialist, working now in Chile, as a modest homage to his many publications on polychaetes, and especially because he sampled and processed the specimens including this newly described species. The specific epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Variations.

The paratype was complete. It is 9.5 mm long with 70 chaetigers, but last three chaetigers are hookless. The median antenna is twice as long as the laterals, and the tentacular cirri reach chaetiger 2 or 3 as in the holotype. In the paratype the dorsal hooks start on chaetiger 4, as in the holotype, but although in the holotype the additional capillary is seen from chaetiger 13, in the paratype they are visible from chaetiger 24.

Remarks.

Sigambra diazi sp. nov. resembles S. tentaculata (Treadwell, 1941) and it has been identified as such in previous studies, but the redescription by Moreira and Parapar (2002) of S. tentaculata helps for clarifying their differences. They differ in the relative shape of dorsal cirri, and in the size of ventral cirri in comparison to neurochaetal lobe. In S. diazi dorsal cirri are tapered, without basal enlargement, and ventral cirri in median and posterior chaetigers are as long as neurochaetal lobes, whereas in S. tentaculata , dorsal cirri are basally widened, and ventral cirri are shorter than neurochaetal lobes along body.

Distribution.

Only known from the southern Caribbean coast of Venezuela, in shallow muddy bottoms.

Figures

Figure 2. Sigambra diazi sp. nov. A holotype (ECOSUR 214), stained with Shirlastain-A, anterior region, dorsal view B same, frontal view of pharynx C Chaetiger 16, right parapodium, anterior view (arrow points to gonopore; inset: notohook) D Paratype (ECOSUR 215), stained with methyl green, posterior end, dorsal view E Chaetiger 40, right parapodium, anterior view (arrow points to gonopore; inset: hypertrophied gonopore with sperm, indicated with an asterisk, and central pectinate neurochaetae). Scale bars: 0.3 mm (A, B), 150 µm (C), 0.1 mm (D), 90 µm (E).