Sigambra hernandezi, 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 hernandezi sp. nov. Figs 5 , 6 , 7

Sigambra grubii : Liñero-Arana and Díaz-Díaz 2005: 68, fig. 1 (non Müller 1858).

Type material.

Holotype (ECOSUR 216), and paratypes (8) (ECOSUR 217), Northwestern Caribbean, Chetumal Bay, Quintana Roo, México, Cayo Venado (18°45'04.51"N, 88°06'58.81"W), sandy substrate, 1.5 m, 5 Aug. 2004, J.A. Hoil-Baeza, coll.

Additional material.

Gulf of México. Tamiahua Lagoon, Veracruz, México, collected by J. A. de León González and M. E. García Garza. One specimen (UANL 4048), collapsed, 4 Nov. 1999 (6.5 mm long, 0.5 mm wide, 86 chaetigers, first dorsal hooks from chaetiger 24). Two specimens for SEM. One mature (UANL 4047), breaking into two parts, Sta. 1-09, 5 Nov. 1999 (11.5 mm long, 0.8 mm wide, 104 chaetigers, first dorsal hooks from chaetiger 14). Another one (UANL 5799), 23 Aug. 2002 (13 mm long, 0.9 mm wide, 103 chaetigers; first dorsal hooks from chaetiger 26). 131 specimens: One, Sta. T-02, 21°42'01"N, 97°35'54"W, 2.2 m. One, Sta. T-09, 21°36'10"N, 97°37'39"W, 2.5 m, 4 Nov. 1999. Three, Sta. T-02, 21°42'01"N, 97°35'54"W, 2.8 m, 7 Mar. 2000; Two, Sta. T-01, 21°42'01"N, 97°39'00"W, 2.8 m; Three, Sta. T-02, 21°42'01"N, 97°35'54"W, 2.8 m; three, Sta. T-04, 21°42'01"N, 97°32'52"W, 2.8 m: One, Sta. T-09, 21°36'10"N, 97°37'39"W, 3 m; one, Sta. T-10, 21°36'10"N, 97°34'45"W; one, Sta. T-11, 21°36'10"N, 97°32'09"W, 4 m; one, Sta. T-12, 4 m, 16 Aug. 2000; One, Sta. T-01, 21°42'01"N, 97°39'00"W, 3 m; three, Sta. T-02, 21°42'01"N, 97°35'54"W, 2.5 m; four, Sta. T-04, 21°42'01"N, 97°32'52"W, 1.5 m; three, Sta. T-05, 21°38'47"N, 97°39'13"W, 2 m; one, Sta. T-07, 21°38'47"N, 97°34'01"W, 3.5 m; two, Sta. T-08, 21°38'47"N, 97°31'14"W, 2.8 m; one, Sta. T-09, 21°36'10"N, 97°37'39"W, 2.5 m; one, Sta. T-10, 21°36'10"N, 97°34'45"W, 3.5 m; five, Sta. T-12, 21°36'10"N, 97°28'59"W, 3.8 m; four, Sta. T-13, 21°32'09"N, 97°36'04"W, 2 m; one, Sta. T-15, 21°32'09"N, 97°30'47"W, 2.5 m; one, Sta. T-16, 21°32'09"N, 97°27'19"W, 2.5 m, 25 Nov. 2000; four, Sta. T-01, 21°42'01"N, 97°39'00"W, 3.5 m; six, Sta. T-02, 21°42'01"N, 97°35'54"W, 2.5 m; one, Sta. T-05, 21°38'47"N, 97°39'13"W, 2.5 m; one, Sta. T-06, 21°38'47"N, 97°36'46"W, 3.8 m; six, Sta. T-07, 21°38'47"N, 97°34'01"W, 4 m; one, Sta. T-08, 21°38'47"N, 97°31'14"W, 2.5 m; five, Sta. T-09, 21°36'10"N, 97°37'39"W, 2 m; two, Sta. T-10, 21°36'10"N, 97°34'45"W, 3 m; five, Sta. T-11, 21°36'10"N, 97°32'09"W, 3.5 m; five, Sta. T-12, 21°36'10"N, 97°28'59"W, 3.5 m; eight, Sta. T-13, 21°32'09"N, 97°36'04"W, 2 m; four, Sta. T-14, 21°32'09"N, 97°32'48"W, 2.5 m; one, Sta. T-15, 21°32'09"N, 97°30'47"W, 2 m; one, Sta. T-16, 21°32'09"N, 97°27'19"W, 3 m, 12 Jul. 2001; three, Sta. T-01, 21°42'01"N, 97°39'00"W, 2.5 m; four, Sta. T-02, 21°42'01"N, 97°35'54"W, 2 m; two, Sta. T-03, 21°42'01"N, 97°34'19"W, 2.5 m; one, Sta. T-04, 21°42'01"N, 97°32'52"W, 1.8 m; two, Sta. T-05, 21°38'47"N, 97°39'13"W, 2 m; two, Sta. T-06, 21°38'47"N, 97°36'46"W, 2.2 m; three, Sta. T-07, 21°38'47"N, 97°34'01"W, 2.6 m; one, Sta. T-09, 21°36'10"N, 97°37'39"W, 2 m; one, Sta. T-10, 21°36'10"N, 97°34'45"W, 2.8 m; five, Sta. T-12, 21°36'10"N, 97°28'59"W, 3 m; one, Sta. T-13, 21°32'09"N, 97°36'04"W, 1 m; two, Sta. T-14, 21°32'09"N, 97°32'48"W, 2.5 m; one, Sta. T-15, 21°32'09"N, 97°30'47"W, 2 m; three, Sta. T-16, 21°32'09"N, 97°27'19"W, 2 m, 23 Feb. 2002. Chetumal Bay, Q. Roo, México. Two specimens (ECOSUR), N off Isla Tamalcab (18°38'30.45"N, 88°11'12.84"W), 1 m, sand, 1 Oct. 1996, P. Salazar-Silva, coll. (both complete, 9-10 mm long, 1.1-1.4 mm wide, 69-77 chaetigers; first dorsal hooks from chaetiger 22-28; two last chaetigers hookless). Three specimens (ECOSUR), Río Hondo (18°29'21.99"N, 88°18'32.97"W), sandy mud, 1.5 m, 3 Aug. 2004, J.A. Hoil-Baeza, coll. (anterior fragments, 3.0-3.5 mm long, 0.3-0.5 mm wide, 7-26 chaetigers; dorsal hooks from chaetiger 13-15). Seven specimens (ECOSUR), Punta Amainada (18°42'21.64"N, 88°09'12.36"W), sandy substrate, 1.5 m depth, 4 Aug. 2004, J.A. Hoil-Baeza, coll. (1.7-7.0 mm long, 0.2-0.4 mm wide, 29-68 chaetigers; dorsal hooks from chaetiger 10-32). Twelve specimens (ECOSUR), Cayo Venado (18°45'04.51"N, 88°06'58.81"W), sandy substrate, 1.5 m, 5 Aug. 2004, J.A. Hoil-Baeza, coll. (1.8-11.3 mm long, 0.2-0.8 mm wide, 25-63 chaetigers; dorsal hooks from chaetiger 11-28). Five specimens for SEM (ECOSUR), Cayo Venado, sandy substrate, 1.5 m, 5 Aug. 2004, J.A. Hoil-Baeza, coll. (1.7-6.5 mm long, 0.2-0.4 mm wide, 25-70 chaetigers; dorsal hooks from chaetiger 11-23). Southwestern Caribbean, Venezuela. Chacopata or El Maguey lagoons, seven specimens (ECOSUR), 2 m, 15 Feb. 2000, M. Liñero & O Díaz-Díaz, coll. (damaged, some without posterior region, antennae or tentacular cirri broken; smallest specimen with subdermal eyespots in bases of lateral antennae; 4.5-13.0 mm long, 1-2 mm wide, 56-102 chaetigers, first dorsal hooks from chaetiger 13-24).

Diagnosis.

Sigambra with median antenna reaching chaetiger 2-3, twice as long as laterals; tentacular segment 4 times wider than long, anterior margin smooth; dorsal cirri larger than ventral ones; chaetiger 2 without ventral cirri; notopodia with dorsal hooks from chaetiger 4-5, without capillaries; posterior region with two hookless chaetigers; pharynx with 13-16 marginal papillae.

Description.

Holotype (ECOSUR 216) slightly twisted along posterior region. Body contracted, cylindrical anteriorly, depressed medially and posteriorly, 9 mm long (paratypes 2.7-9.0 mm long), 2 mm wide (paratypes 0.6-2.0 mm wide), 76 chaetigers (paratypes with 33-82 chaetigers); right parapodia of chaetigers 19, 36, 37, and 62 removed for observing parapodial features. Dorsal integument smooth along chaetigers 1-9 ( Figs 5A , 6A ), areolate along chaetigers 10-22, smooth, annulated medially and posteriorly.

Prostomium blunt, 2.5 times wider than long ( Fig. 5B ). Palps with palpophores massive, as long as wide, palpostyles minute, short, barely exposed; interpalpal area indistinct. Antennae tapered, median antenna twice as long as laterals (smaller in smallest specimen, Fig. 6B , larger in largest specimen, Fig. 6F ), laterals surpassing palps anterior margin, median antenna reaching chaetiger 2 or 3. Lateral antennal depressions indistinct.

Pharynx fully exposed ( Figs 5B, C , 6D, J ), with 14 thick, prismatic papillae of similar size, with a short, globular tip. Basal pharynx ring rugose, without distinct papillae.

Tentacular segment six times wider than long, with a single series of transverse globular papillae, barely duplicate or with a few middorsal papillae ( Fig. 6G ); dorsal tentacular cirri slightly longer than ventral ones, approx. half as long as dorsal cirri of chaetiger 1.

Parapodial cirri tapered throughout body. Dorsal cirri slightly expanded basally, longer than ventral ones. Ventral cirri as long as neurochaetal lobes in anterior and median chaetigers, longer in posterior ones ( Fig. 5D, E ), missing on chaetiger 2. Prechaetal lobes truncate, not projected along its upper margin, postchaetal lobes long, acute. Anterior and median parapodia with hypertrophied gonopores, margin smooth ( Fig. 6F, H, I ).

Some smaller features are worth mentioning after their observation with SEM. In anterior chaetigers ( Fig. 7A ) there are some small round papillae or tubercles in the upper, posterior surface of parapodia ( Fig. 7B, C ), but their tips have 2-5 long cilia, and they probably are sensory structures. The hypertrophied gonopore has a cover of globular smooth, external protuberances ( Fig. 7B, D ).

Notochaetae include dorsal hooks from chaetiger 28 (in paratypes from chaetigers 11-28), barely exposed initially, handles progressively exposed, without accessory capillaries. Neurochaetae include two or three supracicular, short wide pectinates, 4-6 infra-acicular narrow pectinates, and abundant, long, finely denticulate capillaries.

Posterior region ( Figs 5F , 6C, E, K ) tapered into a small blunt cone; last two chaetigers hookless. Pygidium with two ventrolateral anal cirri, as long as last 2-4 chaetigers.

Oocytes inside parapodial spaces ( Fig. 5D , inset), ca. 100 µm in diameter.

Variation.

Specimens were 1.7-13.0 mm long, 0.2-2.0 mm wide, 25-104 chaetigers, with dorsal hooks starting on chaetiger 10-28 with a posterior displacement in larger specimens. The specimens from Tamiahua were slightly larger than those in Chetumal (up to 13 mm long, 104 chaetigers) but because the dorsal hooks start from chaetiger 24-26 whereas they start from chaetiger 14 in the smallest specimen (6.5 mm long), they are regarded as belonging to the same species as the one from Chetumal (up to 11.3 mm long, 76 chaetigers, dorsal hooks from chaetiger 26-28; specimens 6-7 mm long had dorsal hooks on chaetiger 19-26). There were no accessory capillaries with notohooks. The supracicular, wider pectinates ( Fig. 7 E–G ) have small lateral, paired denticles, when compared to those present in S. grubii . Oocytes and sperm are present along coelom, but in the posterior region, there are mostly spermatids ( Fig. 7 H–J ), each ca. 1.3 µm in diameter.

Etymology.

This species is named after Dr. Héctor A. Hernández-Arana, quantitative benthic ecologist in ECOSUR-Chetumal, in recognition of his many studies on brackish water environments in southeastern México, and especially because he led the research study where Chetumal Bay specimens were collected. The specific epithet is a noun in the genitive case ( ICZN 1999, Art. 31.1.2).

Remarks.

Sigambra hernandezi sp. nov. resembles S. grubii Müller, 1858 because they have dorsal hooks without capillaries. They differ especially in the relative size of median antenna, and in the number of posterior chaetigers without hooks. In S. hernandezi the median antenna is short, reaching chaetiger 2-3, and there are two hookless chaetigers in the end of body, whereas in S. grubii the median antenna is medium sized, reaching chaetiger 3-4, and there are six hookless posterior chaetigers. Another subtle difference is the relative size of papillae along body, which are smaller in S. hernandezi and larger in S. grubii .

In Tamiahua Lagoon, S. hernandezi was an important member of the colonizing benthic polychaetes, being rare after defaunation and progressively becoming one of the more abundant species ( Sánchez-Hernández 2009), along a wide range of salinity (5-30‰). In Chetumal Bay, S. hernandezi was not among the most abundant species ( Hoil-Baeza 2009), and it was common in brackish water seagrasses ( Halodule sp.). The specimens included in this study were collected along the western shore of Chetumal Bay, which has the lowest salinity values ( Carrillo et al. 2009). The specimens from Venezuela are included here with hesitation because they are in suboptimal conditions, but they have a similar pattern in parapodial development and start of the dorsal hooks.

Distribution.

Grand Caribbean region, from Tamiahua Lagoon in northern Veracruz, México, to Chetumal Bay, Quintana Roo, in sediments in shallow brackish water; probably reaching the southeastern Caribbean in similar environments.

Figures

Figure 5. Sigambra hernandezi sp. nov., holotype (ECOSUR 216), stained with Shirlastain-A A anterior region, dorsal view B anterior end, dorsal view C same, right lateral view D chaetiger 19, right parapodium, posterior view (inset: close-up of oocytes exposed after body wall fracture) E chaetiger 62, right parapodium, posterior view F posterior region, dorsal view. Scale bars: 0.6 mm (A), 0.2 mm (B, C), 140 µm (D), 80 µm (E), 0.3 mm (F).

Figure 6. Sigambra hernandezi sp. nov. A small specimen, dorsal view, body dehydrated B same, anterior end, oblique dorsal view C same, posterior region, dorsal view (asterisk indicates last chaetiger with hooks) D another specimen, anterior end, frontal view E another specimen, posterior region, dorsal view (asterisk indicates last chaetiger with hooks). largest specimen (UANL 5799) F Anterior region, dorsal view (asterisk indicates globular structures enlarged in C) G same, close-up of papillae series in tentacular segment H same, close-up of interramal globular structures, outer wall broken I left parapodia, chaetigers 11 - 16, oblique frontal view (asterisk indicates gonopore) J another specimen (UANL 4047), anterior end, oblique frontal view K same, posterior region, dorsal view (asterisk indicates last chaetiger with hooks). Scale bars: 150 µm (A), 80 µm (B, C), 140 µm (D), 170 µm (E), 330 µm (F), 90 µm (G), 60 µm (H), 200 µm (I), 220 µm (J), 140 µm (K).

Figure 7. Sigambra hernandezi sp. nov. A larger specimen, Chetumal, dorsal view (asterisk indicates left chaetigers 8 - 9) B same, chaetigers 8 - 9, left parapodia, partial dorsal view (asterisk indicates cilia, arrow points to gonopore) C chaetiger 9, left parapodium, axillary ciliated papillae, seen from above D same, gonopore papillae, seen from above E large specimen, Tamiahua, anterior region, dorsal view, asterisk indicates left parapodia of chaetigers 3 - 4 F same, close-up of chaetae, seen from above G same, rotated, details of denticles in pectinate chaeta H another specimen, posterior region, dorsal view (arrow points to broken posterior chaetiger I same, rotated about 90 degrees, showing inner contents J same, spermatozoa. Scale bars inserted in micrographs.