Chrysopetalum elegantoides

Description. Based on the best-preserved specimen (ECOSUR- 2991): complete with 78 segments. TL = 10.2 mm, TW = 1.5 mm. Body long, broad, tapered posteriorly (Fig. 20 A). Body whitish to pale yellow. Paleae fan bright yellow, slightly imbricated dorsally. Prostomium visible between the first two segments. Lateral antennae short, inserted on the antero-ventral prostomial margin, median antenna slightly shorter than lateral ones, inserted in front of the first pair of eyes. Eyes red-violet, two pairs, first pair larger. Nuchal organ, small, not covering the prostomium (Fig. 20 B). Palps long, cylindrical, visible in dorsal view. Mouth fold large, placed between segment 3 and 4. Pharynx eversible, not exposed, stylets thick. Parapodium from segment 35, notochaetae in three main groups (Fig. 20 E). Notochaetae: lateral group inserted below notaciculum, 2 – 6 paleae, narrow and asymmetrical, with 2 – 3 (4) internal ribs and 1 raised rib (Fig. 20 G). Main group, 10 – 14 paleae; lateral-most paleae, slender and asymmetrical, with (4) 5 – 6 internal ribs and 0 – 1 raised rib (Fig. 20 H); mid-most paleae, asymmetrical or symmetrical, with (5) 6 – 7 (8) internal ribs (Fig. 20 I); midlinemost paleae, broad and asymmetrical, with 6 – 7 internal ribs (Fig. 20 J). Median group, 2 – 4 paleae, shorter, narrow and asymmetrical, with 3 – 4 internal ribs and 1 raised rib (Fig. 20 K). All paleal groups with margins markedly serrated, including the small dorsal spines (Fig. 20 F); paleal dorsal surface ornamented with tiny tubercles. Neuropodium conical, longer than notopodium. Neurochaetae: unit 1, 1 – 2 falcigers, blades straight and long, 14 – 15 times longer than wide (Fig. 20 L). Unit 2, 7 – 8 falcigers, blades straight and medium-sized, 6 – 7 times longer than wide (Fig. 20 M). Unit 3, 5 – 6 falcigers, blades straight and medium-sized, 5 – 7 times longer than wide (Fig. 20 N). Unit 4, 4 – 5 falcigers, blades straight and short, 4 – 5 times longer than wide. Pygidium rounded with two anal cirri (Fig. 20 C). Oocyte size: 25.6 – 30 µm (n = 4) (Fig. 20 D). Habitat. Intertidal to subtidal (1 – 11.7 m). Specimens of this species were collected in rocks, dead coral, pier piles, and as epibionts on sponge, mollusk, and sabellariids tubes. The species has been collected on living and dead coral, coarse sand and pier piles (Aguado et al. 2003; Cruz-Gómez & Bastida-Zavala 2018).

Figs 20, 25, 26

Remarks. The specimens of C. elegantoides revised herein agree with the description by Aguado et al. (2003). Originally, Aguado et al. (2003) stated that specimens of C. elegantoides lack interramal gland, and this feature was used to differentiate it from other related species such as C. elegans Bush in Verrill, 1910. However, the morphological significance should be reevaluated in order to confirm if the feature is useful to separate species. According to Watson (Pers. Comm. 2020), the development of the interramal gland, along with the cirrophoral gland, depends on the maturity of the specimen examined.

Distribution. From La Paz Bay, Baja California Sur to Uvas Island, Panama (Fig. 26).

Type locality: Rosario Beach, Coiba Island, Panamá, on dead coral at 2.5 m (Aguado et al. 2003). Material examined. Nine specimens. Baja California Sur: ECOSUR- 2991, El Caimancito Beach, February 29, 2004; ECOSUR- 2981, La Paz Bay, 1 m, March 02, 2004. Sinaloa: UANL- 0046, 2 spec. Mazatlán, July 18, 1985, coll. SSV. Jalisco: ECOSUR-XXX Melaque, December 01, 2004. Michoacán: UMAR-Poly 938, 2 spec. Caleta de Campos, pier piles, 3 m, October 7, 1994, coll. RBZ & SGM. Guerrero: ECOSUR- 3001, Los Cantiles, 5 m, May 26, 2000; ECOSUR-P 2985, La Quebrada, on Pinctada sp., 2 m, May 25, 2000; ECOSUR-PXXX, La Quebrada, on Pinctada sp., 6 m, May 25, 2002, coll. AM; UMAR-Poly 939, 2 spec. Coral Beach, 17 º 40 ’ 36 ” N, 101 º 39 ’ 22 ” O, Ixtapa, on dead coral, 1. 5 m, September 19, 2007, coll. SGM et al. Oaxaca: ECOSUR- 2993, La Entrega, on stromatolite, 3 m, May 23, 2000; UMAR-Poly 940, Estacahuite Bay, 15 º 40´05 ” N, 96 º 28´56 ” W, on dead coral, June 3, 2007, coll. JJG & PHM; UMAR-Poly 941, Corralero Lagoon, 16 º 14´11 ” N, 98 º 11´36 ” W, on sand, June 18, 2009, coll. JMM & JRC.

(Figures 4 A – J, 5, 8, 14 F, 15 C)

Description. Based mainly on the largest complete specimen, 8.7 mm long, 1.3 mm wide, 68 segments. Body rectangular and wide in the most anterior segments. Body yellow to orange. Paleae fans yellow and iridescent, slightly imbricated over dorsum. Prostomium rounded and completely visible among the first four segments. Two lateral subulate antennae; a small median antenna inserted between two pairs of eyes. Two pairs of reddish eyes, first pair slightly larger than second pair. Nuchal fold smaller than prostomium. Two pear-shaped palps, visible under the lateral antennae. Small and subtriangular mouth fold between third and fourth segment. Eversible proboscis with two slim stylet. Parapodium from the tenth segment. Notochaetae separate in three main groups and two subgroups (Fig. 4 A). Lateral group inserted over the dorsal notoaciculum, comprising 3 – 6 slender and symmetrical paleae with 2 – 5 ribs and one raised rib (Fig. 4 E); over dorsal cirrus 3 – 5 small and slender spines (Fig. 4 F). As sub-unit 1, 1 – 2 asymmetrical and serrated paleae with 6 – 7 ribs and one raised rib (Fig. 4 G). Main group, comprising 12 – 15 asymmetrical and strongly serrated paleae with 5 – 7 raised ribs (Fig. 4 H). As sub-unit 2, three larger paleae (1 / 4 larger than main paleae) with 6 – 7 ribs and one raised rib (Fig. 4 I). Median group, comprising 3 – 4 symmetrical and spine-like paleae, slightly smaller than main paleae with 4 – 5 ribs and 1 raised rib (Fig. 4 J). The serration on all paleae groups is present in both lateral margins of each palea, in main and median group the serration is more marked only in one side margin. Neuropodium large and leaf-shape. Heterogomph neurochaetae composed of three groups (Figs 4 B – D). Neurochaetiger with 1 – 3 superior spinigers with a serrated straight blade. First three segments neurochaetaewith superior spinigers only. Mid-superior group and mid-inferior group indistinguishable, composed of 13 – 16 falcigers with medium and toothed blades (1 / 2 of spiniger blade length). Inferior group of 3 – 4 falcigers with short and serrated blades (1 / 4 of spiniger blade length). Pygidium rounded, with two anal cirri. Habitat. Intertidal to subtidal (0.5 – 11.7 m). Collected from sponges, pier pilings, as epibionts of mollusks, in dead coral and rocks.

Remarks. Chrysopetalum elegantoides was described from the Pacific coast of Panama. The specimens from Oaxaca accord with the description by Aguado et al. (2003). Nevertheless, we noticed possible intraspecific differences in the number of dorsal paleae. For comparison purposes, 14 complete specimens of Chrysopetalum elegantoides Aguado, Capa & San Martín, 2003, were measured: total length and total number of dorsal paleae from the 15 th segment. An average was obtained from the number of paleae from the left and the right bundles, assuming that descriptions of chrysopetalids paleae are based on the number of paleae of these bundles. Through statistical analysis we confirmed that variability in the number of paleae is size related, showing a direct association of 79 % (t cal = 4.51, t 0.05 (12) = 1.79; p <0.05) (Fig. 5).

Distribution. Central Pacific of America, from Ixtapa, Guerrero, to Uvas Island, coast of Panama (Aguado et al. 2003) (Fig. 8).

Material examined. Guerrero: ECOSUR-P 2939, five spec. (La Quebrada, Acapulco, 16 ° 50 ’ 47 ’’ N, 99 ° 54 ’ 55 ’’ W, on Pinctada mazatlanica (Hanley, 1856), 6 m, May 25, 2000, coll. A. Medina); ECOSUR-P 2940, one spec. (Los Cantiles, Acapulco, 16 ° 50 ’ 45 ’’ N, 99 ° 54 ’ 55 ’’ W, on bivalve shells, 8 m, May 26, 2000, coll. A. Medina); UMAR- Poly 856, five spec. (Coral Beach, Ixtapa, 17 ° 40 ’ 36 ’’ N, 101 ° 39 ’ 22 ’’ W, on dead coral, 4 m, September 19, 2007, coll. M. S García-Madrigal); UMAR-Poly 857, one spec. (La Ropa Beach, 17 ° 37 ’ 37 ’’ N, 101 ° 32 ’ 46 ’’ W, rocks, 0.5 m, September 19, 2007, coll. M. S. García-Madrigal); UMAR-Poly 858, four spec. (Manzanillo Beach, 16 ° 50 ’ 31 ’ N, 99 ° 54 ’ 37 ’’ W, on sponge from pier piling, 4 m, September 21, 2007, coll. M. S. García-Madrigal); UMAR-Poly 859, two spec. (La Quebrada, Acapulco, 16 ° 50 ’ 45 ’’ N, 99 ° 54 ’ 55 ’’ W, September 21, 2007, coll. M. S. García-Madrigal); UMAR-Poly 860, four spec. (La Roqueta Island, Acapulco, 16 ° 49 ’ 21 ’’ N, 99 ° 54 ’ 29 ’’ W, 0 – 4 m, September 21, 2007, coll. M. S. García-Madrigal); UMAR-Poly 861, one spec. (Zacatoso, 17 ° 03 ’ 46 ’’ N, 100 ° 19 ’ 46 ’’ W, on stony coral, 9.1 m, December 1, 2010, coll. S. D. Güenduláin); UMAR-Poly 862, one spec. (Caleta de Chón, 17 ° 36 ’ 49 ’’ N, 101 ° 33 ’ 18 ’’ W, on stony coral, 4.3 – 6.1 m, December 2, 2010, coll. S. D. Güenduláin); UMAR-Poly 863, three spec. (Morros de Potosí, 17 ° 38 ’ 49 ’’ N, 101 ° 37 ’ 44 ’’ W, on Pocillopora damicornis (Linnaeus, 1758), 6.1 – 11.7 m, December 3, 2010, coll. S. D. Güenduláin); UMAR-Poly 864, two spec. (Morros de Potosí, 17 ° 38 ’ 49 ’’ N, 101 ° 37 ’ 44 ’’ W, on P. damicornis, 11.7 m, December 7, 2010, coll. S. D. Güenduláin & R. N.); Oaxaca: ECOSUR-P 0339, one spec. (Tangolunda Bay, Huatulco, 15 ° 46 ’ 20 ’’ N, 96 ° 05 ’ 49 ’’ W, on coral, April 1, 1986, coll. G. Sandoval); UMAR-Poly 865, three spec. (El Arrocito Beach, 15 ° 45 ’ 38 ’’ N, 96 ° 06 ’ 00 ’’ W, on dead coral, 3 m, May 25, 2000, coll. J. R. Bastida- Zavala); UMAR-Poly 866, six spec. (Estacahuite Bay, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, dead coral, 3 m, April 9, 2005, coll. J. R. Bastida-Zavala et al.); UMAR-Poly 867, three spec. (La Tijera, 15 ° 41 ’ 14 ’’ N, 96 ° 26 ’ 34 ’’ W, on dead coral, 3 m, April 30, 2005, coll. J. R. Bastida-Zavala); UMAR-Poly 868, one spec. (Estacahuite Bay, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, on rocks, 3 m, July 30, 2005, coll. G. Ruíz-Cancino); UMAR-Poly 869, five spec. (Estacahuite Bay, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, on dead coral, 1 m, September 10, 2005, coll. J. R. Bastida-Zavala et al.); UMAR-Poly 870, four spec. (Estacahuite Bay, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, on rocks, 3 m, August 25, 2006, coll. J. R. Bastida-Zavala et al.); UMAR-Poly 871, thirty eight spec. (La Tijera, 15 ° 41 ’ 14 ’’ N, 96 ° 26 ’ 34 ’’ W, on dead coral, 2 – 4 m, September 12, 2006, coll. J. R. Bastida-Zavala); UMAR-Poly 872, sixteen spec. (Estacahuite Bay, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, 4 m, December 1, 2006, coll. M. S. García-Madrigal); UMAR-Poly 873, one spec. (mouth of Corralero Lagoon, 16 ° 14 ’ 11 ’’ N, 98 ° 11 ’ 36 ’’ W, on sabellariid tubes, 1 m, December 8, 2006, coll. J. R. Bastida-Zavala et al.); UMAR-Poly 874, one spec. (Panteón Beach, 15 ° 39 ’ 50 ’’ N, 96 ° 29 ’ 43 ’’ W, on dead coral, March 31, 2007, coll. Y. Solís & P. Maza); UMAR-Poly 875, two spec. (main pier, Puerto Ángel, 15 ° 39 ’ 55 ’’ N, 96 ° 29 ’ 28 ’’ W, on dock pilings, 0.5 m, May 20, 2007, coll. F. Cortés-Carrasco); UMAR-Poly 876, one spec. (El Arrocito Beach, 15 ° 45 ’ 38 ’’ N, 96 ° 06 ’ 00 ’’ W, July 4, 2007, coll. B. Martínez et al.); UMAR-Poly 877, one spec. (Chacahua Lagoon, 15 ° 58 ’ 07 ’’ N, 97 ° 41 ’ 01 ’’ W, on rocks, intertidal, November 10, 2007, coll. P. Hernández); UMAR-Poly 878, two spec. (Chacahua Lagoon, 15 ° 58 ’ 07 ’’ N, 97 ° 41 ’ 01 ’’ W, on sabellariid colony, 0.5 m, April 3, 2008, coll. J. Jarquín); UMAR-Poly 879, one spec. (Chacahua Lagoon, 15 ° 58 ’ 07 ’’ N, 97 ° 41 ’ 01 ’’ W, on artificial mount, April 3, 2008, coll. J. Jarquín); UMAR-Poly 880, two spec. (La Tijera, 15 ° 41 ’ 14 ’’ N, 96 ° 26 ’ 34 ’’ W, on dead coral, 3 m, April 17, 2009, coll. F. Cortés-Carrasco); UMAR-Poly 881, six spec. (Montosa Island, 15 ° 45 ’ 52 ’’ N, 96 ° 05 ’ 04 ’’ W, on Pocillopora damicornis, 2.7 – 5.8 m, February 22, 2010, coll. R. Granja-Fernández & S. D. Güenduláin); UMAR-Poly 882, two spec. (San Agustín Bay, 15 ° 41 ’ 23 ’’ N, 96 ° 14 ’ 05 ’’ W, on P. damicornis, 3.3 – 6.4 m, February 23, 2010, coll. R. Granja-Fernández & S. D. Güenduláin); UMAR-Poly 883, six spec. (Estacahuite Bay, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, on P. damicornis, 6.4 – 9.7 m, March 26, 2010, coll. A. López- Pérez & R. Zepeta); UMAR-Poly 884, four spec. (Salchi, 15 ° 40 ’ 05 ’’ N, 96 ° 28 ’ 56 ’’ W, stony coral, 6.1 – 7.9 m, March 26, 2010, coll. A. López-Pérez); UMAR-Poly 885, three spec. (Mazunte, 15 ° 39 ’ 42 ’’ N, 96 ° 33 ’ 21 ’’ W, on stony coral, 4.5 m, June 3, 2010); UMAR-Poly 886, six spec. (Mazunte, 15 ° 39 ’ 42 ’’ N, 96 ° 33 ’ 21 ’’ W, on P. damicornis, 7.5 m, August 11, 2010, coll. A. López-Pérez & R. Zepeta).