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.