Paleaequor psamathe Watson-Russell, 1986

Cruz-Gómez, Christopher & Bastida-Zavala, J. Rolando, 2018, Chrysopetalids (Phyllodocida: Chrysopetalidae) from the southern Mexican Pacific, including a new species, Zootaxa 4521 (1), pp. 61-88 : 76-77

Paleaequor psamathe Watson-Russell, 1986

( Figures 10 A–J, 13, 14J, 15G)

Paleaequor psamathe Watson-Russell, 1986: 168 –170, figs. 22–24. Type locality: Pelican Point (31°20’00’’N, 113°38’W), Sonora, Gulf of California at 13 m depth.

Material examined. Guerrero: ECOSUR-P2941, twelve spec. (La Quebrada, Acapulco, 16°50’47’’N, 99°54’55’’W, on Pinctada mazatlanica , 6–8 m, May 25, 2000, coll. A. Medina); ECOSUR-P2942, one spec. ( La Quebrada , Acapulco, 16°50’47’’N, 99°54’55’’W, on Muricanthus sp., 6–8 m, May 25, 2000, coll. A. Medina) ; ECOSUR-P2943, one spec. ( Los Cantiles , Acapulco, approx. 16°51’32’’N, 99°55’37’’W, on bivalves, 8 m, May 26, 2000 coll. A. Medina) ; UMAR-Poly 912, seven spec. ( Coral Beach , Ixtapa, 17°40’36’’N, 101°39’22’’W, on dead coral, 1.5 m, September 19, 2007, coll. M.S. García-Madrigal) ; UMAR-Poly 913, two 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 914, one spec. (Morro del Cerro Colorado, 17°40’47’’N, 101°30’31’’W, on Pocillopora damicornis , 3 m, August 30, 2010, coll. S.D. Güenduláin) ; UMAR-Poly 915, one spec. ( Manzanillo Beach , 16°50’31’’N, 99°54’37’’W, on P. damicornis , 3–6.1 m, December 4, 2010, coll. S.D. Güenduláin et al.) ; UMAR-Poly 916, 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 et al.); Oaxaca : UMAR-Poly 917, fifteen spec. (Carrizalillo Beach, Puerto Escondido, 15°85’95’’N, 97°07’87’’W, on bivalves, August 12, 2006) ; UMAR-Poly 918, one spec. ( Chacahua Lagoon , 15°58’07’’N, 97°41’01’’W, April 14, 2007) ; UMAR-Poly 919, one spec. ( Chacahua Lagoon , 15°58’07’’N, 97°41’01’’W, November 10, 2007, coll. P. Hernández) ; UMAR-Poly 920, one spec. ( Chacahua Lagoon , 15°58’07’’N, 97°41’01’’W, April 3, 2008) .

Description. Based mainly on the largest incomplete specimen, 2.2 mm long, 1 mm wide, with 21 anterior segments. Largest complete organism, 2.5 mm long, 0.7 mm wide, 29 segments. Body rectangular and tapered on final segments, pale yellow to reddish. Paleae fan yellow, with hyaline and iridescent tips, paleae fan slightly imbricated over dorsum. Prostomium semi-rectangular and retracted among the first two segments. Two large lateral antennae; a small median antenna inserted anterior to first pairs of eyes. Two pairs of reddish eyes, first pair bigger than second, some specimens with pair eyes fused. Nuchal fold semicircular and smaller than prostomium. Two cylindrical palps, visible in ventral view. Mouth fold wide along the segment, inserted just below to prostomium. Eversible proboscis with two slim stylet.

Parapodium from the fifteenth segment. Notochaetae separated in three main groups and one subgroup ( Fig. 10A ). Lateral group inserted over the notoaciculum; comprising 2–3 slender and feather-like paleae with 6–7 ribs (in posterior segments the number of lateral group increase to 5–7 paleae) ( Fig. 10G ); as sub-unit 1, 1–2 wide and symmetrical palea with 10–13 ribs ( Fig. 10H ). Main group, comprising 15 symmetrical paleae with 17–20 ribs and 0–6 raised ribs ( Fig. 10J ). Median group comprising three symmetrical and wide paleae, distal palea with 15 ribs and three raised ribs ( Fig. 10I ), the next proximal palea smaller with 17 ribs and three raised ribs, the most proximal and the smallest palea with 10–13 ribs and three raised ribs. Neuropodium conical and smaller than notopodium. Heterogomph neurochaetae composed of four groups ( Figs 10 B–F). Neurochaetigers with 1–3 superior spinigers heterogomph with a long and curved slim blade. In first five segments neurochaetae superior spinigers only. Mid-superior group with 3–4 falcigers with medium length blades (1/2 of spiniger blade length) and basal serration. Mid-inferior group with 6–9 falcigers with medium to short blades (1/2 of spiniger blade length) light serration basally. Inferior group of 4–7 falcigers with short and smooth blades (7/2 of spiniger blade length) with fine serration basally. Every blade of falcigers ending in terminal curve. Pygidium rounded, with two anal cirri, ventral view with a terminating ventral cone.

Habitat. Subtidal (1.5–11.7 m). Usually associated with bivalves and dead coral. Watson-Russell (1986) mentioned that the species is frequently associated with bottom substrata like rocks, algae, gorgonids, corals and mollusk shells.

Distribution. Tropical Eastern Pacific, from Sonora, Mexico to Gulf of Guayaquil, Ecuador; the apparently disjunct distribution of this species ( Watson-Russell 1986) is broken with this record from the southern Mexican Pacific ( Fig. 13 ).

Remarks. Specimens of Paleaequor psamathe from the southern Mexican Pacific accords with the description by Watson-Russell (1986). However, SPM specimens show differences in the number of lateral paleae and the shape of sub unit 1. In the first four segments, the number of lateral paleae was 2–3, similar to Watson-Russell (1986, 3–4 paleae). The difference became evident in the widest segments (10–15), where the number of lateral paleae increased to 5–7 in our specimens. On the other hand, Watson-Russell (1986) described the sub unit 1 as 1– 2 paleae with 10–13 ribs, similar to what was found in the revised specimens; nevertheless, the illustration of these paleae shows that they are slimmer than the ones present in our specimens. These differences may depend on the segment observed; Watson-Russell (1986) described the species from the 33th segment, while the segment used in our description was the 15th.

Figures

FIGURE 10. Paleaequor psamathe. A, parapodium middle segment; B–F, neurochaetal types; G, lateral palea; H, subunit 1 palea; I, median palea; J, main palea. Scale bars: 30 µm (BCDEF), 50 µm (GHIJ), 200 µm (A).

FIGURE 13. Historical and new records of Hyalopale sp., Paleaequor psamathe, Paleanotus bellis and P. purpurea. Empty symbols indicate previous records.