Apionsoma (Edmondsius) pectinatum (Keferstein, 1867)

Fig. 12A, C

Phascolosoma pectinatum Keferstein, 1867: 47–48, pl. 6 figs 9–12 (type locality: Pacific of Panamá).

Siphonides rickettsi Fisher, 1952: 386–388, pl. 22 (type locality: Punta Lobos, Espíritu Santo Island, Baja California Sur; under rocks; based on specimens reported in Steinbeck & Ricketts 1941 as Phascolosoma cf. gouldii).

Phascolosoma cf. gouldii (not de Pourtalès, 1851) – Steinbeck & Ricketts 1941: 345 (Punta Lobos, Espíritu Santo Island, Baja California Sur; under rocks).

Phascolosoma (Edmondsius) pectinatum – Gibbs & Cutler 1987: 54–55 (establishment of the subgenus).

Apionsoma (Edmondsius) pectinatum – Cutler 1994: 197–198 (generic transfer).

Material examined

MEXICO • 1 spec.; Nayarit, Banderas Bay, Manzanilla Beach, 20°44ʹ35ʺ N, 105°23ʹ14.8ʺ W; 26 Nov. 2004; depth 1 m; PSS et al. leg.; under rocks; ECOSUR-S0281.

Description (ECOSUR-S 0281)

Trunk 10 mm in length; rough yellowish brown body wall (Fig. 12A); scattered mammillate papillae on trunk and introvert. Introvert four times as long as trunk, with twenty digitiform tentacles surrounding nuchal organ; with claw-like hooks with seven basal spinelets (Fig. 12C), 40 µm long, arranged in 40 complete rings.

Longitudinal musculature divided in anastomosing bands. Four retractor muscles, attached equally close to ventral nerve cord near anterior quarter of trunk, negating the appellations ventral and dorsal. A pair of bilobed nephridia, posterior lobe twice as long as anterior lobe; nephridiopores open posterior to anus. Spindle muscle attached anterior to anus; free intestine.

Habitat

Intertidal; under rocks.

Distribution

Eastern Pacific: from southern Gulf of California to Panamá.

Remarks

This specimen agrees with the original description in Keferstein (1867) and the redescription in Cutler (1994). Recently, Silva-Morales & Gómez-Vásquez (2021) recorded the species from the southern Mexican Pacific, including a brief discussion of its apparent disjunctive distribution in the Tropical Eastern Pacific. The record of this specimen offers a new location for its distribution in the Eastern Pacific and confirms its continuous distribution in the Mexican Pacific.