Stenoplax limaciformis (G.B. Sowerby I, 1832)

Reyes-Gómez, Adriana, Flores-Garza, Rafael, Galeana-Rebolledo, Lizeth, Hernández-Vera, Gerardo, Galván-Villa, Cristian M., Torreblanca-Ramírez, Carmina, Flores-Rodríguez, Pedro, García-Ibañez, Sergio & Ríos-Jara, Eduardo, 2022, Intertidal chitons (Mollusca: Polyplacophora) from the rocky coastline of Guerrero, México, with the description of a new species, Zootaxa 5155 (4), pp. 451-492 : 466

Stenoplax limaciformis (G.B. Sowerby I, 1832)

Figures 2I–L , 9E–K , 10A–J

Distribution. Isla Tiburón and Isla Carmen, Gulf of California, México to Inner Lobos Island, Perú, western coast of Central America ( Bullock 1985).

Type specimens. Holotype BMNH 1980007 /1 (in Kaas & Van Belle 1987).

Type Locality. According to Kaas & Van Belle (1987) Inner Lobos Islands , Perú; Central America at Guacomayo .

Material examined. 115 specimens, maximum size of 33.5 mm long, 11.2 mm wide. K (n=12); L (n=10); M (n=8); N (n=12); D (n=12); B (n=9); F (n=10); A (n=8), U (n=13); J (n=5); G (n=5); H (n=7).

Habitat. This species is present in a variety of habitats and represents one of the most common chitons found in our surveys. It is also distributed in the shallow subtidal (6–12 m). Adult and juvenile specimens were found on medium-sized and smaller rocks, with crustose brown and red and filamentous green algae; it was occasionally found in tide pools and down to 12 m under stones in sand. It was found with C. lurida , C. albolineatus and occasionally with C. elenensis .

Remarks. Stenoplax limaciformis displays a highly variable tegmentum color and sculpturing patterns. Our examination revealed individuals with ribs formed by aligned nodules, while others show irregular, uninterrupted ribs. Some specimens bear irregular nodules (in size and shape) at the periphery of the valve’s tegmentum, which progressively become more regular towards the apex. Other specimens have ribs that are strongly discontinuous at the periphery and show a zigzag pattern around the mucro and on the jugal areas of the head and tail valve.

Figures

FIGURE 2. Dorsal view of the whole specimens that represent the analyzed species. A, Chaetopleura lurida, BL 27.48 x 15.70 mm, Majahua, Acapulco (CNMO 5229). B, Chaetopleura hanselmani, BL 11.02 x 7.16 mm, Tlacopanocha, Acapulco (CNMO 5804). Ischnochiton muscarius, C, BL 16.62 x 9.77 mm, Angosta, Acapulco (CNMO 5202); D, BL 15.12 x 9.55 mm, Barra de Potosí Protegida, Petatlán (CNMO 5338); E, BL 18.30 x 10.17 mm, Troncones, La Unión (CNMO 5327); F, BL 14.98 x 9.51 mm, La Barrita, Petatlán (CNMO 5315). G, Callistochiton elenensis, BL 12.32 x 7.76 mm, La Barrita, Petatlán (CNMO 5823). H, Callistoplax retusa, BL 20.41 x 9.68 mm, Parque de la Reina, Acapulco (CNMO 5185). Stenoplax limaciformis, I, BL 17.56 x 7.21 mm, Parque de la Reina, Acapulco (CNMO 5179); J, BL 20.12 x 9.15 mm, Tlacopanocha, Acapulco (CNMO 5208); K, BL 17.65 x 8.29 mm, Las Gatas, Zihuatanejo de Azueta (CNMO 5254); L, BL 19.78 x 9.84 mm, Isla Grande, Zihuatanejo de Azueta (UAGRO 0024). Chiton albolineatus, M, BL 23.84 x 14.63 mm, Piedra de Tlacoyunque, Tecpan de Galeana (CNMO 5337). Tonicia forbesii, BL 33.41 x 17.86 mm, Isla Grande, Zihuatanejo de Azueta (CNMO 5255). Acanthochitona arragonites, O, BL 8.80 x 5.2 mm, Las Salinas, Copala (CNMO 5267). Lepidochitona salvadorensis, P, BL 10.63 x 5.7 mm, Barra de Potosi Protegida, Zihuatanejo de Azueta (CNMO 5332).

FIGURE 9. Callistoplax retusa, SEM images of a specimen BL 15.1 mm, A, girdle bristles detail; B, detail of the ventral girdle spicules; C, radular teeth; D, detail of central and major lateral teeth. Stenoplax limaciformis, disarticulated valves of a specimen BL 20.45 mm, Tlacopanocha, Acapulco (CNMO 5310). Dorsal view of valves, E, head valve; F, intermediate valve IV; G, tail valve. Ventral view of valves, H, head valve; I, intermediate valve IV; J, tail valve. SEM images of a specimen BL 15.6 mm, valves in dorsal view; K, head valve.

FIGURE 10. Stenoplax limaciformis, SEM images of a specimen BL 20.45 x 9.25 mm, Tlacopanocha,Acapulco (CNMO 5310); dorsal view of valves, A, detail of intermediate area sculpturing; B detail of postmucronal area sculpturing; C, articulamentum detail of valve IV; D, insertion teeth; E, head valve in dorsal view; F, head valve sculpturing detail; G, detail of intermediate and lateral area of valve IV; H, girdle scales; I, radular teeth; J, detail of central teeth. Chiton albolineatus, disarticulated valves of a specimen BL 18.23 mm, Piedra de Tlacoyunque, Tecpan de Galeana (CNMO 5337); valves in dorsal view, K, head valve; L, intermediate valve IV; M, tail valve.