Chiton articulatus 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 : 471-472

Chiton articulatus G. B. Sowerby I, 1832

Figures 11F–K , 12A–C

Distribution. From Mazatlán, Sinaloa to La Ventosa, Oaxaca, including Isla Socorro, Revillagigedo, México ( Reyes-Gómez 2016).

Type specimens. According to Bullock (1988) and Kaas et al. (2006) holotype in BMNH? but not found.

Type Locality. Guaymas, Sonora, Gulf of California; Bullock (1988) mentioned that the record from Guaymas is doubtful. To date there are no reports of C. articulatus at Guaymas. According to the first author of this study ( Reyes-Gómez ) and based on her explorations at Bahía Navachiste , Sinaloa ( northern Mazatlán ), Puerto de Guaymas , Bahía San Carlos and Bahía Kino , Sonora there is no evidence that this species ranges up north of Mazatlán .

Material examined. 153 specimens, maximum size of 65.9 mm 32.8 mm wide. N (n=9); K (n=12); R (n=7) ; T (n=11); P (n=6); M (n=16); C (n=4); B (n=9); D (n=13); U (n=6); S (n=7); H (n=5); E (n=10); L (n=5); N (n=4); J (n=6); I (n=3); Q (n=14); F (n=2); A (n=4).

Habitat. This species was found abundant in all of our surveys. It was mostly found in the intertidal during low tides, between rocks and crevices and occasionally in tide pools, and in high energy wave areas. Juvenile specimens were found at 3–5 m depth on small rocks buried in sand.

Remarks. Examination of specimens from Oaxaca (Puerto Ángel, Estacahuite, Salina Cruz), Guerrero (Costa Chica, Acapulco, Costa Grande) and Mazatlán (Playa Norte, Playa Faro, Isla Venados) revealed an unique color pattern for specimens from each region. We identified that the specimens from Oaxaca display a mostly light to dark olive-green tegmentum, while tegmentum color of specimens from Guerrero showed a variety of, vary from red to brown, and from dark to lighter green. Specimens from Sayulita, Nayarit (e.g., CNMO 40012) are mostly olivegreen with irregular dark lines (6–9), arranged longitudinally along the diagonal ridge and on the posterior margin of intermediate valves which show a “zebra” like pattern ( Figs. 20N ). Specimens from Mazatlán exhibit radial bands (to the valve apex) of purple or dark red color, which turn brown post mortem. These bands are exclusive of chitons from this region ( Figs. 20A–C ).

Chiton articulatus is the most studied chiton species from México ( Avila-Poveda & Abadia-Chanona 2013; García-Ibáñez et al. 2013; Ramírez-Álvarez et al. 2013; Abadia-Chanona et al. 2016). These works have contributed greatly to the knowledge of its reproductive cycle. It is important for local fisheries. These studies also emphasized the negative effects of its human consumption and how this has contributed to the decrease in abundance and density of the natural populations year after year. Other studies ( Holguín-Quiñones & Michel-Morfín 2002; HolguínQuiñones 2006; Ríos-Jara et al. 2006; Flores-Campaña et al. 2007; García-Ibáñez et al. 2013; Flores-Rodríguez et al. 2014) have focused on the rocky intertidal community composition including this species, and its importance within this habitat from Mazatlán, Jalisco, Michoacán, Colima, Guerrero and Oaxaca. García-Ibáñez et al. (2014) have addressed the decline of C. articulatus populations and how it has negatively modified the population´s structure and assemblage of other species like the gastropod Plicopurpura pansa ( Gould, 1853) , which feeds on this species. Álvarez-Cerrillo et al. (2017) reported a variety of epibionts (Arthropoda, Bryozoa, Annelida, Chordata, and Mollusca) inhabiting the valves of a single specimen of C. articulatus .

Figures

FIGURE 11. Chiton albolineatus, disarticulated valves of a specimen BL 18.3 mm, Piedra de Tlacoyunque, Tecpan de Galeana (CNMO 5337), valves in ventral view, A, head valve; B, intermediate valve IV; C, tail valve. SEM images of a specimen BL 12.4 mm length; valves in dorsal view, D, detail of girdle scales; E, radular teeth. Chiton articulatus, disarticulated valves of a specimen BL 26.4 mm, Barra de Potosí, Zihuatanejo de Azueta (CNMO 5291), valves in dorsal view, F, head valve; G, intermediate valve IV; H, tail valve. Valves in ventral view, I, head valve; J, intermediate valve IV; K, tail valve.

FIGURE 12. Chiton articulatus, SEM images of a specimen BL 28.3 mm length; A, detail of girdle scales; B, radular teeth; C, detail of central and minor lateral teeth. Tonicia forbesii, BL 19.5 mm, Isla Grande, Zihuatanejo deAzueta (CNMO 5255). Valves in dorsal view, D, head valve; E, intermediate valve IV; F, tail valve. Valves in ventral view, G, head valve; H, intermediate valve IV; I, tail valve; J, detail of lateral and central area of intermediate valve IV; K, detail of lateral area ocelli.

FIGURE 20. Chiton articulatus, specimen BL 27 mm, El Faro, Mazatlán (CNMO 5661); shows the tegmentum color details A, head valve; B, intermediate valves III-V; C, tail valve. Specimen BL 24.45 mm, Santa Elena, Oaxaca (CNMO 1066); shows color tegmentum details; D, head valve; E, detail of intermediate valves III-V; F, tail valve. Chaetopleura lurida, G, dorsal view of whole specimen BL 21.3 x 13.7 mm, Estacahuite, Oaxaca (CNMO 5813). Chaetopleura lurida, specimen of 27.9 x 15.4 mm, dorsal view of valve I and IV, Isla Partida, Baja California Sur (CNMO 1004), H, head valve and I, valve IV; J, whole specimen BL 25.8 mm, Sayulita, Nayarit; K, Ischnochiton muscarius, whole specimen BL 27.6 mm in dorsal view.Callistochiton elenensis, L, whole specimen BL 19.46 mm, La Paz, Baja California Sur (UAGRO 0060); M, detail of sculpturing of valves II-IV; N, Chiton articulatus, N, whole specimen in dorsal view, BL 37.2 mm, Sayulita, Nayarit (CNMO 40012).