Caecum chilense Stuardo, 1962

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 106-109

Caecum chilense Stuardo, 1962

Figures 84 A–K, 85A–P, 86A–B, 127Q

Caecum chilense Stuardo, 1962: 5 , figs. 1–2, holotype MZUC 10345 (ex MZUC 1350 ), Bio Bio River delta, Concepcion Province, Chile.

Caecum chilense — Stuardo, 1970: 183, figs 1a, 2a; Marincovich, 1973: 30, figs. 62–63; Draper, 1985: 5, fig. 6; di Geronimo et al. 1995: 116, fig. 8; Ramírez et al. 2003: 259; Mattano & Zelaya 2013: 170.

? Caecum cf. orcutti — Cruz, 2007: 134, fig. 5.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1975 - 19.17 , Antofagasta Bay , Antofagasta Prov., Chile, intertidal to 7 m, 12 sh ; LACM 1975 - 28.13 , Los Molles , Aconcagua Prov., Chile, intertidal, 6 sh ; LACM 1975 - 21.12 , Antofagasta, Antofagasta Prov., Chile, 8–24 m, 75 sh ; LACM 1975 - 33.9 , Algarrobo , Valparaiso Prov., Chile, 3–8 m, 100+ sh ; LACM 1975 - 10.12 , Iquique , Tarapaca Prov., Chile, intertidal, 9 sh ; LACM 1964 - 16.25 , Iquique , Tarapaca Prov., Chile, intertidal, 1,500+ sh ; LACM 1972 - 76.21 , Pucusana , Lima Dept., Peru, intertidal to 7 m, 400 sh ; LACM 1935 - 155.3 , Independencia Bay , Ica Dept., Peru, 22 m, 420 sh ; LACM 1974 - 24.18 , San Lorenzo Island , Lima Dept., Peru, intertidal to 5 m, 65 sh ; LACM 1934 - 264.11 , Wenman Island , Galapagos Islands, 80 m, 34 sh ; LACM 1974 - 11.16 , Lobos de Tierra Islands , Piura Dept., Peru, 2–5 m, 20 sh ; LACM 1974 - 12.19 , Lobos de Tierra Islands , Piura Dept., Peru, 3–12 m, 5 sh ; LACM 1970 - 66.12 , Iquique , Tarapaca Prov., Chile, intertidal, 38 sh ; LACM 1935 - 156.5 , Independencia Bay , Ica Dept., Peru, 36 m, 32 sh ; LACM 1938 - 218.5 , 18 miles SE of Foca Island , Piura Dept., Peru, 21 m, 34 sh ; LACM 1938 - 216.4 , Sechura Bay , Piura Dept., Peru, 16 m, 32 sh ; LACM 1935 - 175.3 , Callao, Lima Dept., Peru, 5 m, 1 sh ; LACM 1935 - 160.1 , Lobos de Afuera Islands , Lambayeque Dept., Peru, 40 m, 60 sh ; LACM 1938 - 205.4 , Independencia Bay , Ica Dept., Peru, 15 m, 6 sh ; LACM 1974 - 23.6 , Ancon , Lima Dept., Peru, 2 m, 35 sh ; LACM 1974 - 7.4 , Lobos de Afuera Islands , Lambayeque Dept., Peru, 45 m, 75 sh ; LACM 1974 - 21.19 , Ancon , Lima Dept., Peru, 1–3 m, 50 sh ; LACM 1972 - 78.17 , North Chincha Island , Ica Dept., Peru, 6–13 m, 75 sh ; LACM 1974 - 4.4 , Guanape Island , La Libertad Dept., Peru, 32 m, 35 sh ; LACM 1938 - 208.3 , Hormigas de Afuera Islands , Peru, 88 m, 3 sh ; LACM 1973 - 75.3 , Westhoff Island , Los Lagos Prov., Chile, 23 m, 32 sh ; LACM 1973 - 74.4 , Darwin Channel , Aysen Prov., Chile, 8 m, 200+ sh . SBMNH: SBMNH 620158 , Isla Los Chimus , Ancash, Peru, 10–15 m, 25 sh ; SBMNH 621377 , Playa Pocoma , Arequipa, Peru, intertidal, 2 sh ; SBMNH 133100 , Iquique Harbor , Iquique, Tarapaca, Chile, 10–25 m, 1 sh ; SBMNH 622517 , Iquique , Tarapaca, Chile, 12 sh. BCD: Iquique, Chile, intertidal, 24 sh .

Original diagnosis. “Concha tubular, algo curvada. Su diámetro es un poco menor en el extremo distal o septal. Color amarllento, opaco o más o menos transparente, según el grosor de la concha. Con 26 a 29 anillos redondeados (a veces de seccion rectangular), sobresalientes, lisos y algo doblados siguiendo la curvatura de la concha. A veces se fusionan formando anchos anillos aplastados. Los anillos están separados por surcos que se hacen más anchos a medida que se alejan del extremo proximal u opercular. Como en otras especies, el borde concavo de la concha muestra los anillos más juntos que en el borde convexo. Abertura circular, con bordes más o menos afilados e inclinados hacia adentro. Septo generalmente erosionado; más elevado hacia el borde convexo de la concha. No se inserta muy profundamente de modo que está rodeado por un reborde bajo. Opérculo concavo, café amarillento con un núcleo central y alrededor de 10 anillos concéntricos.” Stuardo (1962: 5).

Description. Protoconch multispiral (about 2.0 whorls), planispiral, smooth ( Figs. 85 A–B), transition to teleoconch I marked by apertural varix ( Figs. 85 A–B). Teleoconch I short, sculptured with axial growth marks or irregular, flat, axial ribs, and fine longitudinal striae in interspaces ( Figs. 85 C–D), transition to teleoconch II marked by incised axial line ( Figs. 85 A–B, E). Teleoconch II about three times length of teleoconch I, smooth or sculptured with flattened, axial ribs, and fine longitudinal striae in interspaces ( Figs. 85 F–G), transition to teleoconch III marked by slight axial constriction, followed by increase in diameter ( Figs. 85 H–I). Teleoconch III smooth or sculptured with axial ribs and fine longitudinal striae in interspaces ( Figs. 85F, J ), transition to teleoconch IV marked by suture, followed by increase in diameter ( Fig. 86A ). Teleoconch IV smooth or sculptured with axial ribs and fine longitudinal striae in interspaces ( Figs. 85F, K ), transition to teleoconch V marked by suture, followed by increase in diameter ( Fig. 86A ). Teleoconch V (last growth stage) small for genus [Tol 1.68–2.38 mm], larger than previous stage, tubular, stout, mildly to moderately and regularly arched [Larc: 0.54–0.73 mm; Arc: 0.13–0.19 mm], subcylindrical with slight increase in diameter from posterior to aperture, semi-translucent to creamy white ( Figs. 84 A–D). Axial sculpture of up to 30 rather closely arranged flattened ribs ( Fig. 85O ). Axial interspaces shallow to obsolete, narrower than ribs ( Figs. 85 O–P). Surface smooth to glossy and sculptured with numerous, dense, longitudinal striae in interspaces ( Fig. 85K ). Posterior [Dpe: 0.35–0.49 mm] with rather thin edge, squared shoulder ( Figs. 85 O–P). Septum mucronate ( Figs. 85 O–P). Mucro blunt wedge, positioned along dorsal margin ( Figs. 84G, I ). Aperture [Da: 0.42–0.58 mm] with slight constriction ( Figs. 84G, I ). No varix. Lip smooth, weakly developed, with deflected peristome ( Figs. 84G, I ). Periostracum not observed. Operculum thin, light brown; exterior surface with 8–10 concentric rings ( Figs. 84 E–F). Conceptual reconstruction of growth stages shown in Fig. 86A .

Distribution and Habitat. Caecum chilense is known from Puerto Cayo, Ecuador to the O’Higgins National Park, Chile, as well as the Galapagos Islands. Intertidal to 150 m. Abundant on sand and rocky substrates.

Remarks. The type material of Caecum chilense is comprised of both late subadult and adult specimens. Unfortunately, the holotype of C. chilense (MZUC 10345, ex MZUC 1350) is in such poor condition that it is unrecognizable, and only two paratypes remain undamaged. It should also be noted, the museum has changed its numbering system. The holotype is now MZUC 10345, and the paratype lot is MZUC 10346.

Adult sculpture can range from being completely smooth to entirely ribbed within a single population. Neither locality nor depth appears to influence the surface sculpture. When found in ideal environments such as intertidal rocky areas, it is common to find Caecum chilense in large numbers.

Mattano & Zelaya (2013) reported the species from as far south as 50 o S, while NHMLAC has specimens from as far north as the Galapagos Islands. This is a significant range extension in both directions for Caecum chilense . Cruz (2007) reported a species that he referred to as C. cf. orcutti from Ecuador. However, his description is more consistent with the smoother form of C. chilense .

Figures

FIGURE 84. Caecum chilense. A–D. Profile views depicting sculpture variations (LACM 1964-16.25). E. Operculum, exterior surface (LACM 1964-16.25). F. Operculum, interior surface (LACM 1964-16.25). G. Ventral view of smooth form (LACM 1934-264.11). H. Close-up of smooth surface (LACM 1934-264.11). I. Ventral view of ribbed form (LACM 1934-264.11). J. Close-up of ribbed sculpture (LACM 1934-264.11). K. Paratype, MZUC 10346.

FIGURE 85. Caecum chilense shells at different growth stages. A. Protoconch and teleoconchs I to II (LACM 1964-16.25). B. Protoconch and teleoconchs I to II (LACM 1964-16.25). C. Surface of teleoconch I (LACM 1964-16.25). D. Surface of teleoconch I (LACM 1964-16.25). E. Teleoconchs I to II (LACM 1964-16.25). F. Surface of teleoconchs II to V (LACM 1964- 16.25). G. Surface of teleoconch II (LACM 1964-16.25). H. Teleoconchs II to III (LACM 1974-23.6). I. Teleoconchs II to III (LACM 1974-23.6). J. Surface of teleoconch III (LACM 1974-23.6). K. Surface of teleoconchs IV to V (LACM 1974-23.6). L. Teleoconchs II to III (LACM 1974-23.6). M. Teleoconch IV (LACM 1974-23.6). N. Teleoconch IV (LACM 1974-23.6). O. Teleoconch V (LACM 1974-23.6). P. Teleoconch V (LACM 1934-264.11).

FIGURE 86. Caecum chilense. A. Conceptual reconstruction of growth stages (smooth form). B. Species distribution map.