Acanthopleura echinata (Barnes, 1824)

Araya, Juan Francisco & Araya, Marta Esther, 2015, The shallow-water chitons (Mollusca, Polyplacophora) of Caldera, Region of Atacama, northern Chile, Zoosystematics and Evolution 91 (1), pp. 45-58 : 45

Taxon classification Animalia Chitonida Chitonidae

Acanthopleura echinata (Barnes, 1824) Plate 1, Fig. 1; Table 2

Chiton echinatus Barnes, 1824: 71, pl. 3, figs 4a, b. Chiton spiniferus Frembly, 1827: 196, suppl. pl. 16, fig. 6; Sowerby 1833, pl. 1, fig. 47. Acanthopleura echinata : Dall 1909: 180, 248, pl. 23, fig. 6; Marincovich 1973: 44, fig. 100; Osorio 2002: 52.

Description.

Animal of very large size, up to 158 mm in examined specimens. Tegmentum smooth to shiny (but often eroded), dark reddish-brown, with occasional small blue spots. Lateral areas hardly raised, smooth except for two radial rows, one of 5-9 round granules indenting sutural edge. Anterior valve with some 10 radial rows of round granules; space between rows smooth. Central areas with raised, well-defined, smooth jugal band bordered by shallow, longitudinal grooves with short, wavy, longitudinally oriented riblets on pleural areas. Girdle upper surface with erect, strong, spike-like spines, round in cross section, up to 8 mm long in large specimens (longer if not broken), often encrusted. Girdle bridges empty (After Ferreira 1986). According to Osorio (2002) this is a dioecious species, which can reach a maximum length of 200 mm.

Material examined.

Specimens found in two locations; Norte Bahía de Caldera (MPCCL 3072014A, 1 specimen) and in Playa Mansa, in subtidal areas in exposed rocks and in rocks associated with the giant kelp Lessonia nigrescens Bory de Saint-Vincent, 1826.

Distribution.

According to Ferreira (1986) this species is found from Talara, Peru (04°34'S; 81°16'W) to Punta Tumbes, Bahía de Concepción, Chile (36°49'S; 73°03'W), and is limited to the intertidal zone and shallow subtidal, 0-4 m depth, on rocks often exposed to heavy surf.

Remarks.

This is one of the largest polyplacophoran in Chile, differing from the also large Enoplochiton niger in having conspicuous spines in the girdle, not sparse scales as in Enoplochiton niger . This species prefers the subtidal zone and wave-exposed shores, and it is often covered with algae and epibionts ( Scurria species, Mytilus species, etc) which allow this species to blend in with its surroundings. The spines are often covered with encrusting algae in older specimens. This is a commercially important species ( Osorio 2002).