Research Article |
Corresponding author: Juan Francisco Araya ( jfaraya@u.uchile.cl ) Academic editor: Matthias Glaubrecht
© 2015 Juan Francisco Araya, Marta Esther Araya.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Araya JF, Araya ME (2015) The shallow-water chitons (Mollusca, Polyplacophora) of Caldera, Region of Atacama, northern Chile. Zoosystematics and Evolution 91(1): 45-58. https://doi.org/10.3897/zse.91.8536
|
The Molluscan species of the northern littoral of Chile have been sparsely studied. This work reviews for the first time the diversity of polyplacophoran molluscs around the port of Caldera, in the Region of Atacama (26°45’49”S; 70°45’17”W to 27°20’23”S; 70°56’46”W), northern Chile. Eleven species were found in this study: Acanthopleura echinata (Barnes, 1824); Callistochiton pulchellus (Gray, 1828); Calloplax vivipara (Plate, 1899), Chaetopleura peruviana (Lamarck, 1819); Chiton cumingsii Frembly, 1827; Chiton granosus Frembly, 1827; Chiton magnificus Deshayes, 1827; Enoplochiton niger (Barnes, 1824), Radsia barnesii (Gray, 1828), Tonicia atrata (G. B. Sowerby II, 1840) and Tonicia chilensis (Frembly, 1827). All of the species occurring in the area have distributions in the southeastern Pacific Ocean, from Ecuador to central Chile, and three of them are species endemic to the Chilean coasts (Calloplax vivipara, Radsia barnesii, and Tonicia atrata). This diversity of species is comparable to that of better surveyed faunas of central and southern Chile or Patagonia. Of the eleven species recorded, the geographic distribution records for Callistochiton pulchellus, Radsia barnesii and Tonicia atrata are extended, and Calloplax vivipara is found alive again after 40 years, filling a gap in its known distribution. Illustrations of living specimens in their habitat, distribution records and a taxonomic key for all the studied taxa are also provided.
Chile, Calloplax , Callistochiton , Chaetopleura , Enoplochiton , Radsia , Tonicia , Southeastern Pacific, intertidal
Research on marine molluscs of northern Chile began with the descriptions of some species by
Regarding the Chilean Polyplacophora — apart from the early works of
This molluscan class is often overlooked in Chile, as their species are mostly small and hard to collect and to preserve, however, three of the large species of Chilean chitons (Acanthopleura echinata (Barnes, 1824), Chiton (Chiton) magnificus Deshayes, 1827 and Chiton (Chiton) granosus (Frembly, 1827)) are collected with gastronomic purposes (
The coast of the Region of Atacama consists of rocky formations of volcanic origin with a few sandy beaches. The intertidal area of most of the coast, with the exception of a few scattered bays, is narrow (up to 20 m) and presents a diverse geography including cliffs, rocky platforms, intertidal pools, and boulder fields. The exposed side of rocks and boulders are exposed to strong surf, with just a few sheltered areas, particularly in the area of the Bay of Caldera, Obispito and Calderilla (Table
Locality | Habitat type/Macroalgae | Coordinates | Species present |
---|---|---|---|
Obispito | Rocky coast with tidal pools, crustose coralline algae. | 26°45’49”S; 70°45’17”W | Calloplax vivipara, Chiton cumingsii. |
Aguas Verdes | Rocky coast with tidal pools, large phaeophyta algae (Lessonia sp). | 26°52’20”S; 70°49’25”W | Chiton cumingsii, Chiton magnificus, Tonicia chilensis. |
Playa Granito Orbicular | Pebble beach, minor algae covering. | 26°58’22”S; 70°47’43”W | Chiton cumingsii. |
Playa Rodillo | Exposed rocky coast and pebble beach. | 26°59’48”S; 70°47’27”W | Enoplochiton niger. |
Sur de Playa Ramada | Rocky coast with tidal pools and rock intrusions in sandy beach. Great diversity of algae. | 27°00’37”S; 70°48’04”W | Callistochiton pulchellus, Calloplax vivipara, Chaetopleura peruviana, Chiton cumingsii, Chiton magnificus, Radsia barnesii, Tonicia chilensis. |
Islote Playa Ramada | Rocky coast, big boulders. Holdfasts of Lessonia nigrescens. | 27°00’41”S; 70°48’23”W | Chaetopleura peruviana, Chiton cumingsii, Enoplochiton niger. |
Playa El Pulpito | Pebble beach, rock formation. Several algae. | 27°01’22”S; 70°48’30”W | Chaetopleura peruviana, Callistochiton pulchellus, Chiton cumingsii, Enoplochiton niger. |
Playa El Pulpo | Rocky coast with protected sandy beach. Great diversity of algae. | 27°01’37”S; 70°48’39”W | Chaetopleura peruviana, Callistochiton pulchellus, Chiton cumingsii, Chiton granosus, Radsia barnesii. |
Norte Bahía de Caldera | Rocky coast, rock slabs and pockets of sand. Encrusting algae, Ulva lactuca, etc. | 27°03’01”S; 70°48’30”W | Acanthopleura echinata, Chaetopleura peruviana, Chiton granosus, Enoplochiton niger. |
Sur de Playa Negra | Sandy beach with rock formation. Minor algal covering. | 27°03’38”S; 70°48’51”W | Chaetopleura peruviana, Chiton cumingsii. |
Sur de Playa Brava | Rock formation among sandy beaches, Ulva lactuca and red algae. | 27°03’50”S; 70°49’13”W | Chaetopleura peruviana, Chiton cumingsii. |
Playa Mansa | Limestone slabs on sandy beach. Small algae covering, encrusting algae. | 27°03’58”S; 70°49’36”W | Acanthopleura echinata, Chaetopleura peruviana, Chiton cumingsii, Chiton granosus, Tonicia atrata, Tonicia chilensis. |
Sur Bahía de Caldera | Rock slabs, pebble beach. Encrusting algae. | 27°03’33”S; 70°49’55”W | Chaetopleura peruviana, Chiton cumingsii, Chiton granosus, Tonicia chilensis. |
Calderilla | Loose boulders on sandy beach, Gracilaria algae. | 27°05’30”S; 70°50’56”W | Chaetopleura peruviana, Chiton cumingsii, Tonicia chilensis. |
Peninsula Calderilla | Rocky coast with small pebble beach, Ulva lactuca and red algae. | 27°05’15”S; 70°51’27”W | Calloplax vivipara, Chaetopleura peruviana, Chiton cumingsii, Radsia barnesii. |
Norte Bahía Inglesa | Rocky beach, scattered sandy pockets. | 27°05’14”S; 70°51’49”W | Chaetopleura peruviana, Chiton cumingsii. |
Sur Playa Rocas Negras | Rocky formation on sandy beach. Encrusting corallines. | 27°07’39”S; 70°54’53”W | Chaetopleura peruviana, Chiton cumingsii. |
Playa Chorrillos | Rocky coast with scattered pebble beaches. Large algae holdfasts (Lessonia nigrescens, Lessonia trabeculata) | 27°12’44”S; 70°57’05”W | Chaetopleura peruviana, Chiton cumingsii, Chiton magnificus. |
Bahia Cisne | Sandy beach with rock platforms. Filamentous algae. | 27°14’57”S; 70°57’42”W | Chiton cumingsii. |
Puerto Viejo | Sandy beach with limestone rocks intrusions. Minor algae communities. | 27°20’23”S; 70°56’46”W | Chiton cumingsii. |
This work presents an overview, with distributions and illustrations, of all the species of Polyplacophora found in the Region of Atacama, northern Chile. The distribution range and a taxonomic key to all the studied species is also provided. The aim of this preliminary paper is thus to contribute on the knowledge of the molluscan fauna, in particular of northern Chile.
The material considered in this study was mostly obtained by sampling in the rocky coastal areas around the port of Caldera (27°04’S; 70°50’W), between Caleta Obispito (26°45’49”S; 70°45’17”W) and Puerto Viejo (27°20’23”S; 70°56’46”W), and in specific localities along the coasts of the Region of Atacama, northern Chile, during the summers of 2011 to 2012 and in August–December 2012. A synopsis of all the stations is given in Table
Callistochiton palmulatus Carpenter MS, Dall, 1879, by monotypy.
Chiton pulchellus Gray, 1828: 6, pl. 3, fig. 9. Chiton bicostatus d’Orbigny, 1847: 486, pl. 81, figs 7–9. Callistochiton shuttleworthianus:
Animal of small size, up to 11.5 mm in examined specimens, elongate oval, moderately elevated, color of tegmentum creamy white or bright white. Head valve semicircular, sculpture with 10–15 low rounded, equally spaced, nodulose, annulate, radial ribs, becoming obsolete towards the apex, the posterior ribs being strongest and more nodulose. Intermediate valves rectangular, lateral areas well defined, sculptured with two strong radial ribs. Central area with two series of equally spaced, diagonal lirae, forming rounded depressions in the interspaces. Tail valve semi-oval, slightly less wide than head valve, sculptured like head valve, with 8–11 weaker radial ribs. Girdle rather wide, yellowish white, dorsally covered with small, oval, imbricating scales (After
Chiton species photographed in situ; 1. Acanthopleura echinata, Playa Mansa; 2. Callistochiton pulchellus, Playa El Pulpo; 3. Calloplax vivipara, Peninsula Calderilla; 4. Chaetopleura peruviana, Sur Playa Ramada; 5. Chiton cumingsii, Playa El Pulpo; 6. Chiton granosus, Playa Mansa. Scale bars are: 2 cm for 1, 2, 3 and 1 cm for 4, 5, 6.
Specimens found under sunken rocks in tidal pools in Playa El Pulpito (SBMNH 452240, 1 specimen), Sur de Playa Ramada and Playa El Pulpo (Table
This species has records from Islay (17°03’S; 72°06’W), Peru to Chanavayita cove, 54 km south of Iquique, Chile (20°42’S; 70°09’W), with records also in the Galápagos Islands (01°40’N; 92°01 W), Ecuador (
Species | Distribution | References |
---|---|---|
Acanthopleura echinata (Barnes, 1824) | Talara, Peru (04°34’S; 81°16’W) to Punta Tumbes, Bahía de Concepción, Chile (36°49’S; 73°03’W). |
|
Callistochiton pulchellus (Gray, 1828) | Islay (17°03’S; 72°06’W), Peru to Ramada Beach, Caldera (26°56’S; 70°47’W). |
|
Calloplax vivipara (Plate, 1902) | Pozo Toyo, South of Iquique (20°25’S; 70°10.5’W) to Valparaiso (33°02’S; 71°38’W), Chile. |
|
Chaetopleura (Chaetopleura) peruviana (Lamarck, 1819) | Cape San Lorenzo, Ecuador (01°04’S; 80°55’60”W) to the Chonos Archipelago, Chile (45°00’S; 74°00’W). | Kaas and Van Belle (1983) |
Chiton (Chiton) cumingsii Frembly, 1827 | Paita, Peru (05°05’34”S; 81°06’07”W) to Puerto Montt (41°28’S; 72°56’W), Chile. |
|
Chiton (Chiton) granosus Frembly, 1827 | Paita, Peru (05°05’34”S; 81°06’07”W) to Boca de Guafo (43°39’S; 74°00’W), Region of Aysén, Chile. |
|
Chiton (Chiton) magnificus Deshayes, 1827 | San Lorenzo Island, Peru (12°05’23”S; 77°13’26”W) south to Bahía Tictoc, Chiloé Province, Chile. (43°36’40”S; 72°57’15”W). |
|
Enoplochiton niger (Barnes, 1824) | Talara, Peru (04°34’S; 81°16’W) to Coquimbo Bay, Chile (29°58’S; 71°21’W). |
|
Radsia barnesii (Gray, 1828) | Ramada Beach, Caldera (26°56’S; 70°47’W) to the Chonos Archipelago (45°0’0”S; 74°0’0”W), Chile. |
|
Tonicia atrata (Sowerby II, 1840) | Playa Mansa, Caldera (27°03’58”S; 70°49’36”W) to Tierra del Fuego (54°S), Chile. |
|
Tonicia chilensis (Frembly, 1827) | Peru (12°S) to Chile (54°S). |
|
This is a small (under 12 mm) chiton, easily overlooked but for its bright whitish color. It is a fairly rare species; they were not abundant and were found only in two of the studied locations (Table
Chiton janeirensis Gray, 1828, by monotypy.
Callistochiton viviparus Plate, 1899: 154, pl. 9, figs 267–281;
Animal of small size, up to 12 mm in examined specimens, elongate oval, moderately elevated, color of tegmentum tan or creamy white. Head valve semicircular, sculpture with about nine equally spaced, nodulose, annulate and well defined radial ribs. Intermediate valves rectangular, lateral areas well defined, sculptured with two strong radial ribs. Central area with about eight longitudinal riblets per side, well-marked in the pleural areas but becoming obsolete at the jugum. The riblets tend to converge anteriorly and are not latticed. Posterior valve semi-oval, elevated at the central mucro, with nine well defined radial ribs. Girdle yellowish white, dorsally covered with small scales (After
Specimens found under rocks in a tidal pool at Obispito (MPCCL 3072014B, 1 specimen), Sur de Playa Ramada and under rock slabs sunken under boulders in Peninsula Calderilla (SBMNH 452241, 1 specimen).
This is a rare species, found in only two of the locations under study; in both places this species was found under rocks sunken in tidal pools, associated to encrusting sponges and to communities of the small mussel Brachidontes granulata (Hanley, 1843). According to
Chiton peruvianus Lamarck, 1819, by subsequent designation.
Chiton peruvianus Lamarck, 1819: 321;
Animal of medium to large size, up to 45 mm long in examined specimens. Oval to elongate oval, slightly depressed, color of tegmentum greenish-brown to dark brown. Head valve semicircular, front slope straight, posterior margin V-shaped. Intermediate valves broadly rectangular. Tail valve less than semicircular, almost as wide as head valve. Girdle profusely beset with very long (up to 10 mm) thick, coarse, corneous hairs, not only interspersed throughout girdle but in girdle bridges, protruding at sutures and extending over valves. Tegmentum pustulose sculptured with minute and neatly separated pustules, on the end valves the pustules are arranged in radiating rows. Body width/length, mean 0.66; height/length, mean 0.22 (After
Specimens found in almost all locations, with the exception of Bahia Cisne, Puerto Viejo and Playa Rodillo up to Obispito (Table
This species is easily distinguished from all other chitons in the region by the presence of hairs covering the valves and sutures. A similar species, Chaetopleura (Chaetopleura) benaventei Plate, 1899 is slightly smaller in size and differs in the overall coloration and in the absence of the corneous bristles. Chaetopleura hennahi (Gray, 1828) found between El Callao, Peru and Arica, Chile (
Chiton spinosus Bruguière, 1792, by subsequent designation.
Chiton echinatus Barnes, 1824: 71, pl. 3, figs 4a, b. Chiton spiniferus Frembly, 1827: 196, suppl. pl. 16, fig. 6;
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
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.
According to
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 E. 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 (
Chiton niger Barnes, 1824, by monotypy.
Chiton niger Barnes, 1824: 71, pl. 3, fig. 3. Enoplochiton niger:
Animal very large in size, up to 190 mm in examined specimens. Tegmentum dark chocolate-brown, shiny, but easily eroded. Anterior valve with 4–6 concentric, zig-zagged furrows. Lateral areas elevated, well defined by strong round rib at diagonal line, with zig-zagged furrows as on anterior valve. Central areas well defined, smooth jugum bordered by narrow, depressed area with irregular, short, oblique furrows; para-jugal area smooth; pleural area with longitudinal, parallel furrows, not usually reaching anterior border of valve. Girdle thick, muscular; dorsal surface dark brown, conspicuously dotted with light brown scales, scales irregular in size (larger in middle 1/3 of girdle), up to 1.5–2 mm long in specimens 50 mm long (larger in larger specimens), vaguely striate, usually eroded at upper edge, clearly separated from each other by area as wide as scale; on outer 1/5 of girdle, scales much smaller, shorter, dark brown, erect, spine-like; girdle surface completely covered otherwise with minute, dark brown, lanceolate spicules, up to 100 μm long, 25 μm thick. Girdle bridges, empty in middle third, but crowded with small, dark brown spiculoid elements (akin to those on girdle proper) in outer thirds (After
Specimens found exposed on large boulders in the surf–zone, in Playa Rodillo, Playa El Pulpito (MPCCL 3072014E, 1 specimen) and in Norte Bahía de Caldera.
This species is confined to the western temperate coast of South America, from Talara, Peru (04°34’S; 81°16’W) to Coquimbo Bay, Chile (29°57’S; 71°20’W). Its bathymetric range is limited to the intertidal zone (
With sizes up to 200 mm (
Chiton tuberculatus Linnaeus, 1758, by subsequent designation.
Chiton cumingsii Frembly, 1827: 198, suppl. pl. 16, fig. 3;
Animal of large size, reaching almost 60 mm in length in examined specimens. Anterior valve straight; post-mucronal slope of posterior valve slightly concave. Shell color yellowish white with concentric brown bands crossing lateral triangle longitudinally, then proceeding antero–medially over ribs of central area. Girdle light olive green or pinkish-brown. Interior of shell white with some dull green in posterior depression (After
Specimens found in all the rocky shore stations (except Playa Rodillo and Norte Bahía de Caldera). Collected under rocks and rock slabs, Sur de Playa Brava (MZUC 39613, 1 specimen).
This colorful species is the most common and abundant chiton distributed in the zone; found in almost all the locations. It is commonly found in accumulations of several individuals on the underside of rocks at low tide, crawling quickly to the dark if exposed to sunlight. Among the examined specimens, some of them had a pink/orange coloration when juveniles with some adult specimens retaining a uniform pink coloration. This species has been cited as an introduced species in Las Palmas Port, Canary Islands (28°06’N, 15°25’W), being one of the few alien polyplacophoran found in European waters (
Chiton granosus Frembly, 1827: 200, suppl. pl. 17, fig. 1;
Animal of large size, up to 45 mm in examined specimens. Intermediate valves often eroded and rather flat. Anterior valve convex, post-mucronal slope straight. Mucro moderately blunt; centrally located on posterior valve. Jugal tract smooth, central areas with somewhat beaded longitudinal ribs. Lateral triangle barely raised; low, broad, nodular rib extends along diagonal line. Often a few other radiating rows of nodules appear on lateral triangle. Terminal areas with 10–12 radiating rows of widely spaced nodules. Color of tegmentum nearly totally dark brown to greenish brown, with occasional streaks of cream white on jugal and central areas. Girdle black. Interior of valves white with dull blue muscle scars and reddish brown on posterior slope of callus (After
Specimens found in Playa El Pulpo, Norte de Bahía de Caldera, Playa Mansa and Sur de Bahía de Caldera, in crevices in large rocks, often in surf zone in large colonies. Playa el Pulpo (MPCCL 3072014D, 1 specimen).
This species is somewhat uncommon in shallower waters; it is found mostly in crevices and in rocky outcrops, mostly in clustered distributions. Juvenile specimens are somewhat similar to the juvenile specimens of Chiton cumingsii differing in the paler coloration (of various shades of green), the granulation on the valves and in the overall wider body. It has been reported that this species feeds on barnacle cyprids (
Chiton (Chiton) magnificus Deshayes, 1827: 454. Chiton magnificus:
Animal of large size, reaching 115 mm in examined specimens. Body dark bluish-grey, broad-oval, slightly carinated, rather flat. Valves flattened to moderately carinated. Anterior valve sligthtly convex, semicircular, with wide V-shaped to straight posterior margin unnotched in middle, with numerous radially arranged, shallow ribs; intermediate valves rectangular with slightly concave posterior margin at both sides of faintly protruding apex, lateral areas slightly elevated, sculptured with up to 5 radial ribs between a wider diagonal ridge and a very wide posterior rib; tail valve semicircular with an anterior mucro; post-mucronal area with same sculpture as head valve and lateral areas (After
Specimens found in Aguas Verdes, Sur de Playa Ramada and in Playa Chorrillos, in subtidal areas attached to large boulders.
A shiny, large and conspicuous chiton, this species has been overlooked in recent molluscan literature, being cited by
Chiton barnesii Gray, 1893 by monotypy.
Chiton barnesii Gray, 1828: 5;
Animal of medium size, reaching a length of 28 mm in the examined specimens. Anterior valve straight; post-mucronal slope of posterior valve straight to slightly concave. Valves quite flat. Jugal region smooth; central area with numerous uneven longitudinal ribs. Lateral triangle barely raised, with 5–7 irregular nodules. Shell color cream white with reddish brown splotches on central areas, irregular longitudinal dark reddish brown bands on lateral triangles, and occasional dark reddish brown on jugum. Girdle light greenish brown with faint trace of alternating lighter bands in some specimens. Interior of valves white (After
Specimens found in three locations; Peninsula Calderilla, Sur de Playa Ramada and in Playa El Pulpo Beach (Table
This species was uncommon in the zone under study; only a few specimens were found in the undersides of rocks at low tide. This species is clearly identified from the other species found in this work by having a wide, flat shell, with narrower valves and a pattern of clear and darker alternating bands in the girdle. It can be misidentified as Chiton granosus; differing from this species in the smaller size, the much smaller girdle scales, a much weak valve sculpture and in the alternating bands of the perinotum, absent in Chiton granosus.
Chiton chilensis Frembly, 1827, non De Blainville 1825 (= Chiton chilensis Frembly, 1827), by subsequent designation (Gray 1847: 168).
Chiton atratus G.B. Sowerby II, 1840: 294. Tonicia atrata Aldea & Valdovinos, 2005: 368, Table 1, fig. 5I;
Animal of medium to large size, reaching 51 mm in examined specimens. Shell elongate-oval, moderately elevated, subcarinated dorsum. Color reddish brown to blackish purple. Head valve semicircular, with straight posterior valve margin unnotched in middle; intermediate valves broadly rectangular, with distinct protruding apex and concave posterior valve margins. Lateral area hardly elevated, but clearly indicated by faint depression in front of diagonal ridge. Jugal area weakly developed, but showing partly a more or less distinct keel, especially in the more posterior intermediate valves. Tail valve with centrally situated, forward-directed, and slightly elevated mucro, straight antemucronal area and rather steep, straight postmucronal slope. Jugal area of tail valve extending towards anterior. Tegmentum without sculpture, except for growth marks and faint radial striations on terminal valves and lateral areas. Perinotum wide and fleshy (After
Specimens collected in a single location; Playa Mansa, in submerged rocky platform (Table
According to
Two specimens of this species were found in a single location; among a community of Tonicia chilensis, from which it distinguishes in attaining larger sizes and in having a darker body and almost smooth valves with minute granulation at the sides. It is interesting to note also that the valves of the examined specimens were widely separated, almost as in Tonicia disjuncta (Frembly, 1827). The presence of this species extends considerably the northernmost record of this species in about 1040 km (from 40°S to 27°S).
Chiton chilensis Frembly, 1827: 203, pl. 17, fig. 6;
Animal of medium to large size, reaching 43 mm in examined specimens. Shell elongate-oval, not much elevated, the dorsal ridge rounded, side-slopes straightened. Color umber-brown at the sides, becoming chestnut in the middle, delicately and peculiarly speckled and blotched and streaked with buff or buff-white. Lateral areas hardly raised, but separated from the central areas by an obtuse diagonal ridge bearing a series of low tubercles, sometimes subobsolete; sculptured with subradiating rows of small granules, and showing a band of irregularly placed black eyes on the forward part. Central area of second valve having in the middle, a keel or a group of lirae; central areas of the other valves having a narrow smooth dorsal band with several longitudinal furrows on each side of it; and at the sides there are longitudinal diverging delicate rows of granules. End valves radially sub-granulate, and crowded with eye-spots subradially arranged (After
Specimens found on rocks at low tide in Aguas Verdes, Sur de Playa Ramada, Playa Mansa (MPCCL 3072014F, 1 specimen), Sur Bahía de Caldera and in Calderilla.
According to
This species has large and colorful mantles and plates of variable shades, which are similar to the encrusting calcareous algae commonly found in the rocky coasts. Due to the high diversity of forms, several synonyms have been described (see
All of the studied species can be classified in two main groups according to their habitat; species with a higher relative frequency on exposed areas include the very large species Acanthopleura echinata and Enoplochiton niger. The other group includes species associated with protected intertidal areas: Callistochiton pulchellus, Calloplax vivipara, Chiton cumingsii, Chiton granosus (mostly found in rock fissures and crevices) and Radsia barnesii. Chiton magnificus was found in the Region of Atacama only in subtidal areas, always near large boulders in holdfast communities of the giant kelp Lessonia nigrescens. Chiton magnificus, however, is much more common in central and southern Chile, being found mostly in intertidal areas (
The new distribution records of Callistochiton pulchellus, Radsia barnesii and Tonicia atrata and the new record of Calloplax vivipara may reflect the lack of sampling in the Atacama region or in northern Chile in general, where the scientific studies on invertebrates are still lacking. In particular, Callistochiton pulchellus and Calloplax vivipara may be more widespread in the country; however their particular habitat (and small adult size) may prevent their sampling by traditional methods. Some of these species may have also been overlooked or misidentified as juvenile specimens of other chiton species (for example Radsia barnesii as Chiton granosus). The considerable new range extension of Tonicia atrata found in this study may reflect the current complicated, unresolved status of the genus Tonicia in Chile; the revision of some particular species or species-groups is thus imperative, considering the great diversity in the valve and mantle morphology, which has derived in a large synonymy for some species, for instance for Tonicia chilensis (
The absence of other species, for example those cited by
This key is primarily macroscopic (intended for identification of adult specimens) including external characters as shell features and general girdle features.
1 | Whitish or cream colored chiton, of small size (up to 14 mm) | 2 |
1a | Animal of green, brown, pink or black coloration | 3 |
2 | Animal bright whitish in color, with 10–16 radial ribs on head valve, with rounded depressions on the lateral areas of the valves | Callistochiton pulchellus (Gray, 1828) |
2a | Animal whitish-cream in color, with about nine radial ribs on head valve, with longitudinal riblets in the lateral areas | Calloplax vivipara (Plate, 1902) |
3 | Girdle naked or covered with small scales or by blunt spines | 4 |
3a | Girdle covered by hairs, which can be also found between the valves, fleshy girdle | Chaetopleura peruviana (Lamarck, 1819) |
4 | Girdle covered by visible round scales, in neat rows | 5 |
4a | Girdle fleshy, naked or with spare spines | 8 |
5 | Valves visible granulose, often eroded and rather flat, with two white fringes on the central areas of the valves, terminal areas with 10–12 radiating rows of widely spaced nodules, girdle black | Chiton granosus Frembly, 1827 |
5a | Valves striated in the middle, central valves narrow | 6 |
6 | Valves carinate, of green, light brown or pink-yellowish color, girdle with alternating bands of color | Chiton cumingsii Frembly, 1827 |
6a | Valves rather flat, olive green to black | 7 |
7 | Girdle with alternating pale and dark bands, central valves with uneven longitudinal ribs, color olive green, size small (up to 35 mm) and rather flat | Radsia barnesii (Lesson, 1828) |
7a | Girdle black, valves flattened with central areas with fine longitudinal lirae, color dark green to nearly black, with tiny blue points, size up to 174 mm | Chiton magnificus Deshayes, 1827 |
8 | Girdle naked, ample, decorated with green and pink spots, plaques with variegated colouration | 10 |
8a | Girdle muscular, covered by blunt spines or lanceolate spicules | 9 |
9 | Girdle covered by blunt spines, anterior valve with some ten radial rows of rounded granules, valves usually encrusted with algae | Acanthopleura echinata (Barnes, 1824) |
9a | Girdle covered with irregularly–sized scales, anterior valve with 4-6 concentric, zig-zagged furrows, valves often eroded | Enoplochiton niger (Barnes, 1824) |
10 | Valves sculptured with minute granulation, central areas with a narrow smooth dorsal band or a group of lirae, with an obtuse diagonal ridge bearing a series of low tubercles | Tonicia chilensis (Frembly, 1827) |
10a | Valves almost smooth; only sculptured by growth marks and faint radial striations on terminal valves and lateral areas | Tonicia atrata (G. B. Sowerby II, 1840) |
We are thankful to Raúl Zuñiga and to Edison Villalobos (Caldera, Chile), for their help in field collections. We also give our thanks to Douglas Eernisse (Department of Biological Science, California State University Fullerton, Fullerton, California, U. S. A.) and to an anonymous reviewer for their helpful corrections, suggestions and comments, which greatly improved our manuscript. We are also indebted to the academic editor, Matthias Glaubrecht (Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany) for his essential collaboration with this work.