Tonicia calbucensis, PLATE, 1898

TONICIA CALBUCENSIS PLATE, 1898 View in CoL

( FIG. 4 View Figure 4 )

Tonicia calbucensis Plate, 1898: 205 View in CoL , pl. 12, fig. 134. – Sirenko, 2006a: 85, fig.10. – Schwabe et al. 2006: 14 View Cited Treatment , figs 10, 16, 21–30 (bibliography). – Schwabe, 2009: 410.

Chiton ‘ elegans View in CoL ’ Frembly, 1827: 203, suppl. pl. 17, fig. 6.

Chiton grayii Sowerby View in CoL in Broderip & Sowerby, 1832: 58.

Chiton chiloensis Sowerby View in CoL in Broderip & Sowerby, 1832: 58.

Chiton graniferus Sowerby View in CoL in Broderip & Sowerby, 1832: 104.

Chiton glaber Clessin, 1903: 118 View in CoL , pl. 41, fig. 4.

Tonicia ‘ elegans View in CoL ’ Leloup, 1956: 69, figs 38–46 (pro parte).

Tonicia chilensis Schwabe et al., 2006: 15 View in CoL View Cited Treatment , figs 8, 11, 17 (pro parte, non Chiton chilensis Frembly, 1827 View in CoL ). – Schwabe, 2009: 412 (pro parte, non Chiton chilensis Frembly, 1827 View in CoL ).

Type material repository: Natural History Museum Berlin ( ZMB) .

Type locality: Calbuco , Chile (~ 41°S) .

There are two ecotypes of the species with different features, one found in southern Chile (40– 53°S) and one found in northern Chile (18– 40°S) . However, both ecotypes and intermediates can be found among samples collected at the Golfo de Ancud (~ 41°S) .

Description of southern ecotype of T. calbucensis

The animals are of medium size, ≤ 40 mm long ( Table 2). Valves subcarinated, side slopes minimally convex with low elevation (dorsal elevation ratio 0.28). Tegmentum orange brown to brownish red, with darker radial streaks on the terminal valves and lateral areas; central areas with streaks oriented longitudinally. Jugal area chestnut brown in general, with two wider white streaks on both sides (after Schwabe et al., 2006). Specimens collected near Punta Huinay (−42.36, −72.44) and Isla Lilihuapi (−42.16, −72.59) have typical colouration or have yellow orange tegmentum and girdles. Head valve semi-circular and the posterior margin widely V-shaped. Intermediate valves broadly rectangular, and anterior margin almost straight in the central part and somewhat slanting towards the rounded side margins. Posterior margin straight, not beaked, and lateral areas not raised. Tail valve small and slightly narrower than head valve, mucro antemedian, antemucronal and postmucronal slopes straight. All areas of tegmentum smooth, with the exception of one to four weak, short, narrow grooves on both sides of the jugum and several growth lines and ocelli. Articulamentum well developed, with wide and rather long apophyses connected by a slightly dentate jugal plate. Slit formula 8/1/8. Teeth strongly pectinated on the outside. Girdle rather wide and leathery, usually rose with spots or rarely orange in specimens with orange tegmentum; dorsally covered with rare small elongate sharppointed spicules and rare short bristles. Ventral side with radial rows of squarish scales. Specimens with a body length ~ 20 mm have a radula ~ 7.5 mm long, with 43 transverse rows of mature teeth. Central tooth narrows with a long, curved blade. Major lateral tooth with unicuspid rounded head. From valve II to valve VIII, there are 34 gills on each side of specimens with body lengths of ~ 20 mm.

Remarks

The southern ecotype of Tonicia calbucensis differs from other congeneric species by having a practically smooth tegmentum. The form differs from T. lebruni , which is found in the same area, by having white apophyses (vs. brown in T. lebruni ) and shorter valve VIII antemucronal areas. Given that T. ‘ elegans ’ is the type species of the genus and this name is not valid, we suggest T. calbucensis as the new type species for the genus Tonicia .

Distribution: Southern South America from Puerto Montt to the Magellan Strait (40– 53°S) and also found in Estados and the Falkland Islands. Specimens have been found from 3 to 48 m depth.

Description of the northern ecotype of T. calbucensis

Body length medium sized, ≤ 50 mm, elongated and oval with low elevation (dorsal elevation 0.24–0.26). Valves minimally beaked ( Table 2). Tegmentum very variable in colour and streaked with various combinations of dark brown, buff, yellow, pale, reddish brown and wine red. Tegmentum and girdle are both rarely uniform orange. Head valve semi-circular, with widely V-shaped posterior margin. Intermediate valves broadly rectangular. Ratio of the width of valve V to its length is 2.7–3.0. Anterior margin slightly concave in the jugal area and slanted at the pleural area. Posterior margin weakly concave at both sides of the prominent pointed apex. Tail valve slightly less wide than the head valve. Antemedian portion of mucro not raised; antemucronal slope straight or slightly convex, and postmucronal slope concave. Tegmentum sculptured with numerous granules or pustules and longitudinal grooves. Head valve, lateral area, pleural area and postmucronal area sculptured with small granules or pustules. Pleural area with low granules arranged in longitudinal rows, which become obsolete in some specimens. Both sides of the jugum have one to three longitudinal grooves that reach the anterior margin. Articulamentum white, with all valves having a reddish spot in the apical area and in the centre of the valve. Apophyses wide, rounded and connected to the dentate jugal plate. Slit formula is 8/1, rarely 2/9–10. Slit rays are hardly noticeable. Girdle moderately wide and spotted in live specimens, uniformly yellow in fixed specimens. Girdle dorsally beset with few calcareous spicules ≤ 34 µm long. Ventral side of the girdle covered with radiating rows of subquadrangular scales 35 µm long. Radula of specimens with body lengths of 17.5 mm are 6.7 mm long, with 40 transverse rows of mature teeth. Central tooth narrows to a long, curved blade; major lateral tooth has a unicuspid rounded head. There are 43 gills on each side of specimens with body lengths of 17.5 mm, spanning from valve II to valve VIII.

Remarks

The northern ecotype of T. calbucensis differs from the southern ecotype by having granules, pustules and long longitudinal grooves on both sides of the jugum (the southern ecotype has a smooth tegmentum with short, weak grooves). Additionally, the northern ecotype has no bristles on the dorsal side of the girdle (the southern ecotype has short bristles).

Distribution: The northern ecotype of Tonicia calbucensis has a wide distribution from Arica ( Chile, ~ 18°S) to the Golfo de Ancud (~ 41°S). The form lives in the intertidal zone ≤ 19 m deep.