Chaetopleura hennahi ( Gray, 1828 )

Araya, Juan Francisco & Araya, Marta Esther, 2017, On the presence of Chaetopleura hennahi (Gray, 1828) (Polyplacophora: Chaetopleuridae) in Chile, Turkish Journal of Zoology 41 (3), pp. 554-557 : 554-556

Chaetopleura hennahi ( Gray, 1828) ( Figures 1A–1C )

Chiton hennahi Gray, 1828 6. Sowerby I, 1832: pl. 38, fig. 1. Gray, 1839: 148, pl. XL, fig. 1.

Chiton jaspideus Gould, 1846: 143. Smith, 1977: 244. Ferreira, 1983: 210.

Chaetopleura hennahi Pilsbry, 1892: 29 , pl. 12, figs. 47, 48, 49; pl. 17, fig. 39. Thiele, 1908: 17. Dall, 1909: 180, 244. Leloup, 1956: 33, figs. 14, 15, 16. Ferreira, 1983: 220. Lyons, 1985: 42. Valdovinos, 1999: 122. Ramirez et al., 2003: 257. Kaas and Van Belle, 1987: 64, fig. 28, map 11. Álamo and Valdivieso, 1997: 4. Ramírez et al., 2003: 257.

Material examined: Two specimens, attached to rocks, collected from commercial fisheries off Caldera (27°01′S, 70°48′W; 25 m depth), Región de Atacama, northern Chile. Measurements : 33 mm length, 24 mm width, 6 mm height (Specimen 1, reference collection of the first author); 19 mm length, 15 mm width, 4 mm height (Specimen 2, MPCCL 010316 ) .

Description (after Kaas, 1987): Animal of relatively large size (largest examined specimen 33 mm long, without girdle; Figure 1A ), oval, depressed (dorsal elevation 0.26–0.30), carinated, side slopes straight to very slightly convex, valves not beaked. Color of tegmentum generally wine-red to reddish brown, often with longitudinal streaks of darker and lighter tones, especially on the jugal areas; some specimens are white to greenish white, marked with brown. Girdle clothed with spicules and corneous bristles. Head valve semicircular, posterior margin widely V-shaped, notched in the middle. Intermediate valves broadly rectangular, jugal part of front margin somewhat forwardly produced, side margins rounded, hind margin mostly straight, apices inconspicuous in valves II–IV, slightly perceptible in valves V–VII, lateral areas little elevated. Tail valve less than semicircular, almost 3 times as wide as long, and definitely as wide as the head valve, anterior margin somewhat convex, mucro in front of the middle, slightly prominent, postmucronal slope slightly concave. Tegmentum glossy, sculptured with numerous, closely beaded, fine threads, longitudinally directed on the central areas, the pustules more or less obsolete, radially on the end valves and the lateral areas of the intermediate valves, where the pustules are somewhat larger and more clearly visible, growth lines weakly indicated in the end valves, obsolete in the intermediate valves, teeth sharp, prominently grooved on the outside, 2–4 lobes, though not forming any secondary slits, eaves narrow, not spongy. Girdle moderately wide, brownish, or with alternating olivaceous and light brown bands, dorsally covered with randomly dispersed, pointed spicules; 36 × 14 µm, with about 5 longitudinal grooves in the distal half, and numerous yellowish, hollow bristles of different forms, mostly in pairs, up to 1 mm long, bearing a terminal, calcareous spicule. Ventral scales elongate oval, obtusely pointed, weakly longitudinally striated, 60 × 24 µm on mid-girdle.

Distribution: Chaetopleura hennahi has been recorded from Ancón (11°47′S), Callao and Pucusana, to Isla Chincha Norte (13°38′S, 76°23′W), in Peru ( Ferreira, 1983; Álamo and Valdivieso, 1997); it has also been cited, unconfirmed, from Arica (18°S), in northern Chile ( Kaas and Van Belle, 1987). A single record near Ringdove Inlet in Smyth Canal, c. 52°S, at a depth of 30 m ( Thiele, 1908), has not been corroborated; considering the lack of subsequent reports of this species in further and more recent works made in southern Chile or similar areas in southern South America ( Reid and Osorio, 2000; Osorio and Reid, 2004; Aldea and Rosenfeld, 2011), this record is considered to be incorrect or dubious at least. Valdovinos (1999) presented a rather extensive distribution for this species from 15°S to 55°S in Chile; however, this was partly based on the unconfirmed records given by Thiele (1908) and by Kaas and Van Belle (1987). The present material examined constitutes the southernmost confirmed record of this species.

Remarks: The examined specimens concur with all of the characteristics given for the species in all previous descriptions, the only exception being slightly broader shells with rather narrow girdles. Among the chiton species found in the area, Chaetopleura hennahi can only be misidentified as Chaetopleura benaventei , from which it differs in having a wider profile, with more granulose valves and with finer rows of pustules; the tail valve of C. hennahi is also narrower and has more rows of fine pustules than that of C. benaventei . Chaetopleura peruviana , a common species in northern Chile, is easily distinguished from C. hennahi in presenting black or reddish hairs in between the valves, which are absent in the latter species. Chaetopleura hennahi seems to have a subtidal habitat, living in rocky areas, which is possibly the reason why it was not cited in a recent review of chitons in the area ( Araya and Araya, 2015).

Considering the present record—and further unpublished records of Ischnochiton pusio (Sowerby I, 1832) and Tonicia swainsoni (Sowerby in Broderip and Sowerby, 1832) from the same areas—the polyplacophoran

Figures

Figure 1. General view of Chaetopleura hennahi (Gray, 1828) from Caldera, northern Chile: A) dorsal view; B) side view; C) detail of valves showing the characteristic sculpture.