Lepidochitona liozonis (Dall & Simpson, 1901)

Reyes-Gomez, Adriana, Ortigosa, Deneb & Simoes, Nuno, 2017, Chitons (Mollusca, Polyplacophora) from Alacranes Reef, Yucatan, Mexico, ZooKeys 665, pp. 1-36 : 4

Lepidochitona liozonis (Dall & Simpson, 1901) Figures 6 D–E, 8 A–I

Material examined.

One specimen of 10 mm long, 6 mm wide. Isla Perez (CNMO5002).

Description.

Small-sized chiton, of elongate-oval shape. Tegmentum dark orange, mottled with small white spots, tail valve showing a large irregularly shaped white spot on the postmucronal area; girdle with irregular lighter and darker longitudinal bands (Figure 6D). Tegmentum micro-granular, smooth, usually with growth lines. Head valve (Figure 8A) semicircular; posterior margin “V” shaped and notched. Tail valve (Figure 8B), wider than long, semicircular, the antemucronal and postmucronal area are indicated by a weak diagonal ridge; mucro somewhat elevated, antemedian; postmucronal slope slightly concave. Intermediate valves (Figure 8C) broadly rectangular, side margins somewhat rounded, posterior margin convex, with a prominent beak; lateral areas not rosy, with a faint diagonal ridge line. Articulamentum thin and translucent; apophyses well separated, long and narrow; slit formula 10/1/12. Megalaesthetes large (Figure 8D), arranged longitudinally, forming a depression on the tegmentum. Girdle covered with small, short, distally rounded spicules (Figure 8E, F), scattered with hyaline curved spicules (Figure 8E), arranged in groups of 2-3. Radula (Figure 8G) with a long, spatulate central tooth, distally wider, with its anterior end curved outwards; major lateral tooth tricuspid, the cusps around the same size (Figure 8H), the minor lateral tooth sub triangularly shaped, almost half the size of the central tooth (Figure 8I).

Habitat.

Found in the intertidal on rocks, associated with crustose coralline red and brown algae.

Remarks.

This species was considered by Ferreira (1985) as a synonym of Lepidochitona beanii (Carpenter, 1857). According to him, there were no particular differences between similar appearing specimens from the Caribbean or Eastern Pacific. However, in our opinion, there are major differences between them. As earlier noted by Kaas and Van Belle (1985), L. liozonis has an antemedian mucro, the apophyses are sinuated and somewhat elongated, and the girdle shows irregular slender spicules. In contrast, L. beanii bears a postmedian mucro, has shorter and semi-rectangular shaped apophyses, and hyaline long spicules interspersed and bunched at the sutures in groups of 3-4.

Recently, García-Ríos (2015) compared the morphologic features and DNA sequences (mitochondrial cytochrome oxidase subunit I or COI) of L. liozonis from its type locality (Puerto Rico, Culebra Island, Ensenada Honda) to specimens from Florida Keys, which were considered as variety “tropica” ( Pilsbry 1940). His results showed that these have to be considered as two different species. Lepidochitona pseudoliozonis García-Ríos, 2015 from Florida Keys is characterized by its larger body size (average of 9.7 mm), the deep concave postmucronal slope, and the longer marginal spicules. The Puerto Rico specimens (representing L. liozonis ) can be distinguished by their smaller body length (average of 7 mm), the postmucronal slope being almost straight to somewhat concave, and with shorter marginal spicules. The examination of the L. liozonis type specimen (USNM161920) (Figure 14B) revealed that the postmucronal slope of the tail valve is somewhat concave (Figure 6E), and the intermediate valves are carinated with a pointed apex. The PNAA specimens resemble the holotype and the specimens from Puerto Rico, both with a slightly concave postmucronal slope, which seems to be a morphologic feature that discriminates both species.