Chiton Linnaeus, 1758

Arias, Andrés & Anadón, Nuria, 2013, Tonicia atrata and Chiton cumingsii (Polyplacophora: Chitonidae): First records in European waters, Zootaxa 3626 (4), pp. 593-596 : 595

Genus Chiton Linnaeus, 1758

Type species: Chiton tuberculatus Linnaeus, 1758

Chiton cumingsii Frembly, 1827 Fig. 1 D

Material examined: Las Palmas Port -Canary Islands, 28º06’N, 15º25’W (Aug. 2012): BOS-CHI16, BOS-CHI17, BOS-CHI18.

Habitat and distribution: On undersides of rocks, lower intertidal areas from Peru to Chile (Leloup 1956).

Diagnosis and description: Animal with oval shape. Intermediate plates not separated by spaces of exposed mantle, slightly superimposed over one another, growth lines on intermediate plates evident to naked eye. Only jugal area with uniform pale colour, remainder with greyish striped. Girdle with imbricating rhombus-shaped, never whitish scales well ordered one beside another. Tail plates elliptical to round in outline, with subcentral mucro; postmucronal area with concentric growth marks.

Remarks: The biggest specimen was 42 mm long, 25 mm broad.

Conclusions: Many alien species arrived on the Iberian Peninsula as a result of secondary spread from other nearby European countries where their introductions were attributed to ship transport from distant locations such as Asia or South America (Kaas & van Belle 1987; Streftaris at al. 2005). The South American Ch. angulata was recorded on the Iberian Peninsula in the early 20th century (Hidalgo 1916) and has subsequent expanded along the Bay of Biscay and south of Portugal to the Straits of Gibraltar (Anadón 1979; Rolán 1983; Carmona & García 2000). This study revealed the presence of not only Ch. angulata , but also T. atrata in the Atlantic Iberian Peninsula estuaries, demonstrating that T. atrata is not a species that has emerged in recent years, but had been present in the seventies.

Generally one explains the arrival of marine exotic species in European waters by the unintentional co-transport of their larvae and/or juveniles into commercial bivalve cultures, mainly clams and oysters from the American continent (Rolán 1983; Zenetos et al. 2010; Arias & Anadón 2012; Rolán & Horro 2005; Arias et al. 2012). This may also apply to the introduction of T. atrata to the Iberian Peninsula because the two estuaries with this species are locations of intensive mariculture with high traffic of exotic aquaculture species (Arias & Anadón 2012; Arias et al. 2012). On the other hand, for C. cumingsii in the Canary Islands, the “shipping” would be the most plausible way of introduction for this species. Since due to its proximity to a port area, C. cumingsii may be introduced either by “biofouling” on the ship’s hulls.

We wish to express our gratitude to Dr. Schwabe, Zoologische Staatssammlung München, for confirming T. atrata and C. cumingsii . Our thanks are due to the anonymous reviewers for helpful comments, which substantially improved the ms.

Figures

FIGURE 1. European alien Polyplacophora. Colour polymorphisms in Tonicia atrata specimens A—BOS-CHI 15; B—BOS-CHI 10; C—BOS-CHI 12; D— Chiton cumingsii BOS-CHI 16. All scale bars 1 cm.