Vol. 46 No. 3, 2007

Use of a Morphometric Analysis to Differentiate Adelomelon ancilla and Odontocymbiola magellanica (Caenogastropoda: Volutidae) of Southern Chile

Alejandra Urra*, Doris Oliva, and Maritza Sepúlveda

Facultad de Ciencias, Universidad de Valparaíso Av. Gran Bretaña 1111, Playa Ancha, Valparaíso, Chile

Alejandra Urra, Doris Oliva, and Maritza Sepúlveda (2007) The volutid snails Adelomelon ancilla and Odontocymbiola magellanica are of economic importance to the fishery of Chile,s southern zone.  These species are direct developers, which make them very sensitive to localized catches, but there are no fishery regulations to control their catches. Although these sympatric species may be distinguished by their radular morphology, their external characteristics (used in field recognition) are so similar that they are confusedly lumped under the common name of “piquilhue” snail and registered as A. ancilla in the fisheries national statistics.  With the aim of identifying external population characters which can facilitate discrimination between taxa, common samples of piquilhue snails were taken and separated into 330 A. ancilla and 54 O. magellanica using identification guides.  The radular morphology, and shell and body characteristics of these 2 species were evaluated through traditional and landmark-based geometric morphometric methods.  The results revealed that the species cannot be distinguished by meristic traits (number of whorls and columella folds), or by the thickness or weight of their shells, but they do exhibit significant differences in shell shape and body weight.  Adelomelon ancilla has a fusiform shell shape (a small aperture and a high-spired shell) that accommodates a smaller body mass than that of O. magellanica, which has a globose shape (a larger aperture and a low-spired shell).  The external differences found by traditional and geometric analyses are sufficient to discriminate between the 2 species, which will be useful in establishing proper fisheries statistics and adequate management strategies.

Key words: Geometric morphometrics, Shell shape, Allometry, Radular morphometry.

*Correspondence: Tel: 56-32-2508346.  Fax: 56-32-2508072. E-mail:alejandra.urra@uv.cl