Journal of the Marine Biological Association of the United Kingdom

Research Article

Using morphological and molecular tools to identify megalopae larvae collected in the field: the case of sympatric Cancer crabs

Luis Miguel Pardoa1 c1, David Ampueroa2 p1 and David Véliza3

a1 Laboratorio Costero Calfuco, Instituto de Biologia Marina, Universidad Austral de Chile, Casilla 567, Valdivia, Chile

a2 Instituto de Oceanología, Facultad de Ciencias del Mar, Universidad de Valparaíso, Casilla 13-D, Viña del Mar, Chile

a3 Instituto de Ecología y Biodiversidad (IEB), Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile. Casilla 653, Ñuñoa, Santiago, Chile

Abstract

Studies of recruitment dynamics in meroplanktonic organisms are dependent on the correct identification of each ontogenic stage of each species. This is particularly difficult when studying the larval stages, which are not easy to identify due to their lack of resemblance to conspecific adults and their high degree of similarity with congenerics at the same stage of development. This is the case with the crustacean megalopae of the genus Cancer along the coast of the south-eastern Pacific. This fact represents a serious limitation on ecological studies of populations of these species which constitute a heavily exploited local resource. In this study we describe in detail field collected megalopae larvae of three sympatric crab species of the genus Cancer (C. edwardsii, C. setosus and C. coronatus). As a result of this analysis we were able to identify easily visible diagnostic characters which allow the species to be distinguished from one another. The megalopae were easily distinguished by the form of the cheliped and the presence of spines on these. Cancer edwardsii has an elongated globulose cheliped, whereas C. coronatus has a subquadrate one. Both species possess a prominent ischial spine, which is absent in C. setosus. We corroborated the utility of these diagnostic characters by comparing the COI gene sequences of mitochondrial DNA of larvae identified by morphology with sequences taken from samples of the adults of all species of Cancer found in the region. We discuss the morphological variations between larvae found across the region (i.e. at sites separated by more than 800 km) and between megalopae obtained from the field versus those cultivated in the laboratory. We conclude that the simultaneous use of morphological and molecular tools for identification of decapod larvae appears useful for the study of cryptic species.

(Received May 30 2008)

(Accepted October 20 2008)

(Online publication January 20 2009)

Correspondence:

c1 Correspondence should be addressed to: L.M. Pardo, Laboratorio Costero Calfuco, Instituto de Biologia Marina, Universidad Austral de Chile, Casilla 567, Valdivia, Chile email: luispardo@uach.cl

p1 Current address: 1469 Motueka Valley Highway, Ngatimoti, Motueka, New Zealand