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Titre : Revisión sistemática del género Macrobrachium de la península de Baja California

Auteur : Hernández Moreno, Luis Gerardo

Etablissement de soutenance : Centro de Investigaciones Biológicas del Noroeste (CIBNOR)

Grade : Doctorado en Ciencias en el Uso, Manejo y Preservación de los Recursos Naturales 2007

Résumé
ABSTRACT Shrimp of the genus Macrobrachium are probably the best known freshwater shrimp not only because of their great species number, but also due to their wide geographical distribution and commercial interest. This genus comprises about 200 species distributed in circumtropical freshwater bodies close to estuaries. In Mexico, there are about 150 decapod freshwater species, of which 17 belong to the genus Macrobrachium . Depending on locality and species, these shrimp have different common names, but in the present study they will be referred as “langostinos”. In spite of the large si ze of these shrimp and their potential for aquaculture, there are few works about this genus in Mexico, and little is known about its biological and ecological aspects. In the Baja California peninsula, the “langostinos” have been recorded since the end of the 18th century, but to date there is no important study of their diversity. From an extensive field survey and examination of specimens in several scientific collections, this thesis provideas a detailed description of the diversity and phylogenetic relationships of “langostinos” in the Baja California peninsula, using morphological and molecular approaches. The survey sampled 83 freshwater bodies and “la ngostinos” were collected in 35 of them. Based on morphological characteristics, six species were identified : three represent new records in the peninsula and two have an amphiamerican distribution. These six species represent 84% of the richness of “langostinos” on the Pacific slope of Mexico. To determine if these species are native or cryptic entities, a discriminant function analysis was applied to some measurements performed on the second largest pereopod. Results indicated that the species from the peninsula are morphologically similar to specimens from freshwater streams of the mainland of Mexico. However, cluster analysis showed only four clades : the first was composed of M. hobbsi and M. olfersii  ; the second was composed of M.  digueti and M . michoacanus  ; the third was represented by M . americanum  ; and the fourth included M . tenellum .

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