Abstract (EN):
Two species of the genus Alosa (A. alosa Linne, 1758 -allis shad- and A. fallax Lacepede, 1803 -twaite shad-) colonized the East Atlantic and the Mediterranean Sea. Their systematics is still confused without genetic characterization. Indeed, six subspecies of A. fallax are actually identified only on the basis of morphometric and meristic characters. One of these subspecies (A. fallax rhodanensis Roule, 1924) is endemic of the Rhone River. Although this taxon has the same morphometric and meristic characters as A. fallax, it is closer to A. alosa for the size and the ecological features. So a genetic study, with electrophoretic analysis of liver (electrophoresis in starch gel) and blood (isoelectric focusing in polyacrylamid gel) proteins, has been carried out to elucidate the taxonomic status of this population. We used two of the most discriminating loci between the two Atlantic shad species : MPI (Mannose Phospho Isomerase) and HBA (alpha haemoglobin chain). Allelic frequency puts in conspicuous the appartenance of A. fallax rhodanensis to the taxon A. fallax. Then, we used a locus known to discriminate the populations of A. fallax in Atlantic (ADH Alcohol Deshydrogenase). Through ADH allelic frequency, twaite shad from the Rhone River is close to populations of the north of Portugal. Results are discussed according to recent genetic studies made on Atlantic shads. They showed that further information had to be regarded on the genetic characteristics of this allis shad in relation to its particular status.
Language:
English
Type (Professor's evaluation):
Scientific
No. of pages:
11