Genetic and Morphological Differentiation of the Sea Lamprey Between Portuguese River Basins

Genetic and morphological differentiation of spawning adults of sea lamprey (Petromyzon marinus L.) entering different Portuguese river basins was addressed. Our main objective was to identify the biometric characteristics that better contribute for group segregation and to relate the observed variations with the ecological and/or geographical constraints of each population. To achieve this, a total of 201 individuals were collected from eight river basins and analysed for a total of 42 morphometric and 10 meristic characters. Diferences between male and female morphometric characters were found but not for meristics. Additionally, morphometric traits were more useful than meristic ones to discriminate populations, and the cephalic region was identified as the most important body area to discriminate populations of sea lamprey spawners. Genetic differentiation was addressed with samples from the same Portuguese river basins and additional populations from Europe and North America. A total of 674 samples were collected. Two mitochondrial genes (ATPase and cytochrome b) were sequenced and 11 microsatellite loci are being genotyped. Preliminary results show that there are no major differences in mtDNA between individuals from different basins. Microsatellite data will be used to clarify this since these markers are particularly useful in inferring phylogenetic relationships at levels below the species level or for recently diverged species.