Within the last few years, freshwater Crayfish Procambarus clarkii (P. clarkii) has been successfully
established in various sites of the river Nile and its branches. The main aim of this study was to describe
improved techniques for obtaining good quality metaphase from a variety of tissues, the mitotic chromosome
number and to evaluate the genetic variation among three geographic populations of freshwater Crayfish P.
clarkii, which inhabits the Nile River in Egypt using the Random Amplified Polymorphic DNA-Polymerase Chain
Reaction (RAPD-PCR) technique. Our results provided that, good metaphase chromosomes were obtained
from the regenerated blastema treated with 0.025% for 1 h and hepatopancreas tissues treated with 0.01%
colchicine in vivo for 5 – 6 h, and then treated with the hypotonic solution for 1h. From 100 mitotic
metaphases, the number of chromosome ranged from 184 to 208 per metaphase with a mode of 190 for 38 %
of metaphases. The genetic diversity among three crayfish populations from three different regions (Giza,
Qaluabia and Sharkia) generates 159 loci with 10 oligodecamers primers and RAPD profiles exhibited bands
between 200 to 2778 bp in length. Average genetic distances among populations ranged from 0.0076 to
0.1735. The estimated average of gene differentiation (GST) value across all loci was 0.2884, suggesting, very
low gene flow among the different localities. The phylogenetic tree constructed by unweighted pair-group
method of analysis (UPGMA) shows that, Giza, Qaluabia and Sharkia populations, respectively, seems to be
approximately as closely linked to each other from the dendrogram. However it can be seemed that, Qaluabia
population is more related to Giza populations. We conclude that, the number of mitotic chromosome ranged
from 184 to 208 and there is a high level of genetic variation and population differentiation indicated dynamic
evolution in these populations as revealed by variation at RAPD loci. This information will help in the selection
of high-quality individuals for artificial reproduction. |
