Bilocus phylogenetic diversity and biogeographic distribution of isopods infesting Egyptian fishes

Phylogenetic diversity studies of parasitic isopods in Egyptian fisheries are very limited, based on a few records of the single mitochondrial gene, COI. Consequently, there has been no mapping study to monitor the phylogenetic diversity and biogeographic distribution of parasitic isopods among a wide range of Egyptian fisheries, leading to gaps in our understanding of the origin and expansion of these parasites. Hence, this study focused on validating the taxonomy and phylogenetic distribution of parasitic isopods using two marker genes, nuclear 18S rDNA and mitochondrial COI. Isopods were collected from seven fish species, Liza ramada, Solea aegyptiaca, Tilapia zillii, Pomadasys sp., Dicentrarchus sp., Atherinomorus lacunosus, and Nemipterus japonicus at four distant Egyptian lakes, Lake Qarun, Bitter Lakes, Lake Burullus, and Lake Manzala; and two marine localities, Red Sea and Suez Gulf, respectively. Sequence analysis revealed 10 and 19 haplotypes of 18S rDNA and COI, respectively. Lake Qarun showed the highest haplotype intra-diversity and is considered a pool of haplotypes with ancestors from other distant lakes. The Red Sea and Suez Gulf haplotypes showed genetic divergence from those recovered from lakes, implicating endemic isopod species. Some haplotypes had mutations in COI-deduced catalytic amino acids. The lake haplotypes belonged to Livoneca redmanii, suggesting a biogeographic expansion of this species among distant Egyptian fisheries. A new genus belonging to the family Cymothoidae was recorded in the Red Sea fish A. lacunosus. Elthusa vulgaris-like haplotypes were recorded in the Suez Gulf fish N. japonicus. Hence, this study clarified the expansion of isopod phylogenetic diversity among varieties of fish species from distant localities.