Genetic evidence for an undescribed species previously considered as Sillago sihama from the northern Red Sea

The augmentation of traditional taxonomy by the addition of genetic methods, particularly DNA analysis, has revealed that many species that appeared identical morphologically throughout their distribution range are actually divided into two or more genetically distinct species. The whiting, Sillago sihama, is a fish that was considered to be of a wide Indo-Pacific distribution. Not long ago, what was considered to be S. sihama invaded the Mediterranean from the Red Sea via the Suez Canal. In our study we sequenced a 655-bp region of the mitochondrial cytochrome c oxidase subunit I gene (COI) from Hong Kong, southern Red Sea and Mediterranean populations of Sillago. We discovered that the first two (HK and southern Red Sea) are genetically similar while the sequencing of the Mediterranean population shows a significant divergence, confirming the existence of two distinct species. We further sequenced a segment of 178 bp (of the 655 bp) from a formaldehyde-fixed specimen from the northern Red Sea (Gulf of Suez) and found it to be identical to that of the Mediterranean population. We were thus able to confirm that the northern Red Sea population is the source for the invading population. The mitochondrial control region (D-loop) analysis of the Mediterranean population revealed that all 38 specimens have a single mitochondrial haplotype.