Shark Colors 67
South Africa was thought to come in two forms, Cape and Natal, that dif-
fered mainly in the color of their dark saddles and white spotting. A study
of mitochondrial DNA genes showed that these are in fact two species, H.
edwardsii and the Natal Shyshark, H. kistnasamyi.
Just the opposite applies to another scyliorhinid, the Saddled Swellshark
(Cephaloscyllium variegatum) of the east coast of Australia. When the discov-
erers originally described this shark, they thought it was part of a three-
species complex, with the species differing in their saddles and spots. But
the coloration followed a latitude trend from north to south, with darker
saddles in tropical individuals than in temperate animals. C. variegatum is
now recognized as one species. Its species name, variegatum, refers to this
within-species color variation.
Porbeagles are high-latitude lamnids that seldom enter tropical waters.
Their coloration differs in northern and southern areas, evidence that little
genetic exchange occurs between populations. Porbeagles in the Northern
Hemisphere are mostly white under their head and abdomen, whereas the
undersides of the heads of Southern Hemisphere adults may be dark, with
dark blotches on an otherwise white abdomen.