Puzzling Diversity
Frederick McCoy was puzzled that Victorian catchments often possessed a fauna distinct from that of adjacent rover systems. As an example, he noted that the Murray Tortoise was 'very common in the River Murray and its branches ... It is not found in the rivers flowing south into the sea on the Victorian coast'.
In contrast he observed that the opposite was true for spiny crayfish of the genus Euastacus. In an attempt to come to grips with their subtle differences, he commissioned illustrations of several crayfish that he assumed were merely varieties of the same species.
McCoy's hostility to Darwin's theories rendered him unwilling to consider the possibility that each 'variety' had evolved independently, in the isolation of a particular catchment. He postulated they were mere varieties of the Murray Spiny Crayfish rather than, as has subsequently been established by Museum taxonomists, a group of sibling species associated with a distinct catchment.
Our plate 160 illustrates a remarkable variety of the typical A. serratus of the Murray, common in the Yarra and its numerous effluents flowing southwards into the sea of the south coast of the colony; and as very few of the inhabitants of these river systems are identical ... this form is worthy of special note. It is usually less than half the size of the Murray individuals, being usually only five inches and rarely six inches long; it further differs in the whole thorax and abdomen above being of an intense Prussian-blue color, the spines, chelæ, and under surface ivory-white, with the membrane of the joints red. All the proportions and the number and disposition of the spines seem to me to agree so closely with the large pale Murray form, that, although so unlike at first glance, I have no doubt the southern race is merely a variety, which, for convenience of reference, may be distinguished by the name of the river in which it is chiefly found, from its mouth at Melbourne to its highest branches. The colors of those from the Watts River are particularly intense.