Blind mole-rats are in the familySpalacidae, but are unique enough to be given a separate subfamily, Spalacinae. Alternate opinions on taxonomy consider the blind mole-rats to be the only members of the family Spalacidae and rank other spalacid subfamilies as full families. Other authors group all members of the superfamilyMuroidea into a single family, Muridae. The Spalacinae contains two genera and eight species. Some authorities treat all species as belonging to a single genus, Spalax, but more recent studies indicate a deep divergence between both lineages dating back to the Late Miocene, supporting them as being distinct genera.[1][2]
Blind mole-rat diggings
Spalacinae mole-rats are truly blind.[3] Their very small eyes are completely covered by a layer of skin. Unlike many other fossorialrodents, blind mole-rats do not have enlarged front claws and do not appear to use their forearms as a primary digging tool. Digging is almost exclusively conducted using their powerful front teeth, which are separated from the rest of the mouth by a flap of skin. When a blind mole-rat closes its mouth, its incisors are still on the outside. Blind mole-rats may have evolved from spalacids that used their front limbs to dig, because their olecranon processes are large relative to the rest of their arms. The olecranon process is a part of the ulna bone where muscles attach, and digging animals tend to have enlarged olecranon processes to provide a large surface for their large and powerful muscles to attach.[4]
Because they are completely blind, blind mole-rats have been important laboratory animals in tests on how eyes and eye proteins function. Although blind mole-rats have only atrophied subcutaneous eyes and are sightless, their circadian rhythm is kept. A few publications, such as Avivi et al., 2002, have proven that the circadian genes that control the biological clock are expressed in a similar manner as in sighted, above-ground mammals.[5]
