Blesmol - Anatomy

Anatomy

Blesmols are somewhat mole-like animals with cylindrical bodies and short limbs. They range from 9 to 30 cm (3.5 to 12 in) in length, and from 30 to 1,800 g (1.1 to 63 oz) in weight, depending on the species. Blesmols, like many other fossorial mammals, have greatly reduced eyes and ear pinnae, a relatively short tail, loose skin, and (aside from the hairless Naked Mole Rat) velvety fur. Blesmols have very poor vision, although they may use the surfaces of their eyes for sensing air currents. Despite their small or absent pinnae, they have a good sense of hearing, although their most important sense appears to be that of touch. Like other rodents, they have an excellent sense of smell, and they are also able to close their nostrils during digging to prevent them from clogging with dirt.

The eyes of blesmols are structurally normal, despite their relatively small size, and include normal light-sensitive cells. However, the visual centres of their brains are reduced in certain respects, especially in those centres concerned with localising objects in the visual field. Research has shown that at least two species of blesmol (Fukomys mechowii and Heliophobius argenteocinereus) are not blind, as commonly believed, and will actively avoid blue or green-yellow light. They do not appear able to detect the presence of red light, and can probably not distinguish between different colours. The ability to sense the presence of light is probably useful in allowing them to detect breaches in their tunnel systems and repair them promptly.

Most blesmol species dig using their powerful incisors and, to a lesser extent, the foreclaws, although dune blesmols dig primarily with their feet, restricting them to soft, sandy soil. Dune blesmols aside, some species have been reported to be able to extend their burrows by an inch (2.5 cm (0.98 in)) into the walls of concrete enclosures. Their unique skull shape is associated with delivering sheer power to the lateral masseter muscle which is responsible for the powerful bite of the anterior portion of the mouth. The incisors of blesmols are projected forward and protrude from the mouth even when the mouth is closed. This condition allows the animals to burrow with their teeth without getting dirt in their mouths. The number of cheek teeth varies greatly between species, an unusual feature among rodents, so that the dental formula for the family is: