Naked Mole Rats: Genus Heterocephalus Glaber - Essay Example

Known taxonomically as Heterocephalus Glaber, belonging to genus Heterocephalus and group Rodentia of family Bathyergidae, naked mole rats are generally found in the hot, semiarid regions of Africa. They usually live in large colonies present underground in subterranean tunnels (Ciszek), where on average 75-mole rats live in each colony. But, if they are separated from their colonies, then they are able to actively reproduce. Worker mole-rats are able to transmit their genes to the next generation if they are sterile through the concept of inclusive fitness (Hamilton 1964:1; Axelrod & Hamilton 1981:1390), according to which if the worker mole-rats share genes with their mother queen, then they are able to assist her in raising future queens, thus, enabling the workers to transmit their genes. This assistance is a special feature of eusociality. Hence, we see close inbreeding in these mole rats since there is high genetic similarity (Faulkes, Abbott & Mellor, 1990). This close inbreeding eliminates the chances of out-breeding in mole-rats which increases their relatedness to the queen’s offspring. This close genetic relatedness maximizes the workers’ potential to do more work.

Frequent workers are assigned the responsibilities of digging the soil, construction, maintenance, and food provision (Jarvis 571). They make trips inside the colonies with food without pausing to eat themselves. Infrequent workers assist the frequent workers in work and make half the amount of effort frequent workers make (Vaughan, Ryan & Czaplewski 2011:594). The male members of these non-workers mate with the breeding female. Since most of these non-workers are sleeping most of the time, thus, the overall energy requirement for the colony is reduced. Their main role is the assistance in the bringing up of the offspring. Female mole rats of all these categories are non-breeding, and will never reproduce. Although they are not sterile, their ovaries have been found to be inactive. Male mole rats are able to inseminate; however, small mole rats have difficulty mating with the bigger breeding female. As far as the breeding female is concerned, she belongs to the category of non-workers and is of the same size as that of non-workers. She is identified through her prominent mammary glands.

The offspring that is born is fed by the breeding female and rests with the sleeping non-workers. If the nest is in some danger, both the sexes of the frequent and infrequent workers pick up the offspring and take him out of the nest. When the danger is over, all the members of all castes bring him back in. During weaning, he feeds on the food brought in by the frequent workers; and, when he is about 2 months old, he joins the army of frequent workers, and is about their size at one year. His joining the caste of frequent workers is evidence that the naked mole-rats share an extended family, which makes them eusocial.

Hence, the naked mole-rats are a perfect example of eusociality. They resemble a lot with eusocial insects but differ in that mole-rats do not have a clearly defined breeding male. The breeding female is not easy to catch which shows that she does not reside in such a place that is frequently exposed to dangers like predators. This feature is also present in eusocial insects. Mole-rats are also similar to eusocial termites in that they have diploid males; both the sexes work; the offspring grows up to join the frequent workers; workers become active breeders when removed from the colonies; and, all the adult members provide food to the young one. The colonies of mole-rats are big enough to accommodate a larger number of workers; their habitat is safe and the food supply is renewable and inexhaustible; there is genetic predisposition because workers share their genes with the breeding female thus passing on their helping traits to the offspring; they provide a significant amount of parental care to their young ones and assist each other in the care; and, there is sibling recognition and kin selection.