A histological study of tail width variation in the greater Japanese shrew-mole, Urotrichus talpoides

Abstract. The greater Japanese shrew-mole, Urotrichus talpoides, has a wide and thick tail like a baseball bat with bristles like bottle brushes. It is known that not only length variations but also the width variations are observed in the tails of U. talpoides. To understand such width variations of the tail, we examined morphological and histological characteristics. The width variation was not related to the season when captured or aging, as indicated by the skull sizes. In addition, tail vertebra width was not correlated with tail width. On the other hand, according to histological observation of tail skin, the ratio of subcutaneous tissue/corium indicating the thickness of the subcutaneous tissue layer was positively correlated with the tail width (p < 0.05). The thickness of the subcutaneous tissue layer means that the rich adipose tissue and cells observed were unilocular, then identified as white adipose cells. It is well known that one of the functions of white adipose cells is to store excess energy as neutral fat. Thus, it is suggested that U. talpoides stores an energy source as adipose cells in the skin of the tail, demonstrating that tail width variations are caused by the thickness of the subcutaneous tissue layer.