Common Indian toad (Bufo melanostictus) of both sexes showed excellent positive correlation between body weight and Snout-to-Vent (S-V) length, body weight and bone weight as well as body weight and gonad weight, suggesting the utility of these parameters as indirect markers of chronological age and indicating continuous structural growth. The relative weight of bone of both sexes increased up to maturation and then gradually decreased with body weight, showing slower rate of growth with advancing age. The observation of gonad indicates that these animals become sexually mature when they attain a body weight of about 38-45 g in male and 36-43 g in females. However, reliability of such morphometric data needed support from a more accurate method of bone histology based on the techniques of `skeletochronology'. Counting of growth rings in histological sections of humerus and femur suggested that in natural surroundings, the life span of common toad of both sexes is 4 years. The animals not showing any growth rings in their skeletal parts were considered to be young and had not completed a year in their natural surroundings.

During recent years, the age determination of animals in ecological, demographical and gerontological studies has been realized as a basic necessity. Bone is a dynamic tissue which exhibits conspicuous `growth marks' and is generally thought to indicate successive bursts of growth. The growth marks obviously offer an opportunity to assess an animal's age. Skeletochronological method aims to study the age of amphibians, the relationship between age and body growth and longevity.

In species capable of breeding in captivity, the young can be reared under standard laboratory conditions and their age determined by keeping the birth record. But for others which breed favorably in a natural habitat, suitable alternative methods are required to evaluate the age. A few researchers have used morphological features to determine the age of amphibians (Senning, 1940; and Organ, 1961). Although these have been successfully employed for indirect measures of chronological age, the reliability is often subject to criticism. But the use of bone histology based on `Skeletochronological' techniques dealing with hard tissues of vertebrates in general (Castanet, 1978) has been recognized as the most meaningful and practicable method not only to assess the individual's age but also the speed of growth, age at sexual maturity and the longevity of various species. In most ectotherms, the occurrence of bands in cortical bone in successive layers of long bones indicates slow and fast growth during colder and warmer seasons respectively. Such cyclical growth marks, considered to be the expression of annual growth periodicity, offer an opportunity to assess the individual's age. The actual age can be determined by counting the annual rings in the cross sections of diaphyses of long bones (humerus and femur) and phalanges of amphibians (Cherry and Francillon-Vieillot, 1992; Kulkarni and Pancharatna, 1996; Sagor et al., 1998; Andia and Behera, 2005; Andia et al., 2009; and Andia et al., 2010). It is analogous to the method used for age determination in fish by counting growth rings in the scales, bones and otoliths (Chugunova, 1959) in reptiles (Smirina, 1974; Castanet, 1978; Patnaik and Behera, 1981; Mohapatra et al., 1989; and Waye and Gregory-Patrick, 1998) and in mammals by layers in bone and tooth tissue (Klevezal, 1988).

Science and Technology Journal, Age Determination, Common Indian Toad, Bufo Melanostictus, Skeletochronology, Microradiography, Fluorochrom Techniques, Morphometric Parameters, Skeletal Parts, Anatomical Parameters, Fluorochrom Labelling.