VOL. 2, NO. 3, April 2012 ISSN 2225-7217 ARPN Journal of Science and Technology ©2011-2012. All rights reserved. http://www.ejournalofscience.org 166 Corticosterone as Inhibitor of Bufo Melanostictus Tadpole Growth Ruqaiya Hasan and Mahmood Ahmad Department of Physiology, University of Karachi, Karachi – 75270, Pakistan Email: ruqaiya55@gmail.com ABSTRACT This investigation reports the effect of corticosterone on the growth of Bufo melanostictus tadpoles. Test tadpoles of experiment I (T-I), maintained in 1μg/ml solution of corticosterone, were 2.39mm shorter than controls by day 11. Test tadpoles of experiment II (T-II), maintained in 5μg/ml solution were 4.32mm shorter than their counterparts. Growth inhibition was dose related and became significant (p<0.05) when the larger amount was administered. Keywords: Metamorphosis, Macrophages, Proteolysis, Anuran tadpoles, Growth inhibitor. 1. INTRODUCTION Only a minute amount of corticosterone has been detected [1] in the blood of Amphiuma. Equally, a very small quantity has been found in the blood of the adult American bullfrog, Rana catesbeiana [2]. Despite these demonstrations, it has not yet been shown that corticosterone is present in the blood of amphibian larvae [3]. However, several studies have demonstrated the influence of exogenous corticosterone on the growth and development of larval amphibians [4, 5, 6]. Kobayashi [4] studied the effects of deoxycorticosterone acetate on metamorphosis of thyroxine induced tadpoles. He also claimed that corticosteroids synergise the destructive phase of shrinking of tails and a shortening of structures. The purpose of the present investigation is to investigate the destructive action of corticosterone in premetamorphic Bufo melanostictus tadpoles. 2. MATERIALS AND METHODS Animals: Bufo melanostictus tadpoles belonging to a single hatching were collected from the rainwater ponds of the University Campus in the month of August 2011. After collection, tadpoles of similar size were divided into several groups of equal number. They were soon given refined suspension of parboiled spinach [7, 8]. They were then allowed to acclimatize for a number of days. On attaining premetamorphic period, tadpoles were used to determine the effect of corticosterone; since physiological connections between pituitary and hypothalamus are established when they enter premetamorphic period of stage 52 [9, 10, 11]. The tadpoles were selected with the help of a binocular microscope; and after measurement, individuals of the same size were randomly divided into comparable groups of control and test. Growth correlations: It may be stated that during development, there appears to be gradual unfolding with time; of anterior pituitary and receptor-gland hormones that regulate the final size, form and body parts. This elaboration of growth is indicative of a second phase of specific constitutional growth potential, provided by the genotype of the egg. During this phase the growth regulating hormones gradually take over the function of the coordination and regulation of final size [12]. However, growth is also dependent upon environmental factors [13]; since nutrients, oxygen supply [14] and temperature have an effect on the physico-chemical background in which the synthetic processes of growth take place. Thus, growth follows the expression of size and weight. Therefore, growth of Bufo melanostictus tadpoles was worked out by measuring its body size and decisive evidence of growth has also been sought through the use of these measurements [15]. Method of measurement: The method adopted for this purpose was similar to that described by Ahmad and Mukarram [16]; and was later adapted by Ahmad et al., [15, 17, 18, 19]. In order to measure each tadpole, nylon net was used to introduce tadpoles into a 6 cm diameter glass Petri dish, in the absence of water. As soon as the tadpole ceased its wriggling movements, the Petri dish was tilted slightly towards the head side. By sliding, the tadpole body was shaped into a straight line. The Petri dish was arranged on a glass bearing a millimeter grid and the length from the head to tail was noted. Design of experiment: Space is a major factor in the growth rate of tadpoles, and crowding has been reported to accelerate metamorphosis by operating through the hypothalamic