Trans-differentiation of iris pigmented epithelial cells of Euphlyctis cyanophlyctis tadpoles into lens in vitro.

Meshed pigmented iris epithelium along with neural retina of tadpoles of the frog Euphlyctis cyanophlyctis were found to undergo dedifferentiation and subsequently transdifferentiate into lens in culture medium. During lag period, depigmentation (dedifferentiation) occurred in many cells. When culture became confluent 3-4 weeks after seeding tiny lens like structures differentiated from foci of cultured pigmented iris epithelium cells. The percentage of lens formation was higher in vitamin A treated cases. The culture system appears to be a suitable for investigating the changes occurred during trans-differentiation of pigmented epithelial cells into lens.

A skeletochronological study of growth, longevity, and age at sexual maturity in a population of Rana latastei (Amphibia, Anura).

Longevity and age at sexual maturity in an Italian population of Rana latastei were studied by skeletochronology performed on the phalanges. Frogs collected in 1998 and 1999 by drift fences and pitfall traps were marked by toe-clipping. After marking, individuals were released and the cut phalanges were processed for skeletochronological analysis. The maximum age so far recorded was 3 years in males and 4 years in females. The smallest male and female that were sexually mature on the basis of histological analysis of the gonads were 36 and 35 mm snout vent length (SVL), respectively. In both sexes, most individuals were estimated to breed shortly after emergence from their first overwintering. Among the European Brown Frogs, Rana latastei appears to be one of the shortest-lived and one of the first to reach sexual maturity.

Short-term and long-term survival studies in Rana tigrina tadpoles with reference to methyl parathion toxicity.

Toxicity of methyl parathion was studied on survival of Rana tigrina tadpoles. The LC50 values for short-term (upto 96 h) and long term studies (hatching to froglet) were determined. The LC50 values for 96 h and the total larval period were 4.36 and 1.30 ppm respectively. The toxicity of methyl parathion enchanced in relation to increase in concentration and duration. Teratological defects such as scoliosis and failure in emergence of fore limb were noticed. Safe levels were calculated for short-term (0.1 ppm) and long-term (0.03 ppm) studies. The present work stresses the neccessity of long term study especially for the developing amphibians.

Effect of vitamin A excess on oral armature in tadpoles of toad, Bufo melanostictus (Schneider) and frog, Rana cyanophlyctis (Schneider).

Tadpoles of B. melanostictus and R. cyanophlyctis were reared in vitamin A solution. Rearing of the tadpoles of B. melanostictus in solutions containing 15, 20 and 30 IU/ml vitamin A palmitate resulted in complete disappearance of the keratinized epidermal material over the jaws and horny labial teeth. However tadpoles of the frog R. cyanophlyctis, were not affected in this way.

Restoration of limb regeneration ability in frog tadpoles by electrical stimulation.

Electrical stimulation of advanced tadpoles of Rana breviceps for 24 hr with 3 microA current after hindlimb amputation through shank and ankle slightly increased the number of perfect regenerates as compared to controls. When amputation was made through thigh in tadpoles of the same stage regeneration failed in all cases of the controls but 24 hr stimulation of these tadpoles after similar operation with 3 and 10 microA currents induced fair degree of regeneration in 9 and 40% cases, respectively.