Histological effects of vitamin A on the tail amputated tadpoles of Bufo melanostictus

Vitamin A has manifold effects on the development, growth and pattern formation of several amphibians. At the same time it causes severe embryonic malformations. The histological changes brought about by vitamin A in the tail tissues of anurans are quite amazing. A common morphological change brought about by vitamin A in tail-amputated tadpoles of Bufo melanostictus include the formation of a large bulbular mass at the distal end of the tail following tail regeneration. Histology revealed that the bulbular mass consisted of notochordal cells only. Other histological changes are: a thickening of the epidermis and the basement membrane, enlargement of the notochord and the nerve cord, thickening of the sheath covering the notochord and the myelin sheath covering the nerve cord and the disorganization of muscle bundles. The significance of such changes is discussed

Unique second Arribada at Gahirmatha

Gahirmatha (20° 42' N, 87° 5' E) in Orissa, India, is one of the largest rookeries for olive ridley sea turtles (Lepidochelys olivacea) in the world. The turtles usually arrive around November for mating. The first mass nesting occurs in January and the second mass nesting occurs about 60 days after the first. In general, the number of turtles nesting during March is less than that of the January mass nesting. But this year in March, the turtles nested in record-breaking numbers, not only more than that of the first mass nesting of 1987, but also the largest number since 1976. The nesting took place from 8 to 14 March 1987. A daily account of the nesting is presented in Table 1. The total number of turtles emerging during the first mass nesting in 1987 was 245,157, restricted to a stretch of four km, from 5 to 14 January. The second mass nesting covered a six km stretch of beach. One of the peculiar features was that the emergence started at 1:30 PM on March 8 in bright sunlight. This is contrary to the usual behavior of the turtles, which usually emerge to nest either after sunset or during the day with an overcast sky. The mass nesting continued until the next morning. On 9 March, the emergence started in the evening, reaching a peak at 9:30 PM, when the beach became totally covered with turtles. The mass nesting occurred in the same area where the turtles had laid eggs during the first mass nesting. The hatchlings resulting from the first mass nesting were ready to emerge when the second took place. The result was that the hatchlings as well as some of the developing eggs were dug out of the sand by nesting turtles. A considerable number of hatchlings were either thrown into the air or buried in the sand due to the nesting activity of the turtles. Thus, a large number of hatchlings died due to the second mass nesting. The number of turtles nesting reached a maximum on the third day. In the frenzy to find a nesting place, the turtles migrated further and further away from the water line and even climbed the sand dunes. What was interesting was that the turtles cut into the wire fence of the 30'X20' hatchery set up by the Wildlife Division by cutting it with their beaks. Some of them even nested there, digging out the transplanted nests. The concentration of turtles was such that 3 to 5 turtles were found digging in the same place with their backs towards the same spot. This was a comical sight, as the simultaneous digging resulted in filling of one's body pit by another. The result was that none could dig a proper nest for laying. Due to the destruction of nests resulting from the high concentration of activities, the beach became littered with broken shells and dead hatchlings

Histological effects of vitamin A on the tail-amputated tadpoles of Polypedates maculatus with special reference to homeotic transformation

Vitamin A is a very common teratogen causing severe embryonic malformations and changes in pattern formation in amphibians. The effects of vitamin A include the induction of duplication of skeletal structures in the anteroposterior, proximodistal and dorsoventral axes. The purpose of this investigation was to study the histological changes in the regenerating tail of the tadpoles of Polypedates maculatus by treatment with vitamin A. The histological changes brought about by vitamin A included the development of multilayered epidermis and thickened basement membrane, enlargement of the notochord and the nerve cord and the clumping of muscles. In addition, single, paired and supernumerary homeotic limbs were visible from day 20 onwards at ectopic sites. Initially, the limb consisted of only procartilage cells. Muscles and digits appeared from day 48 onwards. In contrast, such observations were not found in the control tails. The significance of such changes is discussed

Vitamin A mediated limb deformities in the common Indian toad, Bufo melanostictus (Schneider)

Several types of limb deformities were induced by vitamin A in B. melanostictus. These ranged from total suppression of all the limbs (ectromelia) to partial development of either the forelimb or the hindlimb or both (mesomelia) to reduction or absence of digits in either the forelimbs or hindlimbs or both and absence of long bones in either the forelimbs or hindlimbs or both (phocomelia) or duplication of the hindlimbs (polymelia). All the limb abnormalities were induced in the developing limbs of the tail amputated tadpoles of B. melanostictus following vitamin A treatment, which is all the more interesting. The results suggest that vitamin A induces the above mentioned abnormalities by either switching on or over-expressing or disrupting the limb-specific hox genes by yet unknown mechanisms

Effects of some pesticides on the development of the Indian bull frog rana tigerina

The effects of five insecticides-metasystox, malathion, folithion, rogor and metacid -on eggs, feeding stage and limb bud stage tadpoles were determined. By chronic exposure to descending concentrations of each insecticide, the threshold levels for continuation of development and metamorphosis were determined. In general, at concentrations much lower than the dosage recommended for field application, the insecticides caused a prolongation of life history and a reduction in size at metamorphosis

Observations on food habits of six species of Indian frogs

The analysis of the stomach contents of six species of frogs Rana breviceps, Rana cyanophlyctis, Rana limnocharis, Microhyla ornata, Uperodon systoma and Rhacophorus maculatus were done during July and August 1978. This investigation showed partial selectivily in feeding which probably is based on the ecological niche each occupies and thus provided an insight into the interactions amongst members of the six species

Limbs generated at site of tail amputation in marbled balloon frog after vitamin A treatment

Niazi and Saxena first observed that vitamin A has an inhibitory and modifying influence on tail regeneration in Bufo andersonii tadpoles. A positive relationship was later found between the inhibiting influence of vitamin A and the developmental stage of the regenerating tail in the same species. There have been several subsequent reports on the effects of vitamin A and its derivatives on limb development and regeneration. Thus in regenerating amphibian limbs, application of retinoids produces pattern duplication in the proximodistal and anteroposterior axes of the limb, and local application of retinoic acid to the anterior side of developing chick limbs causes duplications in the anteroposterior axis of limb. Here we show that vitamin A can cause limb development when applied to amputated tail stumps of the tadpoles of the marbled balloon frog Uperodon systoma (Anura Microhylidae). This is the first report of homeotic transformation mediated through vitamin A in vertebrates

Distribution of heavy metals in the eggs and hatchlings of olive ridley sea turtle, Lepidochelys olivacea, from Gahirmatha, Orissa

371-372Shell and yolk-albumen of fresh eggs, hatched egg shells and newly emerged hatchlings of olive ridley sea turtle, Lepidochelys olivacea, along with eight nesting beach sand samples showed higher iron, zinc and lead concentrations than cobalt, chromium, copper and nickel. Beach sand samples recorded higher values of all metals than the egg components. Newly emerged hatchlings also recorded higher values than the fresh eggs. Embryos might have accumulated these metals from the nesting beach during incubation