Rana Temporaria Tadpoles Research Articles

On the Development of the Eminentia Mediana of the Hypophysis in Rana temporaria, Studied in Normal, Hypophysectomized, and Thyroidectomized Tadpoles.

In the Rana temporaria tadpole, the part of the infundibular floor that eventually becomes the eminentia mediana is very thin throughout premetamorphosis; the supply of aminergic and neurosecretory nerves is poor, and the area is covered by a few fenestrated capillaries. The organ begins to thicken around mid-prometamorphosis owing to a marked invasion of nerves. At this stage it is also penetrated by capillaries and perivascular space extensions, which together form the neurovascular link structures. These become more pronounced during metamorphic climax, when the eminentia mediana attains the adult appearance. Development of the organ is arrested at the premetamorphic stage after thyroidectomy in the young premetamorphic tadpole. Removal of the adenohypophysial primordium from the embryo of the tailbud stage prevents the vascular-but not the neural-component of the eminentia from developing beyond the premetamorphic stage. By contrast, in the American Rana-species investigated the neural component also fails to develop after hypophysectomy.

Development of taste organs inRana temporaria

In tadpoles of Rana temporaria two successive generations of taste organs: taste buds (TBs) and taste disks were studied. The TBs are located in the apices of oral premetamorphic papillae. Each TB consists of vertically elongated receptor cells (probably taste) and supporting cells. No basal (Merkel) cells were observed there. Morphologically, two types of receptor cells have been distinguished in a TB. Complete synaptic structures were observed in the TBs between the 30th and 41st of Gosner's (1960) developmental stages, though synaptic vesicles occur already at stage 26. The taste disks consist of taste cells, supporting cells and basal cells. Dense-core synaptic vesicles occur in the gustatory cells at stage 41, but complete synaptic structures were not observed earlier than at stage 45. Synaptic junctions observed at some of the gustatory cells seem to be reciprocal (bidirectional).

Development of the endocrine pancreas during larval phases of Rana temporaria

The pancreatic endocrine component was studied at different stages of development in the tadpoles of Rana temporaria. The material was embedded in Epon, and serial semithin and thin sections were made in order to correlate ultrastructural features and tinctorial traits of the endocrine cells. Serial semithin sections were also stained with the peroxidase-antiperoxidase immunocytochemical method and with silver impregnations for argyrophilia and argentaffinity. In early larvae (legless tadpoles). A and B cells are present. Both can be found within ducts and exocrine tissue or, more frequently, in cellular clusters among the ducts and acini. These primitive islets are solid structures, surrounded but not penetrated by capillaries. Mitoses were observed in A and B cells. In the following phase (tadpoles with hindlegs), D and pancreatic polypeptide-immunoreactive cells are also present, as well as numerous endocrine cells scattered among exocrine tissue. There is also a change in the vascular-insular pattern: capillaries not only surround but also penetrate the endocrine group. The structure of the endocrine pancreas in older tadpoles is similar. Tinctorial traits and ultrastructural features of endocrine cells are described, and the origin of primitive islets is discussed.

Toxicité aigüe et bioconcentration du lindane et de la deltaméthrine par les tetards de Rana temporaria et les gambusies (Gambusia affinis)

Acute toxicity and bioconcentration capacities of lindane and deltamethrin were studied in Rana temporaria tadpoles and in mosquitofish. These studies show that the toxicity of deltamethrin is about 100 to 1 000 times greater than that of lindane and bioconcentration factors are very different for these two insecticides. The bioconcentration factor of lindane, a stable chemical, low volatility, hydrophobic and a poorly metabolized molecule is considerable in either static or flow through contamination systems. For deltamethrin, an quickly metabolized molecule, this factor is weak or null.

A comparison of the distribution of muscle type in the tadpole tails of xenopus laevis and rana temporaria: An histological and ultrastructural study

The types and the distribution of muscle fibres were analysed and compared in the tails of Xenopus laevis and Rana temporaria tadpoles. The filter feeding tadpoles of X. laevis were found to have both white muscle fibres adjacent to the notochord used for normal locomotory swimming and a superficial layer of small red fibres. The red fibres are probably used for the continuous flickering movement of the tail associated with the maintenance of the mid-water filter feeding position. R. temporaria, a grazing detritus feeding tadpole, was found to have only white muscle fibres used for normal locomotory swimming. Smaller superficial fibres were not red fibres but were thought to be immature white fibres.

Pathfinding by dorsal column axons in the spinal cord of the frog tadpole.

Sensory fibres from dorsal root ganglia (DRG) enter the spinal cord and run within a clearly defined ipsilateral pathway, the dorsal column, which lies in the dorsal funiculus. We have examined the characteristics of this pathway as a defined substrate for dorsal column axons in Rana temporaria tadpoles by rotating the thoracic spinal cord through 180 degrees from dorsal to ventral. Using HRP as a neuronal tracer we establish that many dorsal column axons from the hindlimb locate the ipsilateral or contralateral dorsal column pathway in the rotated cord. Other axons locate and grow caudally down the contralateral dorsal column returning to the lumbar region. Axons of the dorsal column never take an inappropriate pathway except at the transection sites where they negotiate abnormal routes to reach the contralateral or ipsilateral dorsal columns in normally positioned or rotated cord. The results demonstrate that the dorsal columns act as highly specific pathways for axons from DRG neurones but the axons' interactions with the pathway do not control the craniocaudal or left-right options for growth.

Effects of aluminium and low pH on growth and development in Rana temporaria tadpoles.

Rana temporaria tadpoles were raised to metamorphosis at 6 levels of pH (pH 3.6-6.5) and 2 levels of aluminium (800 and 1,600 μg l-1) at pH 4.4. Treatments involved both chronic and acute exposure to depressed pH. Decreasing pH reduced maximum body size and delayed metamorphosis. Growth was depressed and metamorphosis delayed by 800 μg l-1 Al, and several tadpoles died at foreleg emergence. At 1,600 μg l-1 Al, small tadpoles suffered arrested growth and development and eventually died, while larger tadpoles metamorphosed without delay, though at a very small size. There was no mortality among controls. The levels of pH and inorganic monomeric aluminium measured in the experiments were similar to field levels at a site in Scotland, and it is concluded that individual tadpoles will, in certain types of water body, be adversely affected by both acidity and aluminium. The impact of these factors on populations remains to be determined.

Genesis and regression of the figures of Eberth and occurrence of cytokeratin aggregates in the epidermis of anuran larvae

In tadpoles of Rana temporaria, Bufo bufo and Xenopus laevis the development of the massive skeins of tonofilaments (cytokeratin intermediate filaments) that form the figures of Eberth follows a similar sequence in all species studied. Increase in the number of filaments is preceded by increase in polyribosomes and rER in the basal layer cells of the epidermis. A filamentous zone develops proximally in the cells concurrently with hemidesmosomes, which assume the typical larval bobbin form as the skeins occupy more of the cytoplasm. The figures of Eberth are at maximum development throughout mid-larval life. The first signs of regression appear before the climax stages, when aggregates of cytokeratin material are found among the filaments of the skeins. Such cytokeratin aggregates have previously been reported only from mitotic mammalian cultured or tumour cells, or in experimental situations. At metamorphic climax they are numerous in the basal layer cells and in some other cells of the epidermis, even when not dividing. This condition persists into the postmetamorphic stage when the figures of Eberth and the bobbin-type hemidesmosomes have gone. The formation of cytokeratin aggregates can be enhanced by chilling the animals before fixation, but does not depend on a drop in temperature, and takes place even if fixation is carried out at room temperature.

Stage-dependent restoration of sensory dorsal columns following spinal cord transection in anuran tadpoles.

In frogs sensory axons from the lumbar dorsal roots ascend in the dorsal column of the spinal cord to terminate in the medulla and cerebellum. The response of these axons to complete transection of the thoracic spinal cord has been analysed in Rana temporaria tadpoles at different stages of development. The presence and position of dorsal column axons were assessed by using the anterograde transport of horseradish peroxidase or by electrophysiological methods. Before developmental stage VIII, dorsal column axons can grow across the transection and reach their normal areas of termination in the brainstem. Axons that do cross the transection follow their normal pathways. From stage VIII onwards this capacity for growth is largely lost. These results are discussed in terms of the relation between neurogenesis, axon growth and axonal regeneration.

A Comparative Study of the Aminergic Structures in the Hypothalamus and the Hypophysis of Amphibian Larvae, with Special Reference to the Innervation of the Pars Distalis

AbstractThe distribution and occurrence of the aminergic structures of the hypothalamus and the hypophysis of the investigated species are very similar, except for the pars distalis. In the tadpoles of the anuran species Rana temporaria, R. arvalis, R. dalmatina, R. escutenta, Bufo bufo and B. calamita, the pars distalis is aminergically innervated (the Falck‐Hillarp technique), but these nerves disappear at the metamorphic climax. In the larvae of the urodelan species Triturus cristatus and T. vulgaris, the pars distalis is devoid of such nerves. Electron microscopical studies of R. temporaria, B. bufo and T. cristatus confirm these observations. A discussion of the functional significance of the pars distalis nerves and the phylogenetic role of the difference between anuran and urodelan species is given.

Transdifferentiation of Pigmented Epithelium Induced by the Influence of Lens Epithelium in Frogs

The influence of lens epithelium (LE) of adult frogs on the character of transdifferentiation of retinal pigmented epithelium (RPE) of adult frogs and tadpoles of Rana temporaria has been studied. After a period of intense proliferation RPE cultured in vivo in contact with LE in the tadpole orbit almost exclusively transforms into retina. RPE precultivated in vitro in contact with LE for three days in protein-free medium does not manifest cell divisions and mostly transdifferentiates into lentoids. The problem of the relative significance of inducing determinants and the role of activation or inhibition of proliferation in transdifferentiation is discussed.

Observations on the routes of infection of Oswaldocruzia filiformis (Nematoda: Trichostrongylidae) in amphibia.

The oral, percutaneous and subcutaneous routes of infection of Oswaldocruzia filiformis were investigated in amphibia. Tadpoles of Bufo bufo and Rana temporaria can be infected with O. filiformis when kept temporarily in a suspension of infective larvae in water. Larval stages and subadults were found in tadpoles. All stages of the parasite, including egg-producing females, were found after metamorphosis of the host. However, under natural circumstances infection of tadpoles seems unlikely. Oral infections in metamorphosed hosts of both species were successful in 97.5% of the host animals used. The first eggs appeared 29 days after infection in the faeces. The oral route seems to be normal for O. filiformis in amphibia. Experiments on percutaneous infections did not reveal actual penetration of larvae in or through the skin nor a subsequent migration through host tissues. Sometimes a few larvae were found in the stomach and intestine, but in these particular cases the experimental conditions did not totally exclude the possibility of oral infections. Consequently, the percutaneous route of infection is not plausible for O. filiformis. Subcutaneous inoculation of infective larvae seems to be a possible way of establishing experimental infections. Erratic localisation of the parasite in the enlarged gall bladder of the host was observed.

Histology of a teratogenic effect of DDT on Rana temporaria tadpoles

Histological examination of a snout abnormality induced by DDT in Rana temporaria tadpoles has indicated that the abnormality is caused by two factors. One is the disruptive effect DDT has on the development of skin glands in the region above the upper mandible, and the other is a result of the hyperactivity that DDT causes in tadpoles. Thus, DDT first seems to disrupt glandnular development, and soon after, hyperactive movements, which are characteristically unco-ordinated, appear to cause the lower mandible to strike the inner surface above the upper. The damage thus caused, together with the disruption in the external skin glands, is sufficient to cause the loss of the upper mandible in many of the affected individuals. Some individuals recover from the abnormality at various stages. Frequently froglets which were affected as tadpoles have blunt snouts and deformed brains. It is suggested that DDT causes disruption of glandular development by preventing the organisation of the epithelial cells into gland units. This may be due to some effect of DDT on a characteristic of the cell membranes by which cells recognise one another. The mechanism of the recovery remains unknown, and it is not possible to explain fully the very specific nature of the abnormality.

The toxicity of the mothproofing chemical eulan WA new to frog Rana Temporaria tadpoles

Eulan WA New is replacing dieldrin as a mothproofing agent. Its toxicity to frog tadpoles has been assessed in a static bioassay system. Eulan, at various concentrations, killed tadpoles or reduced feeding—and subsequently the weight of the tadpoles. It is suggested that these effects could occur in wild animals accumulating between 1 and 10 mg kg −1 of Eulan.

The pars distalis nerves and metamorphosis in Rana temporaria

The length of prometamorphosis in the tadpoles of Rana temporaria is influenced by different treatments: (1) thyroidectomy, (2) propylthiouracil, (3) 1-thyroxine, (4) low temperature. In normally developing tadpoles the fluorescent pars distalis fibers persist until climax. Even when prometamorphosis is artificially prolonged, irrespective of the reason, the fibers still persist until climax. When the prometamorphic period is artificially shortened, or when a prolongation of prometamorphosis is interrupted by thyroxin-induced climax, the fibers disappear. Thus the disappearance of the aminergic nerves is a metamorphic event associated with climax.

Adenohypophysis and growth in tadpoles of Rana temporaria

Growth of the Rana temporaria tadpole was investigated after (1) adenohypophysectomy, (2) autografting the adenohypophysis to the tail, and (3) homografting an extra adenohypophysis into the tail of the otherwise normal tadpole. All operations were performed using the early tail-bud embryo. The three tadpole types displayed (1) reduced, (2) about normal, and (3) somewhat increased growth rates, as compared to the controls. The interpretation of the results is that the adenohypophysis is necessary for normal growth rate and stimulates growth, probably by producing growth-promoting hormone(s), which seem to be secreted at the same rate as when the gland is removed from direct hypothalamic control.

The effect of two pesticides, Miedzian 50 and Gesagard 50, on the development of tadpoles ofRana temporaria

Tadpoles of the frog, Rana temporaria, in two developmental stages were subjected to the action of aqueous suspensions of two pesticides--Miedzian 50 and Gesagard 50. The changes caused by these substances pertain chiefly to the alimentary canal, brain, and muscles, and are connected with the developmental stage of the animals. Miedzian 50 caused a partial sytolysis in the cells of the intestinal epithelium and the parenchyma of the liver. Gesagard 50 was more toxic; under its action strong degenerative changes were obtained in the alimentary canal and the brain. Also, disorders in the development of tadpoles were observed. These consisted in a partial inhibition of growth and a retardation of the process of completion of the operculum as compared with control animals.

Identification of the epidermal "Stiftchenzellen" of frog tadpoles by electron microscopy.

Differentiated surface epidermal cells observed in the skin of tadpoles of Rana temporaria by electron microscopy have been identified with the Stiftchenzellen originally described by Kölliker in 1885. The cells have apical microvilli or a single apical projection and appear to have synaptic associations with nerve fibres in the epidermis. The distribution, dimensions and structure of the cells are in agreement with descriptions from le cells are sensory in nature. In addition, there are fine structural resemblances to the gustatory cells of fish and of amphibians which suggest that the Stiftchenzellen are chemoreceptors.

The ontogenesis of monoaminergic nerve fibres in the hypophysis of Rana temporaria with special reference to the pars distalis.

In Rana temporaria tadpoles, fluorescent fibres appear in the prospective eminentia mediana, the pars intermedia and the pars distalis at Gosner's stage 25. During prometamorphosis the amount of fluorescent material increases around the developing primary capillary plexus in the eminentia mediana. In the pars intermedia the fibres form a dense fluorescent network but in the pars distalis the fibres are few and delicate. At stages 42-43, the onset of climax, the pars distalis fibres disappear. The possible functional significance of the pars distalis fibres is discussed. The background adaptation ability appears at stages 28-29, while the fluorescent pars intermedia innervation is observable at stage 25.

On the development of chicken adenohypophyseal melanophore-expanding activity.

Melanophore-expanding activity (MEA) was detectable at least by stage 30 of Hamburger and Hamilton (6–6.5 incubation days) in 53 whole adenohypophyseal anlagen (plus mesenchyme) from domesticated Gallus gallus embryos. This was estimated from responses to adenohypophyseal implants next to dermal melanophores of intact Rana temporaria tadpoles, as compared with control implants of embryonic myelencephalic tissue. Analyses of 27 implants of adenohypophyseal cephalic- or caudal-region tissue alone indicated that MEA was associated mostly with cephalic regions. This association started at least by stage 35 (8–9 incubation days) and continued until the 1st day post hatching, as compared with control implants of embryonic eyelid tissue.