DNA synthesis decline involved in the developmental arrest of the limb buds in the embryos of the slow worm, Anguis fragilis (L.).

The present study was carried out to try and detect the biochemical mechanism involved in the developmental arrest of the limb bud in a serpentiform Reptile. Autoradiograpy, following tritiated thymidine incorporation, in embryos of the slow-worm (Anguis fragilis, L.) reveals a strong decrease in the rate of DNA synthesis in the mesodermal cells of the limb bud, after the degeneration of the apical ectodermal ridge (AER); the curve (a function of Gompertz) visualizing this decline shows that the drop in DNA synthesis becomes accentuated just after the degeneration of the AER. This decrease precedes the reduction of the mitotic index, the cell degeneration in the mesoderm and the other regressive changes occurring in the limb bud; it thus appears as the main causative factor of the developmental arrest of the limb bud. Furthermore, these results suggest that one of the functions of the AER would be to maintain a high level of DNA synthesis in the mesoderm underlying the AER in a normal limb bud.     

Observations on Eimeria raillieti in the "Slow-worm", Anguis fragilis (Reptilia, Anguidae)

SYNOPSIS. The oocysts, sporulation process, and endogenous stages of Eimeria raillieti (Léger, 1899) Galli-Valerio, 1930 from the slow-worm, Anguis fragilis , in England are described. The oocysts average 18 × 15 μ. Schizonts, microgametocytes and macrogametocytes were found in the ileum, and macro-gametocytes alone in the duodenum.     

Tail regeneration in the lizards Anguis fragilis and Lacerta dugesii

Rates of tail regeneration in the Madeira wall lizard ( Lacerta dugesii ) and the slow-worm ( Anguis fragilis ) were studied.
L. dugesii regenerates very rapidly, the new tail sometimes attaining a maximum rate of growth of 2'6 mm a day during the fifth week after autotomy. By the twelfth week 90% of the original tail length has been replaced. Average regeneration rates of samples of lizards were reduced after repeated autotomies, but our investigation of this problem was probably complicated by another factor, the amount of tail lost, and is inconclusive.
The tip of the regenerate grows more rapidly than the rest; no elongation occurs at its cranial aspect.
Anguis , even when kept at 27°C, regenerates its tail very slowly, the best performance observed being a new tail of 5 mm after 14 weeks. The longest natural regenerate seen (16 mm) may have taken several years to produce in the wild.
The histological features of regeneration in Anguis are basically similar to those in other lizards. The new osteoderms are formed entirely in the subepidermal tissues but have a regular relationship with the scales. Some nerve fibres are regenerated with the ependymal tube.
The scales on the lizard's regenerating tail develop in a different manner from those in the lizard embryo and show suggestive resemblances to mammalian hairs.     

Tooth replacement in adult Xenopus laevis (Amphibia: Anura)

To determine the time scale of tooth replacement in adult Xenopus laevis (Daudin), three large females of similar size were kept in aquaria at 25 °C for ten weeks. They were anaesthetized twice weekly with MS 222 and impressions of their upper jaws were taken using thin sheets of dental gold-casting wax. Because the erupted tips of the teeth were small (100 μm), the impressions were enlarged by projection so that the presence or absence of a tooth at each locus in the jaw could be recorded. Each half of each animal's jaw was analysed separately and a statistical analysis of the records yielded results for the duration of the Replacement Cycle and Functional Life of the teeth. The range of the median Replacement Cycle time between specimens was 910–1,010h, that of the Functional Life 580–700 h and that of the Gap Period (the time over which loci were unoccupied by functional teeth) 230–420 h. A tentative time scale for the complete tooth development cycle (from tooth germ initiation to complete resorption) was calculated by extrapolation from the results and ranged from 59.07 to 71.29 days.     

Tooth replacement in the bowfin (Amia calva — Holostei)

The dissected tooth bearing bones of 20 specimens of Amia calva (Pisces:Holostei) ranging from the third to tenth season have been examined radiographically and in alizarin red S stained and cleared specimens. Although forms of alternate (1:1) tooth series replacement (sensu Edmund, '60) were frequently observed, even in the youngest, immature specimens, many examples of irregular replacement were recorded. In several bones, the maxillae in particular, series with every third (2:1) or fourth (3:1) tooth replacing were seen and possible patterns of 2:2, were recorded. It is concluded that these data are not consistent with the Zahnreihen concept but support a morphogenic field concept of tooth development.     

Tooth implantation and replacement in Sauropterygia

Tooth replacement and implantation of Sauropterygia is described with special reference to the generaPlacodus andNothosaurus. Tooth replacement is horizontal, with the exception of the enlarged crushing tooth plates on the maxilla, palatine, and dentary ofPlacodus (placodonts), which are replaced vertically. Tooth implantation is thecodont, with variable ankylosis of the base of the root. Sauropterygia is unique compared to other reptiles in that replacement teeth are “alveolarized.” The alveolarization of replacement teeth adds to the evidence supporting of a monophyletic Sauropterygia (Placodontia plus Eosauropterygia).      

First record of Neoxysomatium brevicaudatum through the non-invasive sampling of Anguis fragilis: complementary morphological and molecular detection

Relatively few studies have examined the parasite fauna of British reptiles, partly due to the cryptic nature and low population density of these hosts. Here we examined 12 populations of the slow worm Anguis fragilis which, unlike other UK lizards, occurs at locally high population densities. Morphological examination of non-invasively collected faecal samples revealed the presence of Neoxysomatium brevicaudatum and a second unidentified nematode species. Although previously unrecorded from slow worms in the UK, N. brevicaudatum was present in 38% of animals (mean intensity 70.9, range 1-686). Morphological identification was confirmed by sequencing the 18S ribosomal gene. The use of the species-specific, cytochrome oxidase I mitochondrial gene primers proved an efficient alternative to conventional, microscope screening for parasites, although the original identification of N. brevicaudatum was dependent upon morphological characters. Sequencing also identified the second, smaller nematode as belonging to the Rhabdiasidae family: this species was even more common at a prevalence of 83% (mean intensity 102.8, range 1-2000). While increasing our knowledge of the UK macroparasite fauna, this work demonstrates the benefits of a combined morphological-molecular approach.     

Tooth replacement patterns in young Caiman sclerops

Although there are many reports of tooth replacement patterns in lower vertebrates, few show the range of pattern to be found in a number of similar aged specimens of one species. Fifteen specimens of Caiman sclerops, head length 4–5 cms, were examined by a radiographic technique and their tooth replacement patterns analysed. Whole head radiography and dissected head radiographs were compared and the resulting tooth replacement waves were found to be comparable. Wave replacement (sensu Edmund, '60) in odd and even tooth positions in the tooth row was observed in all the specimens examined. Whereas most waves passed in a cephalad direction, wave reversal (caudad) was also observed, particularly in the anterior parts of the jaws. In some specimens simple alternation in tooth replacement was observed, particularly in the mid-portion of each quadrant. The smooth, age-related change-over from cephalad to caudad demonstrated by Edmund ('62) in captive Alligator mississippiensis was not observed in wild specimens of Caiman sclerops.     

Tooth replacement in the upper jaw of the rainbow trout (Salmo gairdneri).

The present paper describes the pattern of tooth replacement in the upper jaw of two size ranges of rainbow trout (standard lengths 12-15 cm and 20-23 cm) as determined from wax impressions of the dentitions taken twice weekly on anaesthetised fish. There was considerable variation in the nature of replacement waves (lines constructed on dental charts linking eruption times of alternate teeth) between fish for both the premaxillary/maxillary and vomerine/palatine rows. The wave patterns obtained showed the same consistency of form for any one animal which is to be expected when consecutive generations show constant or proportionately changing life spans. Data relating to the life span of the teeth is given. The results are compared with those derived for the lower jaw and the significance of wave form discussed.     

Tooth replacement in the red-backed salamander, Plethodon cinereus

The developmental cycle of the teeth in Plethodon cinereus is analyzed on morphological grounds using alizarin preparations. All the stages in development do not occupy the same proportion of the life cycle time. Functional teeth and germs at an early stage in development occupy a large proportion of the life cycle time, whereas the processes of tooth shedding and ankylosis occur very quickly. The time during which any locus does not bear a functional tooth, and is therefore a non-functional locus, is reduced to a minimum. P. cinereus has a basic pattern of tooth replacement which is consistent with Zahnreihen which are 2.0 tooth spaces apart. Variations in the replacement pattern are common and these are produced by relatively small fluctuations in the spacing of the Zahnreihen around the ?mean? of 2.0. Localized disturbances which produce breaks in the replacement pattern and cause waves to cross also occur. These may be due to the failure of tooth germs to develop, the fusion of tooth germs, or may be the result of the inherent variability in a complex biological system. This variability causes individual tooth germs to develop too slowly or too quickly and hence assume an ?abnormal”? position thus causing breaks in the replacement pattern. Tooth replacement may be controlled by an intra-local mechanism(s) rather than by stimuli which travel along the jaw.     

Opuntia fragilis (Cactaceae) verified in Illinois flora

Opuntia fragilis has been reported only once from Illinois. Recent workers have not been able to find a substantiating specimen and have excluded the species from the flora. The missing specimen has now been found and is referable to this species.     

Tooth development in Latimeria chalumnae (Smith)

Tooth development in Latimeria was studied with the use of light microscopy, polarized light microscopy and microradiography. Teeth develop from cells derived directly from the basal layer of the oral epithelium in areas where teeth have been shed or are being resorbed. The teeth are composed of true enamel, orthodentine and pulp tissues. Attachment is accom-plished by bony attachment ankylosing the teeth to the basal bone of dental plates. The histologic picture of Latimeria teeth resembles more closely the teeth of tetrapods than those of most bony fish.