Age at Maturity of Neotenic Ambystoma tigrinum mavortium Baird
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It is well known that in the common tiger salamander of the Great Plains, Ambystoma tigrinum, occasional individuals grow to large size and reach sexual maturity without metamorphosis. The length of time necessary for full neoteny to be achieved, however, seems never to have been c'etermined. A population of larval tiger salamanders, A. t. mavortium, discovered in a pond near Enid, Oklahoma, during April, 1948, pLovicees information Gn the growth rate and age of attainment of sexual maturity in neotenic individuals.Keywords:
Neoteny
Tiger salamander
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Tiger salamander
Salamandridae
Ambystoma mexicanum
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Abstract Background The Mexican axolotl ( Ambystoma mexicanum ) is considered a hopeful monster because it exhibits an adaptive and derived mode of development - paedomorphosis - that has evolved rapidly and independently among tiger salamanders. Unlike related tiger salamanders that undergo metamorphosis, axolotls retain larval morphological traits into adulthood and thus present an adult body plan that differs dramatically from the ancestral (metamorphic) form. The basis of paedomorphic development was investigated by comparing temporal patterns of gene transcription between axolotl and tiger salamander larvae ( Ambystoma tigrinum tigrinum ) that typically undergo a metamorphosis. Results Transcript abundances from whole brain and pituitary were estimated via microarray analysis on four different days post hatching (42, 56, 70, 84 dph) and regression modeling was used to independently identify genes that were differentially expressed as a function of time in both species. Collectively, more differentially expressed genes (DEGs) were identified as unique to the axolotl ( n = 76) and tiger salamander ( n = 292) than were identified as shared ( n = 108). All but two of the shared DEGs exhibited the same temporal pattern of expression and the unique genes tended to show greater changes later in the larval period when tiger salamander larvae were undergoing anatomical metamorphosis. A second, complementary analysis that directly compared the expression of 1320 genes between the species identified 409 genes that differed as a function of species or the interaction between time and species. Of these 409 DEGs, 84% exhibited higher abundances in tiger salamander larvae at all sampling times. Conclusions Many of the unique tiger salamander transcriptional responses are probably associated with metamorphic biological processes. However, the axolotl also showed unique patterns of transcription early in development. In particular, the axolotl showed a genome-wide reduction in mRNA abundance across loci, including genes that regulate hypothalamic-pituitary activities. This suggests that an axolotls failure to undergo anatomical metamorphosis late in the larval period is indirectly associated with a mechanism(s) that acts earlier in development to broadly program transcription. The axolotl hopeful monster provides a model to identify mechanisms of early brain development that proximally and ultimately affect the expression of adult phenotypes.
Tiger salamander
Neoteny
Ambystoma mexicanum
Heterochrony
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SUMMARY The authors provide a detailed description of the skull in neotenic Triturus vulgaris meridionalis (Boulenger) (Amphibia Caudata Salamandridae) and compare it with the morphology of normal adults. The finds are also compared with published data concerning other urodeles. Though some interesting differences are found between the skull of normal and neotenic individuals, these do not plead in favour of the general hypothesis that neoteny has had a general role in the evolution of urodeles. The authors suggest that at an early stage of urodele evolution, telescoping of developmental phases occurred as an adaptation to short seasons favourable to larval development. The cranial kinesis of Triturus vulgaris is described in detail and this supports the contention by IORDANSKY (1982), contrary to current belief, that cranial kinesis is widespread among urodeles. Some features of cranial changes at metamorphosis appear to be linked with functional requirements.
Neoteny
Salamandridae
Triturus
Morphology
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The skull of neotenic individuals of the Alpine Newt Triturus alpestris from the locality Drakolimni (Greece) is described on the basis of models made from magnified serial frontal sections. In order to recognize features associated with neoteny and paedomorphosis, the results were compared with normal development of contemporary Triturus and of other Caudata. The neotenic larvae from Greece correspond to advanced stages of metamorphosis in normal development of Triturus alpestris. Comparison with salamandrids from the Tertiary of Europe in which the hyobranchial skeleton was preserved, namely Brachycormus noachicus, Chelotriton paradoxus, and Palaeopleurodeles hauffi, revealed that both latter taxa were completely metamorphosed adults anatomically similar to their contemporary relatives Tylototriton, Echinotriton, and Pleurodeles, whereas Brachycormus, though apparently related to Chelotriton, was a neotenic amphibian. This is suggested by its incompletely metamorphosed but ossified hyobranchial skeleton. © 1996 Wiley-Liss, Inc.
Neoteny
Salamandridae
Triturus
Pleurodeles
Heterochrony
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Comparison of metamorphosis of skull and hyobranchial system in two species of neotenic salamanders reveals two different types of neoteny. Ambystoma talpoideum is completely neotenic owing to delayed metamorphosis. Notophthalmus viridescens exhibits limited neoteny as a result of incomplete metamorphosis. Morphological details of neoteny are compared to life history in both species in order to discuss the ecological morphology of the two neotenic strategies. Comparisons to Taricha granulosa, Triturus vulgaris, and Ambystoma gracile indicate that these two strategies are widely employed and may represent familial patterns.
Neoteny
Salamandridae
Notophthalmus viridescens
Morphology
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Species with truncated developmental patterns may go undetected if they resemble the juveniles of their close relatives. Herein we present an example of this phenomenon with the description of a highly divergent, relict species of stream-dwelling plethodontid salamander from the Ouachita Mountains of North America. Both mitochondrial and nuclear sequence data show that this new species is most closely related to its syntopic relative, Eurycea multiplicata. Interestingly, E. multiplicata exhibits the ancestral biphasic (metamorphic) life cycle, whereas the new species maintains an aquatic larval form throughout life (paedomorphic) and superficially resembles larval E. multiplicata. The new species is the first known paedomorphic plethodontid from the Ouachita Mountains, and the most divergent paedomorphic salamander discovered in over seventy years. This species represents an independent instance of the evolution of paedomorphosis associated with a porous streambed, which may facilitate vertical seasonal movements. This new species currently has an extremely limited known distribution and is of immediate conservation concern.
Neoteny
Salamandridae
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Neoteny
Tiger salamander
Ambystoma mexicanum
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Effects of varying illumination and temperature cycles on circulating melatonin (mel) in neotenic tiger salamanders were investigated in three experiments. In Experiment I animals were maintained for seven days on a 12:12LD illumination regimen with either normal high temperature (20?C) during the photophase, low (10?C) temperature during the scotophase or reversed thermal periods. Animals maintained in a normal temperature and photic regimen had 87.7 and 141.7 pg mel/ml plasma (mean values) measured midphotophase and midscotophase, respectively. Animals in a reversed temperature environment had mean plasma melatonin titers of 100.8 and 91.6 pg mel/ ml at midphotophase and midscotophase. In the second experiment, the effect of continuous high or low temperature was examined while animals were under a 12:12LD illumination regimen. Animals held at continuously low (10?C) temperature had a mean plasma melatonin titer of 87.3 and 125.1 pg/ml at midphotophase and midscotophase respectively. Animals maintained in contin- uously high temperatures (20?C) had mean plasma melatonin titers of 87.7 and 82.0 pg/ml. Finally animals maintained under either continuous light or darkness but an alternating thermal regimen did not display significant differences in plasma melatonin. It was observed that high nocturnal temperature can cause a depression in the amount of melatonin measured in the plasma of neotenic tiger salamanders.
Tiger salamander
Neoteny
Ambystoma mexicanum
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Abstract Urodele amphibians possess remarkable regenerative abilities, allowing them to rebuild lost body parts. Contrary to lizards, salamanders can fully restore their tails, including the neural spine and components of the vertebral column. The axolotl ( Ambystoma mexicanum ) is the vertebrate model organism for regeneration research due to its ease of breeding in captivity. However, axolotls are paedomorphic, retaining larval somatic features throughout adulthood and do not naturally undergo metamorphosis, a transition phase from aquatic larvae to terrestrial adults with profound morphological and physiological changes. We investigate the influence of metamorphosis on salamander tail regeneration after conspecific biting in the metamorphosing sister taxon Ambystoma tigrinum using histological analysis to answer two key questions: (1) Does regeneration continue during metamorphosis, or is it halted? (2) How does regeneration differ histologically among larval, metamorphosing and postmetamorphic individuals? Our findings demonstrate that regeneration continues even during metamorphic climax, indicating the simultaneous coordination of metamorphosis and regeneration. Additionally, notable distinctions were observed between developmental stages concerning the speed of regeneration and structural differences in the formation of an apical epithelial cap (AEC). While the approach taken in this study necessarily restricts sample size, it offers valuable insights into regeneration in a metamorphosing species under natural conditions.
Ambystoma mexicanum
Neoteny
Tadpole (physics)
Tiger salamander
Salamandridae
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