Development, structure, and protein composition of reptilian claws and hypotheses of their evolution.

Here, we review the development, morphology, genes, and proteins of claws in reptiles. Claws likely form owing to the inductive influence of phalangeal mesenchyme on the apical epidermis of developing digits, resulting in hyperproliferation and intense protein synthesis in the dorsal epidermis, which forms the unguis. The tip of claws results from prevalent cell proliferation and distal movement along most of the ungueal epidermis in comparison to the ventral surface forming the subunguis. Asymmetrical growth between the unguis and subunguis forces beta-cells from the unguis to rotate into the apical part of the subunguis, sharpening the claw tip. Further sharpening occurs by scratching and mechanical wearing. Ungueal keratinocytes elongate, form an intricate perimeter and cementing junctions, and remain united impeding desquamation. In contrast, thin keratinocytes in the subunguis form a smooth perimeter, accumulate less corneous beta proteins (CBPs) and cysteine-poor intermediate filament (IF)-keratins, and desquamate. In addition to prevalent glycine-cysteine-tyrosine rich CBPs, special cysteine-rich IF-keratins are also synthesized in the claw, generating numerous SS bonds that harden the thick and compact corneous material. Desquamation and mechanical wear at the tip ensure that the unguis curvature remains approximately stable over time. Reptilian claws are likely very ancient in evolution, although the unguis differentiated like the outer scale surface of scales, while the subunguis might have derived from the inner scale surface. The few hair-like IF-keratins synthesized in reptilian claws indicate that ancestors of sauropsids and mammals shared cysteine-rich IF-keratins. However, the number of these keratins remained low in reptiles, while new types of CBPs function to strengthen claws.

Aging related changes of retina and optic nerve of Uromastyx aegyptia and Falco tinnunculus.

Aging is a biological phenomenon that involves gradual degradation of the structure and function of the retina and optic nerve. To our knowledge, little is known about the aging-related ocular cell loss in avian (Falco tinnunculus) and reptilian species (Uromastyx aegyptia). A selected 90 animals of pup, middle, and old age U. aegyptia (reptilian) and F. tinnunculus (avian) were used. The retinae and optic nerves were investigated by light and transmission electron microscopy (TEM) and assessments of neurotransmitters, antioxidant enzymes (catalase, superoxide dismustase and glutathione s transferase), caspase-3 and -7, malonadialdhyde, and DNA fragmentation. Light and TEM observations of the senile specimens revealed apparent deterioration of retinal cell layers, especially the pigmented epithelium and photoreceptor outer segments. Their inclusions of melanin were replaced by lipofuscins. Also, vacuolar degeneration and demyelination of the optic nerve axons were detected. Concomitantly, there was a marked increase of oxidative stress involved reduction of neurotransmitters and antioxidant enzymes and an increase of lipid peroxidation, caspase-3 and -7, subG0/G1 apoptosis, and P53. We conclude that aging showed an inverse relationship with the neurotransmitters and antioxidant enzymes and a linear relationship of caspases, malondialdhyde, DNA apoptosis, and P53 markers of cell death. These markers reflected the retinal cytological alterations and lipofuscin accumulation within inner segments.

Sox2 marks epithelial competence to generate teeth in mammals and reptiles.

Tooth renewal is initiated from epithelium associated with existing teeth. The development of new teeth requires dental epithelial cells that have competence for tooth formation, but specific marker genes for these cells have not been identified. Here, we analyzed expression patterns of the transcription factor Sox2 in two different modes of successional tooth formation: tooth replacement and serial addition of primary teeth. We observed specific Sox2 expression in the dental lamina that gives rise to successional teeth in mammals with one round of tooth replacement as well as in reptiles with continuous tooth replacement. Sox2 was also expressed in the dental lamina during serial addition of mammalian molars, and genetic lineage tracing indicated that Sox2(+) cells of the first molar give rise to the epithelial cell lineages of the second and third molars. Moreover, conditional deletion of Sox2 resulted in hyperplastic epithelium in the forming posterior molars. Our results indicate that the Sox2(+) dental epithelium has competence for successional tooth formation and that Sox2 regulates the progenitor state of dental epithelial cells. The findings imply that the function of Sox2 has been conserved during evolution and that tooth replacement and serial addition of primary teeth represent variations of the same developmental process. The expression patterns of Sox2 support the hypothesis that dormant capacity for continuous tooth renewal exists in mammals.

Unraveling the influences of soft-tissue flipper development on skeletal variation using an extinct taxon.

Adaptation to an aquatic habitat results in dramatic changes in tetrapod limb morphology as limbs take on the roles of propulsion and steering and lose their weight-bearing function. Changes include enclosure of the limb in a soft-tissue flipper and proportional lengthening of the distal limb, often accomplished through the addition of skeletal elements (hyperphalangy). The flipper structure itself and changes to the developmental architecture permitting hyperphalangy are hypothesized to increase observed limb variation, based on a cetacean model. These hypotheses are examined in the ichthyosaurs Stenopterygius and Mixosaurus. Hyperphalangy combined with high levels of variation in phalangeal counts were observed in both genera. The amount of variation was not proportional to the number of phalanges in a digit, but was related to functional digit length. In addition, qualitative variants were catalogued in both genera. Polyphalangy, phalangeal fusion, and additional ossifications in the zeugopodial row were not observed in Mixosaurus, but were common in Stenopterygius, even though both genera exhibited a similar degree of hyperphalangy. These results suggest that while the flipper structure and processes resulting in hyperphalangy may increase observed variation in phalangeal counts, these factors are unlikely to be causing high levels of qualitative variation in ichthyosaurs. Patterns of variation in ichthyosaur limbs, and thus variability, are unique to species but can change over evolutionary time.

História natural de Tropidurus oreadicus em uma área de cerrado rupestre do Brasil Central / Natural history of Tropidurus oreadicus in a rocky cerrado area of Central Brazil

Aspectos ecológicos e da biologia reprodutiva de Tropidurus oreadicus foram investigados em uma área de cerrado rupestre do Brasil Central. Foram estudados a morfometria, o uso do microhábitat, o padrão de atividade, a dieta e características da biologia reprodutiva de T. oreadicus em Cocalzinho - GO, de abril a setembro/2003. São animais sexualmente dimórficos, com os machos adultos maiores que as fêmeas. O microhábitat preferencial utilizado pela espécie foi a superfície das rochas (hábito saxícola). A espécie mostrou padrão de atividade unimodal. Foram frequentemente observados parados e expostos ao sol entre 9:00 e 10:59 horas. A alimentação desta população de T. oreadicus é baseada em formigas, larvas de inseto e besouros. Além disso, apresentaram mudanças ontogenéticas e diferenças intersexuais na dieta. Provavelmente essas diferenças estejam associadas à alocação diferenciada dos recursos para o crescimento ou produção dos gametas. A reprodução é provavelmente sazonal ocorrendo principalmente nos meses de maior pluviosidade.

Ecological aspects and of the reproductive biology of Tropidurus oreadicus was investigated in a rocky cerrado area in Central Brazil. It was studied the morphometry, the microhabitat use, the activity pattern, the diet and the characteristics of the reproductive biology of T. oreadicus in Cocalzinho-GO, from April to September/2003. They are sexually dimorphic animals, with adult males larger than females. The preferential microhabitat used by the species was the surface of the rocks (saxicolous habit). The species shows a unimodal activity pattern. It was frequently observed resting and exposed to the sun between 9:00 and 10:59 hours. This T. oreadicus population feed upon ants, larvae of insects and beetles. Besides it presented ontogenetics shift and intersexual differences in the diet. Probably these differences were associated with the differentiated allocation of the resources for the growth or production of gamete. The reproduction is probably seasonal occurring mainly during the months of higher rainfall.

Lagartos da Marambaia, um remanescente insular de Restinga e Floresta Atlântica no Estado do Rio de Janeiro, Brasil / Lizards of Marambaia, an insular remnant of Restinga and Atlantic Forest in the State of Rio de Janeiro, Brazil

Este estudo apresenta os resultados de um inventário da fauna de lagartos da Marambaia, RJ. Foram registradas 12 espécies de lagartos, distribuídas em sete famílias. Teiidae é a família mais rica (3 spp.), seguida por Gekkonidae (2), Scincidae (2), e Tropiduridae (2), Gymnophthalmidae (1), Leiosauridae (1) e Polychrotidae (1). A composição da comunidade de lagartos da Marambaia é semelhante à de outras localidades do litoral sudeste brasileiro, entretanto a área comporta espécies de distribuição restrita às restingas do Estado do Rio de Janeiro e sob ameaça de extinção, como Cnemidophorus littoralis e Liolaemus lutzae. Também protege espécies típicas de florestas, como os lagartos arborícolas Enyalius brasiliensis e Anolis cf. fuscoauratus. Floresta e restinga são contínuas na Marambaia e representam os hábitats mais ricos em lagartos, reunindo, respectivamente, nove e oito espécies. A possibilidade de perda de variabilidade genética, como resultado do isolamento geográfico, e a aparente dificuldade de recolonização em casos de perda local de diversidade, somadas à modificações das paisagens por atividade antrópica, são fatores preocupantes para a conservação da herpetofauna da Marambaia.

This work presents the results of a survey of the lizard species that occur in Marambaia, RJ. Twelve species of lizards, distributed in seven families were registered. Teiidae is the richest family (3 spp.), followed by Gekkonidae (2), Scincidae (2), Tropiduridae (2), Gymnophthalmidae (1), Leiosauridae (1), and Polychrotidae (1). The lizard fauna of Marambaia is similar to that occurring in other localities in the southeastern coast of Brazil. Nevertheless, Marambaia harbors Cnemidophorus littoralis and Liolaemus lutzae, species restricted to restinga habitats in Rio de Janeiro State and considered under threat. The area also protects typical forest species, including the arboreal lizards Enyalius brasiliensis and Anolis cf. fuscoauratus. Forest and restinga are continuous in Marambaia and represent the richest habitats for lizards, comprising nine and eight species, respectively. The possibility of genetic variability loss due to the geographical isolation of the area, and the apparent difficulty of re-colonization in the case of local loss of diversity, added to environmental modifications caused by human activities, are worrying issues for the conservation of Marambaia herpetofauna.

Composição e diversidade de répteis Squamata na região sul do Parque Nacional Grande Sertão Veredas, Brasil Central / Diversity and composition of squamate reptiles in the southern portion of Grande Sertão Veredas National Park, Central Brazil

Neste estudo são apresentados os resultados de amostragem de Squamata do Parque Nacional Grande Sertão Veredas, MG, na área nuclear do Cerrado brasileiro, através de metodologia padronizada. A riqueza, diversidade e distribuição das espécies são comentadas e comparadas com os resultados em outras regiões do Cerrado. A fauna de Squamata na região inclui pelo menos 50 espécies, dentre as quais 25 lagartos, três anfisbenas e 22 serpentes, distribuídas em 12 famílias: Polychrotidae (1), Tropiduridae (3), Scincidae (4), Teiidae (3), Gymnophthalmidae (6), Anguidae (1), Amphisbaenidae (3), Anomalepididae (1), Leptotyphlopidae (1), Boidae (2), Colubridae (16) e Viperidae (2). A riqueza registrada e estimada indica que a região pode figurar entre as mais ricas em todo o Cerrado. As espécies de Squamata parecem possuir preferências previsíveis sobre os diferentes hábitats disponíveis, e admite-se a grande influência de fatores histórico-filogenéticos na distribuição espacial das espécies. A fisionomia do carrasco destacou-se por abrigar duas espécies restritas à região, Stenocercus quinarius e Psilophthalmus sp., sendo promissora para novos estudos. Os ambientes abertos, especialmente as fisionomias savânicas típicas do Cerrado, apresentaram maior riqueza, em concordância com outros locais estudados, e com implicações diretas na conservação da diversidade biológica do Cerrado.

We present the results of an inventory of squamate reptiles from Grande Sertão Veredas National Park region, in the Brazilian Cerrado hotspot. We used standardized sampling methods to provide richness, diversity and distribution data and compared our results with those from other Cerrado localities. The regional squamate fauna is composed of at least 50 species, of which 25 lizards, three amphisbaenians and 22 snakes, distributed in 12 families: Polychrotidae (1), Tropiduridae (3), Scincidae (4), Teiidae (3), Gymnophthalmidae (6), Anguidae (1), Amphisbaenidae (3), Anomalepididae (1), Leptotyphlopidae (1), Boidae (2), Colubridae (16) e Viperidae (2). Recorded and estimated richness indicates that the region can be one of the richest in the Brazilian Cerrado. The recorded species present predictable abundance variations among different available habitats, a probable result of the influence of phylogenetic factors in the spatial distribution of the species. The "carrasco" habitat was distinguished for harboring two restricted species to the region: Stenocercus quinarius and Psilophthalmus sp., and should receive further attention in future studies. The open habitats, especially the typical open physiognomies of Cerrado, present the highest richness levels, in agreement with results in other Cerrado localities, a fact with direct implications for the conservation of central Brazilian savannas.

Physiological effects of a fish oil supplement on captive juvenile tuatara (Sphenodon punctatus).

Tuatara (Sphenodon, Order Sphenodontia) are rare New Zealand reptiles whose conservation involves captive breeding. Wild tuatara eat seabirds, which contain high levels of the long-chain n-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are absent from the captive diet, and consequently, plasma fatty acid composition of wild and captive tuatara differs. This study investigated the effects of incorporating EPA and DHA into the diet of captive juvenile tuatara (Sphenodon punctatus) in an attempt to replicate the plasma fatty acid composition of wild tuatara. Tuatara receiving a fish oil supplement containing EPA and DHA showed overall changes in their plasma fatty acid composition. Phospholipid EPA and DHA increased markedly, reaching 10.0% and 5.9 mol%, respectively, by 18 mo (cf.