Lizards

The evolution of viviparity requires modifications to multiple integrated physiological features to support embryonic development during pregnancy. Embryonic growth during pregnancy is dependent upon the capacity of the uterine vascular system to satisfy increasing embryonic oxygen demand throughout gestation. We tested the hypothesis that total surface area of uterine blood vessels increases in concert with embryonic growth, and hence its oxygen demand, during gestation. We used immunofluorescence and laser-scanning confocal microscopy to quantify uterine microvascular density and morphology during gestation in the oviparous skink Ctenotus taeniolatus and in Saiphos equalis, a skink species with prolonged egg retention. For C. taeniolatus, vessel density (Nv) and vessel length-density (Lv) in the embryonic hemisphere of the uterus is 23% and 17% less, respectively, than that of S. equalis and vascular surface-area does not differ as a function of embryo stage. For S. equalis, overall Nv, Lv, and vessel diameter (Dv), does not change during the first half of gestation but increases by 36% (Nv), 44% (Lv), and 60% (Dv) by near-term embryo stages late in gestation. The chorioallantoic membrane of S. equalis increases in absolute size but vascular density does not differ as a function of embryo stage. The marked increase in uterine vascular density during late gestation coincides with the phase of rapid growth in embryo mass and concomitant increase in metabolic rate. Expansion of the uterine vascular bed in concert with embryo size and metabolism is likely to be an important transitional step in the evolution of viviparity. Anat Rec, 293:829–838, 2010. © 2010 Wiley-Liss, Inc.

This is a draft of the introductory chapter of a book-in-progress entitled Lizard, which has been contracted for publication in the Animal series of Reaktion Books in London. It discusses the changing definitions of "lizard" throughout history, and the  methodological difficulties, together with their philosophical foundation, involved in settling on a single definition today.  These are compared with the problems of settling on a single meaning for "humankind." It concludes that the meaning of "lizard" cannot be fixed, and the animal may only be understood within the context of an evolving tradition. I would be very interested in any comments or suggestions.

The exquisite transitional fossil Tetrapodophis e described as a stem-snake with four small legs from the Lower Cretaceous of Brazil e has been widely considered a burrowing animal, consistent with recent studies arguing that snakes had fossorial ancestors. We reevaluate the ecomorphology of this important taxon using a multivariate morphometric analysis and a reexamination of the limb anatomy. Our analysis shows that the body proportions are unusual and similar to both burrowing and surface-active squa-mates. We also show that it exhibits striking and compelling features of limb anatomy, including enlarged first metapodials and reduced tarsal/carpal ossification e that conversely are highly suggestive of aquatic habits, and are found in marine squamates. The morphology and inferred ecology of Tetra-podophis therefore does not clearly favour fossorial over aquatic origins of snakes.

Our storybooks are full of lizards, but we usually call them something else—dragons, serpents, dinosaurs or monsters. These stories vastly increase their size, bestow wings upon them, make them exhale flame, and endow them with magical powers. Lizards stimulate the human imagination unlike most other animals, despite generally being small, soundless, and hidden from sight in burrows, treetops, and crevices. They can blend into a vast range of environments, from rocky coasts to deserts to rain forests. Their fluid motion can make us think of water, while their curvilinear form suggests vegetation. Their stillness suggests death, while their sudden arousal is like resurrection. This delightful book gives lizards their due, demonstrating how the story of lizards is interwoven with the history of human imagination. Boria Sax considers the lizard as a sensual being—a symbol, a myth, a product of evolution and an aesthetic form. He describes the diversity of lizards and traces the representation of the reptile in cultures including those of pre-conquest Australia, the Quiché Maya, Mughal India, and central Africa. Illustrated throughout with beguiling images, Lizard is a unique and often surprising introduction to a popular but little-understood reptile.

Photoreceptors are the first in the chain of neurons that process visual information. In lateral eyes of vertebrates, light hyperpolarizes rod and cone photoreceptors that synapse onto bipolar and horizontal cells in the first synaptic layer of the retina. The sign of the photoreceptor signal is either conserved or inverted in bipolar cells, resulting in chromatically dependent depolarizing and hyperpolarizing responses to visual stimuli. Visual information is then conveyed to the second synaptic layer for encoding and transmission to the brain by ganglion cells. The parietal (third) eye of lizards does not contain bipolar cells or other interneurons. Photoreceptors synapse directly onto ganglion cells and yet, even in the absence of interneurons, antagonistic chromatic mechanisms modulate the ganglion cell responses. We report here that chromatic antagonism in the third eye originates in the chromatically dependent hyperpolarizing and depolarizing response of the photoreceptors to ...

Ontogenetic variation in venom composition was examined in the Pacific rattlesnakes Crotalus viridis helleri and C. v. oreganus. Venoms were analyzed for protease, phospholipase A2, L-amino acid oxidase, exonuclease and elastinolytic activities, and toxicity toward a native prey (Sceloporus graciosus). Protease activity increased significantly with size; L-amino acid oxidase and exonuclease activities also tended to increase. Phospholipase A2 activity decreased significantly with size, as did venom toxicity. These factors produce a highly toxic venom with low protease activity in juvenile snakes, which facilitates efficient handling of lizards and young rodents. Analysis of gut contents of museum specimens showed that lizards constitute a major fraction of prey taken by juvenile rattlesnakes. Lizards continue to be taken with high frequency until snakes reach approx. 500 mm in total length; above this size, mammals are taken exclusively. As snakes increase in size, they feed on larger mammalian prey, and a functionally different venom is produced. Venom from adult Pacific rattle-snakes is less toxic but has high protease activity, aiding in the digestion of prey in a thermally variable environment.

Lizards of the World is ultimate book on these fascinating creatures, featuring the all the different types of lizard worldwide. As survivors from the time of the dinosaurs, lizards are scaly, cold-blooded, living fossils – relics from a prehistoric world that remain alive and well in ours. Lizards exert a morbid fascination, in many mythologies they are dark creatures, symbolizing death and misfortune. From chameleons and skinks to geckos and iguanas, Lizards of the World brings these creatures firmly into the light, to reveal their extraordinary diversity Found in almost every type of terrain globally, there are almost 6,500 species of lizard, including lizards with frills, horns or wings, those that drop their tails, and others that squirt blood from their eyes. Here, the lizard family and subfamily profiles, organized phylogenetically, are illustrated with stunning photography. Each profile includes a population distribution map, a table of essential information and a fascinating commentary revealing notable characteristics, fresh scientific understanding and the diversity of species. Written by world-renowned herpetologist Mark O’Shea, Lizards of the World is a magnificent showcase of the natural history and beauty of these remarkable reptiles.

A história de vida é o resultado de um desafio ecológico imposto pelo ambiente, tenta explicar como a evolução molda os organismos a fim de atingir o sucesso reprodutivo (Stearns, 2000). Sendo assim está intimamente relacionada com as mudanças climáticas em pauta nesta edição especial. Neste artigo são revistos os efeitos de mudanças de temperatura e precipitação em alguns traços fenotípicos de história de vida de lagartos. Ao final, com base no conhecimento atual sobre os lagartos brasileiros e nas previsões de mudanças climáticas para o Brasil, são feitas algumas previsões de mudanças na história de vida dos lagartos. Palavras-chave. Mudanças climáticas, lagartos, história de vida.

Reproductively, South American Mabuya are among the most extraordinary of squamate reptiles.  Not only have these scincid lizards evolved a degree of placentotrophy that exceeds that of all other known squamates, but they have converged strongly on a pattern usually assumed to be confined to eutherian mammals.  Characteristics of this reproductive pattern include viviparity, a lengthy gestation period, ovulation of small ova, formation of chorioallantoic placentae with chorionic areolae and a placentome, and placental provision of virtually all of the nutrients for development.  The independent evolution of such features among mammals and lizards represents one of the most striking cases of evolutionary convergence in reproductive specializations to be documented among terrestrial vertebrates (Blackburn, 1991).



Aside from their similarities to eutherians, however, South American lizards of the genus Mabuya  are highly worthy of study in their own right.  These lizards represent an extreme in the spectrum of reptilian reproductive features, and their specializations appear to be of functional significance in the environments that they inhabit (Vitt and Blackburn, 1983, 1991; Vitt, in press).  The extent of intra-generic diversity in reproductive mode, placentation, and fetal nutritional mode suggests Mabuya to be a model taxon for inquiries into the evolution of viviparity and placentotrophy, as well as the evolution of structural – functional complexes, such as is represented by the placenta.



Unfortunately, survival of at least some of the South American species of Mabuya  is now threatened over wide portions of their ranges.  For example, during the past ten years of habitat destruction in Pernambuco, M. heathi has become increasingly scarce, and the range of M. bistriata undoubtedly is being diminished by devastation of the Amazonian rainforest.  Extinction of these remarkable species would be an incalculable loss, and protection and maintenance of the genus Mabuya throughout South America is of the utmost urgency.

Se presenta una actualización de la lista de las taxa confirmadas o probables, del Orden Sauria (lagartijas) de Bolivia, con discusiones sobre aspectos sistemáticos, taxonómicos y biogeográficos. Hasta septiembre de 2005, se reconoce 97 especies confirmadas de saurios para Bolivia, con otras 37 especies probables. De los saurios confirmados, 13 especies y una subespecie son endémicas para Bolivia. Se presenta además una serie de regiones prioritarias para inventarios de la saurofauna boliviana.

The behaviour and body temperatures of the bearded dragon (Pogona vitticeps) were recorded during periods with handling and non-handling intervals. Differences in perching and hiding were observed after the animals were handled but basking and locomotory activity remained almost constant. The observed differences in behaviour appeared to have no influence on either set point or variance in body temperatures.

The behaviour, body temperatures and respiratory rates of captive bearded dragons (Pogona vitticeps) were recorded during periods with handling and non-handling intervals. Respiratory rates increased at approximately equal rates with increasing body temperatures irrespective of whether the animals were handled or not. Respiratory rates increased significantly after handling but there were no significant differences in behaviour before and after handling. The implications have been discussed in respect to animal usage in captive husbandry and education programmes.

Autino, A. G. y Montero, R. 2012. Guía de Vertebrados de Bajo La Alumbrera, Catamarca, Argentina. Minera Alumbrera Limited, 224 pp.  Edición rústica: ISBN 978-987-28792-0-4; Edición cartoné: ISBN 978-987-28792-1-1.

Contiene información sobre las 93 especies más conspicuas de los Vertebrados de la región de Bajo De La Alumbrera (Catamarca, Argentina), incluyendo fotografías, dibujos, su descripción, distribución, biología y estado de conservación.