A comparison of lizard claw keratin proteins with those of avian beak and claw

Summary The outer shell of translucent keratin has been dissected from the claws of the lizard,Varanus gouldii. It is free of calcium and hydroxyproline, in contrast to the fibrous support, and contains proteins rich in glycine (28 residues %) and half-cystine (13%). These proteins have been obtained in soluble form by treatment with 2-mercaptoethanol in 8M urea at pH 11 followed by alkylation with iodoacetate to giveS-carboxymethyl kerateines. The three major components resolved by SDS polyacrylamide gel electrophoresis have been isolated by fractional precipitation with ammonium sulfate followed by chromatography on DEAE-cellulose or Sephadex. Two of the components, low in tryptophan content, appear to be homologous and are relatively homogeneous with respect to both size and charge whereas the third, a tryptophan-rich material, appears to contain about 20 different molecular species as judged by gel electrophoresis in urea at pH 8.9. The molecular weights of two of the isolated omponents (the tryptophan-rich and the major of the two tryptophanpoor components) are about 13000 as determined by equilibrium ultracentrifugation studies.The major lizard claw proteins are therefore similar in size and glycine content to the proteins of avian beak and claw but differ in containing more cystine and less tyrosine. On the other hand, the reptilian proteins resemble the mammalian high-tyrosine proteins (Type II) in cystine content and overall amino acid composition, but differ in size with the lizard proteins being larger. It is suggested however that they are unlikely to be homologous.     

迁地驯养孟加拉巨蜥一些繁殖特性的初步研究

2005～2006年对8条孟加拉巨蜥的体重、体长、繁殖行为、卵径等繁殖特性进行了初步研究.雄性巨蜥体重为3390 g±139 g,体长(SVL)为52.9 cm±2.5 cm,雌性巨蜥体重为3320 g,体长(SVL)约49.5 cm.巨蜥发情时间出现在4～8月, 其中50%的发情行为发生在7月份.每次发情持续时间约为8.8±2.1天,两次发情间隔时间约为18.8±3.2天.巨蜥的求偶交配模式包括嗅闻、攀爬、诱导和跨爬4个环节.卵的长径为56.9 mm±2.6 mm(n=21),宽径为33.3 mm±1.5 mm (n=21).繁殖期巨蜥的活动节律表明孟加拉巨蜥是典型的昼行动物.     

Oldest known Varanus (Squamata: Varanidae) from the Upper Eocene and Lower Oligocene of Egypt: support for an African origin of the genus

Abstract: A large collection of lizard vertebrae from northern Africa represents the oldest unambiguous occurrence of the genus Varanus. The fossils come from late Eocene and early Oligocene freshwater deposits of the Fayum, Egypt, an area noted for many significant primate finds. The recovery and identification of this material indicate that the genus Varanus arose in Africa, before dispersing to Australia and Asia. This dispersal occurred prior to the early to mid‐Miocene, by which time fossil Varanus are known from Australia and Eurasia. Although the dispersal route remains unknown, the lizard material reported here supports the hypothesis that a corridor existed allowing freshwater and terrestrial organisms to cross from Africa to Asia.     

A Retrospective Study of Mortality in Varanid Lizards (Reptilia:Squamata:Varanidae) at the Bronx Zoo: Implications for Husbandry and Reproductive Management in Zoos

Varanid lizards have been maintained in zoological parks for more than a century, yet few studies to date have attempted to pinpoint significant health issues affecting their management or areas of captive husbandry that are in need of improvement. In an effort to identify and better understand some of the husbandry‐related challenges and health issues specifically affecting varanids in zoos, this study examined mortality in 16 species maintained at the Bronx Zoo between 1968 and 2009. Out of 108 records reviewed, complete necropsy reports were available for 85 individuals. Infection‐related processes including bacterial (15.3%), protozoal (12.9%), nematode (9.4%), and fungal (3.5%) infections accounted for the greatest number of deaths (47.1%). Noninfectious diseases including female reproductive disorders (7.1%), neoplasia (7.1%), gout (10.8%), and hemipenal prolapse (1.3%) accounted for 29.4% of deaths. Multiple disease agents were responsible for 5.9% of deaths, and a cause for death could not be determined for 17.7% of individuals. Reproductive complications accounted for 11.5% of female deaths, but were identified in 23.1% of females. Although not necessarily the cause for death, gout was present in 18.8% of individuals. Differences in mortality between species, genders, and origin (captive‐bred vs. wild‐caught) were also evaluated. The results of this study corroborate earlier findings that identify bacterial infections, neoplasia, female reproductive disorders, gout, and endoparasitism as major sources of mortality in captive varanids. In light of these results, we discuss potential etiologies and offer recommendations for improving captive management practices in zoos. Zoo Biol. 32:152–162, 2013. © 2012 Wiley Periodicals, Inc.     

Effect of thyroxine and noradrenaline on thermoregulation, cardiac rate and oxygen consumption in the monitor lizard Varanus albigularis albigularis

1. 1. At the preferred body temperature (35°C) resting metabolic rate was 0.155 ± 0.015 ml O₂/g·h and heart rate was 54 ± 11 beats/min. Spontaneous activity at this body temperature caused a two-fold increase in heart rate and a six-fold increase in O₂ consumption. Maximum values being 0.86 ml/g·h with an O₂ pulse of 13.6 × 10⁻⁵ ml/g·beat.

2. 2. Pre-treatment for seven days with thyroxine caused a 27% increase in resting metabolic rate and a 63% increase in the thermal gradient between core and ambient temperature at the preferred body temperature.

3. 3. Noradrenaline reduced heart rate but had no effect at the dosage recommended on metabolic rate at body temperatures of either 35 or 15°C, suggesting that non-shivering thermogenesis is absent in lizards. The evolutionary implications of these results have been briefly discussed.

Vasoactive intestinal peptide-immunoreactive cerebrospinal fluid-contacting neurons in the reptilian lateral septum nucleus accumbens

By means of immunocytochemical demonstration of vasoactive intestinal peptide (VIP) an accumulation of cerebrospinal fluid (CSF)-contacting neurons was found in a circumscribed region of the nucleus accumbens/lateral septum of eleven reptilian (chelonian, lacertilian, ophidian, crocodilian) species. Basal processes of these cells contribute to a subependymal plexus whose density displays considerable interspecific variation. VIP-immunoreactive nerve fibers occur also in the lateral septum and the nucleus accumbens where they encompass immunonegative cells in a basket-like pattern. The CSF-contacting neurons are surrounded by columnar ependymocytes frequently arranged in a pseudostratified manner. These specialized arrays of ependymal cells, however, occupy a more extended area than the VIP-immunoreactive CSF-contacting neurons and can be traced from the rostro-ventral pole of the lateral ventricle to the interventricular foramen. These observations suggest the existence of a telencephalic site of CSF-contacting neurons which may be more widespread than hitherto thought and which may participate in a circumventricular system of the lateral ventricle. Previous studies mainly performed with birds indicate that the VIP-immunoreactive CSF-contacting neurons of the nucleus accumbens might form a part of the encephalic (extraretinal and extrapineal) photoreceptor. However, further experiments are required to test this supposition since the VIP-immunoreactive neurons of the nucleus accumbens remained unlabeled by antibodies against bovine rodopsin and chicken cone-opsin in all eleven species analysed in this investigation.     

Bone vascular supply in monitor lizards (Squamata: Varanidae): influence of size, growth, and phylogeny

Bone vascular canals occur irregularly in tetrapods; however, the reason why a species has or lacks bone canals remains poorly understood. Basically, this feature could depend on phylogenetic history, or result from diverse causes, especially cortical accretion rate. The Varanidae, a monophyletic clade that includes species with impressive size differences but similar morphologies, is an excellent model for this question. Cortical vascularization was studied in 20 monitor species, on three bones (femur, fibula, and tibia) that differ in their shaft diameters, and in the absolute growth speed of their diaphyseal cortices. In all species smaller than 398 mm SVL (133-397 mm in sample), bone cortices lack vascular canals, whereas all larger species (460-1,170 mm in sample) display canals. The size 398-460 mm SVL is thus a threshold for the appearance of the canals. The distribution of vascular and avascular bone tissues among species does not precisely reflect phylogenetic relationships. When present, vascular canals always occur in the femur and tibia, but are less frequent, sparser, and thinner in the fibula. Vascular density increases linearly with specific size but decreases exponentially during individual growth. In most species, canal orientation varies between individuals and is diverse in a single section. No clear relationship exists between canal orientation and vascular density. These results suggest that: a) the occurrence and density of bone vascular canals are basically dependant on specific size, not phylogenetic relationships; b) vascular density reflects the absolute growth rates of bone cortices; c) the orientation of vascular canals is a variable feature independent of phylogeny or growth rate.     

Comparative ecology of Varanus in the Great Victoria Desert

Abstract The ecologies of seven desert species of monitor lizards (Varanus), which are very variable in size, are described and compared. Data are reported on abundance, anatomy, behaviour, body temperature relationships, daily activity patterns, diet, growth, habitat and microhabitat, prey size, reproduction, seasonal patterns of activity, sexual dimorphisms, and tracks. As many as six of the seven species occur together in sympatry at one study site. New results reported here are merged with extensive data collected over the past quarter of a century to provide a comprehensive and detailed overview of numerous aspects of the natural history and ecology of the seven species in the Great Victoria Desert. One species of pygmy monitor has evolved large clutch size for unknown reasons. A food web for 40 species of desert lizards is presented. Hutchinsonian ratios of head lengths (larger/smaller) are significantly greater in two observed assemblages of sympatric varanids than in a null model consisting of all possible pairs of species of all Australian varanids. Evolution of body size and the two adaptive radiations of Varanus in Australia are discussed.     

Effect of cerebro-ventricular administration of noradrenaline and carbachol on behavioural and autonomic thermoregulation in the monitor lizard Varanus albigularis albigularis

1. 1. When exposed to an ambient temperature of 45°C V. a. albigularis began to pant whne core temperature was between 35.4–38.6°C. The skin temperature, however, appeared to be more critical than the core temperature in determining onset of panting.

2. 2. Cerebro-ventricula injections of saline and moradrenaline had no effect on panting but carbachol inhibited pnting and disrupted normal thermoregulatory behaviour in a photothermal gradient. The significance of this is discussed in relation to comparable studies on mammals.