THE EFFECT OF RECENT DIET ON PREY ODOR DISCRIMINATION BY JUVENILE TEGU LIZARD, TUPINAMBIS-TEGUIXIN (SAURIA, TEIIDAE)

Teiid lizards are intesive foragers supposed to rely lagerly on chemoreception for prey detection, an ability that can be modified by previous feeding experiences. We investigated the ability of juvenile lizards, Tupinambis teguixin, in discriminate prey from non-prey odors as well as the effects of recent diet on these ability. Tegu lizards were able to discriminate prey odors and this ability probably is inate. The effect of recent diet was analysed through optimal foraging models and our results does not support in a broad sense the predictions made by theoretical models.

Differential staining and microchromosomal variation in karyotypes of four Brazilian species of Tupinambinae lizards (Squamata : Teiidae)

Kayotypes of four neotropical teiid lizard species (Tupinambinae) were herein studied after conventional as well as silver staining and CBG-banding: Crocodilurus amazonicus (2n = 34), Tupinambis teguixin (2n = 36), Tupinambis merianae and Tupinambis quadrilineatus (2n = 38). The karyological data for T. quadrilineatus as well as those obtained using differential staining for all species were unknown until now. The karyotypes of all species presented 12 macrochromosomes identical in morphology, but differed in the number of microchromosomes: 22 in C. amazonicus, 24 in T. teguixin and 26 in T. quadrilineatus and T. merianae. The Ag-NOR located at the secondary constriction at the distal end of pair 2 is shared by all species, contrasting with the variability observed for this character in species of the related Teiinae. CBG-banding revealed a species-specific pattern in T. quadrilineatus with conspicuous interstitial C-blocks at the proximal region of the long arm of pair 4 and the whole heterochromatic short arm of pair 6. The karyological data reported here corroborates the relationship hypothesis obtained for Tupinambis based on molecular characters. T. teguixin presents the putative ancestral karyotype for the genus with 2n = 36 whereas T. merianae and T. quadrilineatus exhibit 2n = 38, due to an additional pair of microchromosomes.

Helminths of Lizards (Reptilia: Squamata) from Mato Grosso State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Caza y comercio de cueros de Tupinambis spp. en un departamento de la provincia de San Luis y la relación con los mercados mundiales y las políticas de conservación

p.187-196

Helminths From an Introduced Species (Tupinambis merianae), and Two Endemic Species (Trachylepis atlantica and Amphisbaena ridleyi) From Fernando de Noronha Archipelago, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Density of the tegu lizard (Tupinambis merianae) and its role as nest predator at Anchieta Island, Brazil

Mammals has been pointed out to be the main nest predators in islands, but recent studies has shown that tree snakes are also important nest predator in tropical forests. Here we present information on the density tegu lizards Tupinambis merianae and its role as nest predator at Anchieta Island, Ubatuba, in southeastern Brazil. The mean density of tegu lizards wets estimated to be 83 individuals/km2, which is 1.83 times lower than other well-known population (Fernando de Noronha Archipelago). In the dense rainforest, the density was estimated in 20 individuas/ km2, and in the open rainforest, 109 ind/km2. The high density of this lizard may have serious implications for nest predation. We found that 36% of artificial plasticine eggs were "preyed upon" by tegu lizards. Therefore, it is paramount to manage the tegu population on Anchieta Island to assure the survival of ground nesting birds in islands and possibly in forest fragments.

Frugivoria e dispersão de sementes pelo lagarto teiú Tupinambis merianae (Reptilia: Teiidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Seasonal metabolic depression, substrate utilisation and changes in scaling patterns during the first year cycle of tegu lizards (Tupinambis merianae)

The tegus increase in body mass after hatching until early autumn, when the energy intake becomes gradually reduced. Resting rates of oxygen consumption in winter drop to 20% of the values in the active season (Vo(2)=0.0636 ml g(-1) h(-1)) and are nearly temperature insensitive over the range of 17-25degreesC (Q(10)=1.55). During dormancy, plasma glucose levels are 60% lower than those in active animals, while total protein, total lipids and beta-hydroxybutyrate are elevated by 24%, 43% and 113%, respectively. In addition, a significant depletion of liver carbohydrate (50%) and of fat deposited in the visceral fat bodies (24%) and in the tail (25%) and a slight loss of skeletal muscle protein (14%) were measured halfway through the inactive period. Otherwise, glycogen content is increased 4-fold in the brain and 2.3-fold in the heart of dormant lizards, declining by the onset of arousal. During early arousal, the young tegus are still anorexic, although Vo(2) is significantly greater than winter rates. The fat deposits analysed are further reduced (62% and 45%, respectively) and there is a large decrease in tail muscle protein (50%) together with a significant increase in glycogen (2-3-fold) and an increase in plasma glucose (40%), which suggests a role for gluconeogenesis as a supplementary energy source in arousing animals. No change is detectable in citrate synthase activity, but beta-hydroxyacyl CoA dehydrogenase activities are strongly affected by season, reaching a Mold and 5-fold increase in the liver tissue of winter and arousing animals, respectively, and becoming reduced by half in skeletal muscle and heart of winter animals compared with late fall or spring active individuals. From hatching to late autumn, the increase of the fat body mass relatively to body mass is disproportionate (b=1.44), and the mass exponent changes significantly to close to 1.0 during the fasting period. The concomitant shift in the Vo(2) mass exponent in early autumn (b=0.75) to values significantly greater than 1.0 in late autumn and during winter dormancy indicates an allometric effect on the degree of metabolic depression related to the size of the fat stores and suggests greater energy conservation in the smaller young.

Metabolic response to feeding in Tupinambis merianae: Circadian rhythm and a possible respiratory constraint

The diurnal tegu lizard Tupinambis merianae exhibits a marked circadian variation in metabolism that is characterized by the significant increase in metabolism during part of the day. These increases in metabolic rate, found in the fasting animal, are absent during the first 2 d after meal ingestion but reappear subsequently, and the daily increase in metabolic rate is added to the increase in metabolic rate caused by digestion. During the first 2 d after feeding, priority is given to digestion, while on the third and following days, the metabolic demands are clearly added to each other. This response seems to be a regulated response of the animal, which becomes less active after food ingestion, rather than an inability of the respiratory system to support simultaneous demands at the beginning of digestion. The body cavity of Tupinambis is divided into two compartments by a posthepatic septum (PHS). Animals that had their PHS surgically removed showed no significant alteration in the postprandial metabolic response compared to tegus with intact PHS. The maximal metabolic increment during digestion, the relative cost of meal digestion, and the duration of the process were virtually unaffected by the removal of the PHS.

Gas exchange and ventilation during dormancy in the tegu lizard Tupinambis merianae

The tegu lizard Tupinambis merianae exhibits an episodic ventilatory pattern when dormant at 17 degrees C but a uniform ventilatory pattern when dormant at 25 degrees C. At 17 degrees C, ventilatory episodes were composed of 1-22 breaths interspaced by non-ventilatory periods lasting 1.8-26min, Dormancy at the higher body temperature was accompanied by higher rates of O-2 consumption and ventilation. The increase in ventilation was due only to increases in breathing frequency with no change observed in tidal volume. The air convection requirement for O-2 did not differ at the two body temperatures. The respiratory quotient was 0.8 at 17 degrees C and 1.0 at 25 degrees C. We found no consistent relationship between expired gas composition and the start/end of the ventilatory period during episodic breathing at 17 degrees C. However, following non-ventilatory periods of increasing duration, there was an increase in the pulmonary O-2 extraction that was not coupled to an equivalent increase in elimination of CO2 from the lungs. None of the changes in the variables studied could alone explain the initiation/termination of episodic ventilation in the tegus, suggesting that breathing episodes are shaped by a complex interaction between many variables. The estimated oxidative cost of breathing in dormant tegus at 17 degrees C was equivalent to 52.3% of the total metabolic rate, indicating that breathing is the most costly activity during dormancy.

Structure of the posthepatic septum and its influence on visceral topology in the tegu lizard, Tupinambis merianae (Teiidae : Reptilia)

The posthepatic septum (PHS) divides the body cavity of Tupinambis merianae into two parts: the cranial one containing the lungs and liver and the caudal one containing the remaining viscera. The PHS is composed of layers of collagenous fibers and bundles of smooth muscle, neither of which show systematic orientation, as well as isolated blood vessels, lymphatic vessels, and nerves. Striated muscle of the abdominal wall does not invade the PHS. The contractions of the smooth muscles may stabilize the pleurohepatic cavity under conditions of elevated aerobic needs rather than supporting breathing on a breath-by-breath basis. Surgical removal of the PHS changes the anatomical arrangement of the viscera significantly, with stomach and intestine invading the former pleurohepatic cavity and reducing the space for the lungs, Thus, the PHS is essential to maintain the visceral topography in Tupitionibis. J. Morphol. 258:151-157, 2003. (C) 2003 Wiley-Liss. Inc.

Role of the post-hepatic septum on breathing during locomotion in Tupinambis merianae (Reptilia : Teiidae)

Tupinambis merianae increased minute ventilation by increasing both tidal volume and breathing frequency during sustained locomotion at 0.17 m s(-1). Animals in which the post-hepatic septum (PHS) had been surgically removed were not able to increase tidal volume during locomotion. Tegus without PHS compensated, in part, by increasing breathing frequency above the levels observed for tegus with intact PHS, but minute ventilation remained less than in the control animals. The rate of oxygen consumption and the air convection requirement, however, were not significantly different between animals with and without PHS, nor at the tested speeds was endurance affected by the removal of the PHS. These data suggest that the PHS facilitates ventilation by acting as a mechanical barrier, preventing the viscera from moving cranially during physical exertion.

Seasonal changes in blood oxygen transport and acid-base status in the tegu lizard, Tupinambis merianae

Oxygen-binding properties, blood gases, and acid-base parameters were studied in tegu lizards, Tupinambis merianae, at different seasons and temperatures. Independent of temperature and pH, blood oxygen affinity was higher in dormant lizards than in those active during the summer. Haematocrit (Hct) and hemoglobin content ([Hb]) were greater in active lizards resulting in a higher oxygen-carrying capacity. Nucleoside triphosphate content ([NTP]) was reduced during dormancy, but the ratio between [NTP] and [Hb] remained unchanged. Dormancy was accompanied by an increase in plasma bicarbonate ([HCO(3)(-)]PI) and an elevation of arterial CO(2) partial pressure (P(aCO2)) and CO(2) content in the plasma (C(PlCO2)). These changes in acid-base parameters persist over a broad range of body temperatures. In vivo, arterial O(2) partial pressure (Pa(O2)) and O(2) content (Ca(O2)) were not affected by season and tended to increase with temperature. Arterial pH (pH(a)) of dormant animals is reduced compared to active lizards at body temperatures below 15 degreesC, while no significant difference was noticed at higher temperatures. (C) 2003 Elsevier B.V. All rights reserved.

Seasonal changes in daily metabolic patterns of tegu lizards (Tupinambis merianae) placed in the cold (17 degrees C) and dark

Oxygen consumption rate was measured continuously in young tegu lizards Tupinambis merianae exposed to 4 d at 25 degrees C followed by 7-10 d at 17 degrees C in constant dark at five different times of the year. Under these conditions, circadian rhythms in the rate of oxygen consumption persisted for anywhere from 1 d to the entire 2 wk in different individuals in all seasons except the winter. We also saw a progressive decline in standard oxygen consumption rate (at highly variable rates in different individuals) to a very low rate that was seasonally independent (ranging from 19.1 +/- 6.2 to 27.7 +/- 0.2 mL kg(-1) h(-1) across seasons). Although this degree of reduction appeared to take longer to invoke when starting from higher metabolic rates, tegu lizards reduced their metabolism to the low rates seen in winter dormancy at all times of the year when given sufficient time in the cold and dark. In the spring and summer, tegus reduced their standard metabolic rate (SMR) by 80%-90% over the experimental run, but only roughly 20%-30% of the total fall was due to the reduction in temperature; 70%-80% of the total fall occurred at constant temperature. By autumn, when the starting SMR on the first night at 25 degrees C was already reduced by 59%-81% (early and late autumn, respectively) from peak summer values, virtually all of the fall (63%-83%) in metabolism was due to the reduction in temperature. This suggests that the temperature-independent reduction of metabolism was already in place by autumn before the tegus had entered winter dormancy.