Effect of pH, temperature and incubation period on the study of intrinsic innervation of various organs by thiocholine technique in certain vertebrates.

The adrenergic fibres can be demonstrated if the optimal time and temperature are maintained. The cholinergic fibres were demonstrated at pH 5.2, incubation period l4h and temperature 37 degrees C. To ascertain the cholinesterase activity in tongue, heart, lung(birds, mammals and reptiles), gizzard and proventriculus (birds) and penis (rat and embryo of squirrel), pH 4.9, 16h incubation and temperature 37 degrees C, were quite suitable. It was possible to demonstrate the intrinsic innervation in tongue, lung, heart (mammals, birds and reptiles), gizzard and proventriculus (birds) and penis (rat and embryo of squirrel), at pH 5.2, 20h incubation and temperature 40 degrees C.     

Behavioral rise in body temperature and tachycardia by handling of a turtle (Clemmys insculpta)

Three turtles, Clemmys insculpta, were kept together in a terrarium in a climatic chamber at 18 degrees C, with lights on at 07:00 h and off at 19:00 h. In one corner of the terrarium an infrared lamp produced an operative temperature of 42.5 degrees C, thereby allowing behavioral temperature regulation during the light period. When the turtles were handled only once a day for the purpose of taking cloacal temperature, their body temperature held stable at about 22-23 degrees C. Immediately after being handled the turtles sought the radiant heat and regulated their body temperature at about 4 degrees C higher than before the handling. When repeatedly handled every 15 min for 2 h the turtles maintained a high body temperature by their behavior. When not repeatedly handled the turtles returned to their initial preferred body temperature ca 22-23 degrees C within 2 h. It is hypothesized that handling causes in turtles a fever similar to that observed in stressed mammals. The turtles were equipped with an electrocardiogram radio transmitter and their heart rate was recorded at a distance. Heart rate in undisturbed turtles was 28.3+/-0.6 bt/min. During a 1-min handling, their heart rate rose to 40.2+/-0.8 bt/min. This tachycardia persisted several minutes, then their heart rate returned to the baseline value in ca. 10 min. Stress fever and tachycardia are taken as signs of emotion in turtles.     

Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii : comparison of evolution of these toxins in land snakes, sea kraits and sea snakes

Background  

Snake venom composition varies widely both among closely related species and within the same species, based on ecological variables. In terrestrial snakes, such variation has been proposed to be due to snakes' diet. Land snakes target various prey species including insects (arthropods), lizards (reptiles), frogs and toads (amphibians), birds (aves), and rodents (mammals), whereas sea snakes target a single vertebrate class (fishes) and often specialize on specific types of fish. It is therefore interesting to examine the evolution of toxins in sea snake venoms compared to that of land snakes.     

Parathyroid Glands in Reptiles

The parathyroid glands in reptiles generally develop from thethird and fourth pharyngeal pouches. In lizards and crocodiles,usually only one pair of glands (from the third pouch) persists,while turtles and snakes generally retain both pairs of glandsin adults. The glands consist of cell cords and are similarin structure to those of birds and mammals. A common featureof reptilian parathyroids is the organization of cells arounda lumen in a follicular arrangement. The few physiological studieswhich have been made indicate that parathyroid function in reptilesis in many respects similar to that of mammals. For example,in lizards, parathyroidectomy results in tetanic convulsionsand lowered values of plasma calcium, while administration ofparathyroid extract increases mine phosphate and serum calciumin turtles, and increases the number of osteoclasts in boneof lizards and turtles. However, there are some obvious differencesbetween parathyroid function in reptiles and mammals, on whichmuch more work is needed.     

Vertebrate predation by sympatric tamarins, Saguinus mystax and Saguinus fuscicollis

Vertebrate predation was examined in sympatric moustached tamarins (Saguinus mystax) and saddle-back tamarins (Saguinus fuscicollis) in the Amazon rainforest of northeastern Peru. Both species prey on frogs and lizards, and very rarely on nestling birds. As a result of divergent foraging strategies, S. mystax primarily exploited frogs at higher strata of the forest, while S. fuscicollis predominantly preyed on reptiles in the lower strata and on the ground. This difference may strengthen the niche differentiation between these two tamarin species that exists with regard to other prey.     

Thyroid function in a lizard, a tortoise and a crocodile, compared with mammals

1. Thyroid activity was examined in the lizard, Trachydosaurus rugosus, the tortoise Chelodina longicollis and the crocodile, Crocodylus johnstoni, acclimated to 20-22 degrees C and 30-32 degrees C. Thyroidal uptake and release of 125I, plasma concentrations of T3 and T4 were measured as was resting oxygen consumption (at 30 degrees C) before and after both thyroidectomy and thyroxine injections. 2. All three species showed 125I uptake at both temperatures and showed no thyroidal release of 125I at 20-22 degrees C but exhibited thyroidal release of 125I (and presumably hormone secretion) at 30-32 degrees C. 3. Plasma concentrations of thyroxine ranged from 0.55 nM to 3.24 nM and triiodothyronine from 0.14 nM to 0.51 nM. 4. Neither thyroidectomy nor thyroxine injections had any effect on metabolic rate in 20-22 degrees C acclimated lizards. Thyroidectomy resulted in a significant decrease in metabolic rate in 30-32 degrees C acclimated lizards and tortoises and thyroxine injections resulted in significant increases in metabolism in 30-32 degrees C acclimated lizards, tortoises and crocodiles. 5. A comparison of thyroid parameters in reptiles and mammals concluded that although the reptilian thyroid is active at high temperatures it is still considerably less active than it is in mammals.     

Failure of tetracycline as a biomarker in batch-marking juvenile frogs

Recent widespread amphibian declines call for better techniques to assess population dynamics. Tetracycline as a biomarker in capture-recapture studies is one technique used successfully in fish, reptiles, and mammals. A two-phase experimental study was conducted to evaluate tetracycline as a biomarker in green frogs (Rana clamitans) and pickerel frogs (Rana palustris). In the first experimental phase tadpoles were exposed to water containing either 250 mg/l or 500 mg/l tetracycline for a period of 24 hr. During the second phase, juvenile frogs were exposed to tetracycline in water at 500 mg/l or given injections of tetracycline at the dose rate of 100 mg/kg body weight. At selected times several weeks later, under tricaine methanesulfonate anesthesia, a toe was surgically excised from each animal, sectioned and viewed under an ultraviolet microscope. No significant differences were found between the various treatments and control animals (untreated). Therefore, the use of tetracycline as a biomarker in anurans using these techniques is not recommended.     

Metabolic depression induced by urea in organs of the wood frog, Rana sylvatica: effects of season and temperature

It has long been suspected that urea accumulation plays a key role in the induction or maintenance of metabolic suppression during extended dormancy in animals from diverse taxa. However, little evidence supporting that hypothesis in living systems exists. We measured aerobic metabolism of isolated organs from the wood frog (Rana sylvatica) in the presence or absence of elevated urea at various temperatures using frogs acclimatized to different seasons. The depressive effect of urea on metabolism was not consistent across organs, seasons, or temperatures. None of the organs from summer frogs, which were tested at 20 degrees C, or from winter frogs tested at 4 degrees C were affected by urea treatment. However, liver, stomach, and heart from spring frogs tested at 4 degrees C had significantly lower metabolic rates when treated with urea as compared with control samples. Additionally, when organs from winter frogs were tested at 10 degrees C, metabolism was significantly decreased in urea-treated liver and stomach by approximately 15% and in urea-treated skeletal muscle by approximately 50%. Our results suggest that the presence of urea depresses the metabolism of living organs, and thereby reduces energy expenditure, but its effect varies with temperature and seasonal acclimatization. The impact of our findings may be wide ranging owing to the number of diverse organisms that accumulate urea during dormancy. J. Exp. Zool. 309A:111-116, 2008. (c) 2008 Wiley-Liss, Inc.     

Conservation biogeography in North-east India: hierarchical analysis of cross-taxon distributional congruence

Distributional similarity (congruence) between phylogenetically independent taxonomic groups has important biogeographical as well as conservation implications. When multiple groups show congruence, one or two of them can be used as surrogates of diversity in others; thus, simplifying some of the challenges of area prioritization for conservation action. Here we test for congruence in complementarity between amphibians, reptiles and birds across seven tropical rainforest sites in the Eastern Himalaya and Indo-Burma global biodiversity hotspots. The results show that while frogs and lizards are strongly congruent with each other, birds as a whole do not show congruence with either of them. However, certain bird subgroups delineated on the basis of broad ecological niche and life history attributes are significantly congruent with both frogs and lizards. Multiple Mantel regression between environmental variable and species distribution dissimilarity matrices indicate that along with differential response to between-site ecological differences, inherent life-history characteristics shared by certain groups contributes to observed patterns of congruence. Our analyses indicate that examining biologically distinct subsets of larger groups can improve the resolution of congruence analyses. This approach can refine area-prioritization initiatives by revealing fine-scale discordances between otherwise concordant groups, and vice versa. Given that monetary resources do not always allow inclusion of multiple groups in biodiversity inventorying efforts, performing such analyses also makes economic sense because it can provide better resolution even with single-group data. In the context of conservation in North-east India, the results highlight the biogeographical complexity of the region, and also point at future priorities for biodiversity inventorying and conservation prioritization, both in terms of areas as well as taxonomic groups.     

Evolution and Development of Ventricular Septation in the Amniote Heart

During cardiogenesis the epicardium, covering the surface of the myocardial tube, has been ascribed several functions essential for normal heart development of vertebrates from lampreys to mammals. We investigated a novel function of the epicardium in ventricular development in species with partial and complete septation. These species include reptiles, birds and mammals. Adult turtles, lizards and snakes have a complex ventricle with three cava, partially separated by the horizontal and vertical septa. The crocodilians, birds and mammals with origins some 100 million years apart, however, have a left and right ventricle that are completely separated, being a clear example of convergent evolution. In specific embryonic stages these species show similarities in development, prompting us to investigate the mechanisms underlying epicardial involvement. The primitive ventricle of early embryos becomes septated by folding and fusion of the anterior ventricular wall, trapping epicardium in its core. This folding septum develops as the horizontal septum in reptiles and the anterior part of the interventricular septum in the other taxa. The mechanism of folding is confirmed using DiI tattoos of the ventricular surface. Trapping of epicardium-derived cells is studied by transplanting embryonic quail pro-epicardial organ into chicken hosts. The effect of decreased epicardium involvement is studied in knock-out mice, and pro-epicardium ablated chicken, resulting in diminished and even absent septum formation. Proper folding followed by diminished ventricular fusion may explain the deep interventricular cleft observed in elephants. The vertical septum, although indistinct in most reptiles except in crocodilians and pythonidsis apparently homologous to the inlet septum. Eventually the various septal components merge to form the completely septated heart. In our attempt to discover homologies between the various septum components we aim to elucidate the evolution and development of this part of the vertebrate heart as well as understand the etiology of septal defects in human congenital heart malformations.     

A review on the impacts of feral cats (Felis silvestris catus) in the Canary Islands: implications for the conservation of its endangered fauna

Feral cats have been directly responsible for the extinction of numerous species on islands worldwide, including endemic species of mammals, birds and reptiles. The diet of feral cats in the main habitats of the Canary Islands, as generally occurred on oceanic islands, is mainly composed of introduced mammals, and native species of birds, reptiles and insects. The impact of feral cat upon the endangered species was assessed by evaluating their relative abundance in the cats’ diet and by considering their current conservation status. A total of 68 different preys were identified at species level in all studies carried out in the Canary Islands (5 mammals, 16 birds, 15 reptiles and 32 invertebrates). From all the species preyed by feral cats in the Canary Islands, only four of them are considered threatened by the IUCN Red List of Threatened Species: one endemic bird Saxicola dacotiae and three endemic giant lizards, Gallotia simonyi, Gallotia intermedia, and Gallotia gomerana. Although some efforts on management control have been carried out, it is necessary to enforce these conservation activities on those areas of Tenerife, La Gomera and El Hierro where giant lizards are still present. Furthermore some local areas where endangered bird species are highly predated should be protected. Nevertheless, it is important to take into account the presence of other introduced species such as rats, mice or rabbits in order to avoid problems derived from the hyperpredation process and mesopredator release effect.     

Effects of exotic mongoose (Herpestes javanicus) on the native fauna of Amami-Oshima Island, southern Japan, estimated by distribution patterns along the historical gradient of mongoose invasion

We examined the distribution patterns of native animals on Amami-Oshima Island, southern Japan, along a historical gradient of mongoose establishment and estimated the effects of mongoose on the native fauna. To assess the relative abundance of various ground-dwelling animals, we used the following four methods; sensor cameras for exotic mammals, nighttime driving census for nocturnal native vertebrates, line census for ground-dwelling lizards, and adhesive traps for arthropods. The results indicated that seven species with larger body size, including mammals, birds, reptiles, and amphibians, were rarely observed in mongoose-infested area. By contrast, medium-sized animals showed neutral relationships with mongoose establishment. Interestingly, the densities of smaller-sized animals were higher in mongoose-infested area. It could be interpreted that smaller species have increased in abundance through top-down cascades, i.e., decreases in native predators such as frogs and lizards caused by the mongoose have resulted in increases in the abundance of smaller animals. Predation pressures by mongoose and native predators may be canceled out for medium-sized animals, causing neutral responses to mongoose by these animals. This study appears to be the first example that shows the influence of mongoose on a wide variety of native animals. In addition, our findings indicate the importance of considering the food web structure of a recipient ecosystem and contribute to the prediction and assessment of ecological risks caused not only by mongoose, but also by other invasive top predators.     

Response of intestinal flora of laboratory-reared leopard frogs (Rana pipiens) to cold and fasting.

The bacterial flora of the large intestine was examined in 35 laboratory-reared leopard frogs (Rana pipiens) subjected to one of the following four treatments: (i) normal feeding at 21 degrees C (10 frogs); (ii) fasting for 2 weeks at 21 degrees C (8 frogs); (iii) chilling for 1 week at 4 degrees C (9 frogs); and (iv) simulated hibernation for 3 weeks at 4 degrees C (8 frogs). Bacteria from the intestinal contents and mucosa were counted microscopically and by colony counting after strictly anaerobic culturing. The predominant bacteria were isolated and partially characterized. Fasting for 2 weeks produced no significant changes in total counts or in the types of bacteria cultured. Chilling, whether rapid or in the course of simulated hibernation, was associated with a decrease in the numbers and variety of bacteria. Thus it appears that the lowering of temperature rather than the absence of food is the important factor in the reduction of bacterial flora seen in hibernating frogs. However, the bacteria showed some adaptation to the low temperature, as the longer the host had been at 4 degrees C, the higher the proportion of bacteria which could grow when cultured at that temperature.     

Second intermediate host land snails and definitive host animals of Brachylaima cribbi in southern Australia

This study of infection of southern Australian land snails with Brachylaima cribbi metacercariae has shown that all commonly encountered native and introduced snails are susceptible second intermediate hosts. The range of infected snails is extensive with metacercariae-infected snails being present in all districts across southern Australia. C. virgata has the highest average natural metacercarial infection intensity of 6.1 metacercariae per infected snail. The susceptibility of birds, mammals and reptiles to B. cribbi infection was studied in South Australia by capturing, dissecting and examining the intestinal tract contents of animals which commonly eat land snails as a food source. Indigenous Australian little ravens (Corvus mellori), which are a common scavenger bird, and two other passeriform birds, the black bird (Turdus merula) and the starling (Sturnus vulgaris), which are both introduced European birds, were found to have the highest infection rates of all animals examined. Other birds found infected with B. cribbi were an emu (Dromaius novaehollandiae), chickens (Gallus gallus) and a pigeon (Columba livia). Natural infections were also detected in field mice (Mus domesticus) and shingleback lizards (Tiliqua rugosa) although the intensity of infection was lower than that observed in birds. Susceptibility studies of laboratory mice, rats and ducks showed that mice developed patent infections which persisted for several weeks, rats developed a short-lived infection of three weeks' duration and ducks did not support infection. This study has shown for the first time that a brachylaimid can infect a wide host range of birds, mammals and reptiles in nature.     

BIODIVERSITY RESEARCH: Nestedness for different reasons: the distributions of birds,lizards and small mammals on islands of an inundated lake

Aim We examined whether the community compositions of birds, lizards and small mammals were nested in a fragmented landscape in the Thousand Island Lake, China. We also assessed whether the mechanisms influencing nestedness differed among these taxonomic groups. Location Thousand Island Lake, China. Methods Presence/absence matrices were compiled for birds (42 islands) and lizards (42 islands) using line‐transect methods, and for small mammals (14 islands) using live‐trapping methods from 2006 to 2009. Nestedness was analysed using BINMATNEST, and statistical significance was assessed using the conservative null model 3. We used Spearman rank correlations and partial Spearman rank correlations to examine associations of nestedness and habitat variables (area, isolation, habitat diversity and plant richness) as well as life‐history traits (body size, habitat specificity, geographical range size and area requirement) related to species extinction and immigration tendencies. Results The community compositions of birds, lizards and small mammals were all significantly nested, but the causal factors underlying nestedness differed among taxonomic groups. For birds, island area, habitat specificity and area requirement were significantly correlated with nestedness after controlling for other independent variables. For lizards, habitat heterogeneity was the single best correlate of nestedness. For small mammals, island area, habitat heterogeneity and habitat specificity were significantly correlated with nestedness. The nested patterns of birds, lizards and small mammals were not attributable to passive sampling or selective colonization. Main conclusions The processes influencing nested patterns differed among taxonomic groups. Nestedness of bird assemblages was driven by selective extinction, and lizard assemblage was caused by habitat nestedness, while nestedness of small mammals resulted from both selective extinction and habitat nestedness. Therefore, we should take taxonomic differences into account when analysing nestedness to develop conservation guidelines and refrain from using single taxa as surrogates for others.     

Patterns in the geographical range sizes of ectotherms in North America

The distributions of homeothermic mammals and birds in continental North America show a distinct pattern in the configuration of their geographical ranges. Smaller ranges tend to be elongated north-south while larger ranges tend to be elongated east-west. To examine the generality of this pattern in ectotherms, we analyzed the distribution on continental North America of 139 species of mosquitoes, 164 amphibians, and 221 reptiles. Unlike birds and mammals, small ranges of ectotherms were not elongated north-south and the small ranges of snakes were elongated east-west. The distribution of ectotherms with small ranges does not appear to be affected by the major topographic features of North America which tend to run north-south. Like birds and mammals, large ranges of mosquitoes and reptiles but not amphibians are elongated east-west. The east-west orientation of mosquitoes with large ranges is not attributable to the three largest genera in North America taken singly, Aedes, Culex, or Anopheles, but appears only when all genera are pooled. The east-west orientation of reptiles with large ranges is attributable to turtles and snakes but not lizards. Climatic zones may thus affect the distribution of mosquitoes, turtles, and snakes with large ranges but are not the major determinants of range dimensions among ectotherms in general. Received: 1 September 1997 / Accepted: 8 February 1998     

The Reptilian Baroreceptor and Its Role in Cardiovascular Control

Anatomical evidence for the existence of a depressor nerve inreptiles was first reported 100 years ago. Electrical stimulationof the central end of the cut nerve, however, did not producean unequivocal fall in heart rate and blood pressure, so itwas thought not to function as a depressor nerve. This remainedthe state of knowledge for fifty years when Marco Fedele performeda superb anatomical and physiological study of the depressornerves of turtles and lizards. He demonstrated that there weretwo depressor nerves from each vagus; the superior nerve originatedfrom the jugular ganglion or superior laryngeal nerve in turtlesand from the superior laryngeal nerve or vagus in lizards; theinferior nerve originated from the nodose ganglion or slightlycaudad of this ganglion. The nerves were shown to terminatein the proximal truncus arteriosus. Unlike the earlier workers,Fedele obtained a clear depressor effect on stimulating thedepressor nerves. In more recent times baroreflexes have been demonstrated inresponse to hemorrhage and body tilting in reptiles, with snakesreceiving particular attention. The evidence indicates thataquatic snakes are less effective at maintaining blood pressurethan terrestrial and arboreal forms. The sensitivity (gain)of the baroreceptor-heart rate reflex, when it is expressedas a percentage change in heart rate per unit pressure change,is approximately the same in reptiles, amphibians, and mammals.In addition, the ultrastructural appearance of the baroreceptorsof lizards is similar to that of mammals. A quantitative assessmentof the ability of reptiles to correct disturbances in bloodpressure has not yet been made, but techniques for obtainingthis information are now available.     

Structure and function of the hearts of lizards and snakes

With approximately 7000 species, snakes and lizards, collectively known as squamates, are by far the most species‐rich group of reptiles. It was from reptile‐like ancestors that mammals and birds evolved and squamates can be viewed as phylogenetically positioned between them and fishes. Hence, their hearts have been studied for more than a century yielding insights into the group itself and into the independent evolution of the fully divided four‐chambered hearts of mammals and birds. Structurally the heart is complex and debates persist on rudimentary issues such as identifying structures critical to understanding ventricle function. In seeking to resolve these controversies we have generated three‐dimensional (3D) models in portable digital format (pdf) of the anaconda and anole lizard hearts (‘typical’ squamate hearts) and the uniquely specialized python heart with comprehensive annotations of structures and cavities. We review the anatomy and physiology of squamate hearts in general and emphasize the unique features of pythonid and varanid lizard hearts that endow them with mammal‐like blood pressures. Excluding pythons and varanid lizards it is concluded that the squamate heart has a highly consistent design including a disproportionately large right side (systemic venous) probably due to prevailing pulmonary bypass (intraventricular shunting). Unfortunately, investigations on rudimentary features are sparse. We therefore point out gaps in our knowledge, such as the size and functional importance of the coronary vasculature and of the first cardiac chamber, the sinus venosus, and highlight areas with implications for vertebrate cardiac evolution.     

Asynchronous Eye Closure as an Anti-Predator Behavior in the Western Fence Lizard (Sceloporus occidentalis)

Asynchronous eye closure (ASEC), one eye open while the other is closed, is a behavior observed in birds, some aquatic mammals, and reptiles. In birds and aquatic mammals, ASEC is associated with unihemispheric sleep wherein the cerebral hemisphere contralateral to (i.e. neurologically connected to) the closed eye sleeps while the other cerebral hemisphere remains awake with its associated eye open and functional. Evidence from birds suggests that ASEC is an important anti‐predator adaptation to mediate the trade‐off between the need to remain vigilant and the need to sleep. However, the anti‐predator correlates of ASEC remain largely unstudied in other animals. Here, we present behavioral evidence that ASEC in reptiles is also an anti‐predator adaptation used in response to an increase in the risk of predation. ASEC was measured in captive western fence lizards (Sceloporus occidentalis) individually exposed to three experimental treatments: (1) an empty terrarium, (2) a terrarium housing a novel moving object, and (3) a terrarium housing a live predator (snake). Predator exposure elicited significantly higher levels of vigilance, mostly due to an increase in ASEC. This increase in ASEC came largely at the expense of synchronous eye closure (both eyes closed). Lizards in ASEC also showed a strong tendency to orient their open eye in the direction of the predator. We suggest that lizards engaged in ASEC are sleeping unihemispherically and are thus able to maintain a level of vigilance concurrent with sleep.     

Mitochondrial genomes from major lizard families suggest their phylogenetic relationships and ancient radiations

In placental mammals and birds, molecular data generally support a view that they diverged into their ordinal groups in good response to mid-Cretaceous continental fragmentations. However, such divergence patterns have rarely been studied for reptiles for which phylogenetic relationships among their major groups have not yet been established molecularly. Here, I determined complete or nearly complete mitochondrial DNA sequences from seven lizard families and reconstructed phylogenetic relationships between major lizard families. When snakes were included, maximum likelihood analysis did not support a morphological view of the snakes-varanoids affinity, although several other competing hypotheses on the position of snakes still cannot be discriminated presumably due to extremely long branches of the snake lineages. I also conducted clock-free Bayesian analyses to show that divergence times between major lizard families were centered in Triassic-Jurassic times. Thus, lizards include much deeper divergences than the mammals and birds and they appear to have already radiated into various families prior to the mid-Cretaceous major continental fragmentation.