bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of testosterone administration and gonadectomy on nuptial pad morphology in overwintering male leopard frogs, Rana pipiens
Authors: Lynch Laura C. , Blackburn Daniel G. 
Published: April 2008

Abstract
Overwintering Rana pipiens were studied to clarify physiological control of the nuptial pad, a digital specialization of male frogs that is used in mating. Testosterone cypionate implants stimulated nuptial pad growth in both castrated and sham-operated males relative to placebo-treated controls. Androgen-induced changes in the nuptial pad simulated seasonal recrudescence, and included significant increases in thickness of both the epidermis and dermis, formation of keratinized epidermal papillae, hypertrophy of the gland epithelium, enlargement of the gland lumina, and cytoplasmic accumulation of secretory product. Castration did not influence the response to testosterone, nor did it markedly affect nuptial pad morphology, probably because the pads were in maximal regression. These findings, in conjunction with previous work, implicate testicular androgens in seasonal cyclicity of the nuptial pad.
The status of Caiman crocodilus crocodilus and Melanosuchus niger populations in the Amazonian regions of Brazil
Authors: Brazaitis Peter , Rebêlo George H. , Yamashita Carlos 
Published: April 2008

Abstract
Investigations were conducted throughout the Amazonian regions of Brazil to determine the distribution and status of Caiman c. crocodilus populations. Observations were made on the occurrence of Melanosuchus niger populations. Population data for river and lake/pond habitats are reported for 39 localities. Data suggest Caiman populations may be depleted in many regions. Melanosuchus populations are fragmented and have been extirpated from eight localities which had recent populations. Amazonian caiman populations are subject to increased human predation, environmental contamination with heavy metals, habitat modification, and lack of effective protection for wild populations.
Temperature regulation in the tortoise Testudo hermanni, studied with indwelling probes
Authors: Huot-Daubremont C. , Grenot C. , Bradshaw D. 
Published: April 2008

Abstract
Behavioural thermoregulation has been studied in the terrestrial tortoise Testudo hermanni in south-eastern France by implanting temperature-sensitive probes in free-ranging individuals. Three tortoises were monitored over a period of nine months (July to March); they maintained body temperatures close to their preferendum for periods of several hours each day. These results are of interest as doubt has been expressed in the literature on the thermoregulatory capacities of Testudo hermanni in the northernmost part of its range.
Feeding of amphibians during metamorphosis
Authors: Kuzmin Sergius L. 
Published: April 2008

AbstractThe feeding ecology of 28 amphibian species with complete life cycles has been studied from the last pre-metamorphic stages to metamorphosed juveniles. The widespread view that feeding ceases completely during metamorphosis is not confirmed. Generally, however, amphibian feeding rate decreases at metamorphosis. Foraging in Caudata either does not cease (Hynobiidae, rheophilous Salamandridae) or ceases only before the end of transformation, which takes less than one metamorphic stage. The cessation of foraging in Anura coincides with the transformation of the mouth and digestive tract at the beginning of the metamorphic climax. Foraging on small animals starts just after the change from a larval to a post-metamorphic mouth, i.e., before the end of metamorphosis.
The distribution and conservation status of the Danube crested newt, Triturus dobrogicus
Authors: Arntzen J.W. , Bugter R.J.F. , Cogalniceanu D. , Wallis G.P. 
Published: April 2008

Abstract
The range boundaries of the Danube crested newt (Triturus dobrogicus) are estimated from published data and new observations. The species range is restricted to the Pannonian and Dobrogean lowlands of central and eastern Europe. Its conservation status is determined as "vulnerable". The main cause of decline is habitat destruction through the conversion of wetlands, (semi-)natural land and pasture into arable fields.
Natural hybridization and introgression between Rana nigromaculata and Rana porosa porosa in central Japan
Authors: Sumida Masayuki , Ishihara Tatsuo 
Published: April 2008

AbstractIn order to elucidate the extent of natural hybridization and gene introgression between two Japanese pond frog species, Rana nigromaculata and Rana porosa porosa, 16 pond frogs from the Sengokuhara population in the Hakone district in central Japan were analyzed for morphological characters, allozymes, mtDNA and reproductive capacity. The results revealed that they consisted of pure Rana nigromaculata, F1 hybrids and a backcross hybrid.
Different temperature relations of two species of toads that coexist at the border of their geographical distributions
Authors: Katz U. , Gil Nira 
Published: April 2008

AbstractTemperature relations of two species of toads (Bufo viridis and Bufo regularis) that overlap at the border of their geographical distributions were studied in the laboratory in temperatures between 25°C and 2°C. Bufo regularis, a tropical species, could not survive at low temperatures that eventually led to its death in 1-2 days. The two species did not differ in their cooling and heating rates. At temperatures below 8-10°C, Bufo viridis maintained a body temperature that was higher than ambient by 1-2°C, while body temperature of Bufo regularis equaled that of the environment. In Bufo regularis heart beats ceased at low temperatures (< 4°C), whereas in Bufo viridis at the same temperature, a rate of 6-9 beats/min was sustained. Our experiments suggest that Bufo viridis is endowed with particular capacities that allow it to remain active at low temperatures, while in Bufo regularis, a temperature-sensitive central mechanism seems to be damaged at low temperature. The ability of Bufo viridis to endure low temperatures and to remain active in this condition is specific to the species, and is not related directly to the immediate ecological situation of the animal.
Flow cytometry in biodiversity surveys: methods, utility, and constraints
Authors: Murphy Robert W. , Lowcock Leslie A. , Smith Cheryl , Darevsky Ilya S. , Orlov Nikolai , MacCulloch Ross D. , Upton Darlene E. 
Published: April 2008

Abstract
Flow cytometry of blood is a powerful tool for rapidly sorting individual specimens on the basis of cellular DNA content. During biodiversity surveys, the method enabled the early identification of both cryptic sympatric and allopatric species of Vietnamese ranid frogs. This method may be extremely valuable in sorting individuals from other taxa and geographic regions, especially when cellular DNA content is known to vary among closely related taxa, and in tropical situations where crypsis is a relatively common phenomenon. Protocols for preparation of freezing solution, field procedures, preparation of reference standards, and flow cytometric analysis are provided. The best method for field preservation of blood is freezing in liquid nitrogen; field fixation of blood in ethanol was less efficient and resulted in drastically increased coefficients of variation. Once samples have been transferred to freezer storage, they should not be returned to a lower storage temperature in liquid nitrogen.
Independent evolution of squamate olfaction and vomerolfaction and correlated evolution of vomerolfaction and lingual structure
Authors: Cooper William E. 
Published: April 2008

AbstractThe comparative abundances of chemoreceptor cells for olfaction and vomerolfaction, the sense mediated by the vomeronasal organs, were studied in numerous squamate families, with emphasis on lizards, and compared with abundance of lingual taste buds and aspects of lingual structure likely to be related to chemosensory sampling for vomerolfaction. Abundances of vomerolfactory receptors vary greatly among, but little within squamate families. Using Felsenstein's method of independent contrasts, the abundance of vomeronasal receptors is significantly correlated with size of lingual tines, degree of lingual elongation, and condition of sampling surfaces (pallets) on the ventral side of the tongue. This indicates that correlated evolution has occurred. An intimate relationship exists between the chemosensory organ and its primary sampling device, highlighting a lingual-vomeronasal complex that functions to sample and analyze chemical stimuli from external environmental surfaces. Attributes enhancing lingual facility for chemical sampling are forking, which permits scent-trailing by tropotaxis, and possibly elongation, which may permit greater extension beyond the mouth or enhance maneuverability. Ventral lingual pallets, surfaces that directly contact substrates during sampling, are large in forms having low abundances of vomerolfactory receptors, but are reduced and are eventually lost with progressive increases in vomerolfactory receptor abundance. Pallet condition is negatively correlated with tine size and lingual elongation. Large tines appear to take over the sampling function in forms lacking pallets. Lingual taste bud abundance is negatively correlated with vomerolfactory receptor abundance, forking, elongation, and positively with pallet condition. The negative correlation between the abundance of vomerolfactory receptors and lingual taste buds may be attributable to physical incompatibility between taste buds and specialized modifications of the foretongue for vomerolfactory sampling or to loss of opportunity for lingual taste buds to function in vomerolfactory specialists that lack lingual functions such as prey prehension, manipulation, and transport and in which the tongues are ensheathed while in the mouth. The abundances of olfactory and vomeronasal chemoreceptor cells are uncorrelated using Felsenstein's method. Thus, olfaction appears to have evolved independently of vomerolfaction.
A new species of Eleutherodactylus (Anura: Leptodactylidae) from the Andean slopes of Bolivia
Authors: Reichle Steffen , Köhler Jörn 
Published: April 2008

AbstractA new species of frog of the genus Eleutherodactylus is described from Valle del Zongo, Departamento La Paz, Bolivia. This species of the E. discoidalis group is most similar to E. cruralis, but differs in dorsal tuberculation, color, and head proportions.
Reproductive ecology of Bombina variegata: aspects of life history
Authors: Barandun Jonas , Reyer Heinz-Ulrich , Anholt Bradley 
Published: April 2008

Abstract
Individual reproductive behaviour and survival of Bombina variegata was studied in a dynamic habitat with a variety of rain-filled ponds from 1990 to 1992. Most animals reached sexual maturity at the age of two years. Annual adult survival was at least 62%. Individual females, on average, laid between 40 and 70 eggs per "clutch". While about 12% of the breeding females spawned a second time within the season, a similar proportion did not seem to spawn every possible year, probably depending on climatic conditions. The results are consistent with ultimate predictions from life history theory, but the proximate mechanisms of ovulation and spawning in response to environmental conditions remain to be investigated.
Allometry and morphological integration in the skull of Tupinambis merianae (Lacertilia: Teiidae)
Authors: Monteiro Leandro R. , Abe Augusto S. 
Published: April 2008

AbstractThe morphogenetic processes acting in the skull of the lizard Tupinambis merianae were investigated by geometric morphometric techniques. The observed ontogenetic shape change involved a widening of the anterior extremity, stretching and narrowing of the midface, narrowing of the braincase, orbital reduction and elongation of the temporal region (origin of jaw adductor muscles). This change occurred mostly in a localized way in certain cranial regions. The major components identified were: rostrum, midface, dermal elements of braincase (functionally influenced) and endochondral elements of braincase (embryologically influenced). The growth patterns lead to an increased robustness of the skull (particularly the anterior extremity) and a reduction of cranial kinesis. These changes, together with the ontogenetic variation in dentition aid in the ontogenetic variation observed in the diet of these animals, which shift from carnivory to omnivory.
The first record of snakes on the Canary Islands: a vertebra from the Upper Miocene of Lanzarote
Authors: Barahona Fabiola , Rage Jean-Claude , García-Talavera Francisco 
Published: April 2008

Abstract
The Upper Miocene fossil site of Orzola in Lanzarote (Canary Islands) has produced an isolated snake vertebra attributable to the Boidae. This is the first report of a snake, either fossil or living, from these islands, which provides further evidence of a greater faunal diversity in the past.
Migration patterns and diurnal use of shelter in a ranid frog of a West African savannah: a telemetric study
Authors: Spieler Marko , Linsenmair Karl Eduard 
Published: April 2008

Abstract
A telemetric study on Hoplobatrachus occipitalis (Anura: Ranidae) was conducted in the Comoé National Park (Ivory Coast, West Africa) from 1993 to 1995 during the beginning of the rainy seasons. Radio transmitters were implanted into 46 frogs. The locations of individual animals were tracked for 2 to 71 days, at least once per day and once per night. By day, the frogs were found in diurnal shelters that offered favorable temperature and humidity conditions as well as protection against predators. At night, with the beginning of the rainy season, both males and females occupied about equally large home ranges of on average 142 m2 (range: 23-3744 m2) in a partially dried-up river bed. Individuals with home ranges on rocky stretches along the river weighed significantly less (35 ± 9 g) and occupied significantly larger home ranges (median: 944 m2) than did individuals found in places along the river having dense and shady vegetation (median of home range: 45 m2, body weight: 66 ± 21 g). Frogs migrated when precipitation was above 15 mm per day (movement >30 m per animal and day). Movement over longer distance (>600 m per animal and day) took place only once a year, when the first heavy rainfall of the season filled the dried-up ponds in the savannah. On these longer migrations, nearly all radio-tracked frogs moved from the river to newly emerged ponds in the savannah, covering linear distances of up to 1.4 km in a single night. The frogs then stayed in the savannah and most of them repeatedly sought new breeding sites during the rainy season. Thus, the total space covered by the frogs, termed "activity area", amounted to up to 2 km2, for both sexes, during the observation period.
Activity patterns and microhabitat selection of Mallorcan midwife toad (Alytes muletensis) tadpoles in natural torrent pools
Authors: Schley Laurent , Griffiths Richard A. , Roman Alvaro 
Published: April 2008

Abstract
Tadpoles of the Mallorcan midwife toad (Alytes muletensis) displayed a clear diel pattern of activity and microhabitat selection in torrent pools in Mallorca. Tadpoles spent much of the day foraging in a non-aggregated fashion in warm shallow areas, and activity peaked at 1700-1900 hr. In mid-afternoon, however, when much of the water surface was in direct sunlight, tadpoles moved away from the shallows and formed aggregations under rock overhangs at the sides of the pool. Both activity and tadpole density in the shallows dropped dramatically after dark, when there was a movement of the population back into deeper water or hiding places.
The Sexual Behaviour of Two Sibling Drosophila Species
Authors: Manning Aubrey 
Published: April 2008

Abstract1. The courtship behaviour of Drosophila melanogaster and D. simulans has been studied. Melanogaster is a generally more active species than simulans and its courtship is more vigorous. 2. The sexual behaviour of both types of male can be readily classified into the same basic elements, orientation, wing display, licking and attempted copulation. 3. Simulans males have longer lag periods before courtship, longer bouts of simple orientation, fewer changes of element when courting and their chief wing display is 'scissoring'. Melanogaster's chief wing display is 'vibration'. 4. Experiments in which the sexual stimulus situation was changed show that with lower stimulation melanogaster males show an increased proportion of scissoring, while with increased stimulation simulans males show more vibration. Additional reasons are given for considering scissoring to represent a lower level of sexual excitation than vibration. 5. The differences between the males can be most simply ascribed to simulans having a slower rise of sexual excitation during courtship than melanogaster, not to any changes in the basic organization of their behaviour. This slowed rise may be related to higher thresholds of response in simulans. 6. The females of simulans are more responsive to visual aspects of their males' courtship, and less responsive to those stimuli perceived by their antennae, than are melanogaster females. 7. It is argued that these changes in courtship behaviour probably resulted from selection acting upon a common ancestral population so as to favour high activity in some environments and low activity in others. These changes will be most readily produced by mutations affecting reaction thresholds and the changes to courtship pattern will follow. Selection will then favour females responsive to the most easily available stimuli from the males' courtship. 8. It is suggested that similar situations occur in other sibling Drosophila species and that as a first step in behavioural divergence, mutations affecting thresholds will be particularly important.
Suckling Behaviour in Kittens
Authors: Ewer R.F. 
Published: April 2008

AbstractThe feeding behaviour of two litters of four kittens each has been studied. Düring the first few days of life each kitten gradually establishes ownership of one teat, and then rarely feeds from any teat but its own. One kitten was exceptional in establishing ownership of two teats. Teat constancy is well maintained until the kittens become active enough to leave the nest and feed independently of the mother at the age of about 32 days. From this age until the end of lactation, although teat constancy is less rigidly maintained, it doet not vanish completely. The factors which bring about this reduction in teat constancy are discussed. Some incidental observations on the behaviour of the females towards the kittens of the foreign litter are included. The clues which a kitten may utilise in recognising its own teat and the biological significance of teat constancy are briefly considered.
Further Observations On Suckling Behaviour in Kittens, Together With Some General Considerations of the Interrelations of Innate and Acquired Responses
Authors: Ewer R.F. 
Published: April 2008

AbstractThe feeding behaviour of kittens includes an appetitive searching component and a sucking response to a teat once this is found. The searching pattern is shown immediately after birth but the kittens usually do not feed until 1 or 2 hours later. This may be either because the sucking response has not yet matured or because the teats do not provide the correct releaser until milk secretion is well established. As the kittens become older the searching pattern undergoes modification which has the characteristics of trial-and-error learning. The sucking response, after a few days, becomes restricted to one teat but later as the kittens begin to become independent of the mother there is some relaxation in this restriction and teat constancy declines. The birth of two litters within 24 hours of each other allowed tests to be made of the response of the kittens to a foreign mother. At first there is no response to a foster mother's teats, including the one corresponding in position to the kitten's "own" teat. At about the same age as the kitten's teat constancy on its own mother starts to decline it begins to accept a teat on the foster mother. This indicates that the kitten's recognition of its own teat depends on a chemical factor, not on anatomical position. The adaptive significance of this behaviour is discussed. It is suggested that the reason for the difference between endogenous patterns and those synthesised in relation to individual experience is to be sought in the adaptive significance of the end results. Where selection favours a species-specific pattern an endogenous ontogeny necessarily follows. In the course of evolution the basis of certain types of behaviour has shifted from endogenous to experience-synthesised or vice versa. This implies that the differences between the two may not be very fundamental and it is suggested that any attempt to "compartmentalise" the study of behaviour is likely to be unprofitable. It may be heuristically more valuable at the present time to turn our attention to the similarities, rather than the differences, between endogenous and experience-synthesised patterns.
The Motivational Organisation Controlling the Mobbing Calls of the Blackbird (Turd Us Merula). Ii. the Quantitative Analysis of Changes in the Motivation of Calling
Authors: Andrew R.J. 
Published: April 2008

Abstract1. At least two variables must be used for the adequate analysis of the changes observed in calling. The first has been here termed Action Potential (A). When the value of A at calling is above a certain threshold 'tix' is given instead of 'duck'. A is caused to rise both by activity of the neural system controlling flight and by the sight of a frightening object. It is reduced by calling, probably at or just after each call. 2. A second variable, the General Threshold for calling (T), must also be employed to explain the data obtained. When A is below T no calls can occur. T is increased by calling (probably at each call, since there is some evidence that it decays between calls). It therefore rises progressively during bouts. As a result the interval between the last two calls of a bout is an unusually long one, and the change to 'tix' is irreversible within a bout. Between bouts T decays, so that the longer the pause between bouts the shorter the intervals between calls at the beginning of the next bout, and the less likely is it that the first call will be 'tix'. 3. The higher the value of T at the beginning of a bout the longer the intervals between calls and the more likely is the change to 'tix', since A has to rise to equal T before calling can occur. 4. T tends to fall a take-off and rise at landing. 5. High intensity calling may take two forms which are caused by differences in the rate of accumulation of T. When T accumulates slowly the intervals between calls readily decrease until the physical limit is reached, and a scream results, in the course of which the change to a 'tix' type of calling occurs. A scream is initiated only after the activity of flight has continued for more than a minimum period of time, which is longer the lower the intensity of mobbing. When T accumulates readily, long bouts result, which are entirely composed of 'tix' calls, given at unusually long intervals.