Get to the point: Claw morphology impacts frictional interactions on rough substrates.

Claws are a common anatomical feature among limbed amniotes and contribute to a variety of functions including prey capture, locomotion, and attachment. Previous studies of both avian and non-avian reptiles have found correlations between habitat use and claw morphology, suggesting that variation in claw shape permits effective functioning in different microhabitats. How, or if, claw morphology influences attachment performance, particularly in isolation from the rest of the digit, has received little attention. To examine the effects of claw shape on frictional interactions, we isolated the claws of preserved specimens of Cuban knight anoles (Anolis equestris), quantified variation in claw morphology via geometric morphometrics, and measured friction on four different substrates that varied in surface roughness. We found that multiple aspects of claw shape influence frictional interactions, but only on substrates for which asperities are large enough to permit mechanical interlocking with the claw. On such substrates, the diameter of the claw's tip is the most important predictor of friction, with narrower claw tips inducing greater frictional interactions than wider ones. We also found that claw curvature, length, and depth influence friction, but that these relationships depend on the substrate's surface roughness. Our findings suggest that although claw shape plays a critical role in the effective clinging ability of lizards, its relative importance is dependent upon the substrate. Description of mechanical function, as well as ecological function, is critical for a holistic understanding of claw shape variation.

Revision of Varanus marathonensis (Squamata, Varanidae) based on historical and new material: morphology, systematics, and paleobiogeography of the European monitor lizards.

Monitor lizards (genus Varanus) inhabited Europe at least from the early Miocene to the Pleistocene. Their fossil record is limited to about 40 localities that have provided mostly isolated vertebrae. Due to the poor diagnostic value of these fossils, it was recently claimed that all the European species described prior to the 21st century are not taxonomically valid and a new species, Varanus amnhophilis, was erected on the basis of fragmentary material including cranial elements, from the late Miocene of Samos (Greece). We re-examined the type material of Varanus marathonensis Weithofer, 1888, based on material from the late Miocene of Pikermi (Greece), and concluded that it is a valid, diagnosable species. Previously unpublished Iberian material from the Aragonian (middle Miocene) of Abocador de Can Mata (Vallès-Penedès Basin, Barcelona) and the Vallesian (late Miocene) of Batallones (Madrid Basin) is clearly referable to the same species on a morphological basis, further enabling to provide an emended diagnosis for this species. Varanus amnhophilis appears to be a junior subjective synonym of V. marathonensis. On the basis of the most complete fossil Varanus skeleton ever described, it has been possible to further resolve the internal phylogeny of this genus by cladistically analyzing 80 taxa coded for 495 morphological and 5729 molecular characters. Varanus marathonensis was a large-sized species distributed at relatively low latitudes in both southwestern and southeastern Europe from at least MN7+8 to MN12. Our cladistic analysis nests V. marathonensis into an eastern clade of Varanus instead of the African clade comprising Varanus griseus, to which it had been related in the past. At least two different Varanus lineages were present in Europe during the Neogene, represented by Varanus mokrensis (early Miocene) and V. marathonensis (middle to late Miocene), respectively.

Superhydrophobic gecko feet with high adhesive forces towards water and their bio-inspired materials.

Functional integration is an inherent characteristic for multiscale structures of biological materials. In this contribution, we first investigate the liquid-solid adhesive forces between water droplets and superhydrophobic gecko feet using a high-sensitivity micro-electromechanical balance system. It was found, in addition to the well-known solid-solid adhesion, the gecko foot, with a multiscale structure, possesses both superhydrophobic functionality and a high adhesive force towards water. The origin of the high adhesive forces of gecko feet to water could be attributed to the high density nanopillars that contact the water. Inspired by this, polyimide films with gecko-like multiscale structures were constructed by using anodic aluminum oxide templates, exhibiting superhydrophobicity and a strong adhesive force towards water. The static water contact angle is larger than 150° and the adhesive force to water is about 66 µN. The resultant gecko-inspired polyimide film can be used as a "mechanical hand" to snatch micro-liter liquids. We expect this work will provide the inspiration to reveal the mechanism of the high-adhesive superhydrophobic of geckos and extend the practical applications of polyimide materials.

Kisspeptin-like immunoreactive neuron distribution in the green anole (Anolis carolinensis).

Kisspeptins are a recently identified class of neuropeptides belonging to the RFamide peptide family. Despite growing evidence supporting kisspeptin as a key regulator of reproduction, data addressing whether kisspeptin is a conserved reproductive signal are lacking. We investigated the distribution of kisspeptin in adult green anole lizards (Anolis carolinensis) via immunohistochemistry. Additionally, we examined the possibility of a sexual dimorphism in kisspeptin expression. Kisspeptin immunoreactivity was observed rostrally in the preoptic area and caudally in an area lateral to the dorsal hypothalamic nucleus in both male and female anoles. These kisspeptin immunoreactive cells are associated with vesiculated fibers traveling through the paraventricular zone of the hypothalamus and preoptic area and extending into the rostral telencephalon. Preabsorption of the antiserum with gonadotropin inhibitory hormone (GnIH), a second RFamide peptide known to cross-react with the kisspeptin antiserum, eliminated staining of the caudal population of cells but retained staining in the rostral population, suggesting that kisspeptin is present in this area. Preabsorption with kisspeptin eliminated all immunoreactivity. These preabsorption results suggest that kisspeptin is restricted to a single population in the preoptic area in anoles. No sex differences were found in kisspeptin immunoreactive cell number. The presence of kisspeptin RFamide peptide in the green anole suggests that this reproductive regulatory signal is indeed evolutionarily conserved. Whether this reproductive signal functions similarly in regulating the reproductive axis of ectotherms requires further study.

Effects of estradiol, sex, and season on estrogen receptor alpha mRNA expression and forebrain morphology in adult green anole lizards.

Steroid hormones, especially estradiol, facilitate reproductive behaviors in male and female rodents and birds. In green anole lizards estradiol facilitates receptivity in females but, unlike in some other species, is not the activating hormone for courtship and copulatory behavior in males. Instead, testicular androgens directly facilitate male courtship and copulation. Yet, activity of the estradiol synthesizing enzyme aromatase is higher in the brain of male than female green anoles, and it is increased during the breeding compared to the non-breeding season. The functional relevance of these differences in local estradiol production is unknown. They might prime the male forebrain to facilitate production of appropriate sexual behaviors, perhaps by modifying morphology of relevant brain regions. In addition, we recently reported increased expression of estrogen receptor alpha (ERalpha) in selected brain regions in females compared to males [Beck LA, Wade J (2009b) Sexually dimorphic estrogen receptor alpha mRNA expression in the preoptic area and ventromedial hypothalamus of green anole lizards. 55:398-403]. Thus, it is possible that the hormone serves to downregulate its receptor in males to inhibit the expression of estradiol-dependent receptive behaviors. To begin to address these ideas, the present study examines the effects of estradiol treatment, sex, and season on forebrain morphology and ERalpha mRNA abundance in three regions important for anole reproductive behavior-the preoptic area, ventromedial amygdala, and ventromedial hypothalamus. While a number of effects of sex and season on forebrain morphology were detected, direct effects of estradiol treatment on these measures were minimal. ERalpha expression was greatest in the ventromedial hypothalamus, and a large female-biased sex difference was detected in this area alone; it resulted from estradiol-treated animals. These results indicate a sex- and region-specific mechanism by which estradiol can modify ERalpha expression in the green anole and could impact the expression of female-typical receptivity.

Comparison of arginine vasotocin immunoreactivity differences in dominant and subordinate green anole lizards.

The neuropeptide arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP) are believed to be involved in many social behaviors including territorial aggression. Testosterone (T) is also important for controlling territorial aggression, and it is believed to be involved in modulating AVT/AVP levels in the brain. In this study, male Anolis carolinensis were paired (n=11 pairs) in a neutral cage and were allowed to establish a dominant-subordinate relationship for 10 days (experimental groups) or housed in a neutral cage with or without a female (control groups; each n=4). On 10th day animals were sacrificed and their brain sections were processed for AVT immunohistochemistry and their serum was analyzed for testosterone levels. AVT immunoreactive (AVT-ir) cell numbers were counted in the anterior hypothalamus (AH), paraventricular nucleus (PN), posterior hypothalamus (PH), preoptic area (POA), and supra optic nuclei (SON). 2-way randomized block design was conducted to assess AVT-ir cell number differences between dominant and subordinate animals and Pearson's correlations were used to determine if a relationship existed between T levels and AVT-ir cell numbers. Dominant animals had more AVT-ir cells in the POA compared to subordinate animals, and subordinate animals had fewer AVT-ir cells in the POA compared to males housed either singly or with a female. There were no differences in AVT-ir cell numbers between dominant and subordinate animals in other areas. T levels were not correlated with the AVT-ir cell numbers in any area. Thus dominant animals have increased AVT-ir cell numbers compared to subordinate animals in a brain region known to be important in male sexual behavior. However, this difference is not related to differences in T.

Effects of age and size in the ears of gekkotan lizards: auditory sensitivity, its determinants, and new insights into tetrapod middle-ear function.

Do related, differently sized species differ in size-related structural or functional traits merely because they mature at different points of a uniform allometric ontogenetic growth curve, or do they evolutionarily diverge? We tested ears of gekkotan lizards through experiments distinguishing the two. Auditory sensitivity was assessed by compound action potential (CAP) thresholds in eight species. The best thresholds characterizing species ranged 22-72 dB sound pressure level at 0.5-1.0 kHz. Direct acoustic stimulation of the columella footplate elevated thresholds by 25-50 dB. Intraspecific CAP sensitivity was primarily affected by body length in Eublepharis macularius, but by tympanic-membrane velocity in Oedura marmorata. The chief factor determining middle-ear function (difference in CAP sensitivity before and after middle-ear ablation) was body length in both species. A secondary factor was the middle-ear hydraulic lever ratio in E. macularius, but the mechanical lever in O. marmorata. When intra- and interspecific data were compared, the relation of CAP thresholds to body size in E. macularius resembled the interspecific regression. The intraspecific regression of auditory sensitivity over tympanic membrane velocity in O. marmorata differed from that calculated interspecifically. Hence, the evolutionary contribution to size effects on CAP sensitivity exceeds the ontogenetic contribution. Putatively, body length affects CAP sensitivity through absolute sizes of tympanic membrane and columella footplate. These newly discovered effects join those of the hydraulic lever and (interspecifically) hair-cell number to improve the hearing of larger species that vocally communicate across wider spaces, apparently throughout the Tetrapoda.

Effects of age and size in the ears of gekkonomorph lizards: middle-ear sensitivity.

Previous studies of electrophysiological audiograms in gekkonomorph lizards revealed greater sensitivity in adults than in juveniles. We investigated whether this difference, as far as it is affected by the middle ear, is due to animal age or size. The velocity transfer function of the tympanic membrane (TM) was examined using laser interferometry in nine samples: adults of three large gekkonomorph species, adults of three small species (each related to one of the former), and juveniles of the large species, their sizes matching those of the small-species adults. Each transfer function exhibited an inverted 'V' or 'U' shape, with the velocity of TM motion peaking in the mid-frequency range and becoming poorer at lower and higher frequencies. Among samples, maximum TM velocity correlated with animal length, perhaps because of a damping change in the larger TM. The frequency at maximum velocity negatively correlated with measurements of TM area. Presumably, with a larger TM area, the best frequency shifted downward because of increased middle-ear mass or decreased stiffness. The bandwidth of the transfer function negatively correlated with animal length, being broader in smaller animals and sharper in larger animals. This effect can be attributed to increased mass, decreased damping, or both. Among the middle-ear morphological measurements, the one most closely correlated with body length was the length of the extracolumellar anchorage at the TM. Among the physiological variables investigated, maximum velocity was negatively correlated with the frequency at which it occurred. The dependence of these transfer function variables on animal and ear size was similar, regardless of whether the comparison was among adults of species of different sizes, or among age classes within a species, so that age differences appear to be largely the result of size differences.

Mesencephalic and diencephalic afferent connections to the thalamic nucleus rotundus in the lizard, Psammodromus algirus.

The present work is an analysis of the afferent projections to the thalamic nucleus rotundus in a lizard, both at the light- and electron-microscopic level, using biotinylated dextran amine (BDA) as a neuroanatomical tracer. This study has confirmed previously reported afferent projections to nucleus rotundus in reptiles and has also identified a number of new cellular aggregates projecting to this dorsal thalamic nucleus. After BDA injections into nucleus rotundus, retrogradely labelled neurons were observed consistently within the following neuronal groups in the midbrain and the diencephalon: (i) the stratum griseum centrale of the optic tectum; (ii) the nucleus subpretectalis in the pretectum; (iii) the nucleus ansa lenticularis posterior, the posterior nucleus of the ventral supraoptic commissure, and the posteroventral nucleus, in the dorsal thalamus and (iv) the lateral suprachiasmatic nucleus and part of the reticular complex in the ventral thalamus. Tectal axons entering nucleus rotundus were fine and varicose and formed exclusively asymmetric synaptic contacts, mainly on small dendritic profiles. Rotundal neurons had symmetric synapses made by large boutons probably of nontectal origin. After comparing our results with those in other reptiles, birds and mammals, we propose that the sauropsidian nucleus rotundus forms part of a visual tectofugal pathway that conveys mesencephalic visual information to the striatum and dorsal ventricular ridge, and is similar to the mammalian colliculo-posterior/intralaminar-striatoamygdaloid pathway, the function of which may be to participate in visually guided behaviour.

Expression of calcium-binding proteins in the diencephalon of the lizard Psammodromus algirus.

This work is a study of the distribution pattern of calbindin-D28k, calretinin, and parvalbumin in the diencephalic alar plate of a reptile, the lizard Psammodromus algirus, by using the prosomeric model (Puelles [1995] Brain Behav Evol 46:319-337), which divides the alar plate of the diencephalon into the caudorostrally arranged pretectum (p1), dorsal thalamus plus epithalamus (p2), and ventral thalamus (p3). Calbindin and calretinin are more extensively expressed in the dorsal thalamus than in the neighboring alar regions, and therefore these calcium-binding proteins are particularly suitable markers for delimiting the dorsal thalamus/epithalamus complex from the ventral thalamus and the pretectum. Conversely, parvalbumin is more intensely expressed in the pretectum and ventral thalamus than in the dorsal thalamus/epithalamus complex. Within the dorsal thalamus, calcium-binding protein immunoreactivity reveals a three-tiered division. The pretectum displays the most intense expression of parvalbumin within the diencephalon. Virtually all nuclei in the three sectors of the pretectum (commissural, juxtacommissural, and precommissural) present strong to moderate expression of parvalbumin. We compare the distribution of calcium-binding proteins in the diencephalon of Psammodromus with other vertebrates, with mammals in particular, and suggest that the middle and ventral tiers of the reptilian dorsal thalamus may be comparable to nonspecific or plurimodal posterior/intralaminar thalamic nuclei in mammals, on the basis of the calcium-binding protein expression patterns, as well as the hodological and embryological data in the literature.

Light and electron microscopic evidence for projections from the thalamic nucleus rotundus to targets in the basal ganglia, the dorsal ventricular ridge, and the amygdaloid complex in a lizard.

To elucidate the organization and evolution of the tectorotundotelencephalic pathways in birds and reptiles, we reinvestigated at both light and electron microscopic levels the efferent projections of nucleus rotundus in a lizard, using the sensitive tracer biotinylated dextran amine. Our results indicate that nucleus rotundus projects to targets in the basal ganglia (lateral parts of striatum and olfactory tubercle and possibly the globus pallidus), the anterior dorsal ventricular ridge (ADVR), and the amygdaloid complex (the central and possibly lateral amygdaloid nuclei). In these targets, the rotundal axon terminals establish asymmetric, presumably excitatory synaptic contacts, usually with dendrites of local cells. In the ADVR, the rotundal projection terminates in two separate radial regions showing distinct cytoarchitecture: 1) a dorsolateral region that extends radially from the dorsolateral ADVR ventricular surface to the ventral part of the lateral cortex and 2) the lateral part of a ventromedial region that extends radially from the dorsomedial and medial ADVR ventricle to a superficial area interposed between the dorsolateral ADVR and the striatum. These two ADVR regions have different connections with the thalamus and telencephalon, which suggests that they may be involved in different degrees of integration. Our study also suggests that the rotundal projection to the ventromedial ADVR field of lizards may be comparable to the rotundoectostriatal/periectostriatal projection of birds. The connections and pathways involving nucleus rotundus suggest that this nucleus conveys visual information which may play a role in visuomotor, emotional, and visceral functions.

Afferents to the red nucleus in the lizard Podarcis hispanica: putative pathways for visuomotor integration.

The afferents to the red nucleus from visual and nonvisual forebrain centers have been investigated in the lizard Podarcis hispanica by using both retrograde and anterograde transport of tracers. Because the red nucleus constitutes a key structure in the limb premotor system, these sensory afferents probably are involved in visuomotor and other forms of sensorimotor integration. After tracer injections aimed at the red nucleus, retrograde labeling was found in the reticular thalamus, the subthalamus, the nucleus of the posterior commissure, as well as in two retinorecipient nuclei, namely, the ventral lateral and pretectal geniculate nuclei, where labeled cells are especially abundant. These geniculorubral projections have been confirmed by means of anterograde tracing with dextranamine injections. On the other hand, small injections of tracers in the retina demonstrated that its projections to the ventral lateral and pretectal geniculate nuclei are organized in a point-to-point fashion. Moreover, small tracer injections into the optic tectum of Podarcis indicated that the ventral lateral geniculate nucleus also receives a precisely organized tectal afferent. Taken together, these results strongly suggest that geniculorubral projections might constitute the neuroanatomical substrate for the generation of quick locomotor responses to appropriate visual stimuli. Additional ventral thalamic, subthalamic, and pretectal afferents to the red nucleus are likely to subserve other kinds of sensorimotor integration. These results help to clarify the organization of the reptilian motor system, including the telencephalic control of motor responses, and to unravel some of the major trends in the evolution of the limb premotor network of tetrapodian vertebrates.

Species-specific differences in the corticohypothalamic connections of lizards.

In lizards, information from the various senses is relayed to the hypothalamus via the cortico-septo-hypothalamic pathway. It appears that the anatomical organization of the incoming fibres in the medial cortex differs considerably between the various lizard species. In the present account it is shown that it is the location of the termination of the incoming fibres in the medial cortex that determines what kind of sensory information will reach the hypothalamic centres that are responsible for sexual and feeding behaviour.

Septal complex of the telencephalon of lizards: III. Efferent connections and general discussion.

The projections of the septum of the lizard Podarcis hispanica (Lacertidae) were studied by combining retrograde and anterograde neuroanatomical tracing. The results confirm the classification of septal nuclei into three main divisions. The nuclei composing the central septal division (anterior, lateral, medial, dorsolateral, and ventrolateral nuclei) displayed differential projections to the basal telencephalon, preoptic and anterior hypothalamus, lateral hypothalamic area, dorsal hypothalamus, mammillary complex, dorsomedial anterior thalamus, ventral tegmental area, interpeduncular nucleus, raphe nucleus, torus semicircularis pars laminaris, reptilian A8 nucleus/substantia nigra and central gray. For instance, only the medial septal nucleus projected substantially to the thalamus whereas the anterior septum was the only nucleus projecting to the caudal midbrain including the central gray. The anterior and lateral septal nuclei also differ in the way in which their projection to the preoptic hypothalamus terminated. The midline septal division is composed of the dorsal septal nucleus, nucleus septalis impar and nucleus of the posterior pallial commissure. The latter two nuclei projected to the lateral habenula and, at least the nucleus of the posterior pallial commissure, to the mammillary complex. The dorsal septal nucleus projected to the preoptic and periventricular hypothalamus and the anterior thalamus, but its central part seemed to project to the caudal midbrain (up to the midbrain central gray). Finally, the ventromedial septal division (ventromedial septal nucleus) showed a massive projection to the anterior and the lateral tuberomammillary hypothalamus. Data on the connections of the septum of P. hispanica and Gecko gekko are discussed from a comparative point of view and used for better understanding of the functional anatomy of the tetrapodian septum.

Ascending projections from the optic tectum in the lizard Podarcis hispanica.

The ascending projections of the optic tectum, including their cells of origin, have been studied in the lizard Podarcis hispanica by means of a two-step experimental procedure. First, tracers were injected in the tectum to study the anterograde labeling in the forebrain. Second, the cells of origin of these projections have been identified by analyzing the retrograde labeling after tracer injections in the thalamus, hypothalamus, and pretectum. Three main tectal ascending pathways have been described: the dorsal tecto-thalamic tract (dtt), the medial tecto-thalamic tract (mtt), and the ventral tecto-thalamic tract (vtt). The dtt originates in radial cells of layers 5 and 7 and bipolar cells of layers 8 and 10 that project to the lateral neuropile of the dorsal lateral geniculate nucleus (GLD), to the intergeniculate leaflet (IGL), and to the ventral lateral geniculate nucleus (GLV). The mtt arises from radial neurons of layers 3 and 5 and bilaterally reaches the putative reticular thalamus and its boundary with the hypothalamus, the rostral IGL, and the area triangularis (AT). The vtt is composed of fibers from ganglion and multipolar cells of the layer 7 that project bilaterally to the nucleus of the vtt, the ventrolateral thalamic nucleus, the medial posterior thalamic nucleus (MP), the nucleus rotundus (Rot), the IGL, and the cell plate of the GLD. Therefore, the GLD receives not only direct retinal afferents but also two different tectal inputs, thus constituting a convergence point in the two visual pathways to the telencephalon. Moreover, different tectal cells specifically project to the ventrolateral thalamus and to pretectal nuclei. These results are discussed from comparative and functional viewpoints.

[The processing of Gekko gecko and the pharmacological action of its different parts].

Both pharmacologic and toxic experiments are made on different parts of Gekko gecko Linnaeus. The results show that Gekko gecko Linnaeus' heads and its feet have obvious pharmacological action without any toxic or side effects, which provides a sound basis for the increase in its clinical utilization and the expansion of its medicinal parts as well as guarantee of safety and effectiveness after taking the medicine.

Septal complex of the telencephalon of the lizard Podarcis hispanica. II. Afferent connections.

The afferent connections to the septal complex were studied in the lizard Podarcis hispanica (Lacertidae) by means of a combination of retrograde and anterograde tracing. The results of these experiments allow us to classify the septal nuclei into three main divisions. The central septal division (anterior, lateral, dorsolateral, ventrolateral, and medial septal nuclei plus the nucleus of the posterior pallial commissure) receives a massive, topographically organized, cortical projection (medial, dorsal, and ventral areas) and widespread afferents from the tuberomammillary hypothalamus and the basal telencephalon. Moreover, it receives discrete projections from the dorsomedial anterior thalamus, the ventral tegmentum, the midbrain raphe, and the locus coeruleus. The ventromedial septal division (ventromedial septal nucleus) receives a massive projection from the anterior hypothalamus, dense serotonergic innervation, and a faint amygdalohypothalamic projection, but it is devoid of direct cortical input. The midline septal division (nucleus septalis impar and dorsal septal nucleus) receives a nontopographic cortical projection (dorsomedial and dorsal cortices) and afferents from the preoptic hypothalamus, the dorsomedial anterior thalamus, the midbrain central gray, and the reptilian A8 nucleus/substantia nigra. Our results indicate that the cortex provides a physiologically complex, massive input to the septum that terminates over the whole dendritic tree of septal cells. In contrast, most of the ascending afferents make axosomatic contacts by means of pericellular nests. The chemical nature of the main septal afferents and the comparative implications of the available hodological data on the organization of the septal complex of tetrapod vertebrates are discussed.

The retinopetal visual system in the chameleon (Chameleo chameleon).

Intraocular injections of rhodamine and horseradish peroxidase in chameleon, labelled retrogradely neurons in the ventromedial tegmental region of the mesencephalon and the ventrolateral thalamus of the diencephalon. In both areas, staining was observed contralaterally to the injected eye. Labelling was occasionally observed in some rhombencephalic motor nuclei. These results indicate that chameleons, unlike other reptilian species, have two retinopetal nuclei.