Acoustic and Visual Display Behavior of Gekkonid Lizards

Visual and acoustic mechanisms of communication are compared.Their properties are found to be similar except that acousticsystems function more efficiently when light levels are low.The ability of geckos to receive and produce visual and acousticmessages is discussed. Geckos are found to have excellent visionand good hearing. They also possess the visual attributes andsound producing mechanisms necessary for complex displays. Thedisplay behavior of geckos is reviewed. Display types are categorizedaccording to the display mechanism used. Visual displays arefound to utilize color, pattern, posture, and movement. Thesedisplays are used in predator threat as well as in intraspecificsocial contexts such as aggression and courtship. Combined visual-acousticdisplays involve color, pattern, postures, movement, and sound.Combined displays are used in predator threat and in intraspecificaggressive encounters. Acoustic displays have little or no visualcomponent and involve sounds that may be single chirps or temporallypatterned multiple chirps. The single chirps are associatedwith distress while the multiple chirp calls are heard in intraspecificsocial contexts. The displays of diurnal and nocturnal geckosare compared and it is found that differences are correlatedwith differences in their diel activity cycles. In conclusion,it is pointed out that many areas remain to be studied beforegecko display behavior is well understood.     

High-elevation Adaptation of Motion Visual Display Modifications in the Toad-Headed Agamid Lizards(Phrynocephalus)

Understanding the process of adaptation is a key mission in modern evolutionary biology.Animals living at high elevations face challenges in energy metabolism d...     

Display Behavior and Habitat Use in Single and Mixed Populations of Anolis carolinensis and Anolis sagrei Lizards

Introduced species can have a variety of effects on the behavior and ecology of native species. We compared display behavior and habitat use of introduced Anolis sagrei and native Anolis carolinensis lizards across three sites in Southern Louisiana. The chosen sites were similar in that they were all located in urban settings with clumped vegetation. The first site contained only A. sagrei, the second supported sympatric A. sagrei and A. carolinensis populations, and the third site harbored only A. carolinensis. We found that (1) A. carolinensis perched significantly higher when A. sagrei was present, consistent with previous studies, whereas perch height of A. sagrei was not altered by the presence of A. carolinensis; (2) A. carolinensis in single and mixed sites exhibited different proportions of display types, with individuals at the mixed Tulane site performing significantly more C displays than those at the single site; and (3) Anolis sagrei at the Tulane mixed site exhibited less push‐ups than those in the site with A. sagrei alone. These data suggest that the arrival of congeners can affect display behavior of anoles, although such effects are different for the natives and the invaders.     

Predation Cost of Conspicuous Male Coloration in Collared Lizards (Crotaphytus collaris): An Experimental Test Using Clay-Covered Model Lizards

Animal color patterns are a compromise between sexual selection pressures that increase advantages accrued from conspicuousness, and natural selection pressures that decrease those advantages through reduced survivorship. Predation pressure, as a mode of natural selection, often is invoked as a counter‐selective force to sexual selection, yet few studies have demonstrated empirically that more conspicuous individuals experience higher rates of predation. We quantified predator attacks on models of collared lizards, Crotaphytus collaris, in three well‐studied populations (Oklahoma, USA). These populations differ in coloration and in visual backgrounds against which the lizards are viewed by conspecifics and predators. Attack frequencies varied considerably among study sites but at all sites the models exhibiting the strongest color contrast with local rocks were detected and attacked most often. By comparison, inconspicuous models of females were never attacked at any of the sites. These results suggest a survival cost of conspicuous coloration in collared lizards, and reiterate the importance of considering the visual environment as well as differences among populations when examining the influence of predation on the evolution of animal color patterns.     

Copper-Impaired Chemosensory Function and Behavior in Aquatic Animals

Chemosensation is one of the oldest and most important sensory modalities utilized by aquatic animals to provide information about the location of predators, location of prey, sexual status of potential mates, genetic relatedness of kin, and migratory routes, among many other essential processes. The impressive sophistication of chemical communication systems among aquatic animals probably evolved because of the selective pressures exerted by water as a “universal solvent.” Impairment of chemosensation by toxicants at the molecular or cellular level can potentially lead to major perturbations at higher levels of biological organization. We have examined the consequences of metal-impaired chemosensory function in a range of aquatic animals that represents several levels of a typical aquatic ecosystem. In each case, low, environmentally relevant metal concentrations were sufficient to cause chemosensory dysfunction. Because the underlying molecular signal transduction machinery of chemosensory systems demonstrates a high degree of phylogenetic conservation, we speculate that metal-impaired chemosensation among phylogenetically disparate animal groups probably results from a common mechanism of impairment. We propose developing a chronic chemosensory-based biotic ligand model (BLM) that maintains the advantages of the current BLM approach, while simultaneously overcoming known difficulties of the current gill-based approach and increasing the ecological relevance of current BLM predictions.     

Competition Between Insectivorous Lizards and Birds in Central Panama

The following evidence suggests that birds and lizards competefor their arthropod prey on islands in Lake Gatun, Panama: (1)there is extensive overlap between the diets of a representativebird and lizard, (2) at least one insectivorous lizard, Anolislimifrons, appears to be food-limited, (3) birds appear to havea major impact on arthropod abundances, (4) avian abundanceis negatively correlated with the physiological condition and,thus, with the fecundity of female A. limifrons, (5) bird andlizard population densities are negatively correlated. LakeGatun was formed in 1914. In the intervening years, a greatmany bird species have been lost from the smaller islands, butvery few lizard populations have gone extinct. Ninety-six percentof the between-site variation in avian abundances is accountedfor by the number of bird species present at a site. Sites withdepauperate avifaunas are characterized by low avian abundancesbecause the species present do not experience ecological release,and resources which are utilized by birds on species-rich sitesare not exploited by birds on species-poor sites. Thus, avianabundances are controlled by factors extrinsic to the bird-lizardinteraction, and lizards opportunistically increase their abundancesat sites with low avian abundances.     

Two New Trypanosomes from California Toads and Lizards

SYNOPSIS Trypanosoma bufophlebotomi n. sp. and T. scelopori n. sp. are described from the California toad Bufo boreas halophilus and the western fence lizard Sceloporus occidentalis , respectively. T. bufophlebotomi occurred in 15% of 39 toads examined and is characterized by a juxtanuclear, bipolar-staining kinetoplast. The parasite may share a common ancestry with another sandfly-transmitted trypanosome of toads from China. T. scelopori occurred in 0.4% of 758 lizards examined for malarial parasites. It may also develop in sandflies.     

Kinesis in Euplotes vannus-Ethological and Electrophysiological Characteristics of Chemosensory Behavior

ABSTRACT. Equally dispersed Euplotes vannus cells accumulate inside a drop of supernatant of a bacteria suspension that is surrounded by a reference solution. In the drop, frequencies of stops and backward jerks are tenfold increased. The sequences of directional changes and translocations prevent cells from leaving the chemostimulant region, as if they were trapped. This behavior is quickly induced after casual arrival in the drop and not by chemotactic influence over a larger distance. With intracellular recordings, we have found a K⁺ conductance decrease in chemically stimulated cells that prolongs the duration of spontaneously occurring depolarizations to 600-1,700 ms by delaying repolarization. The freely fluctuating membrane potential shifts to more depolarized levels, although the total potential range is expanded in the positive and negative direction by 5.5 and 3.8 mV, respectively. Chemosensory behavior is explained and discussed with respect to these electrophysiological events.     

Display Behavior in Tortoises

When compared to lizards or snakes, signals related to warningand threat are not very important in land tortoises. Withinsocial and sexual contexts, tactile and chemical signals seemmore important than visual, and certainly than auditor)' ones.Color patterns are rarely, if ever, sexually discriminatory.Seasonal color differences are rare. In general, positionalsignals are rather limited, chiefly because of the shell. However,shell positional changes are an important part of the visualand tactile signal repertory of all land tortoises. Head movementsare also important in several groups. Audible signals are poorlydeveloped. They are largely concerned with courtship and theirrole is not understood. Chemical signals are pronounced, especiallyin displays related to sex identification, largely based onscents associated with the cloaca. Tactile displays are importantparticularly during courtship. They include biting and especiallyshell ramming by the male. The tail is used as a tactile organduring courtship of some species.     

Pollinator Behavior Mediates Negative Interactions between Two Congeneric Invasive Plant Species

Simultaneously flowering plant species may indirectly interact with each other by influencing the quantity of pollinator visitation and/or the quality of pollen that is transferred. These effects on pollination may depend on how pollinators respond to floral resources at multiple levels. In this study, we demonstrate pollinator-mediated negative interactions between two invasive plants, Carduus acanthoides and Carduus nutans. Using constructed arrays of the two species, alone and in mixture, we quantified pollinator visitation at the patch and individual plant levels and measured seed production. We found that co-occurrence of our species led to a shift in pollinator services at both levels. Greater interference occurred when arrays were small and spacings between neighboring plants were large. A spatially explicit movement model suggests that pollinator foraging behavior, which mediates the interactions between plants, was driven by floral display size rather than species identity per se. Pollinator behavior significantly reduced the proportion of seed set for both species relative to that in single-species arrays. Overall, the dependence of pollinator behavior on patch size, spacing between plants, and patch composition can lead to pollinator-mediated plant interactions that range from facilitative to competitive.     

草蜥属两种蜥蜴卵和幼体特征的比较研究

比较研究了南草蜥和北草蜥实验条件下的卵及幼体特征。南草蜥产卵雌体的体长、最大窝卵数、平均卵重小于北草蜥 ,相对窝卵重与北草蜥相似。两种蜥蜴均通过增加卵长径和卵短径来增加卵重 ,但卵外形明显不同 ,南草蜥的卵较长。两种蜥蜴卵孵化过程中均吸水增重。相同孵化温度 ( 2 6℃ )条件下 ,南草蜥的孵化期明显比北草蜥长。南草蜥幼体的体重、体长、头长和头宽的实测值小于北草蜥 ,尾长实测值与北草蜥无显著差异。南草蜥幼体的体重、头长和头宽的矫正平均值小于北草蜥 ,尾长矫正平均值大于北草蜥 ,体长矫正平均值与北草蜥无显著差异。     

Two Heteromeric Kinesin Complexes in Chemosensory Neurons and Sensory Cilia of Caenorhabditis elegans

Chemosensation in the nervous system of the nematode Caenorhabditis elegans depends on sensory cilia, whose assembly and maintenance requires the transport of components such as axonemal proteins and signal transduction machinery to their site of incorporation into ciliary structures. Members of the heteromeric kinesin family of microtubule motors are prime candidates for playing key roles in these transport events. Here we describe the molecular characterization and partial purification of two heteromeric kinesin complexes from C. elegans, heterotrimeric CeKinesin-II and dimeric CeOsm-3. Transgenic worms expressing green fluorescent protein driven by endogenous heteromeric kinesin promoters reveal that both CeKinesin-II and CeOsm-3 are expressed in amphid, inner labial, and phasmid chemosensory neurons. Additionally, immunolocalization experiments on fixed worms show an intense concentration of CeKinesin-II and CeOsm-3 polypeptides in the ciliated endings of these chemosensory neurons and a punctate localization pattern in the corresponding cell bodies and dendrites. These results, together with the phenotypes of known mutants in the pathway of sensory ciliary assembly, suggest that CeKinesin-II and CeOsm-3 drive the transport of ciliary components required for sequential steps in the assembly of chemosensory cilia.     

An Analysis of Inter-Population Divergence in Visual Display Behavior of the Green Anole Lizard (Anolis carolinensis)

Variation in habitat structure can profoundly affect the evolution of visual displays in animals. We compared the field display behavior of two populations of the green anole lizard (Anolis carolinensis) in Southern Louisiana. These two populations occupy habitats varying markedly in structure (clumped vs. continuous), ecological setting (urban vs. natural) and the degree of male competition and predation. We filmed 56 large adult male lizards during the active spring reproductive period and detected substantial divergence in display behavior between populations. We found that (1) relative dewlap areas did not differ significantly between populations, (2) Tulane anoles spent about twice as much time displaying compared with Good Hope field anoles, although the average display duration did not differ significantly between populations, and (3) the two populations differed significantly in the relative frequency of display types: lizards from the Tulane population used a higher proportion of A and B display types, whereas Good Hope Field anoles used C displays more often. Finally, we detected differences in other aspects of display behavior (use of display modifiers, volley length distributions). We suggest that these display differences may result from differences in green anole male density (three times higher at Tulane), combined with habitat differences (clumped vs. continuous).     

Single Ionic Channels of Two Caenorhabditis elegans Chemosensory Neurons in Native Membrane

The genome of Caenorhabditis elegans contains representatives of the channel families found in both vertebrate and invertebrate nervous systems. However, it lacks the ubiquitous Hodgkin-Huxley Na+ channel that is integral to long-distance signaling in other animals. Nematode neurons are presumed to communicate by electrotonic conduction and graded depolarizations. This fundamental difference in operating principle may require different channel populations to regulate transmission and transmitter release. We have sampled ionic channels from the somata of two chemosensory neurons (AWA and AWC) of C. elegans. A Ca2+-activated, outwardly rectifying channel has a conductance of 67 pS and a reversal potential indicating selectivity for K+. An inwardly rectifying channel is active at potentials more negative than -50 mV. The inward channel is notably flickery even in the absence of divalent cations; this prevented determination of its conductance and reversal potential. Both of these channels were inactive over a range of membrane potentials near the likely cell resting potential; this would account for the region of very high membrane resistance observed in whole-cell recordings. A very-large-conductance (> 100 pS), inwardly rectifying channel may account for channel-like fluctuations seen in whole-cell recordings.     

Display Plasticity in Response to a Robotic Lizard: Signal Matching or Song Sharing in Lizards?

Many territorial songbirds alter the structure of their songs after listening to and interacting repeatedly with the same neighbors. Here, we use a robotic lizard to test for similar learned changes in signal structure in male Sagebrush lizards, Sceloporus graciosus. Subjects were exposed to two types of headbob displays (species‐typical and unusual) both in short‐term tests and in repeated exposures for 10 d. We found no evidence for immediate changes in signal structure to match a particular opponent (signal matching) or long‐term changes after repeated exposure (‘song’ sharing). If anything, the lizards’ displays became less like that of the robotic stimulus over time. Further tests of other taxa are needed to identify the evolutionary forces that lead to these forms of behavioral plasticity and to determine whether song sharing and signal matching are unique characteristic of songbirds. Lizards also became more agitated and produced more highly aggressive displays of their own when confronted with headbob displays that violated the basic syntactic structure of their display system, confirming that they were paying attention to subtle differences in display structure despite the artificial nature of the treatments. Thus, our study also adds to the growing evidence supporting the use of robotic playbacks to study animal communication.     

Evolutionary Changes in Dopaminergic Modulation of Courtship Behavior in Cnemidophorus Whiptail Lizards

Preoptic dopamine release is integral to the display of copulatory behaviors in male mammals and birds. However, while the anatomical distributions of the dopamine synthesizing enzyme tyrosine hydroxylase are similar among vertebrates, evolutionary changes in the functional role of dopamine are poorly understood. In this study, we tested whether a dopamine D1 receptor agonist would facilitate the display of courtship and copulatory behaviors in two related Cnemidophorine lizards (Cnemidophorus inornatus and Cnemidophorus uniparens). Cnemidophorus lizards offer a unique system to study evolutionary changes in functionality because ancestral (e.g., C. inornatus) and descendant (e.g., C. uniparens) species can be studied in parallel. Cnemidophorus uniparens is an all-female, parthenogenetic species and is the triploid descendant of the sexual and diploid species C. inornatus. Here we report that in castrated male C. inornatus and ovariectomized C. uniparens a dopamine D1 agonist increased the proportion of individuals mounting and decreased the latency to mount. Moreover, there was a species difference in sensitivity to the agonist: Mounting was elicited at a lower dose in C. uniparens than in C. inornatus. One possible explanation for this heightened sensitivity in the triploid parthenogen is that, by virtue of the increased ploidy, the parthenogen has elevated levels of D1 receptor in limbic brain areas modulating courtship behavior.     

Cellular Differences Between True Negative and False Negative Papanicolaou Smears

A matched case-control study of 123 false negative Papanicolaou smears and 488 true negative Papanicolaou smears was undertaken to determine the association between the types of cells present on the smear and the correctness of the cytology report. the false negative slides were significantly more likely to include endocervical columnar cells than the true negative slides (odds ratio 1.90, 95% confidence interval (CI) 1.21–3.01). No statistically significant difference in metaplastic cell status was evident (odds ratio 1.48, 95% CI 0.95–2.30). When considered together, metaplastic and/or columnar cells were significantly more likely to be present in false negative smears than in true negative smears (odds ratio 1.87, 95% CI 1.13–3.08). the implications of these findings for improving the accuracy of cervical cytology for the detection of precancerous lesions are discussed.