How phylogeny and foraging ecology drive the level of chemosensory exploration in lizards and snakes.

The chemical senses are crucial for squamates (lizards and snakes). The extent to which squamates utilize their chemosensory system, however, varies greatly among taxa and species' foraging strategies, and played an influential role in squamate evolution. In lizards, 'Scleroglossa' evolved a state where species use chemical cues to search for food (active foragers), whereas 'Iguania' retained the use of vision to hunt prey (ambush foragers). However, such strict dichotomy is flawed as shifts in foraging modes have occurred in all clades. Here, we attempted to disentangle effects of foraging ecology from phylogenetic trait conservatism as leading cause of the disparity in chemosensory investment among squamates. To do so, we used species' tongue-flick rate (TFR) in the absence of ecological relevant chemical stimuli as a proxy for its fundamental level of chemosensory investigation, that is baseline TFR. Based on literature data of nearly 100 species and using phylogenetic comparative methods, we tested whether and how foraging mode and diet affect baseline TFR. Our results show that baseline TFR is higher in active than ambush foragers. Although baseline TFRs appear phylogenetically stable in some lizard taxa, that is a consequence of concordant stability of foraging mode: when foraging mode shifts within taxa, so does baseline TFR. Also, baseline TFR is a good predictor of prey chemical discriminatory ability, as we established a strong positive relationship between baseline TFR and TFR in response to prey. Baseline TFR is unrelated to diet. Essentially, foraging mode, not phylogenetic relatedness, drives convergent evolution of similar levels of squamate chemosensory investigation.

Measurement of angular distributions of Drell-Yan dimuons in p+p interactions at 800 GeV/c.

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range 4.5

Measurement of Upsilon production for p + p and p + d interactions at 800 GeV/c.

We report a high statistics measurement of Upsilon production with an 800 GeV/c proton beam on hydrogen and deuterium targets. The dominance of the gluon-gluon fusion process for Upsilon production at this energy implies that the cross section ratio, sigma(p+d-->Upsilon)/2sigma(p+p-->Upsilon), is sensitive to the gluon content in the neutron relative to that in the proton. Over the kinematic region 0

Measurement of angular distributions of Drell-Yan dimuons in p+d interactions at 800 GeV/c.

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a deuterium target. The muon angular distributions in the dilepton rest frame have been measured over the kinematic range 4.5

J/psi polarization in 800-GeV p-Cu interactions.

We present measurements of the polarization of the J/psi produced in 800-GeV proton interactions with a copper target. Polarization of the J/psi is sensitive to the ccmacr; production and hadronization processes. A longitudinal polarization is observed at large x(F), while at small x(F) the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus p(T).

Location of fruit using only airborne odor cues by a lizard.

Although squamate reptiles are known to locate conspecifics by scent-trailing and to locate and identify prey by tongue-flicking substrates, an ability to locate food using only airborne cues has previously only been suspected based on observations that dead animals can be used as bait for Komodo dragons and that some nocturnal geckos aggregate on flowers. We conducted a simple field test of the ability of the omnivorous lizard Podarcis lilfordi to find fruit hidden under opaque cups. When a board having two identical cups spaced 1 m apart, one empty and the other hiding a freshly cut piece of apricot, was placed in the habitat, lizards first contacted the cup hiding fruit at well above chance frequency. Upon contact with a cup, lizards were significantly more likely to stay next to the cup, tongue-flick at high rates, climb the cup, and attempt to bite the cup if it hid a piece of apricot. The ability to follow a concentration gradient of airborne volatile chemicals to its source is very likely mediated by olfaction, but participation by or primacy of vomerolfaction cannot be excluded.

Chemosensory responses to sugar and fat by the omnivorous lizard Gallotia caesaris: with behavioral evidence suggesting a role for gustation.

Many lizards can identify food using only chemical cues, as indicated by tongue-flicking for chemical sampling and biting, but the effectiveness of the chemical components of food are unknown, as is the relationship between response strength and concentration. We investigated responses by the omnivorous lizard Gallotia caesaris to representatives of two major categories of organic food chemicals, lipids and carbohydrates. The stimuli, pork fat and sucrose solutions of varying concentration, were presented to lizards on cotton swabs and their lingual and biting behaviors were observed during 60-s tests. In the first experiment, fat elicited more tongue-flicks and bites than saturated sucrose or water (odorless control), biting being limited to the fat condition. Lizards licked at high rates, but exclusively in response to sucrose. A lick was a lingual protrusion in which the dorsal surface of the tongue contacted the swab, in contrast to the anteroventral contact made during tongue-flicks. In a second experiment, the number of licks, but not the number of tongue-flicks, increased with the concentration of sucrose. The results indicate that lipids contribute to prey chemical discrimination and are adequate to release some attacks, but are not as effective as releasers of attack as mixtures of prey chemicals obtained from prey surfaces. The findings with respect to licking are novel, and suggest that licking may be a response to gustatory stimulation by sugar, in contrast to previously observed prey chemical discriminations shown to require vomerolfaction.

Food chemical cues elicit general and population-specific effects on lingual and biting behaviors in the lacertid lizard Podarcis lilfordi.

Actively foraging lizards are capable of identifying prey using only chemical cues sampled by tongue-flicking, and the relatively few omnivorous and herbivorous lizards tested similarly can identify both animal and plant foods from chemical cues. Whether lizards that eat plants respond to cues specific to preferred plant types and whether there is geographic variability in responses to cues from various plants correlated with the importance of those plants in local diets is unknown. In three populations of an omnivorous lacertid, the Balearic lizard Podarcis lilfordi, we studied chemosensory sampling and feeding responses to chemical cues from plant and animal foods presented on cotton swabs. Each lizard population is endemic to one islet off the coast of Menorca, Balearic Islands, Spain. Lizards in all three populations discriminated chemical cues from plant and animal foods from control substances. Our results extend findings of prey chemical discrimination and plant chemical discrimination in omnivores, increasing confidence that correlated evolution has occurred between plant diet and chemosensory response to palatable plants. There were no consistent differences among populations in tongue-flicking and biting responses to stimuli from flowers of syntopic and allopatric plant species. The lizards may respond to cues indicative of palatability in a wide range of plant species rather than exhibiting strong responses only to locally available plant species. Nevertheless, tongue-flicking and biting frequencies varied among plant species, perhaps indicating food preferences. In addition, there were differences among populations in tongue-flick rates, latency to bite, and licking behavior. Licking was observed in only one lizard population as a response to floral chemicals from only one of the plants species tested, raising the possibility of a population-specific linkage between identification of a particular plant species and performance of an appropriate feeding response.

Energy loss of fast quarks in nuclei.

We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of 2H, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is -dE/dz = 2.32+/-0.52+/-0.5 GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in a nuclear environment.

Observation of polarization in bottomonium production at square root of s = 38.8 GeV.

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.

Responses to chemical cues from animal and plant foods by actively foraging insectivorous and omnivorous scincine lizards.

If tongue-flicking is important to lizards to sample chemical cues permitting identification of foods, tongue-flicking and subsequent feeding responses should be adjusted to match diet. This hypothesis can be examined for plant foods because most lizards are insectivores, but herbivory/omnivory has evolved independently in many lizard taxa. Here we present experimental data on chemosensory responses to chemical cues from animal prey and palatable plants by three species of the scincine lizards. When tested with chemical stimuli presented on cotton swabs, the insectivorous Eumeces fasciatus responded strongly to prey chemicals but not to chemicals from plants palatable to omnivorous lizards or to pungent or odorless control stimuli. Two omnivorous species, E. schneideri and Scincus mitranus, responded more strongly to chemical cues from both prey and food plants than to the control chemicals. All available data for actively foraging lizards, including these skinks, show that they are capable of prey chemical discrimination, and insectivores do not exhibit elevated tongue-flicking or biting responses to chemical cues from palatable plants. In all of the several species of herbivores/omnivores tested, the lizards show elevated responses to both animal and plant chemicals. We suggest two independent origins of both omnivory and plant chemical discrimination that may account for the evolution of diet and food chemical discriminations in the eight species of skinks studied, five of which are omnivores. All data are consistent with the hypothesis that acquisition of omnivory is accompanied by acquisition of plant chemical discrimination, but data on a broad diversity of taxa are needed for a definitive comparative test of the evolutionary hypothesis. J. Exp. Zool. 287:327-339, 2000.

Food chemical discriminations by an herbivorous lizard, Corucia zebrata.

Adjustment of chemosensory response to diet should be apparent in evolutionary changes corresponding to dietary shifts. Because most lizards are generalist predators of small animals, relationships between chemosensory behavior and diet are difficult to detect. Nevertheless, the evolution of herbivory by a small number of lizards provides an opportunity to detect any corresponding change in response to plant chemicals. I studied tongue-flicking and biting by the large, herbivorous scincid lizard Corucia zebrata in response to chemical cues from crickets, romaine lettuce, and control stimuli presented on cotton swabs. The skinks exhibited significantly stronger response to plant and animal chemicals than to controls for several variables: greater number of individuals that bit swabs, shorter latency to bite, greater rate of tongue-flicks, and greater tongue-flick attack score. The clearest differences were observed for tongue-flick attack score, a composite variable that combines the effects of tongue-flicking and biting. An insectivorous member of the same subfamily, Scincella lateralis, shows strong tongue-flicking and biting response to chemical prey cues, but not to plant chemicals. This suggests that response to plant chemicals by C. zebrata may have evolved in tandem with the incorporation of plants into the diet and that response to cricket chemicals has been retained, perhaps due to similarities between plant and animal food. The findings support the hypothesis that dietary shifts induce corresponding changes in chemosensory response, but provide only a single independent contrast for a study of correlated evolution between plant diet and chemosensory response to plants. J. Exp. Zool. 286:372-378, 2000.

Effects of estrogen and male head coloration on chemosensory investigation of female cloacal pheromones by male broad-headed skinks (Eumeces laticeps).

Indirect experimental evidence suggests that pheromone production and responsiveness to pheromones in a lizard, the broad-headed skink (Eumeces laticeps), are regulated by sex steroid hormones. For study of estrogenic effects on female pheromone levels, tongue flicking by males was recorded in response to chemical samples from the female cloaca, the secretion site of the female sex pheromone. Cloacal chemicals from estrogen-treated females elicited higher tongue flick rates by all males than samples from sham-injected females. Male head coloration is bright orange in the breeding season, but fades to tan outside the breeding season. The availability of males having the full range of head coloration due to asynchronous onset of breeding condition in a laboratory population made it possible to examine the relationship between head coloration and responsiveness to female pheromones. Males with brightly colored heads, presumably reflecting higher underlying androgen levels, performed more tongue flicks in response to cloacal chemicals from estrogen-treated females than did males with tan heads. Male head coloration did not affect responsiveness to cloacal chemicals from sham-injected females.

Evolution and function of lingual shape in lizards, with emphasis on elongation, extensibility, and chemical sampling.

Major squamate taxa exhibit extreme variation in lingual morphology, presumably due to correlated variation in trophic and chemosensory functions. Data are presented on evolution of lingual shape documenting several trends: (1) Resting lingual elongation is greatest in families specialized for lingual chemosensory sampling. (2) The greatest increase in elongation achievable by intralingual means including elasticity and foretongue retractility occurs in families with intermediate degrees of lingual specialization for chemosensory sampling. Sampling efficiency may be enhanced by the ability to extend the tongue well beyond the mouth, with resting elongation and intralingual extensibility perhaps jointly determining distance extended. In families lacking sufficient resting elongation, augmentation of intralingual extensibility may be a means of approaching optimal protrusion distances. Decreased extensibility evolved in tandem with the greatest resting elongation, suggesting that resting elongation may be more efficient for protrusion and that elasticity declines as optimal resting length is approached. The optimal shape for chemosensory sampling may be predicted to be highly elongate, as in teiids, varanids, and colubrids. The tongue should be broad at the tip for prehension (as in iguanians), fleshy for manipulation and swallowing, and broad at the base for tamping prey into the esophagus. (3) Lingual surface area relative to that of a rectangle of dimensions length × base width varies accordingly. Relative area is high in families that do not tongue-flick much while foraging because tongues are broad and fleshy throughout their length. It is low in families that have wedge-shaped tongues and intermediate specialization for chemosensory sampling. Narrowing of the anterior tongue may improve chemical sampling. Relative lingual area in chemosensory specialists is very high, with progressive narrowing toward the base as optimal sampling shape is approached in taxa lacking lingual function in swallowing, prehension or prey manipulation.

Prolonged poststrike elevation in tongue-flicking rate with rapid onset in gila monster,Heloderma suspectum: Relation to diet and foraging and implications for evolution of chemosensory searching.

Experimental tests showed that poststrike elevation in tongue-flicking rate (PETF) and strike-induced chemosensory searching (SICS) in the gila monster last longer than reported for any other lizard. Based on analysis of numbers of tongue-flicks emitted in 5-min intervals, significant PETF was detected in all intervals up to and including minutes 41-45. Using 10-min intervals, PETF lasted though minutes 46-55. Two of eight individuals continued tongue-flicking throughout the 60 min after biting prey, whereas all individuals ceased tongue-flicking in a control condition after minute 35. The apparent presence of PETF lasting at least an hour in some individuals suggests that there may be important individual differences in duration of PETF. PETF and/or SICS are present in all families of autarchoglossan lizards studied except Cordylidae, the only family lacking linguallly mediated prey chemical discrimination. However, its duration is known to be greater than 2-min only in Helodermatidae and Varanidae, the living representatives of Varanoidea. That prolonged PETF and SICS are typical of snakes provides another character supporting a possible a varanoid ancestry for Serpentes. Analysis of 1-min intervals showed that PETF occurred in the first minute. A review of the literature suggests that a pause in tongue-flicking and delay of searching movements are absent in lizards and the few nonvenomous colubrid snakes tested. The delayed onset of SICS may be a specific adaptation of some viperid snakes to allow potentially dangerous prey to be rendered harmless by venom following voluntary release after envenomation and preceding further physical contact with the prey.

Chemical discrimination by tongue-flicking in lizards: A review with hypotheses on its origin and its ecological and phylogenetic relationships.

Tongue-flicking is a synapomorphy of squamate reptiles functioning to sample chemicals for vomerolfactory analysis, which became possible in primitive squamates when ducts opened from the vomeronasal organs to the roof of the mouth. Extant iguanian lizards in families that do not use the tongue to sample chemical prey cues prior to attack partially protrude it in two feeding contexts: during capture by lingual prehension and after oral contact with prey. These lizards do not exhibit strike-induced chemosensory searching. Lingual prey prehension is present in iguanian lizards and inSphenodon, the sister taxon of Squamata. During attempts to capture prey, the tongues of primitive squamates inevitably made incidental contact with environmental substrates bearing chemicals deposited by prey, conspecifics, and predators. Such contact presumably induced selection for tongue-flicking and ability to identify biologically important chemicals. Most iguanian lizards are ambush foragers that use immobility as a major antipredatory defense. Because tongue-flicking at an ambush post would not allow chemical search beyond the vicinity of the head and would render them easier for predators and prey to detect, typical iguanians tongue-flick neither while foraging nor to identify predators. They do detect pheromones by tongue-flicking. Scleroglossan lizards are typically active foragers that rely on speed to escape. Being freer to move the tongue, they have evolved lingual sampling allowing detection of chemical cues of conspecifics, predators, and prey, as well as strike-induced chemosensory searching, some can follow pheromone trails by tongue-flicking. Some families have lingual morphology and behavior specialized for chemosensory sampling. In varanids and snakes, the taxa showing the greatest lingual specialization, additional prey-related chemosensory behaviors have evolved. In iguanian and scleroglossan families that have secondarily adopted the foraging mode typical of the other taxon, prey chemical discrimination involving tongue-flicking and strike-induced chemosensory searching are typical for the foraging mode rather than the taxon. Because foraging mode and state of prey chemical discrimination are stable within squamate families and to a large extent in higher taxa, both features have been retained from the ancestral condition in most families. However, in three cases in which foraging mode has changed from its ancestral state, the state of prey chemical discrimination has also changed, indicating that prey chemical discrimination is adaptively adjusted to foraging mode. Indeed, acquisition of lingually mediated prey chemical discrimination may have made feasible the evolution of active foraging, which in turn appears to have profoundly influenced the further evolution of squamate chemosensory structures and behavior, placing a selective premium on features enhancing the tongue's efficiency as a chemical sampling device. The advent of tongue-flicking to sample prey chemicals and thus detect hidden prey may have allowed generalist (cruise) or ambush foragers, if early squamates were such, to become specialists in active foraging. Alternatively, if the common ancestors of squamates were active foragers, the adoption of ambush foraging would have selected against participation of the tongue in locating prey. Acting jointly, tongue-flicking and active foraging have had momentous consequences for squamate diversification. Specialization for active foraging would appear to have had ramifying effects on antipredatory defenses, body form, territoriality, mating systems, and reproductive physiology.

Safety restraint usage in fatal motor vehicle crashes.

In 1987, following implementation of the Washington safety restraint mandatory usage law, collision statistics indicated an increase in motor vehicle crashes in which occupants had died while utilizing safety restraints. Because of concerns expressed by restraint use law advocates, a "Fatal Collision Research Team" was established to evaluate and reconstruct collisions in which restrained occupants had died. Collisions were analyzed over a three-year period and included 337 crashes involving 1,058 occupants, of whom 446 died. The team analyzed fatal collisions involving restrained occupants and documented restraint usage as well as severity of the crash. Crash severity was measured using either the Collision Deformation Classification (CDC) system, which defines the extent of crush to the vehicle, and/or intrusion into the passenger occupant area, or by measuring deceleration forces (delta v) acting on the vehicle, where sufficient data existed to do so. The survivability of the crash was determined individually for each occupant and independently of whether the occupant lived or died, as well as whether the occupant was restrained or not. The major findings were: (i) that in the majority of cases where a restrained occupant died, the fatality can be attributed to the extent of vehicle crush and deceleration forces, i.e. the crash forces and dynamics made the crash nonsurvivable, and (ii) restraint misuse seemed not to be a major contributory factor in fatal crash injuries.

Postbite elevation in tongue-flicking rate by an iguanian lizard,Dipsosaurus dorsalis.

The herbivorous iguanid lizardDipsosaurus dorsalis exhibited PETF (postbite elevation in tongue-flicking rate), an increase in tongue-flicking rate after experimental removal from the mouth of food that had been bitten. This was demonstrated by a significantly higher tongue-flick rate after having bitten food than in three experimental conditions controlling for responses to the experimental setting, sight of food, and mechanical disturbance caused by the experimental removal of food from a lizard's mouth. As in most other families of lizards, PETF was brief, occurring only during the first minute. Lizards are divided into two major suprafamilial taxa, Iguania and Scleroglossa, consisting of carnivorous species characterized by two major foraging modes, ambush and active, and of herbivores and omnivores. PETF is absent in the two families of carnivorous iguanian lizards studied that are ambush foragers but present in three families of scleroglossan lizards that are active foragers. However, PETF is absent in the two species studied in a scleroglossan family, Gekkonidae, which forages by ambush, and present in an iguanian herbivore, as reported herein. We propose that the presence or absence of PETF, in addition to its phylogenetic determinants, is adaptively adjusted to foraging mode.

Elevation in tongue-flick rate after biting prey in the broad-headed skink,Eumeces laticeps.

A postbite elevation in tongue-flicking (PETF) rate occurs in adult male broad-headed skinks,Eumeces laticeps. Males having bitten neonatal mice showed significantly higher tongue-flicking rates in the 2 min following experimental removal of the prey than did males in several control conditions. In a second experiment designed to separate the effects of tactile and chemical stimulation of the oral cavity during biting, males tongue-flicked at significantly higher rates in response to swabs bearing surface chemicals from neonatal mice than to identical swabs lacking the surface chemicals. These findings agree with previous data showing that PETF and searching movements occur in those families of lizards that can detect prey chemicals and use the tongue to do so during active foraging. The occurrence of PETF and putative searching movements supports the interpretation that PETF represents an attempt to relocate lost prey by chemosensory means. PETF was much briefer inE. laticeps than in many snakes and in a representative species from another lizard family and was not detectable after the first minute. This brevity is consistent with the prediction that PETF should be brief in squamates that feed on prey not likely to be located by scent-trailing.