Tongue Extrusion Research Articles

Functional morphology of hummingbird bill tips: their function as tongue wringers

Nectarivores are animals that have evolved adaptations to efficiently exploit floral nectar as the main source of energy in their diet. It is well known that hummingbirds can extract nectar with impressive speed from flowers. However, despite decades of study on nectar intake rates, the mechanism by which feeding is ultimately achieved − the release of nectar from the tongue so that it can pass into the throat and be ingested − has not been elucidated. By using microCT scanning and macro high-speed videography we scrutinized the morphology and function of hummingbird bill tips, looking for answers about the nectar offloading process. We found near the bill tip, in an area of strong lateral compression of internal mandibular width, that the tomia (cutting edges of the bill) are thinner, partially inrolled, and hold forward-directed serrations. Aligned with these structures, a prominent pronglike structure projects upward and forward from the internal mandibular keel. Distal to this mandibular prong, another smaller maxillary prong protrudes downwards from the keel of the palate. Four shallow basins occur at the base of the mandibular prong on the mandibular floor. Of these, two are small basins located proximally and at the sides of the mandibular prong. A third, slightly larger basin is positioned distally to the first two and directly under the maxillary prong. And the fourth basin, the largest, is found more proximally where the bill becomes thicker, as seen from the side. We documented that this group of structures is integrated into the area of the bill where tongue extrusion occurs, and we hypothesize that they function to enhance the nectar release at each lick. We suggest that this “wringer”, operated by bill and tongue movements, helps to move nectar towards the throat.

Intersexual chemo-sensation in a "visually-oriented" lizard, Anolis sagrei.

While the conspicuous visual displays of anoles have been studied in great depth, the possibility that these lizards may also interact through chemical signalling has received hardly any consideration. In this study, we observed the behaviour of male brown anoles (Anolis sagrei) when introduced into an environment previously inhabited by female conspecifics, and compared it to when they were introduced into an untreated environment. The males in our tests exhibited significantly more elaborate display behaviour (i.e., greater number of dewlap extensions and head-nods) and a significantly greater number of tongue extrusions while in the cage formerly occupied by females than when placed in the untreated, control cage. The absolute numbers of tongue extrusions, however, were relatively low in comparison to average tongue-flick rates of ‘true’ chemically-oriented lizards. Our results strongly suggest that the males were capable of detecting chemical cues left behind by the females. These observations provide the first evidence of intersexual chemo-sensation in an anole lizard.

Blood corticosterone levels and intersexual selection games: best-of-bad-job strategies of male common lizards

Glucocorticoids affect physiology and behaviour, reproduction and potentially sexual selection as well. Short-term and moderate glucocorticoid elevations are suggested to be adaptive, and prolonged and high elevations may be extremely harmful. This suggests that optimal reproductive strategies, and thus sexual selection, may be dose dependent. Here, we investigate effects of moderate and high elevations of blood corticosterone levels on intra- and intersexual behaviour and mating success of male common lizards Lacerta vivipara. Females showed less interest and more aggressive behaviour towards high corticosterone males and blood corticosterone levels affected male reproductive strategy. Males of moderate and high corticosterone elevations, compared with Control males, showed increased interest (i.e., higher number of chases, tongue extrusions, and approaches) towards females and high corticosterone males initiated more copulation attempts. However, neither increased male interest nor increased copulation attempts resulted in more copulations. This provides evidence for a best-of-a-bad-job strategy, where males with higher corticosterone levels compensated for reduced female interest and increased aggressive female behaviour directed towards them, by showing higher interest and by conducting more copulation attempts. Blood corticosterone levels affected intrasexual selection as well since moderate corticosterone levels positively affected male dominance, but dominance did not affect mating success. These findings underline the importance of female mate choice and are in line with adaptive compensatory behaviours of males. They further show that glucocorticoid effects on behaviour are dose dependent and that they have important implications for sexual selection and social interactions, and might potentially affect Darwinian fitness.

Leaving a bad taste in your mouth but not in my insula

Previous research has implicated regions of anterior insula/frontal operculum in processing conspecific facial expressions of disgust. It has been suggested however that there are a variety of disgust facial expression components which relate to the disgust-eliciting stimulus. The nose wrinkle is predominantly associated with irritating or offensive smells, the mouth gape and tongue extrusion with distaste and oral irritation, while a broader range of disgust elicitors including aversive interpersonal contacts and certain moral offenses are associated primarily with the upper lip curl. Using functional magnetic resonance imaging, we show that activity in the anterior insula/frontal operculum is seen only in response to canonical disgust faces, exhibiting the nose wrinkle and upper lip curl, and not in response to distaste facial expressions, exhibiting a mouth gape and tongue protrusion. Canonical disgust expressions also result in activity in brain regions linked to social cognition more broadly, including dorsal medial prefrontal cortex, posterior cingulate cortex, temporo-parietal junction and superior temporal sulcus. We interpret these differences in relation to the relative functional and communicative roles of the different disgust expressions and suggest a significant role for appraisal processes in the insula activation to facial expressions of disgust.

Chemosensory Response of Desert Iguanas (Dipsosaurus dorsalis) to Skin Lipids from A Lizard‐Eating Snake (Lampropeltis getula californiae)

AbstractSeveral species of lizards respond to chemicals from sympatric lizard‐eating snakes with increased tongue‐extrusion rates. These substances also elicit antipredator behavior indicating that they have important ecological functions and the resulting behavior can have serious implications for individual fitness of lizards. However, the source and type of snake chemical cues that elicit these behavioral changes in lizards have yet to be determined. We tested the ability of adult desert iguanas (Dipsosaurus dorsalis) to detect and identify a potential predator by exposing them to lipids extracted from shed snakeskins. Lipids were extracted from cast skins of a known lizard‐eating snake, the California kingsnake (Lampropeltis getula californiae), using chloroform and methanol. Test subjects were presented with skin lipids as well as clean, pungent, and chloroform controls on cotton‐tipped applicators in random order. Desert iguanas directed significantly more tongue extrusions toward applicators bearing snakeskin lipids when compared with controls. In addition, overall tongue‐extrusion frequency increased following exposure to lipids during the 5‐min trials. Desert iguanas clearly detected snakeskin lipids, but this stimulus failed to elicit changes in body posture and movement patterns previously observed in experiments using chemical cues from live snakes. Increased tongue flicking by lizards in response to snakeskin lipids may represent a generalized response to this class of chemicals. Additional potential sources of chemicals used in the detection of lizard‐eating snakes are discussed.

Food-deprivation affects tongue extrusions as well as attractivity and proceptivity components of sexual behavior in the lizard, Sceloporus jarrovii

AbstractExperiments were conducted to assess the effect of various levels of food deprivation (1, 2, 3, or 4-day periods) on tongue extrusions as well as attractivity and proceptivity components of sexual behavior in the sceloperine lizard Sceloporus jarrovii. Results showed sex differences with respect to effects of food deprivation on the attractiveness of male and female lizard odors toward conspecifics (attractivity). Males spent more time extruding their tongue to touch blocks containing odors of ad libitum-fed females as compared to odors from females deprived of food for 4 days, while spending a similar amount of time investigating blocks containing odors of ad libitum-fed females and females deprived of food for less than 4 days. In contrast, females spent similar amounts of time investigating odors associated with ad libitum-fed as well as food-deprived conspecifics. Results also showed that one day of food deprivation was sufficient to inhibit the desire to initiate or maintain contact with opposite-sex conspecifics (receptivity).

Chemosensory Identification of Lizard-Eating Snakes in the Desert Iguana, Dipsosaurus dorsalis (Squamata: Iguanidae)

Many antipredator behaviors function by hindering the ability of a predator to catch or consume prey once they are encountered. However, prey may also reduce predation risks by detecting predators before an encounter occurs. We tested the ability of the desert iguana (Dipsosaurus dorsalis) to detect and identify snake predators via chemoreception. Desert iguanas were exposed to chemicals from two sympatric snake species. The California kingsnake (Lampropeltis getula californiae), a species known to feed on lizards, was used as the predator stimulus, whereas the western shovel-nosed snake (Chionactis occipitalis), which feeds only on arthropods, served as a control for a general response to snake chemicals. Lizards were placed in terraria that previously housed live snakes or had been treated with distilled water or a pungent control. Overall tongue extrusion frequency and number of tongue extrusions prior to movement increased in response to chemicals from the California kingsnake but not in response to the western shovel-nosed snake. In addition, desert iguanas exhibited unusual slowness of movement and adopted a distinctive body posture in response to the predator stimulus. These results demonstrate that desert iguanas can detect chemical deposits from snakes and can discriminate between a snake species that feeds on lizards and one that poses no threat. In addition, the resulting low posture and slow movement may facilitate crypsis as the lizards attempt to gain information regarding the predator. Desert iguanas are herbivorous lizards and may use chemical cues to detect and avoid snake predators while foraging or when entering burrows.

Chemosensory Identification of Lizard-Eating Snakes in the Desert Iguana, Dipsosaurus dorsalis (Squamata: Iguanidae)

Many antipredator behaviors function by hindering the ability of a predator to catch or consume prey once they are encountered. However, prey may also reduce predation risks by detecting predators before an encounter occurs. We tested the ability of the desert iguana (Dipsosaurus dorsalis) to detect and identify snake predators via chemoreception. Desert iguanas were exposed to chemicals from two sympatric snake species. The California kingsnake (Lampropeltis getula californiae), a species known to feed on lizards, was used as the predator stimulus, whereas the western shovel-nosed snake (Chionactis occipitalis), which feeds only on arthropods, served as a control for a general response to snake chemicals. Lizards were placed in terraria that previously housed live snakes or had been treated with distilled water or a pungent control. Overall tongue extrusion frequency and number of tongue extrusions prior to movement increased in response to chemicals from the California kingsnake but not in response to the western shovel-nosed snake. In addition, desert iguanas exhibited unusual slowness of movement and adopted a distinctive body posture in response to the predator stimulus. These results demonstrate that desert iguanas can detect chemical deposits from snakes and can discriminate between a snake species that feeds on lizards and one that poses no threat. In addition, the resulting low posture and slow movement may facilitate crypsis as the lizards attempt to gain information regarding the predator. Desert iguanas are herbivorous lizards and may use chemical cues to detect and avoid snake predators while foraging or when entering burrows.

Chemical Recognition of Familiar vs. Unfamiliar Conspecifics by Juvenile Iguanid Lizards, Ctenosaura similis

The ability of juvenile black iguanas, Ctenosaura similis, to discriminate between the chemical cue of an unfamiliar and a familiar conspecific was tested. Lizards directed significantly more tongue extrusions toward the chemical cue of a size‐matched conspecific with whom they had never interacted than the chemical cue of a size‐matched conspecific with whom they had interacted for 3 d. We consider the possibility that the social relationship between familiar associates may explain variation in the direction and degree of response to unfamiliar vs. familiar chemical cues.

Varieties of disgust faces and the structure of disgust.

In 3 facial expression identification studies, college students matched a variety of disgust faces to verbally described eliciting situations. The faces depicted specific muscle action movements in accordance with P. Ekman and W. V. Friesen's (1978) Facial Action Coding System. The nose wrinkle is associated with either irritating or offensive smells and, to some extent, bad tastes. Gape and tongue extrusion are associated primarily with what we call core or food-offense disgust and also oral irritation. The broader range of disgust elicitors, including stimuli that remind humans of their animal origins (e.g., body boundary violations, inappropriate sex, poor hygiene, and death), a variety of aversive interpersonal contacts, and certain moral offenses are associated primarily with the raised upper lip. The results support a theory of disgust that posits its origin as a response to bad tastes and maps its evolution onto a moral emotion.

Field observations on the role of tongue extrusion in the social behavior of the desert iguana (Dipsosaurus dorsalis).

Focal animal sampling was used to observe social behavior and chemoreceptive behavior, tongue extrusion, in marked desert iguanas (Dipsosaurus dorsalis) in the natural environment. Results reveal that tongue extrusion is a primary investigatory behavior of the desert iguana. Immature desert iguanas had fewer social encounters than adult males and females and exhibited relatively low overall rates of tongue extrusion. Although females exhibited a lower overall rate of tongue extrusion than males, this difference was not significant. Sex differences in rates of tongue extrusion were observed when the context in which the tongue extrusion occurred was taken into account

Conspecific odor detection by the male broad-headed skink, Eumeces laticeps: effects of sex and site of odor source and of male reproductive condition.

Olfactory stimuli are sufficient for detection and discrimination of sex of conspecific lizards by the male broad-headed skink, Eumeces laticeps, a member of a large group of lizards with pronounced chemosensory abilities, the Autarchoglossa. The capacity of male broad-headed skinks to detect conspecific odors was assessed by measuring tongue extrusion rates in response to odor stimuli presented on moist cotton applicators. Tongue-flick rates of postreproductive males were significantly higher for cloacal odors of postreproductive conspecifics of both sexes than to distilled water and higher to female than male odors over the initial 20- and 60-sec intervals. In a second experiment using testosterone-treated males and estrogen-injected females, testosterone-treated males emitted significantly more tongue flicks to female cloacal odors than to the other stimuli, and two males bit applicators bearing male odors. Testosterone did not affect reaction to male cloacal odors, but markedly increased tongue-flick rates in response to cloacal odors of estrogen-treated females. Postreproductive males also responded to female, but not male, skin odors at a significantly higher rate than to water. Possible sources and presumed adaptive significance of conspecific odors are discussed.

Detection of conspecific odors by the female broad‐headed skink, Eumeces laticeps

AbstractThe potential abilities of adult female E. laticeps to detect conspecific odors and to discriminate between male and female conspecific odors were investigated by comparisons of tongue extrusion rates emitted in response to chemical stimuli presented on moist cotton applicators. Postreproductive females treated with estradiol‐17β to stimulate possible increases in sensitivity to odors associated with the breeding season showed significantly higher tongue‐flick rates to the cloacal odors of both sexes than to distilled water. There was no evidence that the females discerned any difference between male and female odors. Estrogen‐injected females had somewhat higher tongue‐flick rates than did untreated postreproductive females, but the differences were not significant. Tongue extrusion rates of estrogen‐injected females were substantially lower than those of testosterone‐implanted males for all odor stimuli. It is argued, but not demonstrated, that female E. laticeps respond to the cloacal odors as stimuli arising from conspecific or at least closely related skinks.

Tongue Extrusion as an Aid to Blind Nasal Intubation

Tongue Extrusion as an Aid to Blind Nasal Intubation

Tongue extrusion as an aid to blind nasal intubation

Blind nasal intubation often results in esophageal placement of the tube because reflex swallowing and supralaryngeal structures direct the tube posteriorly. Extrusion of the tongue, which inhibits swallowing and shifts the supralaryngeal structures anteriorly, facilitated blind placement of a nasotracheal tube in 14 of 16 critically ill patients. The technique avoids manipulation of the neck, the use of heavy sedation or anesthesia, and requires no specialized training or equipment.

The Chemical Detection of Conspecifics by Juvenile Yarrow's Spiny Lizard, Sceloporus jarrovi

The role of tongue extrusions in the chemical detection of conspecifics was examined in juvenile Yarrow's spiny lizard (Sceloporus jarrovi). A comparison was made between the number of tongue-touches performed under three different experimental conditions: home cage, unfamiliar clean cage and an unfamiliar cage previously occupied by conspecifics of the same sex. Both males and females exhibited the same number of tongue-touches in each condition. As a result data were combined before analysis of the differences between the three experimental conditions. The rate of tongue-touching in the home cage was significantly less than the rate in the clean unfamiliar cage, which in turn was less than the rate in the unfamiliar marked cage. This indicates that juvenile S. jarrovi deposit chemicals that are detected by conspecifics. DeFazio et al. (1977) determined that adult Yarrow's spiny lizards, Sceloporus jarrovi, exhibit an increase in substrate tongue-touches (touching the tongue to the substrate) when placed in an unfamiliar cage as compared to the home cage, and an even greater increase when placed in a cage where another lizard had been kept. The authors suggest that the tongue is used to explore new situations, that pheromones may be deposited and detected by the lizards and that the tongue-Jacobson's organ system plays a role in chemical detection, as it does in snakes. Bissinger and Simon (1979) further explored these three possibilities for a variety of lizard species. Field experiments also indicate that chemicals deposited by adult S. jarrovi during the breeding season are detected by conspecifics (Gravelle and Simon, submitted). Both sexes spent less time in the section of the enclosure containing chemical cues left by lizards of the same sex, while males remained in the female's area, after she was removed, for longer periods of time. Additionally, tongue-touches performed by both males and females decreased in areas previously inhabited by a same-sex adult, while males responded to the absent female's home area with an increase in tongue-touches. Males also showed a significant increase in marking behavior (defecations and pelvic rubs) in the female's home area. Recently, Duvall (1979) observed that male western fence lizards, S. occidentalis, can discriminate between unmarked surfaces and those labelled by conspecifics of the same sex.

The role of chemoreception in the iguanid lizard Sceloporus jarrovi

We examined the role of tongue extrusions for the detection of chemicals in the iguanid lizard Sceloporus jarrovi, prior to the breeding season. Most extrusions resulted in the tongue touching the substrate and are referred to as tongue-touches. A total of 2819 tongue-touches were observed for four age/sex classes of lizards. We could not demonstrate that the tongue is involved in the detection of a natural predator, the Arizona kingsnake ( Lampropeltis pyromelana), and it was clear that it was not used to find food. It did, however, seem to be involved in the exploration of temporally and spatially unfamiliar areas. The possibility that the tongue is involved in the detection of conspecifics is discussed for this study, as well as for complementary studies. Possible marking attempts in the form of chin wipes, pelvic rubs, and defaecations were examined. The latter two possibilities were not important at this time of year. Chin wiping may result in the depositing of chemical markers, although no external chin glands were found and the possibility is still uncertain.

Comparison of Tongue Extrusions in Representatives of Six Families of Lizards

It has been widely noted that many species of lizards extend the tongue frequently under natural conditions. Although several reasons, including chemoreception, have been hypothesized for this behavior, sufficient quantitative data have not been collected to indicate its importance. We compared baseline rates of tongue extrusions for six different families of captive lizards and found significant differences between all six families. The range of variation in frequency was from a low of 3.4 tongue extrusions/30 minutes for the Cordylidae to a high of 299.5/30 minutes for the Teiidae. The frequency of tongue extrusions was: Cordylidae < Iguanidae < Gerrhosauridae < Scincidae < Helodermatidae < Teiidae. An increase in the frequency of tongue extrusions seemed to be correlated with increased bifurcation of the tongue. Possible uses of this tongue extrusion are explored for the six different families. The differences in frequency of tongue extrusion in different families may indicate the relative importance of the tongue-Jacobson's organ system.