ISSN:0006-8977    

DOI:10.1159/000113828

出版商:S. Karger AG    

年代:1993

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113829

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Recent advances in the field of squamate reptile chemoreception have been paralleled by the growth and preeminence of cladistics in the field of systematics, but for the most part, workers in the former have failed to incorporate the conceptual and informational advances of the latter. In this paper, I attempt a preliminary rapprochement by combining the methods of phylogenetic systematics and current hypotheses of squamate relationships with an overview of squamate chemosensory biology. This purely phylogenetic approach leads to a number of falsifiable generalizations about the evolution of chemoreception in squamates: 1) Evolution of this system is conservative rather than plastic, reflecting to a large extent suprafamilial attributes rather than adaptation to local conditions; Anguimorphs are highly chemosensory and teiids show convergence with this group; 3) Tongue-flicking, a bifurcated tongue tip, a vomeronasal (VNO) mushroom body, and a complete circular muscle system in the tongue are a correlated character complex associated with the attainment, in squamates, of a direct VNO-oral connection and the loss of a VNO-nasal connection; 4) There is little support for a visual-chemosensory dichotomy within Squamata; 5) Gekkotans are allied with Autarchoglossa, both phylogenetically and in terms of chemosensory biology; 6) Iguania are highly variable in chemosensory development; iguanids represent the primitive iguanian condition, while agamids and chamaeleonids have secondarily reduced or lost their chemosensory abilities; 7) Apparent contradictions in chemosensory behavior among iguanids probably represent intrafamilial divergence; 8) Ecological correlates within Iguanidae and other taxa might be spurious, resulting from historical factors unrelated to the adaptations in question; 9) The mechanical demands of lingual food prehension have constrained chemosensory evolution in Iguania; chemosensory evolution within Scleroglossa was permitted by the liberation of the tongue from this ancestral role.

ISSN:0006-8977    

DOI:10.1159/000113830

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Reptiles offer a rich diversity for the study of chemoreception, and snakes are a particularly appropriate group for comparative, evolutionary, genetic, developmental, and mechanistic studies. A long-term program of research is described that attempts to integrate these approaches, focusing on the widespread North American genus Thamnophis (Natricinae). Prior to their first meal, neonatal snakes respond to aqueous surface substances from species-typical prey with increased tongue-flicking and open-mouth attacks; these responses are mediated by the vomeronasal organ. Such responses predict what prey snakes will eat and can also predict relative prey preference. Species, population, litter, and individual differences exists and are important at different levels of analysis. Chemoreceptive responses are heritable, although they may show different developmental trends. Some species respond to prey types they do not eat in nature. In the earthworm specialist, T. butleri, response to fish chemicals can be interpreted as a chemoreceptive response inertially inherited from ancestral species, decoupled from prey capture techniques, and in the process of being lost. Ontogeny and experience can modify behavior of the neonate in various ways. Feeding experience can alter response to some prey more than others, and ambient prey odor may shift prey preference. Psychophysical studies show that prey preference and threshold sensitivity to prey chemicals can be independent and differ between closely related species, indicating that neural tissue is devoted to recognition of specific types of prey. In site choice tests, garter snakes can also discriminate between feces derived from conspecific snakes fed similar or different diets. Diet, relationship, and familiarity can all influence spacing with conspecifics. Here, too, species differences are apparent. Since the direction and extent of experiential and genetic effects is so contingent on the species studied, it is argued that groups of related species should be studied rather than selecting a single one to serve as a ''model'' for a particular neurological level of organization or taxonomic group.

ISSN:0006-8977    

DOI:10.1159/000113831

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The present account is a review of the main and accessory olfactory bulb projections in reptiles. From previous studies by means of the classical degeneration techniques and recent studies using the autoradiographic method or the Phaseolus vulgaris-leucoagglutinin (PHA-L) tracing technique, it has become evident that, in the brain of reptiles, the vomeronasal and main olfactory systems are segregated. Moreover, the PHA-L studies have demonstrated that the main olfactory bulbs project not only to the anterior olfactory nucleus, the olfactory tubercle, and the lateral cortex, but also to the rostral portions of the external and central amygdaloid nuclei. The latter studies also provided evidence that, apart from a massive projection to the nucleus sphericus, at least in some reptilian species, the accessory olfactory bulbs project to the caudal portion of the central amygdaloid nucleus and the bed nucleus of the stria terminalis. A comparison of the olfactory projections between the various reptilian species studied revealed a considerable variation in the course of the main olfactory bulb efferents that reach the contralateral hemisphere.

ISSN:0006-8977    

DOI:10.1159/000113832

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The amygdaloid formation of the lizard Podarcis hispanica can be divided into three main groups of nuclei on the basis of their input from the main and accessory olfactory bulbs: the vomeronasal amygdala, the olfactory amygdala and the dorsal amygdaloid group, the latter group receiving afferents from neither the main (MOB) or the accessory olfactory bulb (AOB). The vomeronasal amygdala has a centrifugal projection to the AOB, an important commissural connection to the contralateral vomeronasal amygdala, a minor projection to nucleus accumbens, and a bilateral projection to the lateral cortex. The olfactory amygdala displays a bilateral afferents from the MOB, receives a contralateral afferent, and is reciprocally connected with the lateral cortex. Moreover, it receives an important input from the vomeronasal amygdala. The dorsal amygdaloid group receives projections from the other two amygdaloid groups, multimodal inputs from the anterior dorsal ventricular ridge and the dorsal cortex, and a putative cholinergic input from the basal telencephalon. Moreover, it is the site of origin of a prominent bilateral amygdalo-striatal projection that extends to the bed nucleus of the stria terminalis and the so-called amygdalo-striatal transition area, through which it may control both visceral and motor activities. The main extratelencephalic output of the amygdala courses through the stria terminalis and terminates in the ventromedial hypothalamic nucleus. The extratelencephalic afferents of the amygdala arise from several hypothalamic and anterior thalamic nuclei, from the mesencephalic and rhombencephalic aminergic cell groups, and from the rhombencephalic parabrachial nucleus.

ISSN:0006-8977    

DOI:10.1159/000113833

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The development of the nasal chemical senses of reptiles is of particular interest since evidence suggests that neonatal reptiles use both their olfactory and vomeronasal systems. This review focuses on the embryonic development of these nasal chemosensory systems in garter snakes (Thamnophis spp.). Three approaches have been used to examine development: (1) Normal morphological studies, (2) 3H-thymidine autoradiographic studies, and (3) metabolic mapping of the accessory and main olfactory bulbs with cytochrome oxidase histochemistry. In addition, garter snake embryos have been grown in vitro to facilitate experimental procedures. The results of these studies show that reptiles are a rich and diverse group for investigating the developmental processes that form the neurobiological basis for naturally occurring chemosensory-mediated behaviors.

ISSN:0006-8977    

DOI:10.1159/000113834

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Electroolfactogram and electrovomeronasogram recordings were made from garter snakes stimulated with vapor of amyl acetate, butanol and of earthworm wash. The olfactory epithelium was more sensitive than the vomeronasal epithelium to all three stimuli. Volatiles from prey washes were capable of stimulating the olfactory epithelium when delivered as airstreams. The vomeronasal epithelium was sensitive only to the air delivery of vapor of amyl acetate. Single unit recordings from the mitral cell layer of the accessory olfactory bulb of garter snakes were made in response to liquid delivery of a variety of chemical stimuli including classical odorants, amino acids and proteins derived from prey. All three classes of stimuli altered unit firing in the accessory olfactory bulb. Amyl acetate, earthworm wash, goldfish wash and non-volatile amino acids delivered as liquid stimuli to the vomeronasal epithelium produced responses in the accessory olfactory bulb that were more distinct and reliable than the electrovomeronasogram responses to airborne odorants recorded at the periphery. Both excitatory and inhibitory responses were observed in the accessory olfactory bulb of garter snakes. The direction of the response to a given stimulus differed for different neurons. Responses were frequently biphasic and could last longer than 50 seconds. Individual neurons responded to different classes of stimuli suggesting that they are broadly tuned.

ISSN:0006-8977    

DOI:10.1159/000113835

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The number of vomeronasal receptor cells and olfactory receptor cells were determined in several turtles and tortoises. Using semi-aquatic turtles with developed vomeronasal organs, neural responses to various odor stimuli were recorded as extracellular unitary spike responses of vomeronasal receptor cells, compound action potentials from vomeronasal nerve twigs, induced wave responses on the accessory olfactory bulb (AOB) surface and unitary responses of AOB neurons. The vomeronasal system in turtles responded to various volatile and non-volatile chemicals. These results yield insights concerning functions of the vomeronasal organ in semi-aquatic turtles.

ISSN:0006-8977    

DOI:10.1159/000113836

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Electrical recording from small twigs of olfactory nerve and electro-olfactogram (EOG) from olfactory epithelium in a turtle shows that olfactory receptors in the nose are responsive to various odors. I have used the effects of cross-adaptation to odor stimulation on the olfactory receptors to investigate the stimulus-specific components of these responses and to provide information about the responsiveness of cells. The results of the cross-adaptation experiments strongly support the hypothesis that different categories of receptor cells exist in the olfactory epithelium.

ISSN:0006-8977    

DOI:10.1159/000113837

出版商:S. Karger AG    

年代:1993

数据来源: Karger