摘要:

It is generally believed that odorants bind to receptor proteins and activate cAMP-dependent channels located in olfactory cilia. In the present paper, we discuss whether or not this mechanism holds for in vivo transduction in the olfactory and vomeronasal organs of a turtle: (1) Elimination of salts from the olfactory epithelium did not affect the responses to odorants; changes in concentration of NaCl or CaCl2 did not affect the olfactory responses. (2) The sensitivity of the vomeronasal system to various general odorants was essentially similar to that of the olfactory system, although the vomeronasal cells have no cilia. Elimination of salts from the surface of the vomeronasal organ, similar to the olfactory system, did not affect responses to odorants. (3) Liposomes having certain lipid compositions responded to odorants with a sensitivity comparable to that in the olfactory system. The liposomes containing phosphatidylserine (PS) exhibited strong responses, especially to fatty acids. (4) Application of PS-containing liposomes to the olfactory epithelium greatly enhanced the responses to fatty acids. The results suggest that the cation channels located at olfactory cilia may not contribute to in vivo olfactory transduction. The results also suggest that lipids in olfactory receptor membranes are important in odor reception.

ISSN:0006-8977    

DOI:10.1159/000113838

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

While evidence exists that many squamate behaviors are released by chemical stimuli, the specific sensory system that detects such stimuli and mediates subsequent behavior has been determined infrequently. Techniques and experimental approaches that have been used to determine the roles that the main olfactory and vomeronasal systems play in mediation of specific behaviors are discussed.

ISSN:0006-8977    

DOI:10.1159/000113839

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Six hypotheses for transfer mechanisms to the sensory epithelium of Jacobson''s organ are presented: diffusion, capillary action, ciliary currents, pinocytotic currents, direct tongue insertion, and suction. Of these, diffusion and capillary action are rejected on theoretical grounds, and ciliary and pinocytic currents are seen as playing, at best, a secondary role. Of the two remaining hypotheses, direct insertion of the tongue and suction, experimental evidence is summarized that leads to the rejection of the direct insertion hypothesis. The stimulus transfer mechanism is hypothesized to involve the generation of suction within the lumen of Jacobson''s organ and its duct. It is proposed that this suction is produced by pressure from the tongue and/or the anterior lingual processes.

ISSN:0006-8977    

DOI:10.1159/000113840

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Tongue-flicking in reptiles is frequently seen to increase in novel habitats and is presumed to involve the acquisition of chemical information. Like most behavioral patterns, however, tongue-flicking has both multiple causes and multiple functions, only some of which involve chemosensation. This paper describes units of exploratory behavior, including use of the tongue, in a microsmatic lizard, the green anole, Anolis carolinensis. This species employs its tongue in a manner suggestive of chemosensory exploration, but it possesses modest peripheral chemosensory organs and reduced central representation of chemosensory target cell groups. Further, specific elements of exploratory behavior are affected differently by treatments that involve altering levels of stress-sensitive hormones, androgen, and central catecholamines. Such differential responses suggest that exploratory behavior is an ensemble of individual units, some of which are selectively sensitive to specific physiological elements of the stress response and of elevated arousal.

ISSN:0006-8977    

DOI:10.1159/000113865

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The response of adult red-sided garter snakes, Thamnophis sirtalis parietalis, to airborne odor trails was studied. An airtight T-maze was used, through which a constant airflow was drawn by a vacuum pump. The arms of the ''T'' provided a choice between earthworm extract and distilled water. Experiment 1 tested the snake''s responses to varying concentrations of earthworm extract. Snakes accurately trailed the extract at tested concentrations (0.0, 0.01, 0.1, 1, 10, 100%). At ten percent concentration, tongue-flick rate and speed along the maze increased significantly above lower levels, suggesting the existence of a threshold concentration. A correlation between mean tongue-flick rate and mean speed was demonstrated. Experiment 2 tested the effect of differentially blocked vomeronasal ducts on a snake''s ability to trail. When both ducts were blocked, no trailing was observed, suggesting that vomeronasal stimulation is required. Blocking a single duct resulted in a significant number of snakes turning to the side of the functioning duct, suggesting that the tongue-vomeronasal system may function as a chemotaxic system.

ISSN:0006-8977    

DOI:10.1159/000113841

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

It has been widely believed for several decades that hatchling sea turtles imprint to chemical cues characteristic of their natal beach and use this information as part of a repertoire of mechanisms enabling their return to the same beach for mating and nesting. This has proven very difficult to test. Although the imprinting theory is conceptually simple, functionally it is quite complex. This involves not only chemical imprinting of nestlings but growth and migration to habitats where the adults are found, long-term memory of their earlier chemical exposure, reproductive maturation, and homing. A few studies have been conducted to examine these elements of the imprinting theory. Experiments involving the exposure of embryos and hatchlings to chemicals suggest that juvenile turtles ''imprint'' to the chemical environment of their nest. This can be termed chemical imprinting. Loggerhead turtles, Caretta caretta, and ridley turtles, Lepidochelys kempi, appear to be attracted to chemicals (morpholine and natural seawater, respectively) to which they were exposed as embryos. The strongest support for chemical imprinting is that six-month-old green turtles, Chelonia mydas, exposed to either morpholine or 2-phenyIethanol in the nest and for a period of time after hatching, respond similarly to the chemical to which they were exposed as nestlings. Although chemical imprinting does not ''prove'' the imprinting theory of turtle homing, it is a necessary component of the theory not previously examined.

ISSN:0006-8977    

DOI:10.1159/000113842

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

In Experiment I, homogenized rodent tissue was applied to the lips of prairie rattlesnakes (Crotalus viridis). This treatment produced elevated rates of tongue flicking compared to controls that received water, but the elevations seen following stimulation with homogenate were not as large as those seen after snakes struck prey. In Experiment II, water, rodent blood, and integumentary cues were applied to the lips of rattlesnakes, and only blood resulted in elevated rates of tongue flicking. We conclude that blood is a critical component of the homogenate . It is hypothesized that detection of blood during predatory strikes may be a causal element in the triggering of strike-induced chemosensory searching, a typical component of rattlesnake predatory behavior.

ISSN:0006-8977    

DOI:10.1159/000113843

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

When confronted by an ophiophagous (snake-eating) kingsnake, venomous snakes of the subfamily Crotalinae exhibit a suite of defensive responses including head hiding, thrashing, and an unusual response termed ''body bridging''. Other responses observed, such as biting and ''freezing'', are more general in nature and can occur in a variety of contexts. Various crotalines of differing sizes were tested for their responses to kingsnakes (Lampropeltis getulus). Responses of individuals were recorded for up to 18 months. The results indicate that, if habituation can be overcome by periodically allowing a kingsnake to confront but not harm the crotaline, the response is dependent on the size of the crotaline, in that smaller specimens (1.0 m) tend not to respond. The size of the kingsnake apparently does not have an effect on the crotaline response. These data appear to resolve apparent conflicts in the literature regarding whether certain species respond to ophidian ophiophages. In addition, hexane extracts of kingsnake skin were fractionated using an alumina column. The various fractions obtained were tested to determine which elicited the defensive response. Activity was found only in the most non-polar fraction. Preliminary analysis by gas chromatography/mass spectrometry indicated that this fraction contained straight and branched, saturated and polyunsaturated long-chain hydrocarbons.

ISSN:0006-8977    

DOI:10.1159/000113844

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Anatomical and behavioral aspects of chemoreception in crocodilians are reviewed. Extant crocodilians possess valvular nostrils regulated by smooth muscles; paired nasal cavities, each with three conchae; and flaps closing the rear of the buccopharyngeal passage to channel inspired air through the nasopharyngeal duct. Olfaction is enhanced by gular pumping, whereby the floor of the pharynx is alternately lowered and raised to pulse air through the nasal cavity. Taste buds occur on the tongue, palate, and pharyngeal walls. Crocodilians in nature or in semi-natural enclosures locate distant carrion or concealed meat, implying chemoattraction to food. The American alligator exhibits underwater head-waving and mouth-opening in response to aqueous and chloroform extracts of meat. Alligators increase gular pumping in response to the scents of various meats, indicating that they detect food chemicals by olfaction. Paired gular and paracloacal glands on the integument of crocodilians are thought to produce pheromones. Juvenile crocodilians exhibit heightened gular pumping in response to airborne skin gland secretions. Observations of adults suggest that gular and paracloacal glands produce chemical signals used in mating and/or nesting activities, but behavioral responses to skin gland exudates are too poorly documented to ascribe pheromonal properties.

ISSN:0006-8977    

DOI:10.1159/000113845

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

We have isolated seven proteins from earthworm preparations that are chemoattractive to garter snakes. Three of these proteins have been purified to homogeneity: two from aqueous earthworm wash (EWW) and one from electric shock-induced earthworm secretion (ESS). One of the two highly purified proteins from EWW has a relative molecular mass of 20 kDa and contains free sulfhydryl groups that appear to play a functional role in its chemoattractivity. The other purified protein from EWW has a molecular mass of 3 kDa (low molecular weight protein, LMW). The highly purified chemoattractive protein (ES20) from ESS is a glycoprotein having a minimum molecular mass of 15.4 kDa calculated from its amino acid and carbohydrate contents. It consists of a single polypeptide chain. The sequence of terminal 15 amino acid residues from its amino (NH2–) terminal has been determined. It binds specifically to the membranes of vomeronasal sensory epithelium in a saturable and reversible fashion with a Kd value of about 0.3 µM and Bmax value of 0.4 nmol/mg of protein. This protein causes an increase in firing rate of individual neurons in the accessory olfactory bulb of garter snakes, the projection site for vomeronasal neurons. All the isolated chemoattractive proteins from both earthworm preparations can be divided immunologically into three groups: (i) those closely related to the ES20 snake-attractive protein, (ii) those closely related to the LMW snake-attractive protein, and (iii) those unrelated to either ES20 or the LMW prote

ISSN:0006-8977    

DOI:10.1159/000113846

出版商:S. Karger AG    

年代:1993

数据来源: Karger