The neuronal basis of behavior inTritonia. III. Neuronal mechanism of a fixed action pattern

Abstract Triatomines (Heteroptera, Reduviidae) are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease in America. These true bugs have traditionally been considered to be blood suckers, although some species have been catalogued as being entomophagous. By using their highly specialized mouthparts, these insects have evolved a stereotyped habit which includes lifting up the proboscis, piercing and sucking, when the occasion arises. Most triatomines bite their sleeping and unaware vertebrate or invertebrate hosts, but they can also search for other targets, guided, in part, by visual and chemical stimuli. In this study, we observed that triatomines apparently visually identify a drop of water in the distance, then taste it with their legs, upon which proboscis extension and sucking ensues. This invariant behavior or fixed action pattern, observed in several triatomine species (Rhodnius prolixus, Triatoma infestans and Panstrongylus geniculatus), was also elicited by a dummy drop of water and guava fruit. We discuss evolutionary and ethological aspects of this innate behavior. Digital video images related to this article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo180314rp01a and http://www.momo-p.com/showdetail-e.php?movieid=momo180314rp03a.

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No evidence of contagious yawning in the red-footed tortoise Geochelone carbonaria

Current Zoology ◽

10.1093/czoolo/57.4.477 ◽

2011 ◽

Vol 57 (4) ◽

pp. 477-484 ◽

Cited By ~ 18

Author(s):

Anna Wilkinson ◽

Natalie Sebanz ◽

Isabella Mandl ◽

Ludwig Huber

Keyword(s):

Mental State ◽

Perception And Action ◽

Social Processes ◽

Action Pattern ◽

Social Stimuli ◽

Contagious Yawning ◽

Mental State Attribution ◽

Fixed Action Pattern ◽

Fixed Action ◽

Significant Difference

Abstract Three hypotheses have attempted to explain the phenomenon of contagious yawning. It has been hypothesized that it is a fixed action pattern for which the releasing stimulus is the observation of another yawn, that it is the result of non-conscious mimicry emerging through close links between perception and action or that it is the result of empathy, involving the ability to engage in mental state attribution. This set of experiments sought to distinguish between these hypotheses by examining contagious yawning in a species that is unlikely to show nonconscious mimicry and empathy but does respond to social stimuli: the red-footed tortoise Geochelone carbonaria. A demonstrator tortoise was conditioned to yawn when presented with a red square-shaped stimulus. Observer tortoises were exposed to three conditions: observation of conditioned yawn, non demonstration control, and stimulus only control. We measured the number of yawns for each observer animal in each condition. There was no difference between conditions. Experiment 2 therefore increased the number of conditioned yawns presented. Again, there was no significant difference between conditions. It seemed plausible that the tortoises did not view the conditioned yawn as a real yawn and therefore a final experiment was run using video recorded stimuli. The observer tortoises were presented with three conditions: real yawn, conditioned yawns and empty background. Again there was no significant difference between conditions. We therefore conclude that the red-footed tortoise does not yawn in response to observing a conspecific yawn. This suggests that contagious yawning is not the result of a fixed action pattern but may involve more complex social processes.

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