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Annual Review of Phytopathology,
1977]
There have recently been unprecedented advances in our knowledge of senses and responses in nematodes. As this review is being published data on sensory mechanisms in nematodes continue to flood in from laboratories all over the world. Developments have not come directly from electrophysiology, but rather indirectly, through detailed neuroanatomy and through interpretations based on the behavior of the entire organism. Studies of free-living bacteriophagous species Caenorhabditis elegans have led to many of these advances and are the basis for a major part of this review....
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Canadian Journal of Zoology,
1975]
Nematode movements result from spontaneous myogenic depolarizations, neuromuscular coordination, and localized hydrostatic changes. These components are integrated into activities which are mutually exclusive or interdependent. Nervous connection is not known between all the organ systems, and the pharynx and female tract are somewhat autonomous. This problem is discussed, as is the limitation of a theory involving only cholinergic transmission. Serotonin, 5-hydroxytryptophan (5HTP), and epinephrine were all found to induce rapid and prolonged contractions in the female vagina/vulva of Caenorhabditis elegans, Aphelenchus avenae, Panagrellus redivivus, and Oswaldocruzia filiformis. It also caused spicule extension in males of P. redivivus. The responses are fully described together with dose-response data and the effect of adult age. The potential significance of indolealkylamines in nematode behavioral coordination is discussed, together with the relevance of anthelmintic formulation and the basis of immunological rejection.
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Journal of Zoology,
1975]
The behavioural activities during movement, feeding and defaecation have been recorded and measured in adult females of Caenorhabditis elegans. The postures and components of recognizable wave forms are described. Stress has been laid on the machanism of antagonistic interaction of backward and forward movement, and the rates and characteristics of "spontaneous" and "induced" reversal periods. During feeding, rapid rates of pharyngeal activity are invariably related to low rates of somatic muscle wave propagation. Head oscillations are considered to be separate events not directly linked with feeding or foraging. The combination of certain wave forms, together with other measurements have been used to develop a hypothesis to describe a co-ordinating mechanism to the nematode level of organization.
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Canadian Journal of Zoology,
1976]
When C. elegans bumps into a bead, it stops moving, withdraws a short distance, and then resumes forward movement, often in a new direction. This series of events has been analysed in its constituent parts and the features making up the 'stimulus' have been compared numerically with those making up the 'response'. No significant correlations were found that support the interpretation that this is a simple stimulus-response phenomenon. It is argued that the data support an alternative view that when forward movement is interrupted, C. elegans is primed to undergo a short, rapid reversal and that this is not mediated through sensory mechanoreceptors.
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Worm Breeder's Gazette,
1977]
It remains the feeling of this laboratory that very little is known of the behavior of wild type C. elegans and that detailed analysis of the behavior of individuals still provides the best method of study. We are currently analyzing the behavior of adults, 4 1/2 days + 1/2 day at 20 C as our recent study (Croll, Smith & Zuckerman, 1977, Experimental Aging Research) has shown that age is critical in determining the rates of different behavioral actions. The wave patterns of individuals is significantly altered by L-tryptophan and D- tryptophan (5mM), an approach derived from Dusenbery (J. Exp. Biol. 1975, 193; 413). The patterns are further significantly affected by small temperature changes from the eccritic response. As well as any directional component attributed to chemical or thermal gradients, we are now considering them to be important 'behavior modifiers' in non- directional environments. A full description of defecation has been completed which supports our earlier contention that defecation is a feature of the 'feeding phase' and that its rate is dependent upon an endogenous signal(s) and not upon the rate of ingestion. When not ingesting rapidly there is a spontaneous 'pseudocrap' in which faeces are not voided! Further details (J. Zool. Lon.) can be provided of this study now in press upon request. C. elegans adults respond very strongly to electric currents and potentials between .01-.06 mA and 1.0 to 3.3 V/cm. This is now being investigated with thresholds, habituation phenomena and feeding factors being included. This response could provide a new set of mutants for those in the business of making them. Worms can go either towards the cathode or anode depending upon the current strength. We would like to develop this investigation to see if certain amphid-defective, chemoreceptive-defective mutants had also lost their galvanotaxes - any offers?
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Journal of Zoology,
1978]
Caenorhabditis elegans spends most of its life feeding. When feeding, it moves only short distances but intestinal contents are moved to and fro and thus mixed. The nematodes also defaecate and lay eggs during the feeding phase in bacterial culture. Defaecation is one of a series of events which causes the forward and backward movement of intestinal contents. These rhythmic movements, once initiated, appear to be controlled by a pacemaker and are unrelated to feeding rates. Oviposition is associated with movements of the genital tract and it can occur at any posture and does not influence the rate of other activities. After food-deprivation, C. elegans shows no measureable hunger response on being returned to bacteria. Experiments with excised parts of worms showed that isolated anterior ends will feed both in and out of bacteria and move forward and backward. Isolated posterior halves without a pharynx or circumpharyngeal commissure
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Exp Aging Res,
1977]
While much is known of the morphological and some physiological changes which occur during the aging of Caenorhabditis elegans, little attempt has been made to measure the changes in behavior. Wild type C. elegans (var. Bristol) were cultured axenically, individually observed each day for 15 minutes and their behavioural actions recorded on a multi-channel event recorder or on a video tape recorder of a closed circuit TV. Particular attention was paid to the rate of backwardly directed somatic waves, pharyngeal bulb pulsations, the interval between defecations and oviposition. C. elegans lived significantly longer in axenic culture than in bacteria. A gradual linear decline occurred in the rate of backward waves between maturation (day 4) and death (day 20) for those worms in axenic culture. In striking contrast, the mean maximum rate of pharyngeal bulb pulsations maintained a plateau from day 4 to 18, while the mean interval between defecations doubled from 60 sec (days 4 to 8) to 120 sec (days 10-20). These results are discussed in the context of nematode coordination and the mechanisms of aging.