Ozcelik A et al. (2016) Small "Acoustofluidic Rotational Manipulation of Cells and Organisms Using Oscillating Solid Structures."

Kaynak M, Nama N, McReynolds MR, Huang TJ, Hanna-Rose W, Ozcelik A, Huang PH

[Small, 2016]

A polydimethylsiloxane microchannel featuring sidewall sharp-edge structures and bare channels, and a piezoelement transducer is attached to a thin glass slide. When an external acoustic field is applied to the microchannel, the oscillation of the sharp-edge structures and the thin glass slide generate acoustic streaming flows which in turn rotate single cells and C. elegans in-plane and out-of-plane.

Rozemuller, M. et al. (2019) International Worm Meeting "Individuality in C. elegans turning behaviour affects its motile efficiency."

Rozemuller, M., Shimizu, T.

[International Worm Meeting, 2019]

To survive, organisms continuously make navigational decisions based on limited available information. Even in isogenic populations difference in internal state and experience can result in different phenotypes. We explore reorientation statistics of C. elegans performing three contrasting tasks: (i) roaming for food, (ii) escaping from an SDS stimulus, and (iii) chemotaxis up a salt gradient, and ask how variability impacts its efficiency. In the absence of a stimulus we find that worm crawling demonstrates directional bias, which fluctuates on a ~1 hr time scale . Our results suggest that a strong crawling bias impairs roaming and chemotactic efficiency. Significant worm-to-worm variability (individuality) is observed for the frequency of sharp reorientations (?-turns). An increased sharp-turn rate is associated with less efficient roaming and chemotaxis. Minimalistic modeling of the worm's trajectory statistics confirms that increased crawling bias and sharp-turn frequency reduces roaming efficiency. Interestingly the model predicts that an increased sharp-turn frequency can be beneficial for worms with a strong crawling bias. In addition, during sharp reorientations worms also show individuality in dorso-ventral preference and amplitude, which is not associated with increased roaming efficiency. However, we do find that during SDS avoidance, both the sharp turn turning direction and amplitude are modulated in a meaningful way to minimize the exposure. Our results provide evidence that individual differences and temporal modulations of turning statistics affect the efficiency of motility tasks such as exploration, exploitation and avoidance.

Ohkubo J et al. (2010) J Theor Biol "Long-tail behavior in locomotion of Caenorhabditis elegans."

Iino Y, Yoshida K, Masuda N, Ohkubo J

[J Theor Biol, 2010]

The locomotion of Caenorhabditis elegans exhibits complex patterns. In particular, the worm combines mildly curved runs and sharp turns to steer its course. Both runs and sharp turns of various types are important components of taxis behavior. The statistics of sharp turns have been intensively studied. However, there have been few studies on runs, except for those on klinotaxis (also called weathervane mechanism), in which the worm gradually curves toward the direction with a high concentration of chemicals; this phenomenon was discovered recently. We analyzed the data of runs by excluding sharp turns. We show that the curving rate obeys long-tail distributions, which implies that large curving rates are relatively frequent. This result holds true for locomotion in environments both with and without a gradient of NaCl concentration; it is independent of klinotaxis. We propose a phenomenological computational model on the basis of a random walk with multiplicative noise. The assumption of multiplicative noise posits that the fluctuation of the force is proportional to the force exerted. The model reproduces the long-tail property present in the experimental data.

Sharp PM et al. (1997) "Appendix 3. Codon Usage in C. elegans."

Bradnam KR, Sharp PM

[1997]

Rochester, J.D. et al. (2019) International Worm Meeting "The Vasa DEAD-box helicase GLH-1 promotes differential translation of sperm genes."

Rochester, J.D., Sharp , C., Updike, D., Graber, J.

[International Worm Meeting, 2019]

P granules are a heterogeneous mix of RNA and protein that reside at the nuclear periphery of germ cells.1 Here they receive nascent transcripts as they exit the nucleus.2 Like germ granules in other animals, P granules in C. elegans contain core Vasa DEAD-box helicases called GLHs (germline helicases).3 Vasa proteins have been implicated in both small RNA amplification4 and translational regulation5, but how this conserved multipotency factor works is unclear. GLH-1 and GLH-2 function redundantly and are the only germline helicases in C. elegans that contain all the domains that distinguish Vasa proteins from other DEAD-box helicases. Loss of both glh-1 and glh-2 causes sterility, but glh-1 single mutants are fertile at permissive temperatures, providing a way to compare relatively healthy germlines from both wild-type and glh-1 mutant worms. mRNA-seq was performed, in triplicate, on total and polysome-associated RNA from a wild-type strain and a strain carrying a precision deletion of glh-1. Like previous microarray studies in glh-1 mutants, very few changes in transcript levels were observed. However, results comparing polysome fractions showed a dependence on GLH-1 for the selective translation of hundreds of sperm-enriched transcripts. In contrast, a handful of histone variant transcripts lose association with polysomes in the glh-1 deletion. To validate these observations, translational reporters of histone and sperm genes are being created in wild-type and glh-1 deletion backgrounds and changes in reporter expression area being compared to the spatial expression and abundance of their transcripts using single molecule FISH. These results are providing insight into the male-specific sterility of Vasa/Mvh/DDX4 mutants in mammals and the mechanism of Vasa function across species. 1. Seydoux, G. J. Mol. Biol. 430, 4702-4710 (2018). 2. Sheth, U. et. al. Development 137, 1305-14 (2010). 3. Spike, C. et al. Genetics 178, 1973-87 (2008). 4. Xiol, J. et al. Cell 157, 1698-1711 (2014). 5. Lasko, P. Biochim. Biophys. Acta - Gene Regul. Mech. 1829, 810-816 (2013).

H A Zariwala et al. (2001) International C. elegans Meeting "The trampoline assay: A new method for measuring the step response of the thermotaxis mechanism in C. elegans."

H A Zariwala, S R Lockery, S Faumont

[International C. elegans Meeting, 2001]

Worms in a thermal gradient migrate to the temperature at which they were cultivated (thermotaxis). Qualitative analysis of the effects of mutations and neuronal ablations on thermosensory behavior[1,2] suggests that thermotaxis may involve a mixture of two strategies: isothermal tracking, in which the head is aligned orthogonal to the thermal gradient, and pirouetting, in which course correction is achieved by a cluster of sharp turns, as in chemotaxis[3]. As a direct test of whether pirouettes play a role in thermotaxis, we devised a new procedure--the "trampoline assay"--in which worms were placed on a thin (~100 m m) agarose film suspended over a chamber filled with buffer at the cultivation temperature (21 o C). After a 5 min. adaptation period, we quickly replaced the first chamber with a second containing buffer at a lower temperature (18 o C), and observed the worm for an additional 5 min. Temperature measurements on the surface of the film indicated that the time constant of the temperature shift was ~4 sec. When we shifted wild type worms (n = 14) to the lower temperature (down-shifts), we observed a transient increase in the probability of initiating sharp turns (time to peak = ~30 sec; decay time constant = ~50 sec). This result is consistent with a role for pirouettes in thermotaxis because, in a spatial temperature gradient, a pirouette induced by a temperature drop tends to return the worm to its cultivation temperature. The increase in sharp turn probability is almost certainly not a mechanical artifact because we saw no increase in turning when the second chamber was at the cultivation temperature (n = 8). Conversely, when we down-shifted the cryophilic mutant ttx-3 (ks5) (n = 15), we observed a sustained decrease in sharp-turn probability. In a spatial temperature gradient, a decrease in turning induced by a temperature drop tends to move the worm toward lower temperatures, consistent with the cryophilic phenotype of ttx-3 . We conclude that pirouettes are likely to be important for thermotaxis, at least for excursions below the cultivation temperature. Experiments are in progress to determine if the same is true for excursions above cultivation temperature. 1. Hedgecock, E.M. & Russel, R.L. PNAS 72, 4061-4065 (1975). 2. Mori, I. & Ohshima, Y. Nature 376, 344-348 (1995). 3. Pierce-Shimomura, J.T. & Lockery, S.R. J. Neurosci. 19, 9557-9569(1999).

Schmidt GD et al. (1972) Proc. Helminthological Society of Washington "Nematode parasites of Oceanica. XVIII. C. avicola sp. n. (Rhabditidae) found in a bird from Taiwan."

Schmidt GD, Kuntz RE

[Proc. Helminthological Society of Washington, 1972]

Caenorhabditis avicola sp. n. is described from one male and three female nematodes from the intestine of a plumbeous water redstart, Rhyacornis fuliginosus (Passeriformes, Turdidae), from Taiwan. It is characterized by the extension of the anterior margins of the peloderan bursa into sharp points, giving the male posterior end an arrowheadlike shape in ventral view, and by the spicules, which are 95 u long. It is postulated that the worms were pseudoparasites, possibly symbionts of an insect ingested by the bird.

Aiyar S (1983) Southeast Asian J Trop Med Public Health "Attempts to infect experimentally immunosuppressed iris monkeys (Macaca iris) with Brugia malayi."

Aiyar S

[Southeast Asian J Trop Med Public Health, 1983]

Iris monkeys resistant to repeated infections with B. malayi were subjected to immunosuppression by treatment with cortisone. Degree of immunosuppression was measured by: (a) blood counts, (b) lymphocyte transformation to mitogens and (c) immunofluorescent antibody to microfilarial antigens. Attempts were made to infect such immunosuppressed animals with B. malayi. No microfilariae were detected in the blood of any of the Iris monkeys during the 6 months of study. There was a sharp drop in the percentages of lymphocytes, but a rise in neutrophil counts during the first week of cortisone administration. Treatment with cortisone did not alter the antibody titres. The significance of this line of approach in the understanding of filarial resistance is discussed.

Borgonie G et al. (1996) Fundamental and Applied Nematology "Effect of a nematicidal Bacillus thuringiensis strain on free-living nematodes. 3. Characterization of the intoxication process."

De Waele D, Arnaut G, Coomans AV, Leyns F, Claeys M, Borgonie G

[Fundamental and Applied Nematology, 1996]

The toxicity of Bacillus thuringiensis is temperature sensitive. Incubation of Caenorhabditis elegans with nematicidal B. thuringiensis strains at 16, 20, and 25 degrees C shows that toxicity decreases as temperature declines. At 16 degrees C, toxicity is completely lost, while it is maximal at 25 degrees C. Toxicity is pH sensitive and is significantly reduced when nematodes are incubated with the weak bases NH4Cl, chloroquine, acridine orange, methyl red, and neutral red. Based on these results, we proposed the hypothesis that the nematicidal factor is effectively internalized into the intestinal cells, a sharp deviation from the insecticidal B. thuringiensis toxins acting at the level of the brush border membrane. Although the absence of purified toxins prevents a more definitive elucidation of the mode of action, the results of this third and final part of this series of publications convincingly indicate that nematicidal B. thuringiensis do not hold the same promise as a biological control agent as the insecticidal B. thuringiensis strains.

Ahamed, Tosif et al. (2017) International Worm Meeting "The deterministic dynamics of random search in C. elegans."

MARUYAMA, Ichiro, Ahamed, Tosif, Stephens, Greg

[International Worm Meeting, 2017]

Foraging C. elegans actively modulate their search strategy to effectively sample their environment. These decisions are based on statistical distributions of food patches in the environment, sensory cues and their recent experience. Examples of C. elegans search behaviors include area restricted search, salt chemotaxis and roaming-dwelling. Studies based on centroid measures have suggested a random search framework to explain these behaviors. Within this framework, worms sample an environment by executing straight runs punctuated randomly by sharp turns made by reversals, omega turns or a combination of both. When the frequency of sharp turns is high, worms perform a diffusive search, densely sampling a small area. On the other hand when the frequency of sharp turns is small, they perform a ballistic search, going straight for a long period of time. In this study we take another look at random search in C. elegans by analyzing the continuous dynamics in the low dimensional space of C. elegans postures given by the eigenworm representation. To our surprise, we find that the randomness in random search is largely a result of deterministic chaos instead of sensory or motor noise. Thus, the chaotic nature of the dynamics implies that the behavior of the worms is not random, but predictable for a finite period of time. This prediction window is governed by a quantity called the Maximal Lyapunov Exponent (MLE), which is positive for chaotic systems. Highly chaotic systems have a small prediction window due to a large MLE, while, weakly chaotic systems have a big prediction window resulting from a small MLE. We find that for worms engaged in an area restricted search, the MLE gradually reduces with time as the worms transition from a diffusive search strategy to a ballistic search strategy. Moreover, the reversal frequency of these worms is positively correlated with the MLE, consistent with the observation that worms get more predictable as they reduce their reversal frequency. Furthermore, the variation in MLE enough to describe most of the random search behavior, suggesting the intriguing possibility that only one degree of freedom underlies control of C. elegans foraging behavior. Finally, we use this theoretical framework to probe the biology of random search by studying the roles of monoamines dopamine and serotonin in foraging. In summary, we extend past theoretical work on C.elegans random search by including detailed postural dynamics and find that deterministic chaotic dynamics underlie the apparent randomness of C.elegans search strategies. Our analysis also suggests that the MLE of the dynamics is potentially the only parameter that the worm controls to modulate its search strategy and decide how predictable or unpredictable it wants to be.