Toward a living soft microrobot through optogenetic locomotion control of Caenorhabditis elegans

Learning from the locomotion of natural organisms is one of the most effective strategies for designing microrobots. However, the development of bioinspired microrobots is still challenging because of technical bottlenecks such as design and seamless integration of high-performance actuation mechanism and high-density energy source for untethered locomotion. Directly harnessing the activation energy and intelligence of living tissues in synthetic micromachines provides an alternative route to developing biohybrid microrobots. Here, we propose an approach to engineering the genetic and nervous systems of a nematode worm, Caenorhabditis elegans, and creating an untethered, highly controllable living soft microrobot (called “RoboWorm”). A living worm is engineered through optogenetic and biochemical methods to shut down the signal transmissions between its neuronal and muscular systems while its muscle cells still remain optically excitable. Through dynamic modeling and experimental verification of the worm crawling, we found that the phase difference between the worm body curvature and the muscular activation pattern generates the thrust force for crawling locomotion. By reproducing the phase difference via optogenetic excitation of the worm body muscles, we emulated the major worm crawling behaviors in a controllable manner. Furthermore, with real-time visual feedback of the worm crawling, we realized closed-loop regulation of the movement direction and destination of single worms. This technology may facilitate scientific studies on the biophysics and neural basis of crawling locomotion of C. elegans and other nematode species.

Morphological and Molecular Characteristics of Clinostomid Metacercariae from Korea and Myanmar

Morphological and molecular characterization of clinostomid metacercariae (CMc) was performed with the specimens collected in fish from Korea and Myanmar. Total 6 batches of clinostomid specimens by the fish species and geographical localities, 5 Korean and 1 Myanmar isolates, were analyzed with morphological (light microscopy and SEM) and molecular methods (the cytochrome <i>c</i> oxidase 1 gene and internal transcribed spacer 1/5.8S rRNA sequence). There were some morphological variations among CMc specimens from Korea. However, some morphometrics, i.e., the size of worm body and each organ, ratio of body length to body width, and morphology of cecal lumens, were considerably different between the specimens from Korea and Myanmar. The surface ultrastructures were somewhat different between the specimens from Korea and Myanmar. The <i>CO</i>1 sequences of 5 Korean specimens ranging 728-736 bp showed 99.6-100% identity with <i>Clinostomum complanatum</i> (GenBank no. KM923964). They also showed 99.9-100% identity with <i>C. complanatum</i> (FJ609420) in the ITS1 sequences ranging 692-698 bp. Meanwhile, the ITS1 sequences of Myanmar specimen showed 99.9% identity with <i>Euclinostomum heterostomum</i> (KY312847). Five sequences from Korean specimens clustered with the <i>C. complanatum</i> genes, but not clustered with Myanmar specimens. Conclusively, it was confirmed that CMc from Korea were morphologically and molecularly identical with <i>C. complanatum</i> and those from Myanmar were <i>E. heterostomum</i>.

Californian red worm biomass increase and its cobalt accumulation under different concentrations of the metal in nutrient medium

<p>Californian red worms hybrid biomass is a biologically valuable feed supplement for livestock, poultry and fish. The worm body contains a significant amount of protein, lipids, vitamins and minerals. The chemical composition of worms depends on the nutrient medium in which they were grown. Worms can accumulate minerals from the nutrient medium in the body which called forth conducting research on obtaining worms biomass enriched with Cobalt with the prospect of its further use in fish feeding.<br />It has been found out that the worms quantity and the mass increase depends on the content of Cobalt in the nutrient medium. Adding 20 mg / kg of Cobalt to the nutrient medium contributed to 38.0% and 40.4% increased amount of worms weighing 0.4-0.8 g respectively. The study reveals that the number of immature worms increased by 32.2%. Adding 40 mg / kg of Cobalt to the nutrient medium resulted in worms number and mass increased by 45.9 and 51.1% respectively. Adding 160 mg / kg of Cobalt resulted in 6.5-27.7% smaller amount of worms weighing 0.4-0.8 g as compared with the experimental groups. It has been found out that the number of small worms reduced by 24.0-50.7% compared with the experimental groups under adding 160 mg / kg of Cobalt. The weight reduced by 22.4% and amount of young worms compared with the control has been revealed.<br />We have established the pattern that as Cobalt amount in the nutrient medium increases, its concentration in the worms biomass increases as well. The highest content of Cobalt was found in the biomass dry matter of worms grown in the nutrient medium enriched with the studied metal in the amount of 160 mg / kg.<br />Biomass of worms grown in the nutrient medium with 40 mg / kg of the studied metal added can be used in fish feeding as a protein supplement with a high content of Cobalt.</p>

Effects of chronic exposure to clothianidin on the earthworm Lumbricus terrestris

Although neonicotinoids are targeted at insects, their predominant use as a seed dressing and their long persistence in soils mean that non-target soil organisms such as earthworms are likely to be chronically exposed to them. Chronic exposure may pose risks that are not evaluated in most toxicity tests. We experimentally tested the effect of field-realistic concentrations of a commonly used neonicotinoid, clothianidin, on mortality, weight gain, and food consumption to assess the impacts of chronic exposure over four months on fitness of L. terrestris individuals. We undertook three separate experiments, each with different exposure routes: treated soil only (experiment A), treated food and soil combined (experiment B) and treated food only (experiment C). Mortality was negatively affected by exposure from treated soil only with greatest mortality observed in the groups exposed to the two highest concentrations (20 ppb and 100 ppb), but no clear effect on mortality was found in the other two experiments. When clothianidin was present in the food, an anti-feedant effect was present in months one and two which subsequently disappeared; if this occurs in the field, it could result in reduced rates of decomposition of treated crop foliage. We found no significant effects of any treatment on worm body mass. We cannot rule out stronger adverse effects if worms come into close proximity to treated seeds, or if other aspects of fitness were examined. Overall, our data suggest that field-realistic exposure to clothianidin has a significant but temporary effect on food consumption and can have weak but significant impacts on mortality of L. terrestris.

Infectivity, growth, distribution and fecundity of a six versus twenty-five metacercarial cyst inoculum of Echinostoma caproni in ICR mice

Female ICR mice, 6–8 weeks old, were exposed to 6 (group A) or 25 (group B) metacercarial cysts/host of Echinostoma caproni to determine the effects of these cyst dosages on infectivity, growth, distribution and fecundity of worms in the small intestines. All 30 mice exposed (15 in group A and 15 in group B) were infected and there was no significant difference in the percentage of worm recovery between group A and B at 2, 4 and 8 weeks postinfection (PI). Growth was rapid in both groups with worm body areas increasing from about 3mm2 at 2 weeks PI to about 7 mm2 at 8 weeks PI. More worms from group B were in the anterior sections of the small intestines at 2 and 4 weeks PI than those from group A. However, at 8 weeks PI more worms from Group A were in the anterior sections of the small intestines than those from group B. There were marked differences in our findings on infectivity, growth and distribution of E. caproni in ICR mice using 6 and 25 cyst inocula compared to a previous study using the same echinostome and cyst inocula in NMRI mice, presumably related to the mouse strain. Fecundity studies were somewhat comparable in both studies showing an approximate three to four times increase in the average number of eggs/gram of faeces in mice receiving 25 versus 6 cyst inocula.

The development, composition and maintenance of experimental populations of Haemonchus contortus in sheep

SUMMARYClun Forest sheep, aged between 3 and 18 months and worm-free from birth, were given a single dose of 25000 infective larvae of the nematode Haemonchus contortus. The host animals were killed between 4 and 100 days after infection and the nematode populations were examined to determine size and composition. The relation between worm body length, dry weight and age was studied and growth curves were constructed. Variations in the sex ratio for infections of different ages were noted. No evidence was found for a relation between rate of growth and population density. The rate of expulsion was determined and its variability discussed.