Worm Body Research Articles

A droplet-based microfluidic device for long-term culture and longitudinal observation of Caenorhabditis elegans

A droplet-based microfluidic device for long-term culture and longitudinal observation of Caenorhabditis elegans was presented. The worms were encapsulated in W/O droplets and controllably introduced into separate chambers, where the medium/oil or medium/air interface can be manipulated by a gravity-actuated technique, for lifelong culture. This device also contained clamp structures for reversibly immobilization of each worm separately, and thus we were able to track more details about each worm. Several phenotypes of worms were monitored from their fourth larva stage to death. The relationship between worm body length, stroke frequency and lifespan with this device was then studied. This device had a potential in various longitudinal researches on C. elegans including aging, drug screening, toxicity evaluation and etc.

Effect of oligochaete worm body fluids on biological phosphorus removal in a bench-scale EBPR system

During waste sludge reduction by oligochaetes, phosphorus (P) concentrations in the effluent have been noticed to increase. In the current study, batch experiments were carried out in order to provide explanations for this phosphorus release. The results indicated that increase in effluent phosphorus concentration might not be directly linked to the phosphorus in worm body fluids, as the phosphorus concentration in the system at the start of each operational period did not change significantly. However, the phosphorus removal efficiency rapidly dropped from 93.9%±1.9% to 62.2%±1.3% with increasing addition of oligochaete worm body fluids. Furthermore, an increase in worm body fluids induced a remarkable enhancement of anaerobic phosphorus release rate as well as anaerobic storage of poly-β-hydroxyalkanoate (PHA). At a worm density (wet weight) of 14.4 g/L, the anaerobic phosphorus release rate was elevated by 31.1%±2.8% and 57.3%±4.6% at 2.5% and 5.0% worm death rate, respectively, compared with the control. The contribution of worm body fluids to PHA production was 39.3–67.7 mg/g of dead worm (wet weight), which was mainly attributed to the extra synthesis of poly-β-hydroxyvalerate (PHV). Unfortunately, in the concomitant aerobic stage, inhibition of 3-hydroxybutyric acid (PHB) oxidation and ammonia utilization was observed along with the increasing addition of worm body fluids. Meanwhile, nitrite elevation was found at the beginning of the aerobic stage, which might be negative to the aerobic metabolic processes performed by phosphate-accumulating organisms (PAOs), namely PHB oxidation, phosphate uptake and ammonia utilization for biomass growth.

Locomotion of C. elegans: A Piecewise-Harmonic Curvature Representation of Nematode Behavior

Caenorhabditis elegans, a free-living soil nematode, displays a rich variety of body shapes and trajectories during its undulatory locomotion in complex environments. Here we show that the individual body postures and entire trails of C. elegans have a simple analytical description in curvature representation. Our model is based on the assumption that the curvature wave is generated in the head segment of the worm body and propagates backwards. We have found that a simple harmonic function for the curvature can capture multiple worm shapes during the undulatory movement. The worm body trajectories can be well represented in terms of piecewise sinusoidal curvature with abrupt changes in amplitude, wavevector, and phase.

Size matters: modeling the effects of body shape on locomotive behavior in the nematode C. elegans

The microscopic nematode worm, C. elegans, has a hard wired and comprehensively mapped neural circuit, with only 302 neurons in the adult. The organism's simplicity and the wealth of information available about it make C. elegans an inviting target for computer modeling. Locomotion is the clearest measure of the worm's behavior, and the undulatory waves used in the worm's movement are directly affected by the shape of the animal's body. As the worm develops from a larva to adulthood its body grows and changes in shape. More dramatically, mutant C. elegans exist with bodies that are considerably longer or shorter than in the wildtype, and these worms have severe locomotion phenotypes. Previous models for locomotion have often concentrated on either the worm's nervous system or body, modeling only one area in detail and greatly simplifying the other. This neglects important interactions between the physical and neural aspects of the worm's behavior, such as touch response, proprioception and the effects of its surroundings. We use an integrated neuromechanical model that incorporates the worm's neural circuit for locomotion, its body and its environment. We have previously used the model to predict that the L1 larva maintains robust forward locomotion using a similar gait to the adult worm, and now examine the behavior of the body shape mutants dpy-1, dpy-11 and lon-2, both in liquid and on gel. Testing model predictions against data from biological experiments, we can validate its robustness to such physical differences and its ability to capture the behavior of new phenotypes. Three candidates exist for the cause of behavioral abnormalities seen in such mutants; differences in the worm's neural circuit, muscle properties, or passive body properties. We make clear experimental predictions on the locus of change and the specific pathways through which it is effected.

Identification and characterization of myophilin-like protein: a life stage and tissue-specific antigen of Clonorchis sinensis

Clonorchiasis, caused by Clonorchis sinensis infection, has been an important public health problem in China. More messages about biology and pathogenicity of C. sinensis will be better for development of new strategies for clonorchiasis control. In the current study, using data from the published genomic and cDNA sequences for C. sinensis, we identify a gene encoding a myophilin-like protein (Cs myophilin-like). The cDNA sequence is 573 bp in length which encoded a protein of 190 amino acids. DNA sequence of Cs myophilin-like consists of four extrons and three introns. By mapping the draft genome of C. sinensis, single copy of myophilin-like gene is annotated. Bioinformatic analysis shows Cs myophilin-like comprises a calponin homology domain and three actin binding surfaces. It expresses at the life stage of adult worm and metacercaria but not in eggs. It intensively distributes in muscular locations such as oral sucker and pharynx of adult worm and sucker of metacercaria. The transcript level of Cs myophilin-like in oral sucker and pharynx is significantly higher than that in the rest of adult worm. Moreover, recombinant Cs myophilin-like is obtained and of antigenicity and immunoreactivity. It can be probed by sera from patients infected with trematode or cestode. Our data suggests that Cs myophilin-like may be involved in the host tissue invasion besides regulating the contraction of smooth muscle and movement of worm body. Taken together, the stable and soluble expression in Escherichia coli and immunogenicity of recombinant Cs myophilin-like proteins suggest that Cs myophilin-like may be a potential candidate for vaccine and drug target for clonorchiasis.

Gastrointestinal: Capsule endoscopy assists in the complete deworming of parasites

A 67-year-old man presented with the complaint of ribbon-like substances in the feces. In the beginning of August 2010, he was referred to our hospital for treatment of parasitic worm infection. The patient did not have symptoms such as diarrhea, anemia, or weight loss; the results of physical and hematological examinations and of thoracoabdominal radiography were normal. Although he did not have a history of parasitic worm infection and had never traveled abroad, he had eaten raw salmon 1 month ago. On the first day of the hospital visit, the patient was diagnosed with diphyllobothriasis after examination of the helminth eggs found in the feces. After diatrizoic acid swallow on the second day, the presence of the worm body was confirmed by colonoscopy, and the worm body was extirpated from the anus by using grasping forceps. Although approximately 1 m of the worm body together with most of the neck portion was successfully extirpated, removal of the scolex was not confirmed. On the fourth day, after obtaining the patient’s consent, we performed capsule endoscopy because of possible incomplete deworming. Capsule endoscopy confirmed parasitization by a cestode and detected the scolex attached to the jejunal mucosa (Figure 1). Parasite-specific drugs, i.e., praziquantel and magnesium citrate, were administered, and complete deworming was subsequently confirmed by microscopic identification of the scolex (Figure 2). The worm body was pathologically confirmed as Diphyllobothrium nihonkaiense by performing trichrome and carmine staining (Figure 3). For the successful treatment of diphyllobothriasis, it is essential to remove the scolex of the parasite. The use of capsule endoscopy now allows for (1) easy capture of images of parasites, such as that of the scolex of Diphyllobothrium nihonkaiense, in the small intestine, which was previously considered difficult; and (2) provides information critical for therapeutic decision making before administering anthelmintics.

Impact of two insect growth regulators on the enhancement of oxidative stress and antioxidant efficiency of the cotton leaf worm, Spodoptera littoralis (Biosd.)

The present study was conducted for evaluating of the impact of two insect growth regulators (IGRs) namely, Applaud (buprofezin) as a chitin synthesis inhibitor and Admiral (pyriproxyfen) as juvenile hormone analogue (JHA) in the larval body of the cotton leaf worm, Spodoptera littoralis. This evaluation was achieved via (1) Estimating the antioxidant system response present in the 4 th larval instar of S. littoralis through estimating the activity of two enzymes; catalases (CAT) and glutathione-S-transferase (GST), as well as an antioxidant compound; glutathione reduced (GSH). (2) Estimating the accumulated lipid peroxidation in the larval tissues by evaluating the level of Malonaldehyde (MDA) as an indicator for lipid peroxidation. Both tested IGRs used in this study showed more or less similar trend in their mode of action relative to the tested biomarkers in the present work. CAT showed a significant increase in its activity (42.02%) and (139.26%) for buprofezin and pyriproxyfen, respectively. This activity lasts for only one day post treatment then it was inhibited to be very close to that level in normal untreated larvae. This may be due its consumption in scavenging reactive oxygen species (ROS) produced due to significant accumulation of MDA. One the other hand, GST showed persisted increase in its activity especially with buprofezin treated larvae may be to overcome the deleterious effect of accumulating MDA. Similarly, GSH which serves as a free radicals scavenger also showed a significant increase in its level especially due to treatment. The present study which is conducted for the first time, documented the occurrence of lipid peroxidation due to IGRs treatment in the larval tissues in S. littoralis larvae which enhanced different antioxidant defensive system to overcome its effect.

Settlement behaviour and description of the lessepsian immigrant of the serpulid polychaete Pomatoleios kraussii in the Suez Bay

Pomatoleios kraussii is a lessepsian migrant in the Suez Canal and form the most abundant serpulid (sessile polychaetes) in Suez Bay. It firstly appeared in western side of the Suez Gulf. But it is now present in all regions of Suez Gulf. P. kraussii live at the intertidal zone in the Suez Bay. It forms dense aggregations in shallow water on natural hard submerged substrates. A quadrate made of wood with 20×20cm was used to collect the dense populations of P. kraussii, at monthly intervals from January to December 2008. The population density of P. kraussii reached 193797worms/m2 and its annual settlement reached 16150worms/m2 in the Bay. The species appears preferentially in Winter while its least presence was detected in summer. The lengths of both the worm body and tube are mentioned for a year. The tube is extending from 19mm to 42mm in length. The worm body length ranged from 7mm to 35mm. There is a direct correlation between the lengths of both the tube and the worm. This means that the greater the length of the worm the greater the length of the tube. Tube is pale blue in colour and carries a projecting flattened dorsal ridge. Operculum is flat with winged stalk and desk shaped. No collar setae. The body symmetrical, with 6 thoracic setigers and long abdomen. Thoracic dorsal setae limpate capillaries; ventral uncini with numerous teeth and gouge. All body regions are described in details.

Reduced muscle contraction and a relaxed posture during sleep-like Lethargus

Sleep is characterized by reduced muscle activity resulting in reduced movement and a typical posture compatible with relaxed muscles. Prior to each molt, C. elegans larvae go through a phase of behavioral quiescence called Lethargus. Lethargus has sleep-like properties, but a specific posture has not yet been described. Do C. elegans larvae relax their muscles during sleep and do they assume a typical posture? We measured worm posture and body wall muscle activity using calcium imaging across the sleep-wake-like cycle. We found that worms were less curved and had less muscle activity during the sleep-like state. We conclude that during Lethargus, muscle activity is reduced, resulting in a relaxed body posture typical for a sleep-like state.

Towards a virtual C. elegans: A framework for simulation and visualization of the neuromuscular system in a 3D physical environment

The nematode C. elegans is the only animal with a known neuronal wiring diagram, or "connectome". During the last three decades, extensive studies of the C. elegans have provided wide-ranging data about it, but few systematic ways of integrating these data into a dynamic model have been put forward. Here we present a detailed demonstration of a virtual C. elegans aimed at integrating these data in the form of a 3D dynamic model operating in a simulated physical environment. Our current demonstration includes a realistic flexible worm body model, muscular system and a partially implemented ventral neural cord. Our virtual C. elegans demonstrates successful forward and backward locomotion when sending sinusoidal patterns of neuronal activity to groups of motor neurons. To account for the relatively slow propagation velocity and the attenuation of neuronal signals, we introduced "pseudo neurons" into our model to simulate simplified neuronal dynamics. The pseudo neurons also provide a good way of visualizing the nervous system's structure and activity dynamics.

Intelligent Worm Sorting Using Robot Vision

In this paper, the application issues of vision sensing techniques to analysing the body postures of worms are discussed. The worm targeted here is the nematode C. elegans (short for Caenorhabditis elegans), which is widely used for pursuing research in developmental biology and neurology. The image of C. elegans is firstly segmented based on pixel grey-values, and the extracted worm region is skeletonized. The worm body shape is then modelled with a chain of multiple links. As the link connection is in the same structure of a robot manipulator, a variety of analysis techniques developed in robotics can be readily employed in the automatic analysis of worm images.

Effectiveness of synthetic trioxolane OZ78 against Schistosoma japonicum in mice and rabbits

Antischistosomal activities of a synthetic peroxide OZ78 (an ozonide carboxylic acid) against Schistosoma japonicum have been studied in mice and rabbits. Among 132 mice used, 30 of them were infected with 80-100 S. japonicum cercariae for collection of juvenile and adult schistosomes applied in in vitro tests. The remaining 102 mice were infected with 40 schistosome cercariae used for experimental treatment. Other 13 rabbits infected each with 200 schistosome cercariae were treated orally with OZ78 42 days post-infection. Most treated mice and rabbits were sacrificed 4 weeks post-treatment to collect residual schistosomes for evaluation of the drug efficacy. OZ78 and its sodium salt (OZ78-Na salt) 10-60 μg/mL alone exhibited no in vitro effect against day 14, day 21 schistosomula, and day 35 adult schistosomes. But OZ78 and OZ78-Na salt 10 and 20 μg/mL together with hemin 80 μg/mL showed decrease in worm motor activity and severe damage to the worm tegument and intestine, and all worms died within 3 days post-incubation. After infected mice were treated orally with OZ78 at a single dose of 400 mg/kg for 1 day, 34.9% of the worms shifted to the liver. Three and 7 days post-treatment, 100% of the worms were recovered from the liver. Fourteen days post-treatment, 92.3% of the worms still remained in the liver and 7.7% of the worms returned back to the mesenteric veins. Male and female worms shifted to the liver revealed in apparent shrinkage, degeneration of worm body, depigmentation in gut, and disappearance of ova in the uterus of some female worms. Meanwhile, dead worm and dead worm fragments were found in the liver tissues. In mice infected with various stages of schistosomes and treated orally with single OZ78 400 mg/kg, moderate or potential effect of the drug against day 0 (3-h-old worm), day 7, day 14, and day 21 juvenile worms and day 28, day 35 as well as day 42 adult worms were observed, the differences of total or female worm burdens between each treated group and control group were statistically significant (P < 0.01 or P < 0.05). Among the various stages of juveniles, day 7 worms were more susceptible to OZ78 with worm reduction of 83.8%, while the effect of OZ78 against day 28 to day 42 adult worms were similar. Finally, rabbits infected with adult schistosomes and treated with OZ78 at a single dose of 45 mg/kg or a daily dose of 35 mg/kg for three consecutive days resulted in significantly lower total and female worm burdens in comparison with that of control (P < 0.05) with total and female worm reductions of 84.1% and 84.7% as well as 74.3% and 77.4%, respectively. The results demonstrate that OZ78 possesses effect against both juvenile and adult S. japonicum in mouse model, and also shows effect against adult schistosomes in rabbits.

Confocal laser scanning microscopic observation on adult Schistosoma japonicum harbored in mice following treatment with single-dose mefloquine

The aim of the present study is to assess the mefloquine-induced alteration of adult Schistosoma japonicum using confocal laser scanning microscopy (CLSM). Eight out of ten mice infected with 60-80 S. japonicum cercariae for 35 days were treated orally with mefloquine at a single dose of 400 mg/kg. Four groups of two mice were killed at 24 h and 3, 7, and 14 days post-treatment, and schistosomes were collected by perfusion from the liver and mesenteric veins, fixed in 70% alcohol, stained with acid carmine, and examined by CLSM. Worms obtained from untreated mice served as controls. Twenty-four hours post-treatment, focal tegument of adult male and female worms, which composed of fine and short villus-like materials, became thicker and longer, or disorder arrangement, while the musculatures beneath the tegument revealed in focal and irregular swelling with various degrees. In the gut of male and female schistosomes, severe dilatation accompanied by swelling, collapse, and peeling of gut mucosa was universal. In the reproductive organs, no apparent alteration in the testis structure of male worms was seen, while in female worms, slight damage to the ovary included loose arrangement of mature ovary cells accompanied by some of them degenerated and collapsed. As to vitelline glands, severe damage, such as swelling, indistinction, fusion or collapse of vitelline cells, and apparent swelling of parenchymal tissues in vitelline gland lobules, was seen. Meanwhile, abnormal ova emerged in the uterus at this time point. Three to 7 days post-treatment, the damage to the worms aggravated either in extent or in severity along with time. In some focally swollen worm body, the parenchymal tissues revealed in severe swelling. In addition, a large piece of degenerated and necrotic parenchymal tissues emerged closed to the severe destructed oral or ventral sucker. In the gut of male and female worms, the major alterations manifested by focal collapse or peeling of mucosa, and desquamation of gut epithelial cells. As to the reproductive organs, the testes of male worms revealed in reduction of size, decrease in number of germinative cells, and some of them showed degeneration and collapse, or destruction of the capsule around the testis. In female worms, some ovaries only showed degenerated and collapsed cells accompanied with many cell fragments. Meanwhile, almost all of the vitelline cells lost their definition, which revealed in indistinct cell structure, fusion of some cells, and formation of many cell fragments due to their collapse. Fourteen days post-treatment, only some male worms survived the treatment were collected. Their tegument and musculature showed prominent recovery, but severe damage to the gut and testes was still observed. Our results confirm that under the observation by CLSM, mefloquine exhibits destructive effect on adult S. japonicum, particularly the morphological structure of digestive system and reproductive system of the worms.

Histopathological changes of juvenile Schistosoma japonicum harbored in mice treated orally with mefloquine at a smaller single dose

The histopathological changes of 14-day-old Schistosoma japonicum induced by a smaller single dose of mefloquine have been studied. Twenty-three mice infected with 60-80 S. japonicum cercariae for 14 days were treated orally with mefloquine at a single dose of 200 mg/kg (free base), and groups of three mice were killed at various intervals posttreatment. The liver of each mouse was removed, fixed and processed routinely, and examined by light microscopy. Eight hours posttreatment, 38.2% and 39.8% of schistosomulum sections were classified as degenerated and dead, respectively. The degenerated schistosomula revealed in high dilatation of gut with disruption of gut mucosa, swelling of the worm body accompanied by looseness or extensive lysis of parenchymal tissues, and focal swelling or peeling of tegument, while dead worms showed that their damaged tegument adhered to the vessel and inflammatory cell attached on and penetrated into the worm body. Twenty-four hours to 3 days posttreatment, the degenerated schistosomulum sections decreased from 28.1% to 8.2%, while the sections of dead schistosomula increased from 60.0% to 74.8%. At these time periods, the damage intensity of degenerated schistosomula aggravated, while dead schistosomula showed disintegration of internal structures infiltrated by eosinophil-predominant inflammatory cells to form the dead worm abscess. Seven days to 14 days posttreatment, no normal schistosomulum section was observed, and the percentages of degenerated and dead worms further decreased from 3.4% to 3.0% and 34.4% to 12.6%, respectively. Meanwhile, 62.2% to 84.4% of dead worms developed to dead worm granulomas and part of them situated in early stage. Twenty-eight days posttreatment, only dead worm granulomas were observed in the liver sections and part of them developed to late stage. The results indicate that a smaller single mefloquine dose 200 mg/kg exhibits a potential and fast killing effect against S. japonicum juvenile and induces severe histopathological lesions.

Further studies on mefloquine and praziquantel alone or interaction of both drugs against Schistosoma japonicum in vitro

The aim of the present study is to further understand and analyze the interaction of mefloquine with praziquantel against adult Schistosoma japonicum in vitro. Mice infected with S. japonicum cercariae for 35-37 days were sacrificed, and adult schistosomes were collected by perfusion. Schistosomes were placed to each of 12 wells of a Falcon plate and maintained in RPMI 1640 supplemented by 10% calf serum. For determination of 50% and 95% lethal concentration (LC50 and LC95) of the two drugs in vitro, schistosomes were exposed to mefloquine at concentrations of 1, 2, 3, 4, 5, 6, 7, and 10 μg/mL or praziquantel at concentrations of 0.001, 0.01, 0.05, 0.1, 0.2, 0.5, 1, 10, and 30 μg/mL. The plate was incubated at 37°C in 95% air + 5% CO₂ for 72 h. According to the half-life of oral mefloquine and praziquantel in mice, mefloquine combined with praziquantel simultaneously, mefloquine administered within 1 h after praziquantel and praziquantel administered within 17 h after mefloquine were used to evaluate the effect of mefloquine in combination with praziquantel against S. japonicum in vitro. The results showed that the LC50 and LC95 of mefloquine calculated by the Bliss method were 6.17 μg/mL (95% confidence limits, 5.84-6.517 μg/mL) and 8.703 μg/mL (95% confidence limits, 7.632-9.797 μg/mL), respectively. As to praziquantel, no worm death was seen when schistosomes were exposed to praziquantel at concentrations of 0.005-0.2 μg/mL for 72 h. While in the worms exposed to praziquantel 1, 10, and 30 μg/mL, strong spasmodic contractions of the worm body and vesiculation along the worm surface were observed, but 48-75% of the schistosomes survived the exposure in 72-h incubation. Meanwhile, the number of dead worms that emerged in each group was not proportion to the increasing concentrations. Therefore, it is not appropriate to calculate the LC50 and LC95 of praziquantel. For evaluation of the interaction with the two drugs, praziquantel 0.1 or 0.2 μg/mL, which may induce moderate or strong spasmodic contractions of the worm body and vesiculation along the worm surface, was combined with mefloquine 5, 6, or 7 μg/mL. It was found that when mefloquine combined with praziquantel simultaneously or administered 1 h after addition of praziquantel, the spasmodic contraction of the male worm body was antagonized by mefloquine in various degrees according to the concentrations of mefloquine used. Meanwhile, praziquantel-induced weakened motor activity could be reversed by mefloquine. In female worms, morphological alterations and stimulated motor activity induced by mefloquine still developed. Interestingly, using these two regimens to combine mefloquine with praziquantel resulted in no impact or a decrease in worm mortality. On the other hand, praziquantel 0.2 μg/mL administered within 17 h after mefloquine 5 or 6 μg/mL promoted the damage to the tegument of the worms, which led to enhance the worm mortality compared with that of worms exposed to mefloquine alone. The results indicate that in vitro higher concentrations of praziquantel administered within 17 h after mefloquine may increase the effect against adult schistosomes, while praziquantel combined with mefloquine simultaneously or administered 1 h before addition of mefloquine exhibits no impact or decrease in the effect against schistosomes.

Probing the physiology of ASH neuron in Caenorhabditis elegans using electric current stimulation

Electrical stimulation has been widely used to modulate and study the in vitro and in vivo functionality of the nervous system. Here, we characterized the effect of electrical stimulation on ASH neuron in Caenorhabditis elegans and employed it to probe the neuron's age dependent properties. We utilized an automated microfluidic-based platform and characterized the ASH neuronal activity in response to an electric current applied to the worm's body. The electrically induced ASH neuronal response was observed to be dependent on the magnitude, polarity, and spatial location of the electrical stimulus as well as on the age of the worm.

Increase in Alphaproteobacteria in association with a polychaete, Capitella sp. I, in the organically enriched sediment

We conducted bioremediation experiments on the organically enriched sediment on the sea floor just below a fish farm, introducing artificially mass-cultured colonies of deposit-feeding polychaete, Capitella sp. I. To clarify the association between the Capitella and bacteria on the efficient decomposition of the organic matter in the sediment in the experiments, we tried to identify the bacteria that increased in the microbial community in the sediment with dense patches of the Capitella. The relationship between TOC and quinone content of the sediment as an indicator of the bacterial abundance was not clear, while a significant positive correlation was found between Capitella biomass and quinone content of the sediment. In particular, ubiquinone-10, which is present in members of the class Alphaproteobacteria, increased in the sediment with dense patches of the Capitella. We performed denaturing gradient gel electrophoresis (DGGE) analyses to identify the alphaproteobacterial species in the sediment with dense patches of the worm, using two DGGE fragments obtained from the sediment samples and one fragment from the worm body. The sequences of these DGGE fragments were closely related to the specific members of the Roseobacter clade. In the associated system with the Capitella and the bacteria in the organically enriched sediment, the decomposition of the organic matter may proceed rapidly. It is very likely that the Capitella works as a promoter of bacteria in the organically enriched sediment, and feeds the increased bacteria as one of the main foods, while the bacteria decompose the organic matter in the sediment with the assistance of the Capitella.

An elasto-hydrodynamical model of friction for the locomotion of Caenorhabditis elegans

Caenorhabditis elegans (C. elegans) is one of the most studied organisms by biologists. Composed of around one thousand cells, easy to culture and to modify genetically, it is a good model system to address fundamental physiological questions and in particular to investigate neuromuscular processes. Many C. elegans mutants can be distinguished by their locomotion phenotype and it then important to understand the biomechanics of their locomotion and in particular the mechanics of their undulating crawling motion on agar aqueous gels where they are commonly grown and observed. In this article, we present a mechanical model of the friction of the worms on their substrate where we have included capillarity (which pins the worm of the gel), the hydrodynamics of the lubrication film (between worm and gel) and the substrate/body elasticity. We determine the ratio of the transverse to longitudinal friction coefficients of the worm body on the culture gel as a function of a control parameter which describes the relative role of the deformation of the gel and the viscous dissipation in the lubrication film. Experimentally this ratio is – for soft gels – larger than the maximal value predicted by our model (this maximum is equal to 2, the value for an infinite cylinder in bulk liquid) and we propose to include the plasticity of the gel (i.e. the dissipation of the deformation of the gel) for a better description of the worm/gel interaction.

Gene editing activity on extrachromosomal arrays in C. elegans transgenics

Gene editing by modified single-stranded oligonucleotides is a strategy aimed at inducing single base changes into the genome, generating a permanent genetic change. The work presented here explores gene editing capabilities in the model organism Caenorhabditis elegans. Current approaches to gene mutagenesis in C. elegans have been plagued by non-specificity and thus the ability to induce precise, directed alterations within the genome of C. elegans would offer a platform upon which structure/function analyses can be carried out. As such, several in vivo assay systems were developed to evaluate gene editing capabilities in C. elegans. Fluorescence was chosen as the selectable endpoint as fluorescence can be easily detected through the transparent worm body even from minimal expression. Two tissue specific fluorescent expression vectors containing either a GFP or mCherry transgene were mutagenized to create a single nonsense mutation within the open reading frame of each respective fluorescent gene. These served as the target site to evaluate the frequency of gene editing on extrachromosomal array transgenic lines. Extrachromosomal arrays can carry hundreds of copies of the transgene, therefore low frequency events (like those in the gene editing reaction) may be detected. Delivery of the oligonucleotide was accomplished by microinjection into the gonads of young adult worms in an effort to induce repair of the mutated fluorescent gene in the F1 progeny. Despite many microinjections on the transgenic strains with varying concentrations of ODNs, no gene editing events were detected. This result is consistent with the previous research, demonstrating the difficulties encountered in targeting embryonic stem cells and the pronuclei of single-celled embryos.

Burrow ventilation and associated porewater irrigation by the polychaete Marenzelleria viridis

Burrow ventilation of benthic infauna generates water currents that irrigate the interstices of the sediments surrounding the burrow walls. Such activities have associated effects on biogeochemical processes affecting ultimately important ecosystem processes. In this study, the ventilation and irrigation behavior of Marenzelleria viridis, an invasive polychaete species in Europe, was analyzed using different approaches. M. viridis showed to perform two types of ventilation: (1) muscular pumping of water out of the burrow and (2) cilia pumping of water into the burrow. Flowmeter measurements presented muscular pumping in time averaged rates of 0.15 ml min −1. Oxygen needle electrodes positioned above the burrow openings revealed that muscular undulation of the worm body pumps anoxic water out of the burrow. On the other hand, microscope observations of the animal showed that ventilation of oxygen-rich water in the burrow occurs by ciliary action. The volume of water irrigated by M. viridis appears to vary linearly within the first 24 h incubation, with rates ranging from 0.003 to 0.01 ml min −1. From those rates we could estimate that the time averaged rate of cilia ventilation should be about 0.16 ml min −1. Since the cilia pumping into the burrow occurs in periods of 24 ± 12 min and at 50–70% of the measured time, considerable amounts of water from deeper sediments may percolate upwards to the sediment surface. This water is rich in reduced compounds and nutrients and may have important associated ecological implications in the ecosystem (e.g. affecting redox conditions, organic matter degradation, benthic recruitment and primary production).