Observation Chamber Research Articles

Intraspecific Aggression in Neonate Common Five-Lined Skinks (Plestiodon fasciatus)

Abstract We studied aggressive behavior of neonate Common Five-Lined Skinks (Plestiodon fasciatus) in a controlled laboratory study. Two neonates of differing sizes were placed on opposite sides of a divided observation chamber for 48 h. Then the partition was removed, a single retreat was placed in the center of the observation chamber, and the behaviors of the two neonates were recorded for 60 min. Neonate Five-Lined Skinks did not interact unless they were within one body length of each other. During an encounter, one lizard typically displayed aggressive behavior (lunging) while the other lizard displayed submissive behavior (avoidance/fleeing), though in 24% of encounters the two lizards showed no reaction. Dominant lizards won significantly more encounters than subordinate lizards. The subordinate lizards displayed tail wiggling behavior significantly more frequently than dominant lizards, suggesting this behavior may be a visual signal of subordinate status. The larger lizard was dominant in 75% of...

Soft Lithographic Procedure for Producing Plastic Microfluidic Devices with View-ports Transparent to Visible and Infrared Light.

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable microfluidic devices. Here, a protocol for the fabrication of plastic microfluidic devices is demonstrated, where soft lithographic techniques are used to embed transparent Calcium Fluoride (CaF2) view-ports in connection with observation chamber(s). The method is based on a replica casting approach, where a polydimethylsiloxane (PDMS) mold is produced through standard lithographic procedures and then used as the template to produce a plastic device. The plastic device features ultraviolet/visible/infrared (UV/Vis/IR) -transparent windows made of CaF2 to allow for direct observation with visible and IR light. The advantages of the proposed method include: a reduced need for accessing a clean room micro-fabrication facility, multiple view-ports, an easy and versatile connection to an external pumping system through the plastic body, flexibility of the design, e.g., open/closed channels configuration, and the possibility to add sophisticated features such as nanoporous membranes.

Abstract 3782: Genetic analysis using a novel high-purity enrichment system for circulating tumor cells independent of epithelial cell antigen

Abstract Background Genetic analysis of circulating tumor cells (CTCs) is useful as a liquid biopsy. However, there are 3 challenging issues in processing of CTC samples for clinical use of the analysis: [1] numerous residual blood cells in processed samples, [2] loss of CTCs that do not express epithelial markers, and [3] very laborious process. Here, we developed a novel system capable of overcoming all of these problems. Methods Our CTC analysis system is composed of 3 steps: [1] filtering of whole blood followed by immunostaining and magnetic labeling of cells trapped on the filter, [2] depletion of white blood cells (WBCs) in the cells recovered from the filter by magnetic separation, and [3] trapping the resultant cells at an observation chamber in a microfluidic enrichment device using dielectrophoresis, followed by recovering them as a concentrated sample after fluorescence microscope observation. SNV and CNV analysis was conducted using the collected concentrated sample, and the system performance was substantiated. Genetic mutations of the cells in the collected sample were detected by the Quenching Probe method. On the other hand for CNV analysis, cells in the collected concentrated sample were immobilized on slide glass and analysis of gene amplification conducted by FISH. Results With SNV analysis, our system successfully detected EGFR, KRAS or PIK3CA mutations of cancer cell lines spiked in 8 mL of whole blood (Table). The detection sensitivity of our method was 1 cell/mL, and both the cancer cells and their genetic mutations were detected within 9 hours of starting the processing of whole blood. Additionally, with CNV analysis, HER2 gene amplification was confirmed with cell lines spiked in 8 mL of blood. This detection result was obtained within 48 hours. Conclusion Our system would be useful for the analysis of gene mutations in a wide range of CTC types independent of certain epithelial antigens, such as CK and EpCAM, and can be used for various genetic analyses. Table Results of spiking test for SNV analysisSpiked cell linesExpected count[cells/8ml]No. of detected spiked cells [cells]No. of detected remained WBCs [cells]Detected genotypesNCI-H197512979EGFR L858RNCI-H16508225EGFR exon19 deletionSW6208648KRAS codon12, 13SNU-1124154KRAS codon12, 13MCF-777341PIK3CA G1633A Citation Format: Hidenori Takagi, Masahiro Kozuka, Hiroshi Ito, Soo Hyeon Kim, Mitsuharu Hirai, Teruo Fujii. Genetic analysis using a novel high-purity enrichment system for circulating tumor cells independent of epithelial cell antigen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3782. doi:10.1158/1538-7445.AM2017-3782

Abstract 1862: Direct observation of colorectal cancers using field-emission scanning electron microscopy with a thin polymer membrane, the NanoSuit

Abstract Background: Field-emission scanning electron microscopy (FE-SEM) enables us to observe nano-sized objects with great depth of focus and high resolution. However, the observation of biological samples including colorectal tissues using an FE-SEM has been difficult because it requires to evacuate its inside to prevent electron scattering, therefore all organisms containing ca. 70% water are rapidly evaporated and consequently caused structural disruption and collapse. To overcome the limitations of the conventional SEM, equipment such as low-vacuum scanning electron microscopy and environmental scanning electron microscope was developed. However, they are not reliable enough to investigate living organisms or wet tissues with high resolution level. We have recently reported that a simple surface modification consisting of a thin extra layer, coined the term ‘NanoSuit®’, can keep organisms alive in the high vacuum (10−3 to 10−7 Pa) of the SEM. We now modified the technique and developed a new solution, which enables FE-SEM observations of wet tissues. In this study, we utilized this technique to observe real images of colorectal cancers and their adjacent normal mucosae at high resolution. Materials and methods: Colorectal cancer tissues and their adjacent normal mucosa were cut with a scalpel from specimens surgically resected. All patients enrolled in this study provided written informed consent. Observations were carried out with an FE-SEM (S-4800, Hitachi or JEM-7100F, JEOL, Japan) at acceleration voltage of 1.0 kV. The vacuum level of the observation chamber was 10-3 - 10-7 Pa. The newly developed surface shield enhancer (SSE) solution was used to make NanoSuit® for wet tissue observation. To form the NanoSuit®, the specimens were dipped for 1 min into the SSE solution and blotted briefly thereafter put on dry filter paper to remove excess solution. Specimens were then introduced directly into an FE-SEM to form a NanoSuit® following irradiation of the electron beam. Results: Fine structures of intestinal crypt and villi were observed in normal colon mucosa using FE-SEM with a NanoSuit®, whereas fixed specimens prepared with conventional method showed obvious structural damage. Comparing with the region of normal colon mucosa, colorectal cancer lesion had relatively amorphous surface, therefore the border between non-cancerous mucosa and cancer lesions in colon tissues are able to be distinguished under high magnification. In addition, fiber-like structure was observed at the border between noncancerous mucosa and cancer lesions, suggesting an invasive front of colorectal cancer. Conclusions: We successfully observed the real mucosal surfaces and cancer lesions of colorectum with high resolution by an FE-SEM using a newly developed vacuum-proof suit, the “NanoSuit®”. This novel technique will enable us to investigate further physiopathology of GI tract including cancers. Citation Format: Hirotoshi Kikuchi, Tomohiro Matsumoto, Takanori Hiraide, Yusuke Ozaki, Amane Hirotsu, Tomohiro Murakami, Toshiki Kawabata, Yoshihiro Hiramatsu, Kinji Kamiya, Takanori Sakaguchi, Yasuharu Takaku, Isao Ohta, Takahiro Hariyama, Hiroyuki Konno. Direct observation of colorectal cancers using field-emission scanning electron microscopy with a thin polymer membrane, the NanoSuit [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1862. doi:10.1158/1538-7445.AM2017-1862

Are pioneer mangroves more vulnerable to oil pollution than later successional species?

Propagules of Avicennia marina, Bruguiera gymnorrhiza and Rhizophora mucronata were cultivated in rhizotrons (root observation chambers) and subjected to sediment oiling treatments for 409days to determine the effects of oil on root growth. Oiling reduced root length, specific root length, relative root growth rate and root diameter, while specific root volume increased. Oiling reduced root length by 96% in A. marina, 99% in B. gymnorrhiza and 80% in R. mucronata, while specific root volume increased by 34%, 29% and 23% respectively. Relative root growth rate decreased in the oiled treatments by 84%, 80% and 73% respectively. Avicennia exhibits typical root traits of a pioneer species compared to slower-growing later successional species like B. gymnorrhiza and R. mucronata. These traits of A. marina not only allow more rapid establishment of seedlings, but also expose a larger root surface area and therefore greater susceptibility to oil contamination than the other species.

AGGRESSIVE BEHAVIORS AND THEIR EFFECT ON RESOURCE USE BY MALE LITTLE BROWN SKINKS, SCINCELLA LATERALIS

The aggressive behaviors of adult male Little Brown Skinks, Scincella lateralis, and their effects on access to an important resource (a single retreat) were the subject of a study consisting of 10 laboratory trials in which the behavioral interactions between a pair of individuals was recorded. Analysis of these interactions made it possible to identify a dominant and a subordinate male in each trial; the male with the greater bulk was dominant in 9 of the 10 trials. Aggressive behaviors recorded include lunging, chasing, and biting; the dominant male performed lunging significantly more often than the subordinate male and was the only individual to exhibit chasing. The most common behavior recorded was avoidance which was shown almost exclusively by the subordinate male. Both dominant and subordinate males exhibited tail twitching which we hypothesize to be a sign of agitation. The two males spent significantly more time on opposite sides of the observation chamber than on the same side and almost never occupied the single retreat simultaneously because the subordinate male repeatedly moved to avoid the dominant male. The implications of these results on spacing patterns and resource use of Scincella lateralis in the wild are discussed.

Study on three-dimensional expansion characteristics of four wall combustion-gas jets in confined liquid space

To explore further the launch mechanism of the new underwater launching technology proposed in this paper, the expansion characteristics of four wall combustion-gas jets in confined liquid space must be studied firstly. The experimental device is designed, and the high-speed digital photographic system is adopted to obtain the expansion sequence processes of Taylor cavities formed by the four wall jets. Meanwhile, the influence of the injection pressure on the axial expansion property of the four wall jets is discussed. Based on the experiments, a three-dimensional unsteady mathematical model is established to simulate the turbulent flow process of the four wall jets expanding in liquid, and the temporal and spatial distribution laws of phase, pressure, temperature, and velocity and the evolution rules of vortices are illustrated in detail. Results show that, accompanied by the jets expanding downstream, the four wall combustion-gas jets get close to each other and achieve convergence eventually under induction of the interference effect between multiple jets. Meanwhile, the heads of the Taylor cavities separate from the observation chamber wall and offset to the central axis of the observation chamber with time going on. The numerical simulation results of the four wall combustion-gas jets coincide well with the experimental data.

Study on the gas-curtain generation characteristics by the multiple gas jets in a liquid-filled tube

To further understand the gas-curtain generation characteristics during the launching process of the underwater guns, a simulated gas-injector with multiple nozzles is designed and the expansion process of these multiple combustion-gas jets is experimentally captured. Experiment results indicate that, with turbulent mixing between the gas jets and the liquid medium, the gas curtain is generated in the observation chamber. Based on the experiment, a three dimensional unsteady model is established to simulate the expansion process of the multiple jets. Numerical result shows, with the injection of the gas jets, pressure declines in the Taylor cavity along the axial direction at the beginning. During the expansion process, the multiple jets contact and interact with each other, and pressure rises in the mixing area. After merging, backflow vortexes interact and converge, and the vortexes move along the axial direction with the expansion of the combustion gas jets.

All-in-one 3D printed microscopy chamber for multidimensional imaging, the UniverSlide

While live 3D high resolution microscopy techniques are developing rapidly, their use for biological applications is partially hampered by practical difficulties such as the lack of a versatile sample chamber. Here, we propose the design of a multi-usage observation chamber adapted for live 3D bio-imaging. We show the usefulness and practicality of this chamber, which we named the UniverSlide, for live imaging of two case examples, namely multicellular systems encapsulated in sub-millimeter hydrogel shells and zebrafish larvae. We also demonstrate its versatility and compatibility with all microscopy devices by using upright or inverted microscope configurations after loading the UniverSlide with fixed or living samples. Further, the device is applicable for medium/high throughput screening and automatized multi-position image acquisition, providing a constraint-free but stable and parallelized immobilization of the samples. The frame of the UniverSlide is fabricated using a stereolithography 3D printer, has the size of a microscopy slide, is autoclavable and sealed with a removable lid, which makes it suitable for use in a controlled culture environment. We describe in details how to build this chamber and we provide all the files necessary to print the different pieces in the lab.

Expansion characteristics of multiple wall jets in cylindrical observation chamber

The objective of this study is to investigate the drag reduction effect of a new launch technology by utilizing propellant gases to drain off water in the front of the projectile inside the gunbarrel for submerged launch process of underwater gun. A static analogue visualized device was designed and the high-speed digital photographic system was adopted to investigate expansion processes of multiple wall jets in cylindrical observation chamber. The evolution laws of Taylor cavities can be obtained by dealing with the expansion sequence maps. Based on the experiments, a three-dimensional unsteady mathematical model is established to simulate the interaction process between the multiple wall jets and liquid medium, which can achieve the detailed distribution characteristics of phase, pressure, temperature and velocity in flow field. Results show that, by increasing four wall jets to eight wall jets, the decrease of the inlet turbulent kinetic energy of each jet leads to a decline in the initial axial velocity. However, the Taylor cavities achieve to converge more quickly for the case with more numbers of combustion-gas jets due to less nozzle interval distance. In addition, the convergence of Taylor cavities can enhance the drainage effect of the multiple wall jets and achieve excellent drag reduction effect for the underwater launching process, wherein the drainage effect for the case of six wall jets is the most outstanding.

Development of low temperature atomic force microscopy with an optical beam deflection system capable of simultaneously detecting the lateral and vertical forces.

The atomic force microscopy (AFM) is a very important tool for imaging and investigating the complex force interactions on sample surfaces with high spatial resolution. In the AFM, two types of detection systems of the tip-sample interaction forces have been used: an optical detection system and an electrical detection system. In optical detection systems, such as optical beam deflection system or optical fiber interferometer system, both the lateral and the vertical tip-sample forces can be measured simultaneously. In electrical detection systems, such as qPlus or Kolibri sensors, either the lateral or vertical forces can be measured. Simultaneous measurement of the lateral and vertical interaction forces effectively allows investigation of force interactions because the force is a vector with magnitude and direction. In this study, we developed a low-temperature, frequency-modulation AFM using an optical beam deflection system to simultaneously measure the vertical and lateral forces. In this system, the heat sources, such as a laser diode and a current-to-voltage converter, for measuring the photocurrent of the four-segmented photodiode are located outside the observation chamber to avoid a temperature increase of the AFM unit. The focused optical beam is three-dimensionally adjustable on the back side of the cantilever. We demonstrate low-noise displacement measurement of the cantilever and successful atomic resolution imaging using the vertical and lateral forces at low temperatures.

Microbial Communities in Globodera pallida Females Raised in Potato Monoculture Soil.

Globodera spp. are under strict quarantine in many countries. Suppressiveness to cyst nematodes can evolve under monoculture of susceptible hosts. Females developing in potato monoculture soil infested with G. pallida populations Chavornay or Delmsen were examined for inherent microbial communities. In the greenhouse, nonheated and heat-treated (134°C for 10 min) portions of this soil were placed in root observation chambers, planted with Solanum tuberosum 'Selma', and inoculated with G. pallida Pa3 Chavornay. At harvest in Delmsen soil, cysts had fewer eggs in nonheated than heat-treated soil. In denaturing gradient gel electrophoresis analysis, bacterial and fungal fingerprints were characterized by a high variability between replicates; nonheated soils displayed more dominant bands than heated soils, indicating more bacterial and fungal populations. In amplicon pyrosequencing, females from nonheated portions frequently contained internal transcribed spacer sequences of the fungus Malassezia. Specific for the Chavornay and Delmsen population, ribosomal sequences of the bacteria Burkolderia and Ralstonia were abundant on eggs. In this first report of microbial communities in G. pallida raised in potato monoculture, candidate microorganisms perhaps associated with the health status of the eggs of G. pallida were identified. If pathologies on cyst nematodes can be ascertained, these organisms could improve the sustainability of production systems.

Photoresist Micro-Chamber for the Diffracted X-ray Tracking Method Recording Single-Molecule Conformational Changes

The diffracted X-ray tracking method has been established for capturing conformational changes of single KcsA potassium channels, which records position of X-ray diffraction spot from a gold nanocrystal attached to the channel. The conventional observation chamber setup could trace a diffraction spot; however relatively high background noise resulting from X-ray scattering degraded a spatial resolution. This paper report a novel low-noise microfabricated observation chamber consisting of SiN membrane window supported by Si and embedded microchannel in negative photoresist. The measured noise exhibited lower level compared to the conventional chamber, which almost reached the detection limit of the employed imaging system.

Superresolution live imaging of plant cells using structured illumination microscopy.

Although superresolution (SR) approaches have been routinely used for fixed or living material from other organisms, the use of time-lapse structured illumination microscopy (SIM) imaging in plant cells still remains under-developed. Here we describe a validated method for time-lapse SIM that focuses on cortical microtubules of different plant cell types. By using one of the existing commercially available SIM platforms, we provide a user-friendly and easy-to-follow protocol that may be widely applied to the imaging of plant cells. This protocol includes steps describing calibration of the microscope and channel alignment, generation of an experimental point spread function (PSF), preparation of appropriate observation chambers with available plant material, image acquisition, reconstruction and validation. This protocol can be carried out within two to three working days.

From the back or front: The courtship position is a matter of smell and sight in Drosophila melanogaster males

During courtship, Drosophila melanogaster males usually position themselves behind the target female. To decipher the sensory cues that guide the males to the courting position, we quantitatively analyzed male locomotion traces within a circular observation chamber, at the center of which an immobilized virgin female was placed as a courtship target. Wild-type males preferentially stayed behind the female under not only daylight but also dark conditions, indicating that vision is dispensable for orientation by males. By contrast, olfaction-defective Or83b2 homozygous males often positioned themselves in front of a female to court under dark but not daylight conditions. We conclude that vision and olfaction redundantly guide the male fly to move behind the female to perform courtship actions. The visual and olfactory features that provide a male with cues for differentiating between the front and back end of a female are yet to be determined.

Methods for imaging individual cilia in living echinoid embryos.

The embryos of echinoids (sea urchins and sand dollars) serve as excellent models for studying cilia differentiation and stages of the cilia life cycle including ciliogenic initiation, growth, maintenance, and retraction. Early in echinoid development, uniform motile cilia form on all cells simultaneously but then rapidly differentiate into multiple cilia types that differ in morphology, motility, and signaling sensitivity. Metal ion treatments that shift germ layer boundaries and thereby "animalize" or "vegetalize" embryos can be used to enrich for low-abundance cilia types rendering those specialized cilia and the differentiation processes they exhibit much easier to study. The experimental advantages of having robust cilia growth and differentiation is tempered by the challenge of restraining ciliated embryos well enough to view the process of ciliogenesis live. We have developed four observation chambers as modifications of the Kiehart chamber for long-term light microscopic imaging of ciliated echinoid embryos. One of these systems employs paramagnetic beads to render ciliated larvae magnetic so they can be gently and reversibly trapped directly under the objective lens. With this magnetic trapping system, the larva can be positioned and repositioned until they achieve the orientation with the clearest view of any cilia of interest. These methods of gentle embryo restraint allow normal embryo development and the normal ciliogenic cycle and ciliary differentiation processes to continue in direct view. Sequential image series can then be collected and analyzed to quantitatively study the wide spectrum of cilia behaviors and properties that arise in developing echinoid embryos.

Toward a Speculative Nanoecology: Transscalar Knowledge, Disciplinary Boundaries, and Ecology's Posthuman Horizon

In the iconic 1951 film The Day the Earth Stood Still, an alien messenger, Klaatu, arrives in Washington dc via flying saucer to deliver a warning to the nations of Earth: Earthlings have, through their development of atomic technology, created weapons powerful enough to eventually threaten their galactic neighbors. Therefore, Earth must fully disarm or face immediate annihilation by an autonomous, robotic peacekeeping force, locally represented by Gort, a metallic, humanoid robot capable of vaporizing objects via a ray emitted from its “head.” From its opening shot of a galactic cluster, the film signals a shift in scale. Earth no longer circumscribes the world. Humanity poses a threat to the larger interplanetary ecosystem, represented as a hybrid organictechnological milieu. In the 2008 remake of this sciencefiction classic, gort (Genetically Organized Robotic Technology) looks and acts much the same but has grown in size by at least a factor of ten. Human military forces lock it away in a secure observation chamber in an underground facility. At the climax of the film, however, the appearance of minute, spiderweblike etchings on the observation pane separating the humans from their robotic “captive” signals a scalar jump from the gargantuan to the diminutive, as gort shifts into its offense mode. Its size and armament are revealed as red herrings in this remarkable sequence, which features the robot’s disintegration into a swarm of insectlike nanobots. At the

Jetting microfluidics with size-sorting capability for single-cell protease detection

Activated proteases such as matrix metalloproteinases (MMPs) secreted from cancer cells can degrade the extracellular matrix (ECM) and contribute to tumour formation and metastasis. Measuring MMP activity in individual cancer cells can provide important insights on cancer cell heterogeneity and disease progression. Here, we present a microfluidic platform combining a droplet jetting generator and a deterministic lateral displacement (DLD) size-sorting channel that is capable of encapsulating individual cancer cells inside picoliter droplets effectively. Droplet jetting with cell-triggered Rayleigh-Plateau instability was employed which produced large droplets capable of cell encapsulation (diameter, ~25µm) and small empty droplets (diameter, ~14µm), which were then size-separated using a DLD size-sorting channel to enrich the single-cell encapsulated droplets (~78%), regardless of the cell density of input sample solutions. The droplets containing encapsulated cancer cells were collected in an observation chamber to determine the kinetic profiles of MMP secretion and the inhibitory response in the presence of the drug doxycycline at the single-cell level to reveal their heterogeneous MMPs secretion activities.

The influence of host species and location in the host detection ability of tiphiid (Hymenoptera: Tiphiidae) parasitoids.

Tiphia vernalis Rohwer and Tiphia popilliavora Rohwer are ectoparasitoids of root-feeding larvae of the Japanese beetle, Popillia japonica Newman, and oriental beetles, Anomala orientalis Waterhouse (Coleoptera: Scarabaeidae). Little is known about the influence of host species and location in the host detection ability of tiphiid wasps. In this study, we examined the response of female T. popilliavora wasps, an understudied Tiphia species, to potential host stimuli using dual choice tests in an observation chamber filled with soil. T. popilliavora wasps were able to successfully discriminate the trails containing body odor or frass of P. japonica grubs from trails without cues. Frass trails of P. japonica grubs elicited stronger responses than body odor trails. We also examined the preference of host cues by tiphiid wasps using dual choice behavioral assays. Both T. vernalis and T. popilliavora wasps did not show preference toward trails that either contained P. japonica or A. orientalis cues. In addition, we also determined the detection of host cues by tiphiid wasps in a dual-choice test for cues presented at varying soil depths. Wasps were able to successfully discriminate between the Y-tube arms with and without cues when the cues of P. japonica were buried at a depth of 2 cm. In contrast, both Tiphia species were unable to distinguish between the Y-tube arms with and without cues when the cues were buried at a depth of 5 cm. Thus, our findings suggest that once Tiphia wasps land on the ground, they can detect the presence of their specific hosts, just below the soil surface by exploiting the kairomones present in grub body odor trails and frass and once the wasps are in the soil, they use the same cues to direct themselves to the host grubs.

Microscale Laser Surgery Demonstrates the Grasping Function of the Male Sex Combs in Drosophila melanogaster and Drosophila bipectinata

AbstractMale secondary sexual traits of animals are richly diversified in form and complexity, yet there are many species in which their precise function remains unknown. Within the genus Drosophila, species belonging to the melanogaster and obscura species groups have evolved a remarkable variety of sex combs, male‐limited secondary sexual traits located on the tarsi of both front legs. Information concerning sex comb function is minimal or absent, except for D. melanogaster, where previous studies indicate that the sex combs are used for grasping the female prior to copulation. These studies, however, do not unambiguously demonstrate comb function, because it has not been possible to ascribe observed behavioral outcomes of the various comb manipulations to changes in the combs per se. We used microscale laser surgery to manipulate comb size in D. melanogaster and D. bipectinata, and tested the hypothesis that the sex combs function as grasping devices in courtship, making them essential for copulation to ensue. Results of high‐resolution behavioral analysis in small observation arenas demonstrated that in both species in which sex combs were surgically eliminated, males were unable to grasp, mount or copulate. The combless foretarsi of these altered males slipped off the end (D. melanogaster) and sides (D. bipectinata) of the female abdomen when courting males attempted to grasp. In most cases, males whose sex combs were reduced but not completely removed exhibited similar copulation probabilities as surgical control males, a result we demonstrated in observation chambers as well as under more ecologically realistic conditions inside population cages where males and females interacted on the surface of fruit substrates. Thus, the sex combs in D. melanogaster and D. bipectinata are grasping devices, essential for mounting and copulation.