Epithelial cell cluster size affects force distribution in response to EGF-induced collective contractility

Several factors present in the extracellular environment regulate epithelial cell adhesion and dynamics. Among them, growth factors such as EGF, upon binding to their receptors at the cell surface, get internalized and directly activate the acto-myosin machinery. In this study we present the effects of EGF on the contractility of epithelial cancer cell colonies in confined geometry of different sizes. We show that the extent to which EGF triggers contractility scales with the cluster size and thus the number of cells. Moreover, the collective contractility results in a radial distribution of traction forces, which are dependent on integrin β1 peripheral adhesions and transmitted to neighboring cells through adherens junctions. Taken together, EGF-induced contractility acts on the mechanical crosstalk and linkage between the cell-cell and cell-matrix compartments, regulating collective responses.     

Honeybees Use Celestial and/or Terrestrial Compass Cues for Inter‐Patch Navigation

Foraging honeybees (Apis mellifera) are well known to fly straight from the hive, their primary hub, to distal goals as well as between familiar feeding sites. More recently, it was shown that a distal feeding site may be used as a secondary hub. If not fully satiated, the foraging bee may decide to depart the first feeding site in a new compass direction straight to one of many other feeding sites (inter‐patch foraging). Using a recently developed recording method, we discovered that the chosen departure direction at a secondary hub can be guided exclusively by either celestial or terrestrial compass cues. Given our data, we draw two theoretical inferences. First, the bees must be capable of learning and remembering multiple, spatially distinct, navigation vectors between the hive and among multiple feeding sites. Second, this documented and useful representation of multiple navigation vectors between multiple, identified target locations logically implies composite place‐vector mapping, stored in long‐term memory.     

Inhibition of Rho-associated kinases disturbs the collective cell migration of stratified TE-10 cells

Background

The collective cell migration of stratified epithelial cells is considered to be an important phenomenon in wound healing, development, and cancer invasion; however, little is known about the mechanisms involved. Furthermore, whereas Rho family proteins, including RhoA, play important roles in cell migration, the exact role of Rho-associated coiled coil-containing protein kinases (ROCKs) in cell migration is controversial and might be cell-type dependent. Here, we report the development of a novel modified scratch assay that was used to observe the collective cell migration of stratified TE-10 cells derived from a human esophageal cancer specimen.

Results

Desmosomes were found between the TE-10 cells and microvilli of the surface of the cell sheet. The leading edge of cells in the cell sheet formed a simple layer and moved forward regularly; these rows were followed by the stratified epithelium. ROCK inhibitors and ROCK small interfering RNAs (siRNAs) disturbed not only the collective migration of the leading edge of this cell sheet, but also the stratified layer in the rear. In contrast, RhoA siRNA treatment resulted in more rapid migration of the leading rows and disturbed movement of the stratified portion.

Conclusions

The data presented in this study suggest that ROCKs play an important role in mediating the collective migration of TE-10 cell sheets. In addition, differences between the effects of siRNAs targeting either RhoA or ROCKs suggested that distinct mechanisms regulate the collective cell migration in the simple epithelium of the wound edge versus the stratified layer of the epithelium.

Electronic supplementary material

The online version of this article (doi:10.1186/s40659-015-0039-2) contains supplementary material, which is available to authorized users.     

A generalist brood parasite modifies use of a host in response to reproductive success

Avian obligate brood parasites, which rely solely on hosts to raise their young, should choose the highest quality hosts to maximize reproductive output. Brown-headed cowbirds (Molothrus ater) are extreme host generalists, yet female cowbirds could use information based on past reproductive outcomes to make egg-laying decisions thus minimizing fitness costs associated with parasitizing low-quality hosts. We use a long-term (21 years) nest-box study of a single host, the prothonotary warbler (Protonotaria citrea), to show that local cowbird reproductive success, but not host reproductive success, was positively correlated with the probability of parasitism the following year. Experimental manipulations of cowbird success corroborated that female cowbirds make future decisions about which hosts to use based on information pertaining to past cowbird success, both within and between years. The within-year pattern, in particular, points to local cowbird females selecting hosts based on past reproductive outcomes. This, coupled with high site fidelity of female cowbirds between years, points to information use, rather than cowbird natal returns alone, increasing parasitism rates on highly productive sites between years.     

Priority threat management of invasive animals to protect biodiversity under climate change

Climate change is a major threat to global biodiversity, and its impacts can act synergistically to heighten the severity of other threats. Most research on projecting species range shifts under climate change has not been translated to informing priority management strategies on the ground. We develop a prioritization framework to assess strategies for managing threats to biodiversity under climate change and apply it to the management of invasive animal species across one‐sixth of the Australian continent, the Lake Eyre Basin. We collected information from key stakeholders and experts on the impacts of invasive animals on 148 of the region's most threatened species and 11 potential strategies. Assisted by models of current distributions of threatened species and their projected distributions, experts estimated the cost, feasibility, and potential benefits of each strategy for improving the persistence of threatened species with and without climate change. We discover that the relative cost‐effectiveness of invasive animal control strategies is robust to climate change, with the management of feral pigs being the highest priority for conserving threatened species overall. Complementary sets of strategies to protect as many threatened species as possible under limited budgets change when climate change is considered, with additional strategies required to avoid impending extinctions from the region. Overall, we find that the ranking of strategies by cost‐effectiveness was relatively unaffected by including climate change into decision‐making, even though the benefits of the strategies were lower. Future climate conditions and impacts on range shifts become most important to consider when designing comprehensive management plans for the control of invasive animals under limited budgets to maximize the number of threatened species that can be protected.     

Extrapolation of random forest models shows scale adaptation in egret colony site selection against landscape complexity

Availability of certain habitats or landscape configurations can cause differential habitat selection in animal species. Landscape complexity can affect foraging scales, home ranges and movement, but its effect on habitat selection is not well documented. We aimed to examine differences in colony site selection of herons and egrets in different regions. We studied whether landscape complexities could affect their scale of selection and habitat preferences. We used colony distribution data and land-use maps for two neighboring regions, Ibaraki and Chiba prefectures in Japan, to create random forest models for analyzing habitat preferences and important scales of selection. We did cross-validation of the models, adjusted for its respective region's land-use maps with changing scales. The scales that best explained colony distribution were 1-, 4-, 10- and 15-km in the Ibaraki region, and 1- and 10-km in the Chiba region. Evergreen forest was the most important variable for Ibaraki at 4-km and for the Chiba at 1-km. The importance of other variables differed for other models. Cross-validation showed that herons and egrets had the same habitat preferences at a 4-km scale in Ibaraki and at a 1-km scale in Chiba. The scale of selection was reduced in Chiba, where the main foraging resources for herons and egrets was more complex. Differences in landscape complexities did not affect habitat preferences but resulted in differences in the scale of selection. Habitat selection models created at the landscape level can be useful to study behavioral aspects difficult to describe with direct observation in detail.     

Moving calls: a vocal mechanism underlying quorum decisions in cohesive groups

Members of social groups need to coordinate their behaviour when choosing between alternative activities. Consensus decisions enable group members to maintain group cohesion and one way to reach consensus is to rely on quorums. A quorum response is where the probability of an activity change sharply increases with the number of individuals supporting the new activity. Here, we investigated how meerkats (Suricata suricatta) use vocalizations in the context of movement decisions. Moving calls emitted by meerkats increased the speed of the group, with a sharp increase in the probability of changing foraging patch when the number of group members joining the chorus increased from two up to three. These calls had no apparent effect on the group's movement direction. When dominant individuals were involved in the chorus, the group's reaction was not stronger than when only subordinates called. Groups only increased speed in response to playbacks of moving calls from one individual when other group members emitted moving calls as well. The voting mechanism linked to a quorum probably allows meerkat groups to change foraging patches cohesively with increased speed. Such vocal coordination may reflect an aggregation rule linking individual assessment of foraging patch quality to group travel route.