Trade-offs across life stages: does predator–induced hatching plasticity reduce anuran post-metamorphic performance?

In species with complex life cycles hatching plasticity can provide an effective escape from egg predators, but theoretical studies predict a predation-risk trade-off across egg and larval stages. In this study, we examine whether the presence of an egg predator can alter the timing of hatching in an anuran, Rana temporaria, and the consequences of hatching plasticity after transition to the terrestrial habitat. Predator cues induced earlier hatching, and hatchlings were smaller, less developed and had relatively shorter and deeper tails than control hatchlings. The predator–induced differences in developmental time were compensated throughout the larval period; there was no predator effect on metamorph age or size. Surprisingly, the effects of egg predators were perceptible after metamorphosis. Juveniles emerging from the predator and the no-predator treatments differed in several size-adjusted morphological dimensions. Seemingly these morphological differences were not large enough to give rise to suboptimal growth or locomotor performance after metamorphosis. Thus, our results suggest only a short-term effect on juvenile phenotype, but not a trade-off between hatching time and juvenile performance.     

Pioneer settlement of the cold-water coral Desmophyllum dianthus (Esper, 1794) on plastic

Coral Reefs - Larval settlement is a critical step for sessile benthic species such as corals, whose ability to thrive on diverse natural and anthropogenic substrates may lead to a competitive...     

Boolean analysis of lateral inhibition

Journal of Mathematical Biology - We study Boolean networks which are simple spatial models of the highly conserved Delta–Notch system. The models assume the inhibition of Delta in each cell...     

In vitro antimicrobial activity of plant extracts against Pseudomonas syringae pv. actinidiae causal agent of bacterial canker in kiwifruit

Abstract

Pseudomonas syringae pv. actinidiae (Psa), the causal agent of bacterial canker of kiwifruit, is considered the main pathogen of yellow-, green- and red-fleshed kiwifruit. All major kiwifruit producing countries in the world have been affected by this bacterial pathogen, leading to substantial economic losses. The control of bacterial canker of kiwifruit is based only on preventive methods or on the use of copper compounds that can cause phytotoxicity problems. In this study, the in vitro antibacterial activity of seven different plant extracts against eight Psa strains has been evaluated. The inhibition of 100% of the Psa growth was observed, after 24?h, for the extracts of Polygonum cuspidatum roots (POL-roots), Hypericum perforatum roots elicited with chitosan oligosaccharides (HYP-COS roots) and non-fermented grape pomace (ITA-pomace). The strongest antibacterial activity was exhibited by POL-roots, with a geometric mean of minimum inhibitory concentration of 100% of growth (GMMIC₁₀₀) of 105.11 µg/mL after 24?h, and with a GMMIC₁₀₀ value of 148.65 µg/mL after 48?h. Moreover, POL-roots extract showed the best bactericidal activity with a GMMBC of 210.22 µg/mL. No phytotoxic activity was observed up to 15 days in the leaves of Actinidia chinensis “Belen” treated with plant extracts at 500 µg/mL.     

Genomic analysis of a novel integrative conjugative element in Vibrio cholerae

Integrative conjugative elements (ICEs) are a class of self-transmissible mobile elements that mediate horizontal gene transfer in bacteria, and play an important role in bacterial evolution. Since 1992, ICEs of the SXT/R391 family have been found to be widely distributed among Vibrio cholerae strains isolated in Asian countries. Here we describe ICEVchB33, an ICE found in the genomes of two V. cholerae O1 Eltor strains, one isolated in India, 1994, and the other from Mozambique, 2004. ICEVchB33 revealed a new genetic organization, different from other ICEs of the SXT/R391 family, demonstrating the genomic plasticity of these elements.     

CELL CYCLE AND CELL MORTALITY OF ALEXANDRIUM MINUTUM (DINOPHYCEAE) UNDER SMALL‐SCALE TURBULENCE CONDITIONS1

Decreased net population growth rates and cellular abundances have been observed in dinoflagellate species exposed to small‐scale turbulence. Here, we investigated whether these effects were caused by alterations in the cell cycle and/or by cell mortality and, in turn, whether these two mechanisms depended on the duration of exposure to turbulence. The study was conducted on the toxic dinoflagellate Alexandrium minutum Halim, with the same experimental design and setup used in previous studies to allow direct comparison among results. A combination of microscopy and Coulter Counter measurements allowed us to detect cell mortality, based on the biovolume of broken cells and thecae. The turbulence applied during the exponential growth phase caused an immediate transitory arrest in the G2/M phase, but significant mortality did not occur. This finding suggests that high intensities of small‐scale turbulence can alter the cell division, likely affecting the correct chromosome segregation during the dinomitosis. When shaking persisted for >4 d, mortality signals and presence of anomalously swollen cells appeared, hinting at the activation of mechanisms that induce programmed cell death. Our study suggests that the sensitivity of dinoflagellates to turbulence may drive these organisms to find the most favorable (calm) conditions to complete their division cycle.     

Shovel roots: a unique stress-avoiding developmental strategy of the legume plant Hedysarum coronarium L.

Hedysarum coronarium (sulla) is a legume native to the Mediterranean basin, known for its broad tolerance to various environmental stresses, and its ability to thrive without signs of chlorosis when growing in arid and alkaline soils up to pH 9.6. A unique but poorly known morphological feature of its root system is the production of “shovels”, modified lateral roots that acquire a curved and flattened shape. A combined structural and functional analysis was undertaken to define the nature and role of the shovel roots using various microscopy techniques, histochemical stains, STEM - energy dispersive X-ray microanalysis, infrared spectroscopy, and plant cultivation in different conditions. We found that sulla displays remarkable unique rhizosphere-buffering properties at both ends of the pH scale, and that shovels act as efficient calcium-absorbing organs that accumulate this cation intracellularly as insoluble crystalline salts. Such bioaccumulation results in a localized depletion of CaCO₃ from the soil. As a consequence of this removal of the pivotal carbonate buffering system, the iron-solubilizing acidification activities of the roots can become effective. Further tests revealed that the factor triggering shovel development is exposure of roots to iron oxide. This signal, reporting at once both iron presence and alkalinity, assures the availability of iron nutrient reserves upon acidification of the local microenvironment surrounding the roots. These findings, besides casting light on a novel and unique botanical phenomenon, offer the potential to exploit sulla’s model and genes for the improvement of other crops to sustain productivity in a scenario of climate warming and increasing desertification.