Predation: Prey plumage adaptation against falcon attack

Several plumage types are found in feral pigeons (Columba livia), but one type imparts a clear survival advantage during attacks by the swiftest of all predators--the peregrine falcon (Falco peregrinus). Here we use quantitative field observations and experiments to demonstrate both the selective nature of the falcon's choice of prey and the effect of plumage coloration on the survival of feral pigeons. This plumage colour is an independently heritable trait that is likely to be an antipredator adaptation against high-speed attacks in open air space.     

Short-lived orogenic cycles and the eclogitization of cold crust by spasmodic hot fluids

Collision tectonics and the associated transformation of continental crust to high-pressure rocks (eclogites) are generally well-understood processes, but important contradictions remain between tectonothermal models and petrological-isotopic data obtained from such rocks. Here we use 40Ar-39Ar data coupled with a thermal model to constrain the time-integrated duration of an orogenic cycle (the burial and exhumation of a particular segment of the crust) to be less than 13 Myr. We also determine the total duration of associated metamorphic events to be approximately 20 kyr, and of individual heat pulses experienced by the rocks to be as short as 10 years. Such short timescales are indicative of rapid tectonic processes associated with catastrophic deformation events (earthquakes). Such events triggered transient heat advection by hot fluid along deformation (shear) zones, which cut relatively cool and dry subducted crust. In contrast to current thermal models that assume thermal equilibrium and invoke high ambient temperatures in the thickened crust, our non-steady-state cold-crust model satisfactorily explains several otherwise contradictory geological observations.     

Antipredator defence mechanism in the amphidromous shrimp Xiphocaris elongata (Decapoda: Xiphocarididae): rostrum length

Predators may affect prey through inducible defences that can alter prey phenotype. The shrimp Xiphocaris elongata exhibits a short rostrum (SR) in the absence of fish predators and a long rostrum (LR) in their presence. The long rostrum in X. elongata is inducible by the predatory fish Agonostomus monticola (mountain mullet). Our objective was to test whether the long rostrum is an effective antipredator defence against A. monticola in different stages of predator–prey interactions (i.e. choice, attacks, bites, rejections, handling time and survival). We conducted behavioural experiments in fish tanks in which we fed A. monticola simultaneously with (1) one LR shrimp and one SR shrimp, or (2) one LR shrimp and one shrimp which originally had a long rostrum but whose rostrum was cut (LR[S]). We scored the fish behaviours in terms of choice, unsuccessful attacks, bites, rejections and handling time. We also conducted mortality experiments in closed artificial pools in which we exposed (1) 10 LR and 10 SR shrimp or (2) 10 LR and 10 LR[S] shrimp to A. monticola, and quantified shrimp survival after 24 h. In the trials with LR and SR shrimp, A. monticola tended to attack SR shrimp first. LR shrimp were unsuccessfully attacked, bitten and rejected more than SR individuals. Handling time was higher for LR shrimp. The mortality experiments show higher survival of LR shrimp. In the trials with LR and LR[S] shrimp, A. monticola tended to attack LR[S] shrimp first. Unsuccessful attacks were similar for LR and LR[S]. There were more bites and rejections and longer handling time for LR shrimp. Survival was similar for LR and LR[S] shrimp in the mortality experiments. This study provides evidence in support of the hypothesis that the long rostrum in X. elongata is an effective antipredator defence against A. monticola by conferring benefits in most stages of the predator–prey interactions.     

On Jacobi’s transformation theory of elliptic functions

The main interpretative challenge set by the Fundamenta Nova Theoriae Functionum Ellipticarum lies in Jacobi’s transformation theory upon which the entire theoretical edifice of the treatise depends. Unfortunately, Jacobi did not convey any indication of how he attained his general formulae for rational transformations of elliptic functions. He limited himself to providing a posteriori verification of the validity of his claims. The aim of this paper is precisely to describe the heuristic path by which in 1827 Jacobi succeeded in finding these transformation formulae. The proposed historical reconstruction will hopefully shed new light upon the emergence in Jacobi’s work of the inversion process of elliptic integrals of the first kind and thus of the elliptic function sinam \(u\) itself.     

Discovery of novel intermediate forms redefines the fungal tree of life

Fungi are the principal degraders of biomass in terrestrial ecosystems and establish important interactions with plants and animals. However, our current understanding of fungal evolutionary diversity is incomplete and is based upon species amenable to growth in culture. These culturable fungi are typically yeast or filamentous forms, bound by a rigid cell wall rich in chitin. Evolution of this body plan was thought critical for the success of the Fungi, enabling them to adapt to heterogeneous habitats and live by osmotrophy: extracellular digestion followed by nutrient uptake. Here we investigate the ecology and cell biology of a previously undescribed and highly diverse form of eukaryotic life that branches with the Fungi, using environmental DNA analyses combined with fluorescent detection via DNA probes. This clade is present in numerous ecosystems including soil, freshwater and aquatic sediments. Phylogenetic analyses using multiple ribosomal RNA genes place this clade with Rozella, the putative primary branch of the fungal kingdom. Tyramide signal amplification coupled with group-specific fluorescence in situ hybridization reveals that the target cells are small eukaryotes of 3-5?μm in length, capable of forming a microtubule-based flagellum. Co-staining with cell wall markers demonstrates that representatives from the clade do not produce a chitin-rich cell wall during any of the life cycle stages observed and therefore do not conform to the standard fungal body plan. We name this highly diverse clade the cryptomycota in anticipation of formal classification.     

Using neural networks for recognizing matching among terms

Some experiments have been carried out in order to identify a class of neural networks that would receive as inputs (n+1) terms {T_l,…T_n.T} and would suggest which T_is are matched by a subterm of T, with varying n. A particular net was found that is able to solve the problem for n=1 with a good degree of accuracy. It is shown that the performance of the net is relatively independent of the size of the training set while it is strongly related to the length of the term T. This net was then used as building block for larger nets that were applied to solve the problem for higher values of n. Results of testing such nets are presented.