The grassland of Orkney: An œcological analysis

Summary

World-wide, our coastal waters have been subject to an increased nutrient input since the latter part of the nineteenth century. This has led to the eutrophication or ‘nutrient pollution’ of many coastal sites, including Langstone Harbour and the Ythan Estuary here in the UK. Eutrophication at these and, indeed, at other nutrient enriched sites is evident by the appearance of large blooms of fast-growing opportunistic macroalgae. Blooms of macroscopic species of green algae (Chlorophyta: Ulvophyceae) are particularly common and the phenomenon is often referred to as the occurrence of green tides.

Green tides may have a dramatic environmental impact, causing much damage to the local ecosystem. Numerous strategies have hence been employed in order to combat the problem, but to date there has been limited success. For this reason, current research in the UK is aimed at increasing our knowledge of green tide algae in terms of their ecophysiology, whilst further investigation of the nutrient pathways and fluxes within specific ecosystems has been deemed necessary. It is anticipated that this ‘backto basics’ approach will ultimately contribute to the development of new, successful eutrophication management strategies.     

An experimental analysis of “empathic” response: Effects of pain reactions of pigeon upon other pigeon's operant behavior.

Suppression of operant behavior by exposure to pain reactions of conspecifics was examined with pigeons. Three groups of pigeons were trained on a VI schedule, and were then exposed to the pain reactions of an adjoining bird to electric shocks. Although every subject showed suppression of responding, the suppression decreased with repeated exposures. Following this assessment, a conditioning group received conditioned suppression training in which the pain reaction of the adjoining bird was the CS and an electric shock was the US; a shock exposure group received the electric shock without any explicit CS; and, a no-shock group did not receive any shock. After these treatments, every group was exposed to the pain reactions of the adjoining bird (test 1). The conditioning group and the shock exposure group showed clear suppression in responding, but the no-shock group did not.The no-shock group then received the shock exposure treatment and the conditioned suppression training succesively, and the shock exposure group received the conditioned suppression training. Results of tests with the pain reaction of the adjoining bird supported the results of the test 1, however, suppression caused by the shock exposure was not so clear in the no-shock group.The present results demonstrated that conspecific behavior can become a CS by conditioned suppression training, and, the behavior to an aversive stimulus can acquire aversive properties for other conspecifics when they have shared the exposure to the same aversive stimulus.     

The mechanism of ?C31 integrase directionality: experimental analysis and computational modelling

Serine integrases, DNA site-specific recombinases used by bacteriophages for integration and excision of their DNA to and from their host genomes, are increasingly being used as tools for programmed rearrangements of DNA molecules for biotechnology and synthetic biology. A useful feature of serine integrases is the simple regulation and unidirectionality of their reactions. Recombination between the phage attP and host attB sites is promoted by the serine integrase alone, giving recombinant attL and attR sites, whereas the ‘reverse’ reaction (between attL and attR) requires an additional protein, the recombination directionality factor (RDF). Here, we present new experimental data on the kinetics and regulation of recombination reactions mediated by ϕC31 integrase and its RDF, and use these data as the basis for a mathematical model of the reactions. The model accounts for the unidirectionality of the attP × attB and attL × attR reactions by hypothesizing the formation of structurally distinct, kinetically stable integrase–DNA product complexes, dependent on the presence or absence of RDF. The model accounts for all the available experimental data, and predicts how mutations of the proteins or alterations of reaction conditions might increase the conversion efficiency of recombination.     

Traplining in bumblebees (Bombus impatiens): a foraging strategy’s ontogeny and the importance of spatial reference memory in short-range foraging

To test the relative importance of long-term and working spatial memories in short-range foraging in bumblebees, we compared the performance of two groups of bees. One group foraged in a stable array of six flowers for 40 foraging bouts, thereby enabling it to establish a long-term memory of the array, and adjust its spatial movements accordingly. The other group was faced with an array that changed between (but not within) foraging bouts, and thus had only access to a working memory of the flowers that had been visited. Bees in the stable array started out sampling a variety of routes, but their tendency to visit flowers in a repeatable, stable order (“traplining”) increased drastically with experience. These bees used shorter routes and converged on four popular paths. However, these routes were mainly formed through linking pairs of flowers by near-neighbour movements, rather than attempting to minimize overall travel distance. Individuals had variations to a primary sequence, where some bees used a major sequence most often, followed by a minor less used route, and others used two different routes with equal frequency. Even though bees foraging in the spatially randomized array had access to both spatial working memory and scent marks, this manipulation greatly disrupted foraging efficiency, mainly via an increase in revisitation to previously emptied flowers and substantially longer search times. Hence, a stable reference frame greatly improves foraging even for bees in relatively small arrays of flowers.     

The influence of snow on lynx and coyote movements: does morphology affect behavior?

Summary We studied sympatric lynx (Lynx canadensis) and coyotes (Canis latrans) to assess how morphological disadvantages to locomotion over snow affected movement patterns. Both species are of similar size and mass, but the feet of lynx are much larger, and coyotes were found to have 4.1–8.8 times the foot-load (ratio of body mass to foot area) of lynx. This resulted in greater mean sinking depths of coyote limbs, although the magnitude of the difference was less than that in foot-load. Coyotes exhibited stronger use of behavioral patterns that reduced negative effects of snow on movements. Coyotes were most abundant at low elevations where snow was shallow, whereas lynx were mostly at higher elevations. Coyotes also used areas at both elevations where snow was shallower than average, while lynx used areas where snow was deeper. further, both species used travel routes where snow was shallower than it was near the track. Coyotes traveled on harder snow and used trails more frequently, thereby tending to reduce sinking depths to those similar to lynx. The behavioral repertoire of coyotes reduced the morphological advantage of large feet possessed by lynx; however, overall sinking depths were still greater in coyotes. Snowshoe hares (Lepus americanus) were the main prey of both species, and their foot-load was less than that of either predator. Hare kills by coyotes occurred after fewer bounds than did those by lynx, and the large difference between foot-loads of both species of predators may have forced coyotes to ambush rather than chase hares, as did lynx.     

The effect of wheat-rye substitution on chromosome elimination: An analysis of univalents’ behavior in wheat meiosis with dimonosomy and tetramonosomy

The effect of wheat-rye chromosome 1Rv/1A, 2R/2D and 6R/6A substitutions characterized by differences in the expression of the equational division of sister centromeres in anaphase I on segregation and the elimination of wheat and rye univalents was investigated. To determine the individual effect of each of the studied chromosomal pairs, a comparative analysis of the univalent behavior in the meiosis of dimonosomic 1Rv-1A, 2R-2D, 6R-6A and tetramonosomics 1Rv-2R-1A-2D, 1Rv-6R-1A-6A, 2R-6R-2D-6A was conducted. 2R/2D substitution was experimentally demonstrated to suppress an equational univalents division, while 6R/6A substitution resulted in high frequency chromosomes’ elimination, especially in the meiosis of 2R-6R-2D-6A tetramonosomics. Other meiotic mechanisms, together with the sister chromatids separation at anaphase I, may affect the elimination of the final products of univalent segregation. It was demonstrated that the number and pattern of univalent chromosomal behavior affected hybrid plant fertility.     

“Selling” Value: The Influence of Language on Willingness-to-Accept

In behavioral economics, the “endowment effect” describes the robust finding that prices people are willing to accept (WTA) for a good exceed prices people are willing to pay (WTP) for the same good. The increase in WTA values is often explained by the sellers’ negative hedonic response to losing their item. Recent studies, however, show that subtle cues may change participants’ perspective, influencing their valuations. We hypothesized that implicit connotations of instructional language may be one of those cues. To test this hypothesis we manipulated the wording of instructions in two conditions: in the Sell condition, subjects were endowed with a set of pens and asked to select an amount of money for which they would sell the pens back and in the Take condition, subjects were endowed with the pens and asked to select an amount of money they would take for the pens. Participants in each condition also estimated the market value of the pens. Consistent with our hypothesis, WTA in the Sell condition was higher than in the Take condition, though there were no differences in market values between conditions. These findings show that instructional language does influence participant valuations. Furthermore, we suggest that those being asked to “sell” use their market estimations as the salient reference point in the transaction.     

Hyperepilithics—An overlooked life form of vascular plants on tropical vertical rock walls

Vascular epiphytes are a characteristic life form in many tropical regions and often occur growing on bare rocks. South America has the highest diversity. Here, we describe a neglected life form: hyperepilithics adapted and restricted to growing on vertical (inclination above 70°) and bare rock walls without having roots intruding the substrate. Hyperepilithics are in particular present on Brazilian inselbergs and dominated by highly specialized Bromeliaceae, mainly of the genera Stigmatodon, Tillandsia and Alcantarea, whereas Orchidaceae surprisingly has a low representation. An overview of this habitat, the life form hyperepilithics and a comparison with similar paleotropical habitats (mainly inselbergs in Western/Eastern Africa and India) are provided. Attention is drawn to hyperepilithics as a most promising and not yet exploited source for a sustainable urban ‘vertical gardening’, for example in tropical megacities.     

Barí loricarid collection and the value of information: An application of optimal foraging theory

Analysis of Barí collection of loricarid species suggests that the length of time that has elapsed since each collecting site has last been exploited significantly guides site selection. Information on patch recovery time, gathered through intra-village monitoring of independent foraging groups, allows foragers to choose those sites with a high probability of generating good returns. Comparison of actual returns with those predicted by a model of random site selection indicates that the observed pattern of patch exploitation increases the return of kilograms of loricarids for time invested in foraging substantially above that predicted by random returns to sites. The saving of time as well as the increase in food afforded by this system represent currencies for evaluating the value of information on patch recovery time.     

An analysis of bailer movements responsible for gill ventilation in the crab,cancer novae‐zelandiae

The movements of the bailer during normal ventilation can be resolved into two components, a cycle of pronation and supination being superimposed on a cycle of protraction and retraction. Pronation leads protraction with a phase angle of about 90° in a normal cycle. Pronation is accompanied by flexion of the bailer.

The skeletal anatomy of the bailer is such as to restrict movements of the bailer to those described above. Further the pronated and supinated positions of the limb represent the two stable positions of a skeletal click mechanism, the operation of which may help to resolve the functional duality of the promotor and remotor muscles.

This functional duality arises because the muscles are positioned so as to produce either protraction or supination of the limb. Other muscles in the limb are monofunctional. The bulk of muscle tissue responsible for protraction and supination seems to be greater than that responsible for pronation and retraction.

The sequence of muscular activity during the ventilation cycle follows that expected for a sequence, of protraction, supination, retraction and pronation. Overlap in the periods of activity of the bifunctional muscles and muscles responsible for pronation may also help to resolve the functional duality of the former.

The amplitude of bailer excursion (protraction‐retraction) is not greatly affected by changes in frequency. An advance in the onset of activity in some muscles at higher ventilation ? frequencies suggests that the system is tailored to produce a constant beat amplitude at all frequencies.

Pauses in ventilation occur with the bailer in the retracted position, and it is maintained in this position by tonic activity in the appropriate muscle. During normal ventilation the relative contraction duration of this muscle is positively correlated with cycle period, so that pauses apparently represent a prolongation of the normal retracted phase. The relative contraction durations of some other muscles are negatively correlated with cycle period. The different signs of these correlations may be related to the type of endogenous oscillator present in the central nervous system.     

Threshold foraging behaviour of basking sharks on zooplankton: life on an energetic knife-edge?

The minimum threshold foraging response of basking sharks has not been determined despite the widely held view that has been perpetuated in the literature for the past 45 years that this species cannot use low prey densities for net energy gain and so lives on an energetic ''knife-edge''. An early theoretical estimate suggested basking sharks would expend more energy collecting zooplankton at concentrations less than 1.36 g m^-3 than could be obtained from it. This led to the claim that basking sharks will feed at an energetic loss for much of the annual cycle as zooplankton abundance outside summer months is too low for net energy gain to occur. Here I show from theoretical calculations and behavioural studies on individual and group-feeding sharks in the English Channel that basking sharks have a theoretical threshold prey density of between 0.55 and 0.74 g m^-3 and an observed foraging threshold of between 0.48 and 0.70 g m^-3 (mean = 0.62 g m^-3). The close agreement between theoretical and empirical threshold values suggests basking sharks can achieve net energy gain in much lower zooplankton densities than previously thought. The findings imply that this species may not be reliant upon the ''migration–hibernation'' energy conservation strategy it is purported to exhibit when seasonal zooplankton abundance decreases below 1.36 g m^-3.     

The effect of hexapole and vertical fields on α-particle confinement in heliotron configurations

Collisionless confinement of monoenergetic α particles in three-dimensional magnetic fields produced by the magnetic coils of the Large Helical Device is calculated. It is found that the inward shift of the magnetic axis due to the vertical field improves the α-particle confinement. In contrast to the vertical field, both large positive and negative hexapole fields do not improve the confinement. The study of the β effect and Mercier criterion calculations for different hexapole fields are also presented.