Time evolution of radiation-induced EPR signals in different types of mobile phone screen glasses

Radiation and Environmental Biophysics - In this study, samples of smart phone touch screen glass sheets and tempered glass screen protectors were examined with respect to their potential...     

Begging and bleating: the evolution of parent-offspring signalling

The evolution of biological signalling in the face of evolutionary conflicts of interest is an active area of evolutionary ecology, and one to which Maynard Smith has made important contributions. We explore the major theoretical challenges in the field, concentrating largely on how offspring signal to their parents when there is the potential for parent-offspring conflict. Costly offspring solicitation (begging etc.) has been interpreted in terms of a Zahavi Grafen honest handicap signal, but this has been challenged on the grounds of' the costs of signalling. We review this controversy and also explore the issue of pooling versus separating signalling equilibrium. An alternative explanation for costly begging is that it is due to sibling competition, and we discuss the relationship between these ideas and signalling models in families with more than one offspring. Finally we consider signal uncertainty, how signalling models can be made dynamic, and briefly how they may be tested experimentally.     

Functional evolution of the feeding system in rodents

The masticatory musculature of rodents has evolved to enable both gnawing at the incisors and chewing at the molars. In particular, the masseter muscle is highly specialised, having extended anteriorly to originate from the rostrum. All living rodents have achieved this masseteric expansion in one of three ways, known as the sciuromorph, hystricomorph and myomorph conditions. Here, we used finite element analysis (FEA) to investigate the biomechanical implications of these three morphologies, in a squirrel, guinea pig and rat. In particular, we wished to determine whether each of the three morphologies is better adapted for either gnawing or chewing. Results show that squirrels are more efficient at muscle-bite force transmission during incisor gnawing than guinea pigs, and that guinea pigs are more efficient at molar chewing than squirrels. This matches the known diet of nuts and seeds that squirrels gnaw, and of grasses that guinea pigs grind down with their molars. Surprisingly, results also indicate that rats are more efficient as well as more versatile feeders than both the squirrel and guinea pig. There seems to be no compromise in biting efficiency to accommodate the wider range of foodstuffs and the more general feeding behaviour adopted by rats. Our results show that the morphology of the skull and masticatory muscles have allowed squirrels to specialise as gnawers and guinea pigs as chewers, but that rats are high-performance generalists, which helps explain their overwhelming success as a group.     

The evolution of the dicynodont feeding system

The skull structure of dicynodonts may be regarded as a complex adaptation towards herbivorous feeding. The present work examines how and why this adaptation may have evolved. A cladogram of the dicynodonts is presented and from it a sequence of hypothetical ancestral forms is inferred. The jaw musculature of dicynodonts and other therapsids is described and in particular the early dicynodont Eodicynodon oosthuizeni is described in detail. This information is used to draw up a sequence of ancestral stages whose basic skull anatomy, jaw muscle organization and masticatory properties are described. Differences in masticatory properties between these stages are pinpointed and an explanation to account for the development of these differences is advanced. It is concluded that the changes in skull organization seen during the evolution of dicynodonts are consistent with the hypothesis that a propalinal jaw action was being improved by selection, and that this was required to permit dicynodonts to be efficient herbivores.     

Begging for milk: evolution of teat massaging in suckling pigs

We present a model that simulates the evolution of teat massaging (begging) by suckling piglets (Sus scrofa) and milk distribution among teats (provisioning) by their mothers. Contrary to previous begging models, this one incorporates an ontogenetic dimension in that the inherited begging and provisioning rules are repeatedly allowed to interact, and their consequences for milk intake, growth and death probability are assessed, during each nursing. We test the model under three selection regimes differing in the relative importance of the between-litter selection component. We show that the selection regime with the strongest between-litter selection component leads to lowest begging levels and most effective milk utilization, thus supporting the hypothesis that selection based on whole litters may attenuate sibling competition.     

The ultrastructure of the intestinal epithelium in fishes with different types of feeding

The ultrastructure of the intestinal epithelium has been studied in three species of freshwater fishes, differing from one another in the type of feeding. The pike (a typical predator), the burbot (a predator-facultative benthophage), and the bream (a typical benthophage) were examined. The differences in the condition of epithelial ceils and peculiarities in the structure of the brush border of enterocytes in fishes have been revealed in winter periods. The role of the brush border of enterocytes in the increase of the digestive and transport surface of the intestine in fish is discussed.     

Exploring the evolution of Wolbachia compatibility types: a simulation approach

Wolbachia-induced cytoplasmic incompatibility (CI) is observed when males bearing the bacterium mate with uninfected females or with females bearing a different Wolbachia variant; in such crosses, paternal chromosomes are lost at the first embryonic mitosis, most often resulting in developmental arrest. The molecular basis of CI is currently unknown, but it is useful to distinguish conceptually the male and female sides of this phenomenon: in males, Wolbachia must do something, before it is shed from maturing sperm, that will disrupt paternal chromosomes functionality [this is usually termed "the modification (mod) function"]; in females, Wolbachia must somehow restore embryonic viability, through what is usually called "the rescue (resc) function." The occurrence of CI in crosses between males and females bearing different Wolbachia variants demonstrates that the mod and resc functions interact in a specific manner: different mod resc pairs make different compatibility types. We are interested in the evolutionary process allowing the diversification of compatibility types. In an earlier model, based on the main assumption that the mod and resc functions can mutate independently, we have shown that compatibility types can evolve through a two-step process, the first involving drift on mod variations and the second involving selection on resc variations. This previous study has highlighted the need for simulation-based models that would include the effects of nondeterministic evolutionary forces. This study is based on a simulation program fulfilling this condition, allowing us to follow the evolution of compatibility types under mutation, drift, and selection. Most importantly, simulations suggest that in the frame of our model, the evolution of compatibility types is likely to be a gradual process, with new compatibility types remaining partially compatible with ancestral ones.     

Comparative antioxidant enzyme study in freshwater fish with different types of feeding behaviour

Comparative studies were made of the activities of Cu,Zn-superoxide dismutase, Mn-superoxide dismutase, catalase and glutathione peroxidase in organ homogenates from two herbivorous (grass carp and silver carp) and three omnivorous fish (barbel, crucian carp and common carp). The protein contents and lipid peroxidation of the organ homogenates were also compared. These comparative measurements provided control values for subsequent toxicological examinations. For the herbivorous fish, the highest total superoxide dismutase activity was observed in the kidney, followed in turn by the liver or spleen. In contrast, the highest total superoxide dismutase activity in the barbel was found in the roe, in the crucian carp in the liver, and in the common carp in the liver too. The quantitative distributions of the two peroxide metabolism enzymes glutathione peroxidase and catalase in the organ homogenates present very varied pictures. The results of the lipid peroxidation are similarly difficult to fit into one framework, even for fish following the same diet. It appears that the enzyme activities mentioned in points 4 and 5, together with the lipid peroxidation, depend not on the species, but on the variety.     

Effect of different types of excessive feeding on the state of vascular walls in rats]

Immature male rats were overfed for a long time with an excess of fats or carbohydrates; this caused obesity. Carbohydrate overfeeding led to a greater body weight gain and a greater increase in the weight of epididymal fat and of the adipose cell volume than fat overfeeding, but failed to decrease the lipolytic activity of the aorta. Prolonged fat overfeeding decreased the lipolytic activity of the aorta considerably. Thus, the results of the mentioned experiments showed that the predisposition of the aortic wall to atherogenesis did not correlate with the gain in weight and depended on the character of nutrition.     

Deja vu: the evolution of feeding morphologies in the Carnivora

The fossil record of the order Carnivora extends back at least60 million years and documents a remarkable history of adaptiveradiation characterized by the repeated, independent evolutionof similar feeding morphologies in distinct clades. Within theorder, convergence is apparent in the iterative appearance ofa variety of ecomorphs, including cat-like, hyena-like, andwolf-like hypercarnivores, as well as a variety of less carnivorousforms, such as foxes, raccoons, and ursids. The iteration ofsimilar forms has multiple causes. First, there are a limitednumber of ways to ecologically partition the carnivore niche,and second, the material properties of animal tissues (muscle,skin, bone) have not changed over the Cenozoic. Consequently,similar craniodental adaptations for feeding on different proportionsof animal versus plant tissues evolve repeatedly. The extentof convergence in craniodental form can be striking, affectingskull proportions and overall shape, as well as dental morphology.The tendency to evolve highly convergent ecomorphs is most apparentamong feeding extremes, such as sabertooths and bone-crackerswhere performance requirements tend to be more acute. A surveyof the fossil record indicates that large hypercarnivores evolvefrequently, often in response to ecological opportunity affordedby the decline or extinction of previously dominant hypercarnivoroustaxa. While the evolution of large size and carnivory may befavored at the individual level, it can lead to a macroevolutionaryratchet, wherein dietary specialization and reduced populationdensities result in a greater vulnerability to extinction. Asa result of these opposing forces, the fossil record of Carnivorais dominated by successive clades of hypercarnivores that diversifyand decline, only to be replaced by new hypercarnivorous clades.This has produced a marvelous set of natural experiments inthe evolution of similar ecomorphs, each of which start fromphylogenetically and morphologically unique positions.     

Rotational feeding in caecilians: putting a spin on the evolution of cranial design

Caecilians are a poorly known group of amphibians with a highly derived skull and cranial musculature that has evolved in response to their specialized head-first burrowing lifestyle. They possess a unique jaw-closing system, which is shown to be capable of generating considerable bite forces for its head width (1.09+/-0.34 and 0.62+/-0.31 N for Schistometopum thomense and Boulengerula taitanus, respectively). However, comprehensive dietary studies indicate that there is no need for large bite forces, since most caecilians appear to be generalist predators of subterranean macrofauna. Here, we demonstrate, based on in vivo external and X-ray video recordings of animals feeding, that long-axis body rotations are used independent of prey size by these two species of caeciliid caecilians when feeding underground. Further, we show that individuals are capable of generating a substantial spinning force, which is greater than their bite force (1.35+/-0.26 and 1.02+/-0.18 N, respectively). These observations shed light on the functional and the evolutionary significance of several unique features of the cranial design in derived caecilians; spinning may allow the individuals to judge prey size and subsequently reduce oversized prey within gape limits.     

Within-genome evolution of REPINs: a new family of miniature mobile DNA in bacteria

Repetitive sequences are a conserved feature of many bacterial genomes. While first reported almost thirty years ago, and frequently exploited for genotyping purposes, little is known about their origin, maintenance, or processes affecting the dynamics of within-genome evolution. Here, beginning with analysis of the diversity and abundance of short oligonucleotide sequences in the genome of Pseudomonas fluorescens SBW25, we show that over-represented short sequences define three distinct groups (GI, GII, and GIII) of repetitive extragenic palindromic (REP) sequences. Patterns of REP distribution suggest that closely linked REP sequences form a functional replicative unit: REP doublets are over-represented, randomly distributed in extragenic space, and more highly conserved than singlets. In addition, doublets are organized as inverted repeats, which together with intervening spacer sequences are predicted to form hairpin structures in ssDNA or mRNA. We refer to these newly defined entities as REPINs (REP doublets forming hairpins) and identify short reads from population sequencing that reveal putative transposition intermediates. The proximal relationship between GI, GII, and GIII REPINs and specific REP-associated tyrosine transposases (RAYTs), combined with features of the putative transposition intermediate, suggests a mechanism for within-genome dissemination. Analysis of the distribution of REPs in a range of RAYT-containing bacterial genomes, including Escherichia coli K-12 and Nostoc punctiforme, show that REPINs are a widely distributed, but hitherto unrecognized, family of miniature non-autonomous mobile DNA.     

The genetic basis and evolution of acoustic mate recognition signals in a Ribautodelphax planthopper (Homoptera,Delphacidae) 1. The female call

Both sexes of the planthopper Ribautodelphax imitans produce species specific acoustic signals. Earlier experiments have shown that isolation between Ribautodelphax species in captivity is at least partly due to male preference for calls of conspecific females. The genetic basis of the female call is studied by bi-directional artificial selection for large and small interpulse intervals (IPI). This resulted in non-overlapping distributions of IPI after only five generations. The mean of eight realized heritability estimates over five generations was above 80%; estimates over ten generations were generally well above 50%. The character is shown to be of a polygenic nature, determined by at least 6 segregating genetic factors. The other features of the female call, strophe duration, and modulation of pulse repetition frequency within the strophe, showed significantly correlated responses. Sexual isolation tests after 10 generations of selection revealed significant symmetrical assortative mating, but coselected males did not exhibit a significant preference for playback calls of females from their own selection line. In view of the high heritability for the call character, and the considerable ecological isolation among Ribautodelphax species, it seems unlikely that the female call differentiated as an adaptation to prevent hybridization (reinforcement). More likely, call and call preference were shaped by sexual selection during allopatry, and may have (had) incidentally an effect in species isolation.     

Stress and the evolution of condition-dependent signals

Stressful events are known to initiate a cascade of physiological mechanisms that are potentially costly for metabolic processes. Although these mechanisms are well understood, the long-term costs and the potential implications for individual condition and behaviour have been considered only recently. Combining information from physiological, ecological and behavioural studies can help us to understand the implications of stress for individual life history strategies. Furthermore, the concept of individual variation in stress tolerance has implications for the immunocompetence handicap hypothesis and the evolution of secondary sexual signals.     

Monitoring the feeding activity of individual fish with a demand feeding system

Feeding activity of individual Arctic charr ( Salvelinus alpinus ) was recorded automatically for 29 days using a demand feeding system. Each of three groups of 15 fish was kept in 1 m³ tanks, containing brackish water at 10° C. Individual biting activity was continuously monitored using a PIT-tag (Passive Integrated Transponders) system with unique individual codes. The accuracies of the bite detection system were 91, 93.1 and 99.5% respectively, in the three tanks. In all tanks, most of the individuals (12–14) bit on the releasing trigger a few times during the first 3 days. Thereafter, one or two individuals per tank accounted for almost all of the biting activity. This pronounced shift in bite-number distribution among individuals was probably due to the development of a dominance hierarchy, in which the dominant individuals monopolized the trigger. Growth rates appeared to be highest among high ranking fish. The implications of using demand feeding and PIT-tag devices in feeding studies are discussed.