Predation in the marine intertidal amphipod Echinogammarus marinus Leach: implications of inter- and intra-individual variation

Studies of competition, predator–prey dynamics and food webs typically consider conspecifics as equal, however, individuals from the same population that are seemingly identical can show considerable variation with regards to a number of processes. Such phenomena may be demonstrated in terms of diet, and the quantities and types of resources that are consumed are commonly considered. The marine amphipod Echinogammarus marinus, a recently demonstrated predator on intertidal rocky shores, has been shown to consume a wide range of food types but it is unknown how this may vary between individuals. Here, we investigated the variation that occurs both among and within individuals of a population of E. marinus with respect to the mean numbers consumed of a common prey item, the isopod Jaera nordmanni. First, by comparing the length of starvation times, used as a proxy for hunger level, individuals maintained without food for up to 24 h consumed significantly less prey during feeding trials than those starved for 48 h and longer. The degree of inter-individual variation within each starvation period was also found to differ, with greater variation among individuals starved for shorter periods of time than those starved for longer time periods. Secondly, we tested whether individual amphipods tracked over time consumed consistently similar numbers of prey or whether they showed intra-individual variation, and if so, to what degree. We found that the numbers of prey consumed per individual could be predicted in the short-term between consecutive feeding trials, however over the long-term this relationship broke down. These results are discussed with respect to potential physiological and behavioural mechanisms, as well as the implications that such variation may have for stability of prey populations in the field.

Inter- and intra-individual variation of oxytocin secretion in oestrous mares exposed to stallions

The neuro-peptide hormone oxytocin regulates several reproductive mechanisms in mammals, such as uterine contractions during parturition and milk ejection in the lactating mammary gland. Oxytocin may also influence behavior and behavioral strategies, e.g. pair bonding, social recognition, maternal behavior, trust building, or anxiety. Teasing oestrous mares by a stallion provokes the release of oxytocin. We therefore tested whether such elevated oxytocin levels reveal possible mate preferences as determined in typical preference tests.

Intra-individual variation of flowers in Gunnera subgenus Panke (Gunneraceae) and proposed apomorphies for Gunnerales

A study of inflorescence and flower development in 12 species from four of the six subgenera of Gunnera (Gunneraceae) was carried out. In the species of subgenus Panke, initiation of floral apices along the partial inflorescences is acropetal but ends up in the late formation of a terminal flower, forming a cyme at maturity. The terminal flower is the largest and the most complete in terms of merosity and number of whorls and thus it is the most diagnostic in terms of species-level taxonomy. The lateral flowers undergo a basipetal gradient of organ reduction along the inflorescence, ranging from bisexual flowers (towards the distal region) to functionally (i.e. with staminodia) and structurally female flowers (towards the proximal region). Our results show that the terminal structure in Gunnera is a flower rather than a pseudanthium. The terminal flower is disymmetric, dimerous and bisexual, representing the common bauplan for Gunnera flowers. It has a differentiated perianth with two sepals and two alternate petals, the latter opposite the stamens and carpels. Comparisons with other members of the core eudicots with labile floral construction are addressed. We propose vegetative and floral putative synapomorphies for the sister-group relationship between Gunneraceae and Myrothamnaceae. (C) 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 262-283.

Intra-individual variation of serum prostate specific antigen levels in men with benign prostate biopsies

To determine the intra-individual (physiological) variation of prostate-specific antigen (PSA) measurements in men after a benign prostatic biopsy. Sixty-four men were prospectively assessed, all of whom had a benign prostatic biopsy within the preceding 13 months. The degree of intra-individual variability was established by calculating the coefficient of variation on four PSA levels obtained from each patient weekly over a month. Six patients were subsequently diagnosed with prostate cancer and their data are presented separately. In the remaining 58 patients the median (range) individual mean PSA value was 6.3 (0.5-34.1) ng/mL. The median (range) coefficient of variation within the group was 9.5 (2.4-76.1)%. There was a clear linear relationship between mean PSA level and the standard deviation. In 48 of the 63 patients analysed, the coefficient of variation for serum PSA values in the group as a whole was greater than the variation claimed for the assay technique. The significance of the linear relationship between PSA and the standard deviation is discussed, with particular reference to those men who had a benign prostate biopsy.

Intra- and inter-individual variation of BIS-index and Entropy during controlled sedation with midazolam/remifentanil and dexmedetomidine/remifentanil in healthy volunteers: an interventional study

INTRODUCTION: We studied intra-individual and inter-individual variability of two online sedation monitors, BIS and Entropy, in volunteers under sedation. METHODS: Ten healthy volunteers were sedated in a stepwise manner with doses of either midazolam and remifentanil or dexmedetomidine and remifentanil. One week later the procedure was repeated with the remaining drug combination. The doses were adjusted to achieve three different sedation levels (Ramsay Scores 2, 3 and 4) and controlled by a computer-driven drug-delivery system to maintain stable plasma concentrations of the drugs. At each level of sedation, BIS and Entropy (response entropy and state entropy) values were recorded for 20 minutes. Baseline recordings were obtained before the sedative medications were administered. RESULTS: Both inter-individual and intra-individual variability increased as the sedation level deepened. Entropy values showed greater variability than BIS(R) values, and the variability was greater during dexmedetomidine/remifentanil sedation than during midazolam/remifentanil sedation. CONCLUSIONS: The large intra-individual and inter-individual variability of BIS and Entropy values in sedated volunteers makes the determination of sedation levels by processed electroencephalogram (EEG) variables impossible. Reports in the literature which draw conclusions based on processed EEG variables obtained from sedated intensive care unit (ICU) patients may be inaccurate due to this variability. TRIAL REGISTRATION: clinicaltrials.gov Nr. NCT00641563.

Hierarchical analysis of avian re-nesting behavior: mean, across-individual, and intra-individual responses

© 2015, Springer-Verlag Berlin Heidelberg. Anti-predator behavior is a key aspect of life history evolution, usually studied at the population (mean), or across-individual levels. However individuals can also differ in their intra-individual (residual) variation, but to our knowledge, this has only been studied once before in free-living animals. Here we studied the distances moved and changes in nest height and concealment between successive nesting attempts of marked pairs of grey fantails (Rhipidura albiscapa) in relation to nest fate, across the breeding season. We predicted that females (gender that decides where the nest is placed) should on average show adaptive behavioral responses to the experience of prior predation risk such that after an unsuccessful nesting attempt, replacement nests should be further away, higher from the ground, and more concealed compared with replacement nests after successful nesting attempts. We found that, on average, females moved greater distances to re-nest after unsuccessful nesting attempts (abandoned or depredated) in contrast to after a successful attempt, suggesting that re-nesting decisions are sensitive to risk. We found no consistent across-individual differences in distances moved, heights, or concealment. However, females differed by 53-fold (or more) in their intra-individual variability (i.e., predictability) with respect to distances moved and changes in nest height between nesting attempts, indicating that either some systematic variation went unexplained and/or females have inherently different predictability. Ignoring these individual differences in residual variance in our models obscured the effect of nest fate on re-nesting decisions that were evident at the mean level.

Intra-specific variation for host plant use in Helicoverpa armigera (Hubner) (Lepidoptera : Noctuidae) : implications for management

The polyphagous moth Helicoverpa armigera (Hübner) is one of the world's most important agricultural pests. A number of existing approaches and future designs for management of H. armigera rely on the assumption that moths do not exhibit either genetically and/or non-genetically based variation for host plant utilization. We review recent empirical evidence demonstrating that both these forms of variation influence host plant use in this moth. The significance of this variation in H. armigera in relation to current and future pest management strategies is examined. We provide recommendations on future research needs and directions for sustainable management of H. armigera, under a framework that includes consideration of intra-specific variation for host use relevant in this and other similar pest species.

Forms of capital, intra-ethnic variation and Polish entrepreneurs in Leicester

A study of ten Polish entrepreneurs operating in Leicester, UK is reported in this article. The concepts of social, cultural and economic capital are used as the lens through which to explore the way the capital they access is employed and converted into entrepreneurial activity. Ethnic entrepreneurship takes place within wider social, political and economic institutional frameworks and opportunity structures and so this is taken into account by differentiating two groups – post-war and contemporary Polish entrepreneurs. The differing origins and amounts of forms of capital they can access are shown as is how these are converted into valued outcomes. Combining the mixed embeddedness approach with a forms-of-capital analysis enables looking beyond social capital to elaborate on intra-ethnic variation in the UK’s Polish entrepreneurial community.

Individual variation in in vitro efficacy of antiplatelet medication - aspirin and clopidogrel

Antiplatelet medication is known to decrease adverse effects in patients with atherothrombotic disease. However, despite ongoing antiplatelet medication considerable number of patients suffer from atherothrombotic events. The aims of the study were 1) to evaluate the individual variability in platelet functions and compare the usability of different methods in detecting it, 2) to assess variability in efficacy of antiplatelet medication with aspirin (acetylsalicylic acid) or the combination of aspirin and clopidogrel and 3) to investigate the main genetic and clinical variables as well as potential underlying mechanisms of variability in efficacy of antiplatelet medication. In comparisons of different platelet function tests in 19 healthy individuals PFA-100® correlated with traditional methods of measuring platelet function and was thus considered appropriate for testing individual variability in platelet activity. Efficacy of ongoing 100mg aspirin daily was studied in 101 patients with coronary artery disease (CAD). Aspirin response was measured with arachidonic acid (AA)-induced platelet aggregation, which reflects cyclo-oxygenase (COX)-1 dependent thromboxane (Tx) A2 formation, and PFA-100®, which evaluates platelet activation under high shear stress in the presence of collagen and epinephrine. Five percent of patients failed to show inhibition of AA-aggregation and 21% of patients had normal PFA-100® results despite aspirin and were thus considered non-responders to aspirin. Interestingly, the two methods of assessing aspirin efficacy, platelet aggregation and PFA-100®, detected different populations as being aspirin non-responders. It could be postulated that PFA-100® actually measures enhanced platelet function, which is not directly associated with TxA2 inhibition exerted by aspirin. Clopidogrel efficacy was assessed in 50 patients who received a 300mg loading dose of clopidogrel 2.5 h prior to percutaneous coronary intervention (PCI) and in 51 patients who were given a loading dose of 300mg combined with a five day treatment of 75mg clopidogrel daily mimicking ongoing treatment. Clopidogrel response was assessed with ADP-induced aggregations, due to its mechanism of action as an inhibitor of ADP-induced activation. When patients received only a loading dose of clopidogrel prior to PCI, 40% did not gain measurable inhibition of their ADP-induced platelet activity (inhibition of 10% or less). Prolongation of treatment so that all patients had reached a plateau of inhibition exerted by clopidogrel, decreased the incidence of non-responders to 20%. Polymorphisms of COX-1 and GP VI, as well as diabetes and female gender, were associated with decreased in vitro aspirin efficacy. Diabetes also impaired the in vitro efficacy of short-term clopidogrel. Decreased response to clopidogrel was associated with limited inhibition by ARMX, an antagonist of P2Y12-receptor, suggesting the reason for clopidogrel resistance to be receptor-dependent. Conclusions: Considerable numbers of CAD patients were non-responders either to aspirin, clopidogrel or both. In the future, platelet function tests may be helpful to individually select effective and safe antiplatelet medication for these patients.

Individual variation in the milk yield response to bovine somatotropin in dairy cows

M. T. Rose, T. E. C. Weekes and P. Rowlinson (2004). Individual variation in the milk yield response to bovine somatotropin in dairy cows. Journal of Dairy Science, 87(7), 2024-2031. Sponsorship: industry RAE2008

Genomic instability after targeted irradiation of human lymphocytes: Evidence for inter-individual differences under bystander conditions

Environmental (222)radon exposure is a human health concern, and many studies demonstrate that very low doses of high LET alpha-particle irradiation initiate deleterious genetic consequences in both radiated and non-irradiated bystander cells. One consequence, radiation-induced genomic instability (RIGI), is a hallmark of tumorigenesis and is often assessed by measuring delayed chromosomal aberrations We utilised a technique that facilitates transient immobilization of primary lymphocytes for targeted microbeam irradiation and have reported that environmentally relevant doses, e.g. a single He-3(2+) particle traversal to a single cell, are sufficient to Induce RIGI Herein we sought to determine differences in radiation response in lymphocytes isolated from five healthy male donors Primary lymphocytes were irradiated with a single particle per cell nucleus. We found evidence for inter-individual variation in radiation response (Rid, measured as delayed chromosome aberrations) Although this was not highly significant, it was possibly masked by high levels of intra-individual variation While there are many studies showing a link between genetic predisposition and RIGI, there are few studies linking genetic background with bystander effects in normal human lymphocytes In an attempt to investigate inter-individual variation in the induction of bystander effects, primary lymphocytes were irradiated with a single particle under conditions where fractions of the population were traversed We showed a marked genotype-dependent bystander response in one donor after exposure to 15% of the population The findings may also be regarded as a radiation-induced genotype-dependent bystander effect triggering an instability phenotype (C) 2010 Elsevier B.V. All rights reserved.

Investigating Intra-individual Dietary Changes and Radiocarbon Ages Using High Resolution δ13C, δ15N Isotope Ratios and 14C Ages Obtained From Dentine Increments

Ten medieval permanent teeth were subjected to incremental dentine sectioning and stable isotope analysis to investigate dietary changes in high resolution. In addition to this, eight increments were also selected for 14C measurements to examine possible intra-individual age differences. Results reveal the cessation of weaning, various dietary profiles and in some cases significantly different 14C ages obtained from a single tooth. This case study illustrates how 14C measurements can function as a proxy alongside the commonly used carbon and nitrogen stable isotope values to interpret the diet of past individuals