CO2-driven decrease in pH disrupts olfactory behaviour and increases individual variation in deep-sea hermit crabs

Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species due to the relatively stable conditions in deep waters for most parameters (e.g. temperature, salinity, oxygen, and pH). To explore the potential for deep-sea hermit crabs (Pagurus tanneri) to acclimate to future ocean acidification, we compared their olfactory and metabolic performance under ambient (pH 7.6) and expected future (pH 7.1) conditions. After exposure to reduced pH waters, metabolic rates of hermit crabs increased transiently and olfactory behaviour was impaired, including antennular flicking and prey detection. Crabs exposed to low pH treatments exhibited higher individual variation for both the speed of antennular flicking and speed of prey detection, than observed in the control pH treatment, suggesting that phenotypic diversity could promote adaptation to future ocean acidification.

Individual Variation in VO2peak Response Following Sprint Interval Training: The Role of Peripheral Adaptation

There is a large degree of heterogeneity in response to regular physical activity at the individual level, with some exhibiting no or very small improvements in VO2peak following highly controlled exercise training. The purpose of this thesis was to examine individual variation in VO2peak response to sprint interval training (SIT) in relation to individual responses to multiple measures of peripheral physiological adaptation. Specifically, VO2peak, capillary density, fibre-specific SDH content, and type I fibre % were measured in 23 young, healthy, recreationally active males before and after 4 weeks SIT (Tabata protocol 4 x per week). The key findings of this experiment included that, when separated into tertiles of VO2peak response, the high (HI) and low (LO) groups differed significantly in VO2peak change after training. Secondly, there was no difference between HI and LO groups for response in any of capillary density, fibre-specific SDH content, or fibre type %, with no correlation found between individual VO2peak response and changes in any measured peripheral variable. Together, these results confirm that individuals respond heterogeneously to SIT and suggest that this heterogeneity does not result from differences in individual changes in capillary density, fibre-specific SDH content or type I fibre %. It is speculated that some other combination of peripheral physiological adaptation must explain variability in VO2peak response to 4 weeks of SIT.

Intraspecific individual variation of temperature tolerance associated with oxygen demand in the European sea bass (Dicentrarchus labrax)

The European sea bass (Dicentrarchus labrax) is an economically important fish native to the Mediterranean and Northern Atlantic. Its complex life cycle involves many migrations through temperature gradients that affect the energetic demands of swimming. Previous studies have shown large intraspecific variation in swimming performance and temperature tolerance, which could include deleterious and advantageous traits under the evolutionary pressure of climate change. However, little is known of the underlying determinants of this individual variation. We investigated individual variation in temperature tolerance in 30 sea bass by exposing them to a warm temperature challenge test. The eight most temperature-tolerant and eight most temperature-sensitive fish were then studied further to determine maximal swimming speed (U-CAT), aerobic scope and post-exercise oxygen consumption. Finally, ventricular contractility in each group was determined using isometric muscle preparations. The temperature-tolerant fish showed lower resting oxygen consumption rates, possessed larger hearts and initially recovered from exhaustive exercise faster than the temperature-sensitive fish. Thus, whole-animal temperature tolerance was associated with important performance traits. However, the temperature-tolerant fish also demonstrated poorer maximal swimming capacity (i.e. lower UCAT) than their temperature-sensitive counterparts, which may indicate a trade-off between temperature tolerance and swimming performance. Interestingly, the larger relative ventricular mass of the temperature-tolerant fish did not equate to greater ventricular contractility, suggesting that larger stroke volumes, rather than greater contractile strength, may be associated with thermal tolerance in this species.

Intraseasonal variation in immune defence, body mass and hematocrit in adult house martins Delichon urbica

The intensity of parasite infections often increases during the reproductive season of the host as a result of parasite reproduction, increased parasite transmission and increased host susceptibility. We report within-individual variation in immune parameters, hematocrit and body mass in adult house martins Delichon urbica rearing nestlings in nests experimentally infested with house martin bugs Oeciacus hirundinis and birds rearing nestlings in initially parasite-free nests. From first to second broods body mass and hematocrit of breeding adult house martins decreased. In contrast leucocytes and immunoglobulins became more abundant. When their nests were infested with ectoparasites adults lost more weight compared with birds raising nestlings in nests treated with pyrethrin, whereas the decrease in hematocrit was more pronounced during infection with blood parasites. Neither experimental infestation with house martin bugs nor blood parasites had a significant effect on the amount of immune defences.

Extensive natural variation for cellular hydrogen peroxide release is genetically controlled.

Natural variation in DNA sequence contributes to individual differences in quantitative traits. While multiple studies have shown genetic control over gene expression variation, few additional cellular traits have been investigated. Here, we investigated the natural variation of NADPH oxidase-dependent hydrogen peroxide (H(2)O(2) release), which is the joint effect of reactive oxygen species (ROS) production, superoxide metabolism and degradation, and is related to a number of human disorders. We assessed the normal variation of H(2)O(2) release in lymphoblastoid cell lines (LCL) in a family-based 3-generation cohort (CEPH-HapMap), and in 3 population-based cohorts (KORA, GenCord, HapMap). Substantial individual variation was observed, 45% of which were associated with heritability in the CEPH-HapMap cohort. We identified 2 genome-wide significant loci of Hsa12 and Hsa15 in genome-wide linkage analysis. Next, we performed genome-wide association study (GWAS) for the combined KORA-GenCord cohorts (n = 279) using enhanced marker resolution by imputation (>1.4 million SNPs). We found 5 significant associations (p<5.00×10-8) and 54 suggestive associations (p<1.00×10-5), one of which confirmed the linked region on Hsa15. To replicate our findings, we performed GWAS using 58 HapMap individuals and ∼2.1 million SNPs. We identified 40 genome-wide significant and 302 suggestive SNPs, and confirmed genome signals on Hsa1, Hsa12, and Hsa15. Genetic loci within 900 kb from the known candidate gene p67phox on Hsa1 were identified in GWAS in both cohorts. We did not find replication of SNPs across all cohorts, but replication within the same genomic region. Finally, a highly significant decrease in H(2)O(2) release was observed in Down Syndrome (DS) individuals (p<2.88×10-12). Taken together, our results show strong evidence of genetic control of H(2)O(2) in LCL of healthy and DS cohorts and suggest that cellular phenotypes, which themselves are also complex, may be used as proxies for dissection of complex disorders.

Lipoprotein distribution and biological variation of 24S- and 27-hydroxycholesterol in healthy volunteers.

24S- and 27-hydroxycholesterol are obligatory intermediates of cholesterol catabolism and play an important role in the maintenance of whole-body cholesterol homeostasis. Using an HPLC-MS method for oxysterol quantification, the distribution of esterified and unesterified oxysterols in lipoprotein subfractions as well as the influence of daytime, food intake and menstrual cycle on oxysterol concentrations were investigated in healthy volunteers. Moreover, reference intervals for 24S- and 27-hydroxycholesterol in plasma as well as the corresponding levels for 27-hydroxycholesterol in the HDL subfraction were established in 100 healthy volunteers. Both circulating oxysterols are mainly transported in association with HDL and LDL--primarily in the esterified form. No significant diurnal changes and no variations during menstrual cycle of either absolute or cholesterol-related plasma levels were detected. In contrast to 24S-hydroxycholesterol in plasma and 27-hydroxycholesterol in the HDL subfraction, the 95% reference intervals of 27-hydroxycholesterol both in plasma and the non-HDL subfraction were higher in males than in females. The concentrations of 27-hydroxycholesterol in plasma and the non-HDL subfraction showed strong positive correlations with the concentrations of cholesterol, non-HDL cholesterol and triglycerides. Our data on the lipoprotein distribution of oxysterols as well as on their intra- and inter-individual variation set the stage for future clinical studies.

Individual Differences in Global/Local Processing Bias and the Attentional Blink

When the second of two targets (T2) is presented temporally close to the first target (T1) in rapid serial visual presentation, accuracy to detect/identify T2 is markedly reduced as compared to longer target separations. This is known as the attentional blink (AB), and is thought to reflect a limitation of selective attention. While most individuals show an AB, research has demonstrated that individuals are variously susceptible to this effect. To explain these differences, Dale and Arnell (2010) examined whether dispositional differences in attentional breadth, as measured by the Navon letter task, could predict individual AB magnitude. They found that individuals who showed a natural bias toward the broad, global level of Navon letter stimuli were less susceptible to the AB as compared to individuals who showed a natural bias toward the detailed, local aspects of Navon letter stimuli. This suggests that individuals who naturally broaden their attention can overcome the AB. However, it was unclear how stable these individual differences were over time, and whether a variety of global/local tasks could predict AB performance. As such, the purpose of this dissertation was to investigate, through four empirical studies, the nature of individual differences in both global/local bias and the AB, and how these differences in attentional breadth can modulate AB performance. Study 1 was designed to examine the stability of dispositional global/local biases over time, as well as the relationships among three different global/local processing measures. Study 2 examined the stability of individual differences in the AB, as well as the relationship among two distinct AB tasks. Study 3 examined whether the three distinct global/local tasks used in Study 1 could predict performance on the two AB tasks from Study 2. Finally, Study 4 explored whether individual differences in global/local bias could be manipulated by exposing participants to high/low spatial frequencies and Navon stimuli. In Study 1, I showed that dispositional differences in global/local bias were reliable over a period of at least a week, demonstrating that these individual biases may be trait-like. However, the three tasks that purportedly measure global/local bias were unrelated to each other, suggesting that they measure unique aspects of global/local processing. In Study 2, I found that individual variation in AB performance was also reliable over a period of at least a week, and that the two AB task versions were correlated. Study 3 showed that dispositional global/local biases, as measured by the three tasks from Study 1, predicted AB magnitude, such that individuals who were naturally globally biased had smaller ABs. Finally, in Study 4 I demonstrated that these dispositional global/local biases are resistant to both spatial frequency and Navon letter manipulations, indicating that these differences are robust and intractable. Overall, the results of the four studies in this dissertation help clarify the role of individual differences in attentional breadth in selective attention.

Habitat variability and the individual variability of juvenile Atlantic salmon (Salmo salar)

La variabilité spatiale et temporelle de l’écoulement en rivière contribue à créer une mosaïque d’habitat dynamique qui soutient la diversité écologique. Une des questions fondamentales en écohydraulique est de déterminer quelles sont les échelles spatiales et temporelles de variation de l’habitat les plus importantes pour les organismes à divers stades de vie. L’objectif général de la thèse consiste à examiner les liens entre la variabilité de l’habitat et le comportement du saumon Atlantique juvénile. Plus spécifiquement, trois thèmes sont abordés : la turbulence en tant que variable d’habitat du poisson, les échelles spatiales et temporelles de sélection de l’habitat et la variabilité individuelle du comportement du poisson. À l’aide de données empiriques détaillées et d’analyses statistiques variées, nos objectifs étaient de 1) quantifier les liens causaux entre les variables d’habitat du poisson « usuelles » et les propriétés turbulentes à échelles multiples; 2) tester l’utilisation d’un chenal portatif pour analyser l’effet des propriétés turbulentes sur les probabilités de capture de proie et du comportement alimentaire des saumons juvéniles; 3) analyser les échelles spatiales et temporelles de sélection de l’habitat dans un tronçon l’été et l’automne; 4) examiner la variation individuelle saisonnière et journalière des patrons d’activité, d’utilisation de l’habitat et de leur interaction; 5) investiguer la variation individuelle du comportement spatial en relation aux fluctuations environnementales. La thèse procure une caractérisation détaillée de la turbulence dans les mouilles et les seuils et montre que la capacité des variables d’habitat du poisson usuelles à expliquer les propriétés turbulentes est relativement basse, surtout dans les petites échelles, mais varie de façon importante entre les unités morphologiques. D’un point de vue pratique, ce niveau de complexité suggère que la turbulence devrait être considérée comme une variable écologique distincte. Dans une deuxième expérience, en utilisant un chenal portatif in situ, nous n’avons pas confirmé de façon concluante, ni écarté l’effet de la turbulence sur la probabilité de capture des proies, mais avons observé une sélection préférentielle de localisations où la turbulence était relativement faible. La sélection d’habitats de faible turbulence a aussi été observée en conditions naturelles dans une étude basée sur des observations pour laquelle 66 poissons ont été marqués à l’aide de transpondeurs passifs et suivis pendant trois mois dans un tronçon de rivière à l’aide d’un réseau d’antennes enfouies dans le lit. La sélection de l’habitat était dépendante de l’échelle d’observation. Les poissons étaient associés aux profondeurs modérées à micro-échelle, mais aussi à des profondeurs plus élevées à l’échelle des patchs. De plus, l’étendue d’habitats utilisés a augmenté de façon asymptotique avec l’échelle temporelle. L’échelle d’une heure a été considérée comme optimale pour décrire l’habitat utilisé dans une journée et l’échelle de trois jours pour décrire l’habitat utilisé dans un mois. Le suivi individuel a révélé une forte variabilité inter-individuelle des patrons d’activité, certains individus étant principalement nocturnes alors que d’autres ont fréquemment changé de patrons d’activité. Les changements de patrons d’activité étaient liés aux variables environnementales, mais aussi à l’utilisation de l’habitat des individus, ce qui pourrait signifier que l’utilisation d’habitats suboptimaux engendre la nécessité d’augmenter l’activité diurne, quand l’apport alimentaire et le risque de prédation sont plus élevés. La variabilité inter-individuelle élevée a aussi été observée dans le comportement spatial. La plupart des poissons ont présenté une faible mobilité la plupart des jours, mais ont occasionnellement effectué des mouvements de forte amplitude. En fait, la variabilité inter-individuelle a compté pour seulement 12-17% de la variabilité totale de la mobilité des poissons. Ces résultats questionnent la prémisse que la population soit composée de fractions d’individus sédentaires et mobiles. La variation individuelle journalière suggère que la mobilité est une réponse à des changements des conditions plutôt qu’à un trait de comportement individuel.

Variation, asymmetry and working memory in the process of second language acquisition

Calls for understanding the interface between L2 linguistic knowledge and development (Gregg 1996; Carroll 2001; Towell 2003) provide a context for analysing the role of memory (Paradis 2004), specifically working memory (Baddeley 1986, 2003) in L2 development. Miyake and Friedman (1998) have claimed that Working Memory (WM) may be the key to L2 acquisition, especially in explaining individual variation in L2 acquisition. Recent findings found a robust connection between greater working memory (WM) capacity and rapid, successful acquisition of L2 vocabulary, reading and oral fluency (Service 1992; Harrington and Sawyer 1992; Fortkamp 1999). This study adds to the growing body of research by investigating correlations between WM and variation in grammatical development, focusing on asymmetries in processing L2 English wh-constructions in an immersion setting.

The nested assembly of individual-resource networks

P>1. Much of the current understanding of ecological systems is based on theory that does not explicitly take into account individual variation within natural populations. However, individuals may show substantial variation in resource use. This variation in turn may be translated into topological properties of networks that depict interactions among individuals and the food resources they consume (individual-resource networks). 2. Different models derived from optimal diet theory (ODT) predict highly distinct patterns of trophic interactions at the individual level that should translate into distinct network topologies. As a consequence, individual-resource networks can be useful tools in revealing the incidence of different patterns of resource use by individuals and suggesting their mechanistic basis. 3. In the present study, using data from several dietary studies, we assembled individual-resource networks of 10 vertebrate species, previously reported to show interindividual diet variation, and used a network-based approach to investigate their structure. 4. We found significant nestedness, but no modularity, in all empirical networks, indicating that (i) these populations are composed of both opportunistic and selective individuals and (ii) the diets of the latter are ordered as predictable subsets of the diets of the more opportunistic individuals. 5. Nested patterns are a common feature of species networks, and our results extend its generality to trophic interactions at the individual level. This pattern is consistent with a recently proposed ODT model, in which individuals show similar rank preferences but differ in their acceptance rate for alternative resources. Our findings therefore suggest a common mechanism underlying interindividual variation in resource use in disparate taxa.

Intraspecific Variation of Biological Activities in Venoms from Wild and Captive Bothrops jararaca

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Individual Specialization in the Hunting-wasp Trypoxylon (Trypargilum) agamemnon Richards (Hymenoptera: Crabronidae)

Renan B. Pitilin, Marcio S. Araujo, and Maria L.T. Buschini (2012) Individual specialization in the hunting-wasp Trypoxylon (Trypargilum) agamemnon Richards (Hymenoptera: Crabronidae). Zoological Studies 51(5): 655-662. Individuals of a population may differ with respect to resource use. This among-individual variation in resource utilization is called 'individual specialization' and may substantially impact the ecological and evolutionary dynamics of a population. The aim of this study was to evaluate whether females of 1 population of the hunting-wasp Trypoxylon agamemnon differed in their preferences for spider size and/or taxa. To observe the behavior of wasps, trap-nests were installed in an araucaria forest fragment in the Parque Municipal das Araucarias, Guarapuava (PR), southern Brazil. The indices within-individual component (WIC)/total niche width of a population (TNW) and average of values of the proportional similarity index (IS) were used to measure the degree of individual specialization. We found evidence of strong, significant individual specialization in T agamemnon in terms of both prey size (WIC/TNW = 0.43) and taxa (IS = 0.45). We hypothesized that individual specialization in this species resulted from cognitive tradeoffs that limit individuals to exploring a small subset of available resources. http://zoolstud.sinica.edu.tw/Journals/51.5/655.pdf

The ecological causes of individual specialisation

University of Tennessee, KnoxvilleNational Science Foundation (NSF)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identification of genetic variation influencing apolipoprotein E levels: Follow-up of genome-wide linkage scans in the GENOA study

Apolipoprotein E (ApoE) plays a major role in the metabolism of high density and low density lipoproteins (HDL and LDL). Its common protein isoforms (E2, E3, E4) are risk factors for coronary artery disease (CAD) and explain between 16 to 23% of the inter-individual variation in plasma apoE levels. Linkage analysis has been completed for plasma apoE levels in the GENOA study (Genetic Epidemiology Network of Atherosclerosis). After stratification of the population by lipoprotein levels and body mass index (BMI) to create more homogeneity with regard to biological context for apoE levels, Hispanic families showed significant linkage on chromosome 17q for two strata (LOD=2.93 at 104 cM for a low cholesterol group, LOD=3.04 at 111 cM for a low cholesterol, high HDLC group). Replication of 17q linkage was observed for apoB and apoE levels in the unstratified Hispanic and African-American populations, and for apoE levels in African-American families. Replication of this 17q linkage in different populations and strata provides strong support for the presence of gene(s) in this region with significant roles in the determination of inter-individual variation in plasma apoE levels. Through a positional and functional candidate gene approach, ten genes were identified in the 17q linked region, and 62 polymorphisms in these genes were genotyped in the GENOA families. Association analysis was performed with FBAT, GEE, and variance-component based tests followed by conditional linkage analysis. Association studies with partial coverage of TagSNPs in the gene coding for apolipoprotein H (APOH) were performed, and significant results were found for 2 SNPs (APOH_20951 and APOH_05407) in the Hispanic low cholesterol strata accounting for 3.49% of the inter-individual variation in plasma apoE levels. Among the other candidate genes, we identified a haplotype block in the ACE1 gene that contains two major haplotypes associated with apoE levels as well as total cholesterol, apoB and LDLC levels in the unstratified Hispanic population. Identifying genes responsible for the remaining 60% of inter-individual variation in plasma apoE level, will yield new insights into the understanding of genetic interactions involved in the lipid metabolism, and a more precise understanding of the risk factors leading to CAD. ^