Twin-singleton differences in intelligence?

The twin method has been criticised for its alleged non-generalisability. When population parameters of intellectual abilities are estimated from a twin sample, critics point to the twin-singleton differences in intrauterine and family environments. These differences are suggested to lead to suboptimal cognitive development in twins. Although previous studies have reported twin-singleton differences in intelligence, these studies had two major drawbacks: they tested young twins, and twins were compared with (genetically) unrelated singletons. To test accurately whether twin-singleton differences in intelligence exist, a group of adult twins and their non-twin siblings were administered the Dutch WAIS-III. The group was large enough to detect twin-singleton differences of magnitudes reported in earlier investigations. The data were analysed using maximum likelihood model fitting. No evidence of differences between adult twins and their non-twin siblings on cognitive performance was found. It is concluded that twin studies provide reliable estimates of heritabilities of intellectual abilities which can be generalised to the singleton population.     

Sex differences in cannabinoid pharmacology: A reflection of differences in the endocannabinoid system?

Marijuana is the most widely used illicit drug in the U.S., and marijuana use by women is on the rise. Women have been found to be more susceptible to the development of cannabinoid abuse and dependence, have more severe withdrawal symptoms, and are more likely to relapse than men. The majority of research in humans suggests that women are more likely to be affected by cannabinoids than men, with reports of enhanced and decreased performance on various tasks. In rodents, females are more sensitive than males to effects of cannabinoids on tests of antinociception, motor activity, and reinforcing efficacy. Studies on effects of cannabinoid exposure during adolescence in both humans and rodents suggest that female adolescents are more likely than male adolescents to be deleteriously affected by cannabinoids. Sex differences in response to cannabinoids appear to be due to activational and perhaps organizational effects of gonadal hormones, with estradiol identified as the hormone that contributes most to the sexually dimorphic effects of cannabinoids in adults. Many, but not all sexually dimorphic effects of exogenous cannabinoids can be attributed to a sexually dimorphic endocannabinoid system in rodents, although the same has not yet been established firmly for humans. A greater understanding of the mechanisms underlying sexually dimorphic effects of cannabinoids will facilitate development of sex-specific approaches to treat marijuana dependence and to use cannabinoid-based medications therapeutically.     

Ecological role of volatiles produced by Epichlo?: differences in antifungal toxicity.

Species of Epichlo? (Ascomycota, Clavicipitaceae) are endophytic symbionts of pooid grasses. Sexual reproduction of the fungus depends on gamete-transferring Botanophila flies, which in earlier studies were shown to be specifically attracted by the fungal volatiles chokol K and methyl (Z)-3-methyldodec-2-enoate. As several Epichlo? volatiles are known to have antimicrobial properties, it was hypothesised that the original function of insect-attracting volatiles is microbial deterrence. However, the origin of volatile compounds and their toxicity within an ecological context has not yet been clarified. We examined the inhibitory effect of chokol K and methyl (Z)-3-methyldodec-2-enoate on mycoparasites, plant pathogenic fungi and on Epichlo? itself at ecologically relevant concentrations, and assessed volatile production in pure cultures of Epichlo? on complex and defined media supplemented with inorganic sources of carbon and nitrogen. Chokol K reduced the spore germination of all tested fungi, whereas methyl (Z)-3-methyldodec-2-enoate had no inhibitory effect. Moreover, only chokol K was produced in culture, confirming its fungal origin. Our findings are consistent with the proposed scenario that fungal volatile substances have followed an evolutionary pathway from defence to attraction.     

Sex differences in children’s investment in peers

It is hypothesized from within an evolutionary framework that females should be less invested in peer relations than males. Investment was operationalized as enjoyment in Study 1 and as preference for interaction in Study 2. In the first study, four- and six-year-old children’s enjoyment of peer interaction was observed in 26 groups of same-sex peers. Girls were rated as enjoying their interactions significantly less than boys. In the second study, six- and nine-year-old children were interviewed about the individuals with whom they spend time in their homes and neighborhoods and about the individuals who participate in their favorite activities. The proportion of individuals named by children who were peers was significantly lower for girls than boys both in children’s neighborhoods and in children’s favorite activities. Results strongly support the hypothesis that females and males have evolved differential preferences for interaction with peers.     

Taxonomy-based differences in feeding guilds of fish

It has been taken for granted that feeding guilds and behavior in animals are linked to the taxonomic relatedness of species,but empirical evidence supporting such relationship is virtually missing.To examine the importance of taxonomy on trophic ecology,I here present the first well-resolved dietary taxonomy analysis based on feeding guilds(predation,herbivory,and filtering)among families and genera within the fish order Perciformes.Taxonomic relatedness in feeding did not vary with ecosystem dimension(marine vs.freshwater).Although predation dominates among Perciformes fishes,this study shows that in most cases taxonomic units(family or genus)are composed by species with several feeding guilds.Related species are more similar in feeding compared with species that are taxonomically more distant demonstrating that there is a greater variation of feeding guilds within families than genera.Thus,there is no consistency in feeding guilds between family-and genus-level taxonomy.This study provides empirical support for the notion that genera are more informative than families,underlining that family-level taxonomy should be avoided to infer feeding habits of fish species at finer taxonomic resolution.Thus,the choice of taxonomic resolution(family or genus level)in ecological studies is key to avoid information loss and misleading results.I conclude that high-rank taxonomic units(i.e.,above the generic level)are not appropriate to test research hypotheses about the feeding of fish.     

Are genetic differences in foraging behaviour of laying hen chicks paralleled by hybrid-specific differences in feather pecking?

Feather pecking is a behavioural disorder in laying hens which consists of pecking the feathers of conspecifics, causing feather damage or even injuries to the skin. Its development can be explained by redirection of foraging behaviour. While the occurrence of feather pecking strongly depends on the kind of housing condition, it is also known that there are strain differences in the tendency to feather peck. From the inverse relation between feather pecking and foraging behaviour found earlier, we hypothesised that genetically determined differences in foraging behaviour could be responsible for the observed differences in feather pecking between strains.In a first experiment we tested whether there are differences in the foraging behaviour of two hybrids. As hybrids, we used Lohman selected leghorn (LSL) and Dekalb; eight groups of 20 1-day old chicks each. They were kept in enriched pens (265cmx90cm) with a litter area (200cmx90cm) consisting of wood-shavings, chaff, straw, polystyrene blocks, sand area (65cmx90cm) and elevated perches. Behavioural observations were carried out in week 4. In a subsequent experiment with the same birds we tested how the foraging behaviour of the two hybrids differed when housing conditions were changed from enriched to restricted and to what extent they developed feather pecking. A 2x2 factorial design with hybrid (LSL, Dekalb) and housing condition (restricted, enriched) as factors and with four replicates of each factor combination was used. Half of the pens of each hybrid were changed from enriched to restricted housing conditions by covering the litter area with slats. Behavioural observations were carried out in weeks 5 and 6.In experiment 1, LSL and Dekalb spent the same amount of time foraging, but Dekalb spent significantly more of that time with pecking and hacking at the polystyrene blocks. On the other hand, LSL spent significantly more time at the feeding troughs and rested significantly less than Dekalb. In the restricted environment of experiment 2, again, the total foraging time did not differ between hybrids, but LSL chicks spent significantly less time scratching, while Dekalb spent significantly more time moving. Both hybrids developed feather pecking but LSL showed significantly higher rates than Dekalb.Our results demonstrate genetic differences in the foraging behaviour and in the way hybrids cope with the change in housing condition from enriched to an environment that is restricted in relation to foraging possibilities. We conclude that the results support the hypothesis put forward that genetic differences in foraging behaviour could be the basis for the genetic influence in the development of feather pecking.     

Are age differences in sleep due to phase differences in the output of the circadian timing system?

Our aim was to evaluate whether age-related changes in the phase of the output of the circadian timing system (CTS) can explain age differences in habitual bedtime/wake time and in sleep consolidation parameters. Analyses focused on a group of healthy elderly people (older than 70 years) with no sleep problems and with similar subjective sleep quality as a young control group. The 2-week sleep diary data and 24h laboratory temperature recordings were examined for 70 subjects (22 young men [YM], 19 old men [OM], 29 old women [OW]). Polysomnographic (PSG) sleep data recorded during temperature data acquisition were also available for 62 subjects. These analyses made use of our recently developed technique to demask temperature rhythm data. As expected, compared to the young subjects, older subjects showed earlier habitual bedtime and wake time, more disturbed sleep, and a tendency for an earlier minimum of the circadian temperature rhythm. Despite sleep consolidation differences, the groups showed very similar habitual phase-angle differences (interval between the time occurrence of the fitted temperature minimum and habitual wake time). Both elderly and young subjects woke up on average 3h after the temperature minimum. After controlling for the effects of age group, habitual bedtime and wake time were related to clock time phase of the circadian temperature rhythm, with an earlier phase associated with earlier habitual bedtime and wake time. None of the sleep consolidation parameters were linked to the temperature phase angle. In conclusion, sleep consolidation changes associated with healthy aging do not appear to be related to changes in the phase-angle difference between the output signal from the CTS and sleep.     

Gender-associated differences in metabolic syndrome-related parameters in Göttingen minipigs

Gender-associated differences in pathophysiology and treatment of disease are an evolving area in human medicine that should be addressed in animal models. The aim of this study was to characterize gender differences in metabolic parameters of G?ttingen minipigs and to determine which gender has the metabolic profile that is most appropriate as a model for human metabolic syndrome. Blood samples were collected from fasted, lean male and female G?ttingen minipigs at 8 wk and 8 mo of age. Samples were analyzed for glucose, fructosamine, insulin, C-peptide, glucagon, triglycerides, total cholesterol, high-density lipoprotein cholesterol (HDL-c), free fatty acids, leptin, testosterone, and 17beta-estradiol. Insulin sensitivity and beta cell function were estimated by homeostasis model assessment and degree of obesity by measuring the abdominal circumference. Male minipigs had higher concentrations of both testosterone and estradiol. Female minipigs had a larger abdominal circumference and higher concentrations of C-peptide, insulin, triglyceride, total cholesterol, HDL-c and leptin but a lower concentration of free fatty acids and lower HDL-c:total cholesterol ratio. Compared with male minipigs, female minipigs were more insulin-resistant and had a higher beta-cell function. No gender-associated differences were found in any of the other investigated parameters. In conclusion, female minipigs were more obese and insulin-resistant and had a more atherogenic plasma profile than did their male counterparts and therefore may be better models for metabolic syndrome. Their high concentrations of both testosterone and estradiol may protect male minipigs from obesity and metabolic disturbances.     

Exploring differences in stakeholders’ perceptions of illegal bird trapping in Cyprus

Background

Cyprus is recognised as a hotspot for illegal bird trapping in the Mediterranean basin. A consumer demand for the Eurasian blackcap (Sylvia atricapilla) is driving the use of non-selective trapping methods, resulting in the indiscriminate killing of millions of migratory birds. Efforts to tackle the issue have so far been characterised mostly by a top-down approach, focusing on legislation and enforcement. However, trapping levels are not decreasing and conflict between stakeholder groups is intensifying.

Methods

To understand why efforts to stop illegal bird trapping have not been effective, we used semi-structured interviews to interview 18 local bird trappers and nine representatives from the pertinent environmental non-governmental organisations (NGOs) and the governmental agencies responsible for enforcing the legislation.

Results

We found distinct differences between the views of the local trapping community and the environmental NGOs, particularly on why trapping is occurring and its impact on the avifauna. This disparity has contributed to misrepresentations of both sides and a high degree of conflict, which is potentially proving counterproductive to conservation interventions. In addition, it appears that trappers are a heterogeneous group, likely driven by various motivations besides profit.

Conclusion

We argue that stakeholders interested in reducing illegal bird trapping need to develop anti-poaching strategies that aim at minimising the disparity in the views, and subsequently the conflict, acknowledging also that trappers are not a homogenous group, as often treated.

     

Reconsidering sex differences during place learning in tungara frogs

In tungara frogs, female mate choice requires remembering the location and/or calls of preferred males who advertise from fixed positions within a breeding pond. A previous study found that, when solving a place discrimination task in the laboratory, female tCingara frogs were able to learn a visual cue to solve the task, whereas males were not. In that task, male performance appeared to be inhibited, in part, by their attempt to use egocentric cues. We tested whether the sex difference in place learning previously reported would generalize to other training parameters with different cues available by eliminating the potential to use egocentric cues and increasing the number of trials per day. As before, frogs were given a choice between a red or yellow door, one of which led to shelters and return to their home cage. In the current testing conditions, we detected a preference for the red door;thus, we only considered frogs rewarded to the yellow door. Training was associated with an in crease in correct choices and an in creased preference for the yellow door. However, there was no evide nee for a sex d iff ere nee in learni ng. In summary, un der the curre nt training conditions, we fou nd that the appare nt female advantage in place learning was no Ion ger evide nt. Future studies that in vestigate sex d iff ere nces in cue pref ere nee and/or ability to switch among cues will further illuminate the conditions under which sex differences in learning are manifest in tungara frogs.     

Sex differences in Adélie penguin foraging strategies

Consistent sex differences in foraging trip duration, feeding locality and diet of breeding Adélie penguins (Pygoscelis adeliae) were demonstrated at two widely separated locations over several breeding seasons. Differences in foraging behaviour were most pronounced during the guard stage of chick rearing. Female penguins made on average longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill. In contrast, males made shorter journeys to closer foraging grounds during the guard period and fed more extensively on fish throughout chick rearing. Mean guard stage foraging trip durations over four seasons at Béchervaise Island, Eastern Antarctica and over two seasons at Edmonson Point, Ross Sea ranged between 31 and 73 h for females and 25 and 36 h for males. Ninety percent of males tracked from Béchervaise Island by satellite during the first 3 weeks post-hatch foraged within 20 km of the colony, while the majority (60%) of females travelled to the edge of the continental shelf (80–120 km from the colony) to feed during this period. Received: 10 December 1997 / Accepted: 10 April 1998     

Chromosome segregation from cell hybrids. II. Do differences in parental cell growth rates and phase times determine direction of loss?

The hypothesis that the direction of chromosome segregation in cell hybrids is determined by the interaction of parent cell cycles, or S-phase times, predicts that the segregant parent will always be the one with the longer cycle, or the longer S phase, and that late replicating chromosomes will be more frequently lost. We have tested this hypothesis by studying cell cycle parameters of mouse, Chinese hamster, and platypus parent cells and by observing chromosome loss and replication patterns in hybrids between them. Two types of hybrids have been studied: mouse-hamster hybrids showed gradual segregation, in one or other direction, of 10-60% chromosomes, while rodent-platypus hybrids (which could be selected under conditions optimal for either parent cell) showed rapid and extreme segregation of platypus chromosomes. We found no correlation between the direction of segregation and the relative lengths of parental cycle times, or phase times, nor between sequence of replication and frequency with which segregant chromosomes are lost. We therefore conclude that the direction and extent of segregation is not directly determined by the interaction of parental cycle or phase times.     

White biotechnology: differences in US and EU approaches?

Several predominantly political movements advocate white, or industrial, biotechnology as a means to alleviate economic, ecological and societal problems in petroleum-dependent industrialized nations worldwide. US and European approaches differ significantly and we believe that, in the long-term, only economic drivers will be able to bring about the broad use of renewable resources and a bio-based economy. As long as the cost of fossil fuel and feedstock for key chemicals have not passed their respective critical thresholds, industrial biotechnology and its products will need political support and funding, particularly in the energy and bulk-chemicals sectors. Other uses of industrial biotechnology, however, such as biocatalytic conversions of fine and specialty chemicals and the manufacture of high-value products, such as nutriceuticals, cosmeceuticals and performance chemicals offer dynamic growth opportunities both for established chemical industries, as well as emerging entrepreneurial enterprises.     

Positional proteomics reveals differences in N‐terminal proteoform stability

To understand the impact of alternative translation initiation on a proteome, we performed a proteome‐wide study on protein turnover using positional proteomics and ribosome profiling to distinguish between N‐terminal proteoforms of individual genes. By combining pulsed SILAC with N‐terminal COFRADIC, we monitored the stability of 1,941 human N‐terminal proteoforms, including 147 N‐terminal proteoform pairs that originate from alternative translation initiation, alternative splicing or incomplete processing of the initiator methionine. N‐terminally truncated proteoforms were less abundant than canonical proteoforms and often displayed altered stabilities, likely attributed to individual protein characteristics, including intrinsic disorder, but independent of N‐terminal amino acid identity or truncation length. We discovered that the removal of initiator methionine by methionine aminopeptidases reduced the stability of processed proteoforms, while susceptibility for N‐terminal acetylation did not seem to influence protein turnover rates. Taken together, our findings reveal differences in protein stability between N‐terminal proteoforms and point to a role for alternative translation initiation and co‐translational initiator methionine removal, next to alternative splicing, in the overall regulation of proteome homeostasis.     

A genetic basis for intraspecific differences in developmental timing?

Heterochrony, altered developmental timing between ancestors and their descendents, has been proposed as a pervasive evolutionary feature and recent analytical approaches have confirmed its existence as an evolutionary pattern. Yet, the mechanistic basis for heterochrony remains unclear and, in particular, whether intraspecific variation in the timing of developmental events generates, or has the potential to generate, future between‐species differences. Here we make a key step in linking heterochrony at the inter‐ and intraspecific level by reporting an association between interindividual variation in both the absolute and relative timing (position within the sequence of developmental events) of key embryonic developmental events and genetic distance for the pond snail, Radix balthica. We report significant differences in the genetic distance of individuals exhibiting different levels of dissimilarity in their absolute and relative timing of developmental events such as spinning activity, eyespot formation, heart ontogeny, and hatching. This relationship between genetic and developmental dissimilarity is consistent with there being a genetic basis for variation in developmental timing and so suggests that intraspecific heterochrony could provide the raw material for natural selection to produce speciation.     

Are there ventricle-specific postnatal maturational differences in myocardial beta-adrenoceptors?

Newborn hearts have restricted functional reserve and variable responsiveness to inotropes that could be partly due to differences in myocardial beta-adrenoceptors (beta-AR). To clarify this issue, this study documented ventricle-specific changes in myocardial beta-AR density and affinity during postnatal maturation. In vivo left and right ventricle (LV and RV, respectively) biopsies were obtained from newborn (3-day-old, n = 11), immature (14-day-old, n = 7), and adult (n = 6) pigs. Total beta-AR density (B(max), fmol/g) and dissociation constant (K(d), pmol/L) were determined by radioligand binding with I125 iodocyanopindolol. Overall, beta-AR B(max) in the LV significantly decreased with maturation. Interestingly, newborn animal hearts (LV and RV) subdivided into 2 groups: an adult-like low K(d) group with low B(max) and a fetal-like high K(d) group with high B(max), which were significantly different from one another. The high K(d) newborn group also had significantly higher K(d) and B(max) than both immature and adult hearts. Newborns had similar Bmax but higher Kd in the LV than the RV, whereas immature and adult hearts did not have ventricular differences. During maturation, beta-AR density decreased, whereas LV beta-AR binding affinity increased. Variable beta-AR maturity was also identified immediately post partum, which could potentially explain the newborn heart's variable responsiveness to inotropes. The subset of newborn hearts with lower binding affinity (reduced responsiveness) could also contribute to the newborn heart's overall reduction in functional reserve.     

Regional differences in endothelial function in horse lungs: possible role in blood flow distribution?

We investigated regional differences of in vitroresponses of pulmonary arteries (6-mm OD) from the dorsocaudal (top)and cranioventral (bottom) lung regions to endothelium-dependentvasodilators (methacholine, bradykinin, and calcium ionophore A-23187).Methacholine relaxed endothelium-intact top vessels; however, in bottomvessels, a small relaxation preceded a profound contraction. In topvessels, removal of endothelial cells converted relaxation tocontraction, and in bottom vessels it abolished relaxation and enhancedcontraction. Bradykinin and A-23187 were more potent and caused greaterendothelium-mediated relaxation in top than in bottom arteries. Theendothelium-independent vasodilator sodium nitroprusside caused similarrelaxations in all rings.N-nitro-L-arginine andN^G-monomethyl-L-arginine andmethylene blue abolished relaxation of top and bottom arteries tomethacholine; meclofenamate had little effect. We conclude thatregional differences in endothelium-mediated relaxation are caused bydifferences in the magnitude of the endothelial release of nitricoxide. Similar differences in endothelium-dependent flow-mediatedvasodilation and endothelial nitric oxide release may result inpreferential perfusion of caudodorsal lung regions.

     

Sex differences in young children’s use of tools in a problem-solving task

Three-year-old children were observed in two free-play sessions and participated in a toy-retrieval task, in which only one of six tools could be used to retrieve an out-of-reach toy. Boys engaged in more object-oriented play than girls and were more likely to use tools to retrieve the toy during the baseline tool-use task. All children who did not retrieve the toy during the baseline trials did so after being given a hint, and performance on a transfer-of-training tool-use task approached ceiling levels. This suggests that the sex difference in tool use observed during the baseline phase does not reflect a difference in competency, but rather a sex difference in motivation to interact with objects. Amount of time boys, but not girls, spent in object-oriented play during the free-play sessions predicted performance on the tool-use task. The findings are interpreted in terms of evolutionary theory, consistent with the idea that boys’ and girls’ play styles evolved to prepare them for adult life in traditional environments.