The Effect of Social Environment on Male–Male Competition in Guppies (Poecilia reticulata)

We examined male–male competition in guppies (Poecilia reticulata) to test for evidence of hierarchy formation and any subsequent effects on male mating success by comparing the interactions of pairs of males that were siblings and life‐long tank mates with those of unrelated pairs that had never met. These pairs of males were first observed in the absence of a female; then a female was added to gauge the effects of the initial male–male interactions on male sexual behaviour. The unfamiliar/unrelated pairs engaged in significantly more aggressive interactions such as physical contacts, nipping and chasing than the familiar/related pairs. Based on several previous studies, we suggest that familiarity played a greater role than relatedness in the differences in behaviour that we observed. Our results suggest that, in some circumstances, more aggressive males may have more mating opportunities than less aggressive males. Our results also indicate that males adjust their aggressive and courtship behaviours to the perceived intensity of competition for mates, based on the number of mature males in their rearing tanks. We suggest that male–male competition for mating opportunities may play a more important role in the guppy mating system than previously thought.     

The effects of habitat complexity on aggression and fecundity in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

Female zebrafish housed in aquaria with spatial complexity (plastic plants) over a 13–16-week period showed reduced levels of aggressive behavior compared to females in bare tanks. In tanks with plants, there was no relationship between levels of aggression and fecundity but, in bare tanks, females experiencing the highest levels of aggression showed reduced fecundity. Our results suggest that it may be beneficial, when maintaining zebrafish at moderate to high densities or working with especially aggressive strains, to house them in spatially complex conditions.     

The role of predation in variation in body shape in guppies Poecilia reticulata: a comparison of field and common garden phenotypes

The body shapes of both wild-caught and laboratory-reared male and female Trinidadian guppies Poecilia reticulata from two low-predation and two high-predation populations were studied, but predation regime did not seem to be the most important factor affecting body shape. Instead, complicated patterns of plasticity in body shape among populations and the sexes were found. In particular, populations differed in the depth of the caudal peduncle, which is the muscular region just anterior to the tail fin rays and from which most swimming power is generated. Strikingly, the direction of population differences in caudal peduncle depth observed in wild-caught individuals was reversed when P. reticulata were raised in a common laboratory environment.     

Comparison of linkage disequilibrium and haplotype diversity on macro- and microchromosomes in chicken

Background

Toll like receptors (TLR) play the central role in the recognition of pathogen associated molecular patterns (PAMPs). Mutations in the TLR1, TLR2 and TLR4 genes may change the ability to recognize PAMPs and cause altered responsiveness to the bacterial pathogens.

Results

The study presents association between TLR gene mutations and increased susceptibility to Mycobacterium avium subsp. paratuberculosis (MAP) infection. Novel mutations in TLR genes (TLR1- Ser150Gly and Val220Met; TLR2 – Phe670Leu) were statistically correlated with the hindrance in recognition of MAP legends. This correlation was confirmed subsequently by measuring the expression levels of cytokines (IL-4, IL-8, IL-10, IL-12 and IFN-γ) in the mutant and wild type moDCs (mocyte derived dendritic cells) after challenge with MAP cell lysate or LPS. Further in silico analysis of the TLR1 and TLR4 ectodomains (ECD) revealed the polymorphic nature of the central ECD and irregularities in the central LRR (leucine rich repeat) motifs.

Conclusion

The most critical positions that may alter the pathogen recognition ability of TLR were: the 9^th amino acid position in LRR motif (TLR1–LRR10) and 4^th residue downstream to LRR domain (exta-LRR region of TLR4). The study describes novel mutations in the TLRs and presents their association with the MAP infection.     

Recent trends in the prevalence of overweight and obesity among Canadian children

Background:Previous studies have shown an increase in the prevalence of overweight and obesity among Canadian children from 23.3% to 34.7% during 1978–2004. We examined the most recent trends by applying current definitions of overweight and obesity based on World Health Organization (WHO) body mass index (BMI) thresholds and recently validated norms for waist circumference and waist:height ratio.Methods:We examined directly measured height and weight data from the Canadian Community Health Survey (2004–2005) and the Canadian Health Measures Survey (2009–2013). We calculated z scores for BMI, height and weight based on the 2014 WHO growth charts for Canada, including the new extension of weight-for-age beyond 10 years. To calculate z scores for waist circumference and waist:height ratios, we used new charts from the reference population in the US NHANES III (National Health and Nutrition Examination Survey, 1988–1994).Results:Data were available for 14 014 children aged 3–19 years for the period 2004–2013. We observed a decline in the prevalence of overweight or obesity, from 30.7% (95% confidence interval [CI] 29.7% to 31.6%) to 27.0% (95% CI 25.3% to 28.7%) (p < 0.001) and stabilization in the prevalence of obesity at about 13%. These trends persisted after we adjusted for age, sex and race/ethnicity. Although they declined, the median z scores for BMI, weight and height were positive and higher than those in the WHO reference population. The z scores for waist circumference and waist:height ratio were negative, which indicated that the Canadian children had less central adiposity than American children in historic or contemporary NHANES cohorts.Interpretation:After a period of dramatic growth, BMI z scores and the prevalence of overweight or obesity among Canadian children decreased from 2004 to 2013, which attests to progress against this important public health challenge.Ongoing pan-Canadian surveys such as the Canadian Community Health Survey (CCHS) and Canadian Health Measures Survey (CHMS) are important to evaluate the health of our population using representative national samples.^1,2 Self-reported heights and weights replaced direct measurement during 1978–2004, which underestimated true rates of overweight and obesity.³ A subsequent comparison of directly measured heights and weights during the same period showed an alarming increase in the prevalence of overweight or obesity among Canadian children aged 2–17 years, from 23.3% (95% confidence interval [CI] 20.5% to 26.0%) to 34.7% (95% CI 33.0% to 36.4%) based on the new World Health Organization (WHO) definitions.¹In Canada, the definitions of overweight and obesity changed with the introduction of the 2010 WHO growth charts for Canada.^4,5 Previous definitions were based on body mass index (BMI) percentiles from the 2000 US Centers for Disease Control and Prevention (CDC) growth charts.⁶ In addition to revising these percentile thresholds, the WHO charts were based on a different reference population; as a result, the proportion of Canadian children classified as overweight or obese increased with the introduction of the new WHO charts.^1,7,8 Moreover, the absolute percentile thresholds now vary by age, with toddlers (2 to ≤ 5 yr) having higher thresholds to define overweight and obesity than older children (age > 5 to 19 yr).⁴Results from the United States have shown a decline in obesity rates among toddlers and a plateau in rates among older children;^9,10 stabilization has also been noted in other jurisdictions (e.g., Germany and Australia).^11–16 We undertook this study to determine the most recent trends in the prevalence of overweight and obesity among Canadian children using the current WHO weight charts for Canada applied to a representative sample of children.     

Size-Dependent Female Mate Copying in the Guppy (Poecilia reticulata): Large Females are Role Models but Small Ones are not

Previous work on guppies has shown that small females copy the mate‐choice decisions of larger females, but not vice versa. We extended this work to ask, when put in a situation where they have little information available to distinguish between males, whether large females will also copy large females, and small females will copy small ones. Using Dugatkin's criteria, our study suggests that large females copy the mate‐choice decisions of large females, that small females might copy the decisions of large females, but that neither small nor large females copy small females. Our results provide support for the notion that females are more likely to copy when they perceive that there is an imbalance between their ability to assess a male's quality and the ability of another female to assess that male. However, we did not find evidence of mate copying using criteria used by other researchers.     

Seeing orange: prawns tap into a pre-existing sensory bias of the Trinidadian guppy

Sensory bias, a predisposition towards certain signals, has been implicated in the origin of mate preferences in some species. A risk associated with these biases is that they can be co-opted by predators as sensory lures. Here we propose that the orange spots on the brown pincers of a diurnal, predatory species of prawn function as lures for Trinidadian guppies, which have a sensory bias for orange. We exposed female guppies to (i) a life-like model of this Trinidadian prawn with orange, green or no spots on the pincers or (ii) a live, novel (non-Trinidadian) crustacean (crayfish), also with spotted pincers. First, we provide evidence that guppies sympatric with the prawn recognized our model as a potential predator. Next, we found that guppies spent more time in the dangerous head region of the model prawn with orange-spotted pincers compared with unspotted pincers. Finally, we show that allopatric, but not sympatric, guppies spent more time in the vicinity of the head of a live crayfish when orange spots were added to its pincers than when brown spots were added. Our results suggest that the orange spots on prawn pincers can act as a sensory lure.