Fearful symmetry? Intra-individual comparisons of asymmetry in cryptic vs. signalling colour patterns in butterflies

The signalling role of asymmetry has attracted considerable recent interest among evolutionary biologists. Although it has been studied primarily within the context of sexual selection, symmetry of signals may play a role also in inter-specific communication, such as predator–prey interactions. Both theory and experimental evidence suggest that asymmetry may impair the efficacy of visual warning signals used to deter potential predators, but increase the protective value of non-signalling, cryptic colour patterns used to decrease the risk of detection. Here we tested the prediction from this hypothesis by means of intra-individual comparisons of asymmetry in colour pattern elements in three species of moths (Arctia caja (L.), Noctua orbona (L.), Smerinthus ocellata (L.)) that possess cryptic fore wing patterns and signalling hind wing patterns. Mean asymmetries constituted 4.3% (range 2.1–7.0%) of trait size for colour pattern elements, whereas individual asymmetry levels reached as high as 26%. Asymmetry tended to be somewhat larger in cryptic patterns on fore wings than in signalling patterns on hind wings in five of six comparisons, but in only one case was the difference statistically significant. In addition, pattern elements were somewhat more asymmetric on fore wings also in Saturnia pavonia (L.), which possesses identical signalling eyespots on both fore and hind wings. The relatively low levels of asymmetry also in cryptic patterns imply either that selection does not favour increased asymmetry in cryptic patterns, or that the evolution of pronounced asymmetry is developmentally or genetically constrained.     

Developmental instability and immune function in colour polymorphic pygmy grasshoppers

Random left minus right deviations from symmetry in otherwise bilaterally symmetric traits may arise due to developmental instability in response to environmental stress. Here we test for variation in developmental instability, measured as asymmetry of (femur) size, among individuals belonging to four different genetically encoded colour morphs of the pygmy grasshopper Tetrix undulata (Sow.) (Orthoptera: Tetrigidae). Such a difference is expected under the hypotheses that perturbed growth and development and concomitant morphological asymmetry may result from exposure to unfavourable temperatures or costs associated with melanization, or reflect a by-product of past disease in individuals with poor immune responsiveness. Results from mixed model two-way ANOVAs uncovered no statistically significant directional asymmetry in femur size, whereas non-directional asymmetry was significant in each of the four different colour morphs. The degree of intraindividual, interlateral variance in femur size varied significantly among individuals belonging to different colour morphs, being considerably higher in the black morph, which also suffers the greatest risk of overheating, compared to the brown, striped and grey morphs. Asymmetry in femur size was not associated with one measure of immune responsiveness, the encapsulation response of individuals experimentally implanted with a novel antigen consisting of a nylon mono-filament. These results are consistent with the notion that individual pigmentation pattern may indirectly influence developmental instability and morphological asymmetry, via the effects of coloration on body temperature.Co-ordinating editor: Hurst     

Subspecific relationships and genetic structure in the spotted owl

Hierarchical genetic structure was examined in the three geographically-defined subspecies of spotted owl (Strix occidentalis) to define relationships among subspecies and quantify variation within and among regional and local populations. Sequences (522 bp) from domains I and II of the mitochondrial control region were analyzed for 213 individuals from 30 local breeding areas. Results confirmed significant differences between northern spotted owls and the other traditional geographically defined subspecies but did not provide support for subspecific level differences between California and Mexican spotted owls. Divergence times among subspecies estimated with a 936 bp portion of the cytochrome b gene dated Northern and California/Mexican spotted owl divergence time to 115,000–125,000 years ago, whereas California/Mexican spotted owl divergence was estimated at 15,000 years ago. Nested clade analyses indicated an association between California spotted owl and Mexican spotted owl haplotypes, implying historical contact between the two groups. Results also identified a number of individuals geographically classified as northern spotted owls (S. o. caurina) that contained haplotypes identified as California spotted owls (S. o. caurina). Among all northern spotted owls sampled (n=131), 12.9% contained California spotted owl haplotypes. In the Klamath region, which is the contact zone between the two subspecies, 20.3% (n=59) of owls were classified as California spotted owls. The Klamath region is a zone of hybridization and speciation for many other taxa as well. Analyses of population structure indicated gene flow among regions within geographically defined subspecies although there was significant differentiation among northern and southern regions of Mexican spotted owls. Among all areas examined, genetic diversity was not significantly reduced except in California spotted owls where the southern region consists of one haplotype. Our results indicate a stable contact zone between northern and California spotted owls, maintaining distinct subspecific haplotypes within their traditional ranges. This supports recovery efforts based on the traditional subspecies designation for the northern spotted owl. Further, although little variation was found between California and Mexican spotted owls, we suggest they should be managed separately because of current isolation between groups.     

Female house wrens (Troglodytes aedon) increase the size, but not immunocompetence, of their offspring through extra-pair mating

House wrens are typically socially monogamous, but frequently engage in extra-pair matings leading to multisired broods. Because females do not appear to acquire direct material benefits from their extra-pair mates, we tested the hypothesis that female house wrens derive indirect genetic benefits, such as enhanced immunocompetence (cutaneous immune activity, humoral immunity, and plasma bactericidal activity) and condition (size and haematoserological traits) for their offspring, by mating polyandrously. We predicted that extra-pair young (EPY) should show greater immune responsiveness and better body condition than their within-pair maternal half-siblings (WPY). Contrary to our prediction, WPY had higher cutaneous immune activity than their EPY brood-mates in two of three years, and EPY and WPY did not differ in measures of innate and humoral immunity. WPY also had higher albumin to γ-globulin ratios than EPY; however, they were not in better condition based on other measures. EPY had consistently longer tarsi (a measure of long-bone size) than their WPY half-siblings, suggesting that females engage in extra-pair copulations with larger males. The benefits of large structural size in the study population is unknown, but based on evidence from other passerines, we suggest that structural size may be an important fitness-related trait in house wrens. We conclude that our results are not consistent with the hypothesis that females gain immune-related benefits for their offspring by engaging in extra-pair matings. Further study of the fitness consequences of differences in tarsus length is needed to determine whether females acquire size-related benefits for their offspring from extra-pair mates.     

Role of Productivity and Protozoan Abundance for the Occurrence of Predation-resistant Bacteria in Aquatic Systems

Top-down control of lower trophic levels, e.g., bacteria, has been suggested to increase along aquatic productivity gradients. The response by the bacterial community may be to become more predation resistant in highly productive environments. To test this hypothesis, samples were taken from 20 aquatic systems along a productivity gradient (dissolved organic carbon from 7 to 71 mg/L), during late summer. The results showed that the biomass of bacteria, phytoplankton, and ciliates increased along the gradient (r2 = 0.532, 0.426, and 0.758, P < 0.01, respectively). However, the organisms did not increase equally, and the ratio of protozoan to bacterial biomass showed a 100-fold increase along the gradient. Ciliates dominated the protozoan biomass in the more nutrient-rich waters. The edibility of colony-forming bacteria was tested using a ciliate predator, Tetrahymena pyriformis. Bacterial edibility was found to decrease with increases in nutrient richness and ciliate biomass in the aquatic systems (r2 = 0.358, P < 0.01; r2 = 0.242, P < 0.05, respectively). Quantile regression analysis indicated that the selection pressures on edible bacteria were increasing along the productivity gradient. Thus, inedible forms of bacteria were selected for in the transition from oligotrophic to eutrophic conditions. Isolated bacteria were distributed among the alpha-, beta-, and gamma- Proteobacteria and the Actinobacteria and Firmicutes taxa. We conclude that bacterial predation resistance increases in nutrient-rich waters with high protozoan predation.     

Modeling balance control during sustained waking allows posturographic sleepiness testing

We develop a method to quantify sleepiness. Sleepiness is a major risk factor in traffic and occupational accidents, but lack of convenient tests precludes monitoring impending sleepiness. Posturographic balance testing could address this need because sleepiness increases postural sway. It is, however, unclear how sleepiness influences balance control. Our results, for 12 subjects, show that balance control is more susceptible to increasing time awake (TA) compared to neuromuscular processes. This conclusion is reached since during sustained waking the control process slows down by 3.4% per hour of increased TA. This slowdown accounts for 65% of the variance in diurnal balance. We quantified balance control by modeling the body as an inverted pendulum and by expressing the control as the critical time interval for open-loop control (Deltat(c)) of the center-of-mass movements of this pendulum. To estimate the subjects' TA, we regressed the Deltat(c) scores recorded during sustained waking against increasing TA, and equated separate Deltat(c) test scores with the diurnal Deltat(c) scores. We estimated TA with 68% positive predictive value. The results encourage implementing balance modeling into a device that performs clinical or industrial balance testing because the model-based Deltat(c) score responded to increasing TA.     

Biomonitoring of continuous microbial community adaptation towards more efficient phenol-degradation in a fed-batch bioreactor

The anaerobic degradation of phenol was studied in a fed-batch culture. Nitrate was added as electron acceptor and phenol was provided three times, to a final concentration of 200 mg/l. Randomly amplified polymorphic DNA (RAPD) and terminal fraction fragment length polymorphism (T-RFLP) were used and compared in order to monitor the microbial succession in the reactor. Phenol degradation started after an initial lag phase of 14 days and was then completed within a few days. In addition, the duration of the lag phase was shortened and the degradation rate was increased after each phenol amendment. Nitrate reduction correlated with microbial growth and phenol depletion, confirming that the degradation was carried out anaerobically. Results from the DNA analysis showed that the structure of the microbial community changed after each phenol amendment. This study confirms the potential for anaerobic degradation of environmental pollutants and also confirms that microbial acclimation towards faster degradation rates occurred upon repeated substrate amendments. Furthermore, both of the DNA-based techniques described the phenol degradation-linked community shifts with similar general results. RAPD is a faster, simpler technique that gives a higher resolution and consequently reflects the shifts in the microbial community structure better, whereas T-RFLP is more suitable for phylogenetic studies.     

Production of human UDP-glucuronosyltransferases 1A6 and 1A9 using the Semliki Forest virus expression system

Human UDP-glucuronosyltransferases (UGTs) 1A6 and 1A9 were expressed using Semliki Forest virus (SFV) vectors. Infection of chinese hamster lung fibroblast V79 cells with recombinant SFV-UGT viruses resulted in efficient protein expression as detected by metabolic labeling, Western blot analyses and immunofluorescence microscopy. The expression of UGT 1A6 and UGT1A9 in the SFV-infected cells was approximately two fold higher than in a stable V79 cell line. No UGT signal was detected in noninfected cells. In addition, SFV-UGT viruses also efficiently infected other mammalian cells, such as baby hamster kidney (BHK), chinese hamster ovary (CHO) and human lung (WI-26 VA4) cells leading to high production of recombinant enzyme. The measurement of enzyme activities and kinetic parameters using p-nitrophenol and nitrocatechol (entacapone) as substrates for UGT1A6 and UGT1A9, respectively, showed that the overall kinetic properties of the enzymes produced by the two systems were similar. We conclude that the SFV expression system represents an efficient, fast and versatile method for production of metabolic enzymes for in vitro assays.     

Asymmetry in size, shape, and color impairs the protective value of conspicuous color patterns

The received view of protective coloration in animals is thatconspicuous colors and patterns have evolved because they elicitavoidance behavior in potential predators. In the present study,we examine the spontaneous response of naive predators (Gallusgallus domesticus) to artificial prey to test the hypothesisthat deviations from bilateral symmetry of signaling patternelements may negatively influence the avoidance-inducing effectof conspicuous color patterns. Chicks displayed stronger aversionsto artificial "butterfly" prey items possessing symmetric colorpattern elements than to those possessing asymmetric signalswith pattern elements of different color or shape. Althoughthey attacked signals with a size asymmetry of 5% at the samerate as symmetric signals, signals with a size asymmetry of7.5% or more were attacked more often than were symmetric signals.These results suggest that the protective value of conspicuouscolor patterns is impaired by asymmetry in color, shape, andsize of color pattern elements. Our findings also argue againstthe notion that animals have inherent preferences for symmetricover asymmetric objects, and demonstrate the existence of athreshold for asymmetry detection, beyond which further incrementsin asymmetry have no influence on signal efficacy.     

Will the enigma of Francisella tularensis virulence soon be solved?

Francisella tularensis is one of the most infectious bacterial pathogens known and is the causative agent of the zoonotic disease tularemia. In spite of the importance of this pathogen little is known about its virulence mechanisms. However, it is clear that the bacterium is an intracellular pathogen, replicating mainly in macrophages, with replication in amoebae also having been reported. The genome sequence of a high virulence strain of F. tularensis is close to completion and when available, will stimulate further research into virulence mechanisms.