Identification of Cytauxzoon felis antigens via protein microarray and assessment of expression library immunization against cytauxzoonosis.

BACKGROUND: Cytauxzoonosis is a disease of felids in North America caused by the tick-transmitted apicomplexan parasite Cytauxzoon felis. Cytauxzoonosis is particularly virulent for domestic cats, but no vaccine currently exists. The parasite cannot be cultivated in vitro, presenting a significant limitation for vaccine development. METHODS: Recent sequencing of the C. felis genome has identified over 4300 putative protein-encoding genes. From this pool we constructed a protein microarray containing 673 putative C. felis proteins. This microarray was probed with sera from C. felis-infected and naïve cats to identify differentially reactive antigens which were incorporated into two expression library vaccines, one polyvalent and one monovalent. We assessed the efficacy of these vaccines to prevent of infection and/or disease in a tick-challenge model. RESULTS: Probing of the protein microarray resulted in identification of 30 differentially reactive C. felis antigens that were incorporated into the two expression library vaccines. However, expression library immunization failed to prevent infection or disease in cats challenged with C. felis. CONCLUSIONS: Protein microarray facilitated high-throughput identification of novel antigens, substantially increasing the pool of characterized C. felis antigens. These antigens should be considered for development of C. felis vaccines, diagnostics, and therapeutics.

Spatiotemporal patterns and relationships among the diet, biochemistry, and exposure to flame retardants in an apex avian predator, the peregrine falcon.

Flame retardants (FR) are industrial chemicals and some are proven environmental contaminants that accumulate in predatory birds. Few studies have examined the influence of diet on FR profiles in nestling raptors and the possible physiological implications of such FR exposure. The objectives of this research were (1) to determine spatial patterns of ≤ 48 polybrominated diphenyl ether (PBDE) congeners and ≤ 26 non-PBDE FRs, including organophosphate esters (OPEs), in nestling peregrine falcons (Falco peregrinus) across the Canadian Great Lakes-St. Lawrence River Basin (GL-SLR; 2010) and in the eastern Canadian Arctic (2007); (2) to identify temporal changes in FR concentrations from the mid-2000s to 2010 in GL-SLR peregrine nestlings; (3) to investigate the role of diet using stable isotopes on exposure patterns of quantifiable FRs; and (4) to assess possible associations between circulating FRs and total (T) thyroxine (TT4) and triiodothyronine (TT3), tocopherol, retinol and oxidative status (isoprostanes). The summed concentrations of the top 5 PBDEs (Σ5) (BDE-47, -99, -100, -154, -153) were significantly higher in rural nestlings than urban nestlings in the GL-SLR, followed by the eastern Arctic nestlings. The PBDE congener profile of rural nestlings was dominated by BDE-99 (34‰), whereas BDE-209 (31‰) became dominant in the 2010 urban PBDE profile marking a shift since the mid-2000s. Low (ppb) concentrations of 25 novel non-PBDE FRs (e.g., 1,2-bis-(2,4,6-tribromophenoxy)ethane (BTBPE), decabromodiphenylethane (DBDPE)) were measured in the nestlings in at least one region, with the first report in peregrines of 15 novel non-PBDE FRs (e.g., 2-ethyl-1-hyxyl 2,3,4,5-tetrabromobenzoate (EHTBB), pentabromo allyl ether (PBPAE), tetrabromoethylcyclohexane (α-, ß-DBE-DBCH)) as well as of tris (2-butoxyethyl) phosphate (TBOEP) (0-7.5ng/g ww) > tris(2-chloroisopropyl) phosphate (TCIPP) (0.1-5.5ng/g ww) > tris(2-chloroethyl) phosphate (TCEP) (0.02-2.0ng/g ww) > tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) (0-1.0ng/g ww). Within the GL-SLR, the urban nestlings' diet had significantly more terrestrial sources (greater δ13C values) than the broader, more aquatic-based diet of rural peregrines. Dietary source (δ13C) was significantly associated with concentrations of Σ5PBDE, BDE-209, EHTBB, and 2,2-4,4',5,5'-hexabromobiphenyl (BB-153), with trophic level (δ15N) also positively associated with BDE-209 levels. Compared to urban nestlings, the rural nestlings had significantly lower circulating concentrations of thyroxine (TT4), triiodothyronine (TT3), a greater proportion of TT3 relative to TT4 (TT3:TT4), tocopherol and oxidative status (isoprostanes), but higher retinol levels; the most recalcitrant PBDE congener, BDE-153, in combination with low concentrations of some novel FRs, particularly octabromotrimethylphenyllindane (OBIND), may influence circulating thyroid hormones, especially TT4, and retinol levels of peregrine falcon nestlings. These associations of FR-endocrine-biochemical measures suggest possible exposure-related changes in these birds and further study is warranted.

Evaluation of High Dosages of Oral Meloxicam in American Kestrels ( Falco sparverius ).

To evaluate the toxicity of short-term high doses of meloxicam in American kestrels ( Falco sparverius ), 32 male captive-born, 1- to 4-year-old American kestrels were randomly assigned to 4 groups: 3 groups treated with meloxicam (n = 9 per group) and a control group (n = 5). Meloxicam was administered orally via feeding tube in the proventriculus at 2, 10, and 20 mg/kg every 12 hours for 7 days for the treatment groups, while the control group received saline solution. The birds were evaluated for the presence of clinical signs, abnormalities in the complete blood cell count and in the plasma biochemical panel for the 20-mg/kg group, and gross and histopathologic lesions. No clinical signs or mortality were observed in any group. No significant differences of clinical relevance were found in results of the packed cell volume, total solids, and biochemical panel, and no evidence of renal toxicity was found in the treatment or control groups. A significant correlation was found between hepatic lipidosis and meloxicam dose (P = .02). Two of 9 birds in the 20-mg/kg group developed gastric ulcers, although this result was not significant. None of the birds in the 2- and 10-mg/kg groups had similar lesions. Finally, meloxicam dosages up to 20 mg/kg did not result in nephrotoxicity in American kestrels. Further toxicologic studies to evaluate hepatotoxicity and gastrotoxicity of meloxicam in avian species are needed.

Changes in the incubation by American kestrels (Falco sparverius) during exposure to the polybrominated diphenyl ether (PBDE) mixture DE-71.

Polybrominated diphenyl ethers (PBDE) are persistent environmental pollutants that have been detected in wildlife globally. American kestrels exposed to the commercial PBDE mixture DE-71 have previously demonstrated reduced reproductive success and behaviors during courtship and brood rearing; however, it remains unknown whether DE-71 affects incubation. During breeding, captive kestrels were exposed to the DE-71 mixture dissolved in safflower oil at two environmentally relevant concentrations (low: 283.5 ± 48.2, high: 1104.8 ± 124.5 ng/g wet weight [ww]) via diet for an average of 75 d. Unexpected low in ovo concentrations of hexabromocyclododecane (HBCD) were also detected (low: 3 ± 1 ng/g ww, high: 16 ± 3 ng/g ww). All comparisons are made to control pairs. Kestrel pairs in the low- and high-exposure groups experienced longer incubation periods with increasing exposure to ΣPBDE and some individual congeners. As incubation progressed, pairs exposed to DE-71 had significantly lower nest temperatures, which were on average 19% lower in low-exposure nests and 35% lower in high-exposure nests during late incubation. The DE-71 exposed pairs (low and high) also demonstrated significantly reduced incubation constancy (defined as percent of temperature readings above the maximum daily ambient temperature) during early incubation compared to controls. Nest temperatures (all pairs) and incubation constancy (high pairs) during early incubation (d 1-3) were significantly and positively associated with the proportion of eggs that hatched per pair. Higher incubation constancy and incubating nest temperatures in the low-exposure group were associated with markedly less egg weight loss by mid-incubation. These findings demonstrate that exposure to PBDE significantly affected kestrels during incubation, a critical period for embryonic development.

The flame retardant ß-1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane: fate, fertility, and reproductive success in American kestrels (Falco sparverius).

Captive American kestrels (Falco sparverius) were exposed via diet during reproduction to an environmentally relevant concentration of ß-1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (ß-TBECH). The ß-TBECH isomer was injected into the food source at a daily dosing concentration of 0.239 ng/g kestrel/day (22 pairs); control birds were exposed via diet to the safflower oil vehicle only (24 pairs). Eight pairs in each group were exposed for four weeks and sacrificed for tissue analysis; the remaining pairs completed their breeding cycle, with exposure ceasing at the end of incubation (82 days). α- and ß-TBECH appeared to be rapidly metabolized and/or eliminated from fat, liver, and plasma; both isomers and potential hydroxylated metabolites of ß-TBECH (plasma) were undetected. Notwithstanding, compared to controls, pairs exposed to ß-TBECH laid fewer eggs (p = 0.019) and laid lighter eggs (successful eggs: p = 0.009). Exposed pairs also demonstrated poorer egg fertility (p = 0.035) although testis mass and histology were similar among males. Reductions in egg production and fertility resulted in decreased hatchling success (p = 0.023). The ß-TBECH-exposed pairs also produced fewer males overall (p = 0.009), which occurred concurrently with increased estradiols maternally deposited in eggs (p = 0.039). These findings demonstrate that ß-TBECH may be detrimental for breeding in wild birds receiving similar exposure levels.

Optimal settings and advantages of drones as a tool for canopy arthropod collection.

The growing field of aeroecology is limited by difficulties associated with sampling in the air column. Aerial insects are particularly hard to sample, despite being the main prey in the air column, with some recent studies attempting to use drones as a collection method. We conducted a study to determine the optimal drone settings for collecting insects above the canopy, where drones are seldom used. By attaching a net to the body of a small, commercial drone, we tested yield from different height, speed, and net settings in wetlands, as well as compared insect diversity across different habitat canopies. Height was the most important setting; grazing the canopy yielded significantly more insects than flying one meter above it. Speed, drone type, and net size did not influence the number of insects caught per trial. Wetland canopies had higher abundance, diversity, and species richness in its arthropod populations compared to forest canopies or lakes. Compared to the yield of Lindgren funnels-a traditional sampling method in entomology-drones captured higher diversity and abundance of insects in a fraction of the time. This study confirms that drones are an efficient and accurate way to collect canopy arthropods.

Guidance in Kagome-like photonic crystal fibres II: perturbation theory for a realistic fibre structure.

A perturbation theory is developed that treats a localised mode embedded within a continuum of states. The method is applied to a model rectangular hollow-core photonic crystal fibre structure, where the basic modes are derived from an ideal, scalar model and the perturbation terms include vector effects and structural difference between the ideal and realistic structures. An expression for the attenuation of the fundamental mode due to interactions with cladding modes is derived, and results are presented for a rectangular photonic crystal fibre structure. Attenuations calculated in this way are in good agreement with numerical simulations. The origin of the guidance in our model structure is explained through this quantitative analysis. Further perspectives are obtained through investigating the influence of fibre parameters on the attenuation.

Guidance in Kagome-like photonic crystal fibres I: analysis of an ideal fibre structure.

Propagation of light in a square-lattice hollow-core photonic crystal fibre is analysed as a model of guidance in a class of photonic crystal fibres that exhibit broad-band guidance without photonic bandgaps. A scalar governing equation is used and analytic solutions based on transfer matrices are developed for the full set of modes. It is found that an exponentially localised fundamental mode exists for a wide range of frequencies. These analytic solutions of an idealised structure will form the basis for analysis of guidance in a realistic structure in a following paper.

Diet exposure to technical hexabromocyclododecane (HBCD) affects testes and circulating testosterone and thyroxine levels in American kestrels (Falco sparverius).

Hexabromocyclododecane (HBCD) is a high-production-volume, brominated flame-retardant that is used in items such as polystyrene foams. HBCD has been detected in the environment, wildlife tissues and in humans globally with some of the highest recorded levels in predatory birds. This study examined the effects of exposure to environmentally relevant levels of HBCD on the reproductive physiology of captive male American kestrels (Falco sparverius), a predatory bird. Two sets of males were used: one group not housed with females (unpaired: nc=12, nHBCD=10) and the second group housed with females (breeding: nc=10, nHBCD=20). All treatment birds were exposed to 0.51 µg HBCD/g kestrel/day technical HBCD, and controls to safflower oil only, injected into their food during seasonal testicular development. Unpaired males were exposed for 3 weeks and euthanized for testicular analysis. Breeding males were exposed for 3 weeks prior to pairing and throughout the courtship period. The HBCD-exposed unpaired males had heavier testes (p≤0.017) and a trend towards more seminiferous tubules containing elongated spermatids (p=0.052). There was also a moderate increase in plasma testosterone concentrations (p=0.056) compared to controls. In breeding males, testosterone levels increased during courtship to culminate in higher levels than controls by the time the first egg was laid (p=0.010) and circulating free and total T4 was reduced throughout. The number of sperm cells reaching the perivitelline layer of the first egg for breeding males did not differ between the two groups. This study is the first report that HBCD exposure at environmentally relevant levels alters reproductive physiology in male birds and suggests that birds may be more sensitive to HBCD than mammals.

Sequence and genetic map of Meloidogyne hapla: A compact nematode genome for plant parasitism.

We have established Meloidogyne hapla as a tractable model plant-parasitic nematode amenable to forward and reverse genetics, and we present a complete genome sequence. At 54 Mbp, M. hapla represents not only the smallest nematode genome yet completed, but also the smallest metazoan, and defines a platform to elucidate mechanisms of parasitism by what is the largest uncontrolled group of plant pathogens worldwide. The M. hapla genome encodes significantly fewer genes than does the free-living nematode Caenorhabditis elegans (most notably through a reduction of odorant receptors and other gene families), yet it has acquired horizontally from other kingdoms numerous genes suspected to be involved in adaptations to parasitism. In some cases, amplification and tandem duplication have occurred with genes suspected of being acquired horizontally and involved in parasitism of plants. Although M. hapla and C. elegans diverged >500 million years ago, many developmental and biochemical pathways, including those for dauer formation and RNAi, are conserved. Although overall genome organization is not conserved, there are areas of microsynteny that may suggest a primary biological function in nematodes for those genes in these areas. This sequence and map represent a wealth of biological information on both the nature of nematode parasitism of plants and its evolution.

Fewer bat passes are detected during small, commercial drone flights.

Advances in technological capabilities, operational simplicity and cost efficiency have promoted the rapid integration of unmanned aerial vehicles (UAVs) into ecological research, providing access to study taxa that are otherwise difficult to survey, such as bats. Many bat species are currently at risk, but accurately surveying populations is challenging for species that do not roost in large aggregations. Acoustic recorders attached to UAVs provide an opportunity to survey bats in challenging habitats. However, UAVs may alter bat behaviour, leading to avoidance of the UAV, reduced detection rates and inaccurate surveys. We evaluated the number of bat passes detected with and without the presence of a small, commercial UAV in open habitats. Only 22% of bat passes were recorded in the presence of the UAV (0.23 ± 0.09 passes/min) compared to control periods without the UAV (1.03 ± 0.17 passes/min), but the effect was smaller on the big brown bat/silver-haired bat (Eptesicus fuscus/Lasionycteris noctivagans) acoustic complex. Noise interference from the UAV also reduced on-board bat detection rates. We conclude that acoustic records attached to UAVs may inaccurately survey bat populations due to low and variable detection rates by such recorders.

Changes in plasma retinol of American kestrels (Falco sparverius) in response to dietary or in ovo exposure to environmentally relevant concentrations of a penta-brominated diphenyl ether mixture, DE-71.

Polybrominated diphenyl ethers (PBDE) are ubiquitous, lipophilic, and bioaccumulative brominated flame retardants. Plasma retinol concentrations of captive adult American kestrels were assessed at the beginning of the breeding season following 3 wk of daily dietary exposure to vehicle (control), low (0.3 ng/g wet weight [ww]), or high (1.6 ng/g ww) concentrations of DE-71 and in their 25-d-old nestlings following embryonic exposure by maternal deposition to environmentally relevant low (291 ± 48 ng/g ww) or high (1111 ± 160 ng/g ww) sum (Σ) PBDE concentrations. Unexpectedly, low in ovo concentrations of total-α-hexabromocyclododecane (HBCD) were detected. Plasma retinol concentrations of adult males exposed to higher DE-71 concentrations were negatively correlated with in ovo ΣPBDE, BDE-100, and HBCD levels. Maternal (13%) and nestling (11%) retinol levels were lower in the low-exposure group compared to respective controls, and biologically significant since their retinol levels were correlated with hatching success and growth, respectively. Maternal retinol levels were also correlated with BDE-153. The underlying mechanisms may involve (1) PBDE exposure, hydroxylated (OH-) metabolites, and subsequent changes in retinol mobilization; (2) decreased maternal food consumption; and (3) reduced maternal retinol yolk deposits. The apparent lack of retinol changes in the high-exposure kestrel may reflect compensation occurring, either by increased mobilization and transportation of retinol, and/or higher food consumption in these birds. When highly mobile as evidenced during reproduction or development, retinol concentrations of adult and nestling kestrels are sensitive to environmentally relevant PBDE and HBCD levels.

Comparative genomics of nematodes.

Recent transcriptome and genome projects have dramatically expanded the biological data available across the phylum Nematoda. Here we summarize analyses of these sequences, which have revealed multiple unexpected results. Despite a uniform body plan, nematodes are more diverse at the molecular level than was previously recognized, with many species- and group-specific novel genes. In the genus Caenorhabditis, changes in chromosome arrangement, particularly local inversions, are also rapid, with breakpoints occurring at 50-fold the rate in vertebrates. Tylenchid plant parasitic nematode genomes contain several genes closely related to genes in bacteria, implicating horizontal gene transfer events in the origins of plant parasitism. Functional genomics techniques are also moving from Caenorhabditis elegans to application throughout the phylum. Soon, eight more draft nematode genome sequences will be available. This unique resource will underpin both molecular understanding of these most abundant metazoan organisms and aid in the examination of the dynamics of genome evolution in animals.

Changes in reproductive courtship behaviors of adult American kestrels (Falco sparverius) exposed to environmentally relevant levels of the polybrominated diphenyl ether mixture, DE-71.

Polybrominated diphenyl ethers (PBDEs) are increasing in biota. Here, captive adult American kestrels were exposed daily by diet to safflower oil (controls), or one of two levels of a pentaBDE technical formulation, DE-71 (0.3 or 1.6 ppm), for approximately 75 days, commencing 21 days before breeding. This exposure resulted in eggs having PBDE concentrations similar (low exposure) or within the same order of magnitude (high exposure) reported for wild American kestrels and gulls in the Great Lakes. Compared to controls, kestrels in both exposure groups copulated less, spent less time in their nest boxes, and participated in fewer pair-bonding behaviors. Furthermore, the timing of these behaviors, which is important to creating and maintaining the pair-bond, also differed significantly from the controls. The females in the low-exposure group made fewer compatible trilling calls and ate less frequently. These behavioral changes were compounded by increasing exposure to DE-71 during the 9-day courtship period immediately preceding egg laying, a standard measure of the kestrel courtship period. The birds in the high-exposure group made more food transfers, excited "klee" calls, and copulations, the latter only when compared to the low-exposure birds, whereas the low-exposure males performed fewer pair-bonding behaviors. This study demonstrates that the exposure of kestrels to environmentally relevant levels of DE-71 modifies the quality of the pair-bond, affects the reproductive behavior of both sexes, and occurs when birds are exposed for a short period as adults. In addition, these behavioral effects are consistent with the observed reproductive changes in these birds.

Bioaccumulation and biotransformation of 61 polychlorinated biphenyl and four polybrominated diphenyl ether congeners in juvenile American kestrels (Falco sparverius).

This study examined the bioaccumulation and dietary retention of 61 polychlorinated biphenyl (PCB) and four polybrominated diphenyl ether (PBDE) congeners in juvenile American kestrels (Falco sparverius). American kestrels were exposed to contaminants via egg injection and daily gavage dosing over the posthatch-to-fledgling period. Retention factors for PCBs were dependent on chemical hydrophobicity and chlorine substitution patterns and ranged from less than 1 to 16.4% for PCBs having vicinal hydrogen substitutions at meta-, para- carbons on at least one of the phenyl rings and between 13.2 and 81.5% for congeners containing chlorine substitutions at 4,4'-, 3',4,5'-, 3,4',5-, or 3,3',5,5'-positions. These results indicate that juveniles are capable of biotransforming PCBs according to the same structure-activity rules as adults. A toxicokinetic model, initially parameterized using adult toxicokinetic parameters, was used to describe concentration trends in juveniles over time. The adult model overestimated PCB concentrations but provided an adequate fit when elimination rate constants were increased by a factor of 12.7. Retention factors for the PBDE congeners 2,2',4,4'-tetrabromodiphenyl ether (BDE 47), 2,2',4,4',6-pentabromodiphenyl ether (BDE 100), 2,2',4,4',5-pentabromodiphenyl ether (BDE 99), and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE 153) were from 7.8 to 45.3% of the total dose. The retention of BDE 47 was similar that observed for readily cleared PCBs, whereas the remaining PBDEs exhibited retention factors consistent with those of persistent PCBs. Half-lives for PBDEs in juveniles were estimated to range from 5.6 to 44.7 d. Assuming differences in PBDE toxicokinetics between juveniles and adults similar to those measured for PCBs, adult American kestrel PBDE half-lives are expected to range from 72 to 572 d.

Disparate gain and loss of parasitic abilities among nematode lineages.

Plant parasitism has arisen time and again in multiple phyla, including bacteria, fungi, insects and nematodes. In most of these organismal groups, the overwhelming diversity hampers a robust reconstruction of the origins and diversification patterns of this trophic lifestyle. Being a moderately diversified phylum with ≈ 4,100 plant parasites (15% of total biodiversity) subdivided over four independent lineages, nematodes constitute a major organismal group for which the genesis of plant parasitism could be mapped. Since substantial crop losses worldwide have been attributed to less than 1% of these plant parasites, research efforts are severely biased towards this minority. With the first molecular characterisation of numerous basal and supposedly harmless plant parasites as well as their non-parasitic relatives, we were able to generate a comprehensive molecular framework that allows for the reconstruction of trophic diversification for a complete phylum. In each lineage plant parasites reside in a single taxonomic grouping (family or order), and by taking the coverage of the next lower taxonomic level as a measure for representation, 50, 67, 100 and 85% of the known diversity was included. We revealed distinct gain and loss patterns with regard to plant parasitism per se as well as host exploitation strategies between these lineages. Our map of parasitic nematode biodiversity also revealed an unanticipated time reversal in which the two most ancient lineages showed the lowest level of ecological diversification and vice versa.

Approximate band structure calculation for photonic bandgap fibres.

An approximate method for finding the band structure of simple photonic bandgap fibres is presented. Our simple model is an isolated high-index rod in a circular unit cell with two alternative boundary conditions. Band plots calculated this way are found to correspond closely to calculations using an accurate numerical method.

Changes in the growth, but not the survival, of American kestrels (Falco sparverius) exposed to environmentally relevant polybrominated diphenyl ethers.

Polybrominated diphenyl ether (PBDEs) concentrations are increasing exponentially in biota. We studied the growth of American kestrel (Falco sparverius) nestlings exposed in ovo and during development to environmentally relevant PBDE congeners and concentrations. Eggs within each clutch, divided between groups by laying sequence, were injected into the air cell at 19 days of incubation with safflower oil or penta-BDE congeners BDE-47, -99, -100, and -153 dissolved in safflower oil (18.7 microg total sigmaPBDEs/egg), approximating current levels in Great Lakes herring gulls. The measured proportions of BDE congeners found in the dosing oil were 56.4% of BDE-47; 27.2% of BDE-99; 24.8% of BDE-100; and 0.6% of BDE-153. For 29 days, nestlings were orally gavaged daily with the same sigmaPBDE mixture (15.6 +/- 0.3 ng/g body weight/day). Relative congener abundances in the dosing mixture compared to the carcasses suggest biotransformation of BDE-47; BDE-183 was also detected. PBDE exposure did not affect hatching or fledging success. PBDE-exposed nestlings were larger (weight, bones, feathers) as they gained weight more quickly and ate more food, the latter in association with their SigmaPBDE body burdens. BDE-100 was most influential on nestling growth, being positively associated with size, weight gain, and food consumption. Increasing concentrations of BDE-183 and -153 were related to longer bones, and BDE-99 to longer feathers. The larger size of the PBDE-exposed birds may be detrimental to their bone structure and have excessive energetic costs. The repeated relationships with BDE-100 and growth may be important for wild Falconidae, since this is the predominant penta-BDE congener in these raptors.

Brood patches of American kestrels altered by experimental exposure to PCBs.

Captive breeding (n = 25 pairs) and nonbreeding (n = 25) American kestrels were exposed to a mixture of polychlorinated biphenyls (PCBs) (Aroclor 1248:1254:1260) through their diet of day-old cockerels. Kestrels ingested approximately 7 mg/kg body weight each day of PCBs, and this dosage resulted in environmentally relevant total PCB residues in eggs (geometric mean of 34.1 microg/g). An equal number of unexposed birds served as controls. Bare areas of skin known as brood patches function during incubation to warm eggs; therefore, brood patch size could potentially influence hatching success, or patches may be a confounding factor in the relationship between poor incubation behavior and hatching failure observed in birds in toxicological studies. Exposure to PCBs altered the size of brood patches in American kestrels. PCB-exposed male and female nonbreeders had two of three brood patches that were larger than those of control nonbreeders. Breeding males exposed to PCBs had smaller patches than controls, whereas PCB-exposed female kestrels had one larger and one smaller patch than controls. Patch sizes were not related to total PCB residue levels in eggs of exposed birds. Brood patches were not related to various incubation behaviors or hatching success in either control or PCB-exposed kestrels.

Genetic Drift, Not Life History or RNAi, Determine Long-Term Evolution of Transposable Elements.

Transposable elements (TEs) are a major source of genome variation across the branches of life. Although TEs may play an adaptive role in their host's genome, they are more often deleterious, and purifying selection is an important factor controlling their genomic loads. In contrast, life history, mating system, GC content, and RNAi pathways have been suggested to account for the disparity of TE loads in different species. Previous studies of fungal, plant, and animal genomes have reported conflicting results regarding the direction in which these genomic features drive TE evolution. Many of these studies have had limited power, however, because they studied taxonomically narrow systems, comparing only a limited number of phylogenetically independent contrasts, and did not address long-term effects on TE evolution. Here, we test the long-term determinants of TE evolution by comparing 42 nematode genomes spanning over 500 million years of diversification. This analysis includes numerous transitions between life history states, and RNAi pathways, and evaluates if these forces are sufficiently persistent to affect the long-term evolution of TE loads in eukaryotic genomes. Although we demonstrate statistical power to detect selection, we find no evidence that variation in these factors influence genomic TE loads across extended periods of time. In contrast, the effects of genetic drift appear to persist and control TE variation among species. We suggest that variation in the tested factors are largely inconsequential to the large differences in TE content observed between genomes, and only by these large-scale comparisons can we distinguish long-term and persistent effects from transient or random changes.