bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of glutathione in the growth of Bradyrhizobium sp. (peanut microsymbiont) under different environmental stresses and in symbiosis with the host plant
Authors: Sobrevals Luciano , Müller Peter , Fabra Adriana , Castro Stella
Published: August 2006

Glutathione (GSH) plays an important role in the defence of microorganisms and plants against different environmental stresses. To determine the role of GSH under different stresses, such as acid pH, saline shock, and oxidative shock, a GSH-deficient mutant (Bradyrhizobium sp. 6144-S7Z) was obtained by disruption of the gshA gene, which encodes the enzyme γ-glutamylcysteine synthetase. Growth of the mutant strain was significantly reduced in liquid minimal saline medium, and the GSH content was very low, about 4% of the wild-type level. The defect, caused by disruption of the gshA gene in the growth of mutant strain, cannot be reversed by the addition of GSH (up to 100 µmol/L) to the liquid minimal saline medium, and the endogenous GSH level was approximately the same as that observed without the addition of GSH. In contrast, the wild-type strain increased the GSH content under these conditions. However, the growth of the mutant strain in a rich medium (yeast extract – mannitol) increased, suggesting that at least some but not all of the functions of GSH could be provided by peptides and (or) amino acids. The symbiotic properties of the mutant were similar to those found in the wild-type strain, indicating that the mutation does not affect the ability of the mutant to form effective nodules.Key words: glutathione, γ-glutamylcysteine synthetase, Bradyrhizobium sp., peanut.
Genetic structure and transcriptional analysis of the arginine deiminase (ADI) cluster inLactococcus lactisMG1363
Authors: Budin-Verneuil Aurélie , Maguin Emmanuelle , Auffray Yanick , Ehrlich Dusko S , Pichereau Vianney
Published: August 2006

In a recent proteomic analysis, we showed the overproduction of the ArcA and ArcB proteins in Lactococcus lactis MG1363 at low pH. The corresponding genes belong to the arcABD1C1C2TD2 cluster that encodes components of the arginine deiminase pathway. In this study, we characterized this cluster at the genetic level. Northern blot experiments showed the expression of at least seven transcripts, all induced by acidity. Tran script analysis using 5′RACE PCR (rapid amplification of cDNA ends polymerase chain reaction) in the arcB-arcD1intergenic region. In silico analysis identified nine stem-loop structures, all located in intergenic regions. Collectively, these data suggest a role for RNA processing and (or) premature termination in the differential expression of genes within the arcABD1C1C2TD2 cluster.Key words: lactic acid bacteria, acid stress, arginine catabolism.
Molecular characterization of a G protein α-subunit-encoding gene fromMucor circinelloides
Authors: Meza-Carmen Victor , García-Soto Jesús , Ongay-Larios Laura , Coria Roberto , Pedraza-Reyes Mario , Arnau José , Reyna-Lopez Georgina , Martínez-Cadena Guadalupe
Published: August 2006

Genes encoding the Gα subunit were cloned from Mucor circinelloides, a zygomycete dimorphic fungus. There are at least four genes that encode for Gα subunits, gpa1, gpa2, gpa3, and gpa4. The genes gpa1 and gpa3 were isolated and characterized, and their predicted products showed 36%–67% identity with Gα subunits from diverse fungi. Northern blot analysis of gpa3 showed that it is present in spores and constitutively expressed during mycelium development and during yeast–mycelium and mycelium–yeast transitions. However, during yeast cell growth, decreased levels of mRNA were observed. Sequence analysis of gpa3 cDNA revealed that Gpa3 encodes a polypeptide of 356 amino acids with a calculated molecular mass of 40.8 kDa. The deduced sequence of Gpa3 protein contains all the consensus regions of Gα subunits of the Gαi/o/tsubfamily except the cysteine near the C terminus for potential ADP-ribosylation by pertussis toxin. This cDNA was expressed in Escherichia coli and purified by affinity chromatography. Based on its electrophoretic mobility in SDS–PAGE, the molecular mass of the His6-tagged Gpa3 was 45 kDa. The recombinant protein was recognized by a polyclonal antibody against a fragment of a human Gαi/o/t. Furthermore, the recombinant Gpa3 was ADP-ribosylated by activated cholera toxin and [32P]NAD but not by pertussis toxin. These results indicate that in M. circinelloides the Gα subunit Gpa3 is expressed constitutively during differentiation.Key words: Gα-subunit-encoding genes, Mucor circinelloides, Gpa3 recombinant protein.
Fusarium Tri4encodes a multifunctional oxygenase required for trichothecene biosynthesis
Authors: McCormick Susan P , Alexander Nancy J , Proctor Robert H
Published: August 2006

Fusarium graminearum and Fusarium sporotrichioides produce the trichothecene mycotoxins 15-acetyldeoxynivalenol and T-2 toxin, respectively. In both species, disruption of the P450 monooxygenase-encoding gene, Tri4, blocks production of the mycotoxins and leads to the accumulation of the trichothecene precursor trichodiene. To further characterize its function, the F. graminearum Tri4 (FgTri4) was heterologously expressed in the trichothecene-nonproducing species Fusarium verticillioides. Transgenic F. verticillioides carrying the FgTri4 converted exogenous trichodiene to the trichothecene biosynthetic intermediates isotrichodermin and trichothecene. Conversion of trichodiene to isotrichodermin requires seven biochemical steps. The fifth and sixth steps can occur nonenzymatically. Precursor feeding studies done in the current study indicate that wild-type F. verticillioides has the enzymatic activity necessary to carry out the seventh step, the C-3 acetylation of isotrichodermol to form isotrichodermin. Together, the results of this study indicate that the Tri4 protein catalyzes the remaining four steps and is therefore a multifunctional monooxygenase required for trichothecene biosynthesis.Key words: trichothecene, P450 oxygenase, trichodiene, Tri101, Tri4, multifunctional oxygenase, monooxygenase.
Subcellular location of phage infection protein (Pip) inLactococcus lactis
Authors: Mooney Duane T , Jann Monica , Geller Bruce L
Published: August 2006

The amino acid sequence of the phage infection protein (Pip) of Lactococcus lactis predicts a multiple-membrane-spanning region, suggesting that Pip may be anchored to the plasma membrane. However, a near-consensus sortase recognition site and a cell wall anchoring motif may also be present near the carboxy terminus. If functional, this recognition site could lead to covalent linkage of Pip to the cell wall. Pip was detected in both plasma membranes and envelopes (plasma membrane plus peptidoglycan) isolated from the wild-type Pip strain LM2301. Pip was firmly attached to membrane and envelope preparations and was solubilized only by treatment with detergent. Three mutant Pip proteins were separately made in which the multiple-membrane-spanning region was deleted (Pip-Δmmsr), the sortase recognition site was converted to the consensus (Pip-H841G), or the sortase recognition site was deleted (Pip-Δ6). All three mutant Pip proteins co-purified with membranes and could not be solubilized except with detergent. When membranes containing Pip-Δmmsr were sonicated and re-isolated by sucrose density gradient centrifugation, Pip-Δmmsr remained associated with the membranes. Strains that expressed Pip-H841G or Pip-Δ6 formed plaques with near unit efficiency, whereas the strain that expressed Pip-Δmmsr did not form plaques of phage c2. Both membranes and cell-free culture supernatant from the strain expressing Pip-Δmmsr inactivated phage c2. These results suggest that Pip is an integral membrane protein that is not anchored to the cell wall and that the multiple-membrane-spanning region is required for productive phage infection but not phage inactivation.Key words: phage infection protein, Pip, Lactococcus lactis, subcellular location.
Arsenic-resistant proteobacterium from the phyllosphere of arsenic-hyperaccumulating fern (Pteris vittata L.) reduces arsenate to arsenite
Authors: Rathinasabapathi Bala , Raman Suresh Babu , Kertulis Gina , Ma Lena
Published: August 2006

An arsenic-resistant bacterium, AsRB1, was isolated from the fronds of Pteris vittata grown in a site contaminated with copper chromium arsenate. The bacterium exhibited resistance to arsenate, arsenite, and antimony in the culture medium. AsRB1, like Pseudomonas putida, grew on MacConkey and xylose–lactose–desoxycholate agars and utilized citrate but, unlike P. putida, was positive for indole test and negative for oxidase test. A phylogenetic analysis of the 16S rRNA gene showed that AsRB1 is a proteobacterium of the beta subclass, related to Pseudomonas saccharophila and Variovorax paradoxus. Following an exogenous supply of arsenate, most arsenic occurred as arsenite in the medium and the cell extracts, suggesting reduction and extrusion of arsenic as the mechanism for arsenic resistance in AsRB1.Key words: arsenate reduction, arsenic bioremediation, Pseudomonas saccharophila, Variovorax paradoxus, Pteris vittala.
Purification and characterization of an exochitinase fromBacillus thuringiensissubsp.aizawaiand its action against phytopathogenic fungi
Authors: Morales de la Vega Luis , Barboza-Corona J Eleazar , Aguilar-Uscanga Maria G , Ramírez-Lepe Mario
Published: August 2006

A chitinolytic enzyme from Bacillus thuringiensis subsp. aizawai has been purified and its molecular mass was estimated ca. 66 kDa by sodium dodecyl sulfate – polyacryamide gel electrophoresis (SDS–PAGE). The enzyme was able to hydrolyze chitin to chitobiosides but not carboxymethylcellulose, cellulose, pullulan, and laminarin. Optimal pH and temperature were detected at 6 and 50 °C, respectively. Stability, in the absence of substrate, was observed at temperatures less than 60 °C and pH between 5 and 8. Enzyme activity was significantly inhibited by K+and EDTA and completely inhibited by Hg2+. Purified chitinase showed lytic activity against cell walls from six phytopathogenic fungi and inhibited the mycelial growth of both Fusarium sp. and Sclerotium rolfsii. The biocontrol efficacy of the enzyme was tested in the protection of bean seeds infested with six phytopathogenic fungi.Key words: chitinase, Bacillus thuringiensis, purification, phytopathogenic fungi.
Endophytic Phomopsis species: host range and implications for diversity estimates
Authors: Murali T S , Suryanarayanan T S , Geeta R
Published: August 2006

Foliar endophyte assemblages of teak trees growing in dry deciduous and moist deciduous forests of Nilgiri Biosphere Reserve were compared. A species of Phomopsis dominated the endophyte assemblages of teak, irrespective of the location of the host trees. Internal transcribed spacer sequence analysis of 11 different Phomopsis isolates (ten from teak and one from Cassia fistula) showed that they fall into two groups, which are separated by a relatively long branch that is strongly supported. The results showed that this fungus is not host restricted and that it continues to survive as a saprotroph in teak leaf, possibly by exploiting senescent leaves as well as the litter. Although the endophyte assemblage of a teak tree growing about 500 km from the forests was also dominated by a Phomopsis sp., it separated into a different group based on internal transcribed spacer sequence analysis. Our results with an endophytic Phomopsis sp. reinforce the earlier conclusions reached by others for pathogenic Phomopsis sp., i.e., that this fungus is not host specific, and the species concept of Phomopsis needs to be redefined.Key words: fungal endophytes, Tectona grandis, fungal diversity, Phomopsis, host restriction.
Formate synthesis byClostridium thermocellumduring anaerobic fermentation
Authors: Sparling Richard , Islam Rumana , Cicek Nazim , Carere Carlo , Chow Herman , Levin David B
Published: August 2006

We have detected formate synthesis by Clostridium thermocellum 27405 cultured in both cellobiose and α-cellulose. While formate synthesis has been reported for one strain of C. thermocellum (strain I-1-B), numerous studies of C. thermocellum 27405 fermentation, conducted under different growth conditions, failed to detect the presence of formate. Thus, the status of formate synthesis as a fermentation end product by C. thermocellum has been uncertain. Formate synthesis competes with the synthesis of hydrogen (H2) as a fermentation end product, and thus would negatively impact H2yields in processes designed to generate H2from biomass. Understanding the mechanism of formate synthesis is the first step in devising means of mitigating its production. Transcription of putative pfl, fnr, and adhE genes, encoding pyruvate formate-lyase (PFL), PFL-activating enzyme (PFL-AE), and alcohol dehydrogenase E (ADH-E) enzymes, respectively, were detected by reverse transcriptase polymerase chain reactions using total RNA extracted from stationary phase C. thermocellum cultured on cellobiose. The PCR products observed correspond to the expected amplicon sizes. Nucleotide sequence analysis of the cloned PCR products followed by BLAST analyses confirmed their identity. Formate production was detected throughout growth, and PFL enzyme activity was detected in late log and stationary phase (OD600 = 0.7 and 0.9, respectively) in extracts of C. thermocellum cultured on cellobiose. BLAST analyses revealed that C. thermocellum PFL and PFL-AE have greater amino acid sequence identity with equivalent enzymes from Bacillus and Thermocynechococcus species than with other Clostridium species, but C. thermocellum ADH-E has greater amino acid sequence identity with Clostridium species.Key words: Clostridium thermocellum, formate synthesis, pyruvate formate-lyase, PFL-activating enzyme, alcohol dehydrogenase E.
Production d'enzyme polygalacturonase par des souches microbiennes isolées du lait cru et des olives noires et vertes
Authors: Bekhouche Farida , Bonnin Estelle , Boulahrouf Abderrahmane , Leveau Jean Yves
Published: August 2006

Forty microbial strains isolated from raw milk samples and black and green olives were grown in MP5 (mineral pectin 5) medium containing 0.5% lemon pectin. All strains synthesized an extracellular polygalacturonase. Rhodotorula sp. ONRh9 (0.44 U·mL–1) and Leuconostoc sp. LLn1 (0.16 U·mL–1), which had a more active poly galacturonase in MP5 medium, were studied in MAPG5 medium containing polygalacturonic acid. Highest biomass and polygalacturonase production by these two strains were observed for polygalacturonic acid concentrations of 10 g·L–1(Rhodotorula sp. ONRh9) and 5 g·L–1(Leuconostoc sp. LLn1) and for initial pH values of 6 (Rhodotorula sp. ONRh9) and 5.5 (Leuconostoc sp. LLn1). The two strains grown in fermenters in MAPG5 medium generated the following results: with controlled initial pH, Rhodotorula sp. produced maximum biomass (DO) and polygalacturonase (PG) after 20 h (DO, 3.86; PG, 0.24 U·mL–1) of growth, and this level was sustained until the end of the culture; Leuconostoc sp. LLn1 synthesized more cells and polygalacturonase between 4 h (DO, 1.80; PG, 0.17 U·mL–1) and 24 h (DO, 3.90; PG, 0.27 U·mL–1) of culture. With uncontrolled initial pH, the cultures produced maximum biomass and poly galacturonase after 20 h (DO, 3.30; PG, 0.26 U·mL–1) for Rhodotorula sp. ONRh9 and 10 h (DO, 2.84; PG, 0.17 U·mL–1) for Leuconostoc sp. LLn1.Key words: Leuconostoc, Rhodotorula, polygalacturonic acid, polygalacturonase, cell growth.[Journal translation]
Replicated ecological landscapes and the evolution of morphological diversity amongGasterosteuspopulations from an archipelago on the west coast of Canada
Authors: Reimchen T.E. , Nosil P.
Published: August 2006

We investigated defence and trophic morphology of 40 freshwater stickleback (Gasterosteus aculeatus L., 1758) populations from the Banks–Estevan archipelago for comparison with the isolated stickleback populations from the nearby Haida Gwaii archipelago. Using 14 size-standardized metric traits and 11 meristic or categorical traits from 1706 individuals (14–54/site), we found that the first principal component (PC1) defined a defence apparatus characterized by high loadings for pelvic spine length, number of forks on the ascending process, number of lateral plates, and overlap between lateral and basal plates. The second component (PC2) defined a trophic apparatus characterized by high loadings for gape length, eye diameter, and body depth. Populations with loss of spines, loss of plates, increased gape, increased body depth, and low gill raker number were most prevalent in ponds and shallow lakes with low conductivity. Most traits were sexually dimorphic, with males exhibiting greater armature and increased benthic trophic adaptations. We observed substantially less morphological variability among Banks–Estevan stickleback populations than among the Haida Gwaii populations and one instance of common ancestry or convergence to the giant black stickleback of Haida Gwaii.
Microsatellite DNA and mitochondrial DNA variation in polar bears (Ursus maritimus) from the Beaufort and Chukchi seas, Alaska
Authors: Cronin M.A. , Amstrup S.C. , Scribner K.T.
Published: August 2006

Radiotelemetry data have shown that polar bears ( Ursus maritimus Phipps, 1774 ) occur in separate subpopulations in the Chukchi Sea and the southern Beaufort Sea. However, segregation is not absolute, and there is overlap of ranges of animals in each subpopulation. We used genetic variation at eight microsatellite DNA loci and mitochondrial DNA (mtDNA) to further assess the degree of spatial structure of polar bears from the Chukchi and southern Beaufort seas. Microsatellite allele frequencies and mtDNA haplotype frequencies of bears from the southern Beaufort and Chukchi seas did not differ significantly. Lack of differentiation at both maternally inherited mtDNA and bi-parentally inherited microsatellite loci suggests that gene flow between the two areas is mediated by both sexes. The genetic data indicate that polar bears in the southern Beaufort and Chukchi seas compose one interbreeding population. However, there is considerable fidelity to ranges in each area, particularly by adult females. The combined genetic and movement data suggest that polar bears could be managed as Beaufort Sea and Chukchi Sea subpopulations of a combined southern Beaufort Sea and Chukchi Sea population.
Cost of foraging in the subterranean rodentCtenomys talarum: effect of soil hardness
Authors: Luna Facundo , Antinuchi C. Daniel
Published: August 2006

Subterranean burrows provide inhabitants with shelter, a relatively stable thermal environment, and potentially access to food resources. However, one cost of living in such burrows is the energetically expensive mode of locomotion. Soil hardness and the physiological capabilities of animals are likely important factors that affect the cost of burrow construction, and hence, distribution of burrows. We assessed the effect of soil hardness on the cost of digging by captive individual Ctenomys talarum Thomas, 1898 in soft soils. Digging metabolic rate (DMR) was higher in harder soil than in softer soil (408.30 ± 51.35 mL O2·h–1vs. 267.59 ± 20.97 mL O2·h–1, respectively). In C. talarum, a higher soil hardness augments DMR by increasing, in terms of the cost of burrowing model, the costs of shearing and of pushing the removed soil. Additionally, these costs differ between C. talarum and other subterranean species (e.g., Thomomys bottae (Eydoux and Gervais, 1836)), depending on soil hardness and digging mode. Thus, the relationship between digging cost and soil hardness appears to be one of the most important factors that affect burrowing efficiency in subterranean rodents.
Oxidative balance and immunodetection of antioxidant enzymes in the hepatopancreas of the crabChasmagnathus granulatasubjected to anoxia and reoxygenation
Authors: de Oliveira Ubirajara O. , Belló-Klein Adriane , Kucharski Luiz Carlos
Published: August 2006

The present study shows the activities and concentrations of the antioxidant enzymes superoxide dismutase (SOD) and glutathione S-transferase (GST) in the hepatopancreas of the crab Chasmagnathus granulata (Dana, 1851) (Decapoda, Brachyura) when exposed to periods of anoxia (8 h) and aerobic recovery (20 and 40 min post anoxia). Exposure to anoxia did not cause any change in the activities of the enzymes analyzed. The activities of these enzymes did not change with a decrease in environmental oxygen concentration. During reoxygenation, enzyme activities returned to control levels. The concentrations and activities of SOD and GST presented different response profiles. Exposure to anoxia caused increased lipoperoxidation (conjugated dienes and thiobarbituric acid reactive substances), whereas aerobic recovery reduced lipoperoxidation. The results of this study showed that C. granulata adjusts its antioxidant defense systems in an attempt to reduce and (or) avoid damage resulting from the reintroduction of oxygen.
Shift in feather mite distribution during the molt of passerines: the case of barn swallows (Hirundo rustica)
Authors: Jovani R. , Serrano D. , Frías Ó. , Blanco G.
Published: August 2006

Feather mites show a high diversity of distribution patterns on the wings of birds, but we are currently unable to make precise predictions about the distribution of mites on a given bird at a given time. This is especially intriguing because factors such as air turbulence, humidity, or temperature are already recognized as shaping feather mite distribution. We hypothesize that feather mites, rather than responding to single factors, respond at the same time to different constraints when deciding where to live. To test this hypothesis, we studied the distribution of mites along the wings of barn swallows ( Hirundo rustica L., 1758) in Europe before molting and in Africa during and after molt. Feather mite preferences shifted according to the stage of molt of the bird, with a pattern suggesting a clear compromise between being as close as possible to the non-molting distribution while avoiding the molt of the occupied feather and the early stages of growth of new feathers. Thus, we suggest that interacting factors, rather than single variables, must be studied to further advance the understanding of the distribution of feather mites on the wings of birds.
Minimal overwintering temperatures of red-sided garter snakes (Thamnophis sirtalis parietalis): a possible cue for emergence?
Authors: Lutterschmidt Deborah I. , LeMaster Michael P. , Mason Robert T.
Published: August 2006

Red-sided garter snakes ( Thamnophis sirtalis parietalis (Say in James, 1823)) in Manitoba, Canada, undergo 8 months of continuous winter dormancy prior to spring emergence. As in other ectothermic species, increases in ground temperature may be the cue for emergence from winter dormancy in these populations. To test this hypothesis, we measured body temperatures during winter dormancy by surgically implanting small temperature loggers into 32 female red-sided garter snakes before they entered their native hibernaculum. The following spring, we recaptured seven of the snakes implanted with temperature loggers. Body temperature declined gradually from mid-September (14.7 ± 0.24 °C, mean  ± SE) to early April (1.1 ± 0.16 °C, mean ± SE) during winter dormancy, reaching minimal values approximately 1 month prior to spring emergence. Body temperatures of emerging snakes ranged from 0.5 °C during early spring to 6.3 °C during late spring (3.4 ± 0.84 °C, mean ± SE). These results do not support the hypothesis that an increase in ground temperature (and hence body temperature) is necessary for emergence from winter dormancy. We suggest that critically low temperatures (i.e., 0.5–1 °C) are a Zeitgeber entraining an endogenous circannual cycle that regulates snake emergence. These results offer new insight into the mechanisms regulating seasonal emergence from winter dormancy.
Do parasites matter? Assessing the fitness consequences of haemogregarine infection in snakes
Authors: Brown G.P. , Shilton C.M. , Shine R.
Published: August 2006

Although much research in evolutionary ecology is based upon the premise that high levels of parasitism impair the host's functioning, the assumed link between parasitism and fitness has been assessed for relatively few kinds of animals. At our study site in tropical Australia, keelback snakes ( Tropidonophis mairii (Gray, 1841), Colubridae) are heavily infected with haemogregarine blood parasites: 90% of snakes that we tested carried the parasite, with the proportion of erythrocytes containing haemogregarines averaging 15% and ranging up to a remarkable 64%. Prevalence increased with snake body size, but intensity decreased with age. Unlike lizards studied previously, the snakes did not respond to haemogregarine infection by releasing immature erythrocytes into the circulation. In striking contrast to results from a recent study on a sympatric snake species, we did not find any empirical links between parasite numbers and several measures of host fitness (body condition, growth rate, feeding rate, antipredator behaviour, locomotor performance, reproductive status, reproductive output, and recapture rate). The association between this parasite and its host thus appears to be surprisingly benign, suggesting that host–parasite interactions sometimes may have only trivial consequences for host fitness in natural populations. Plausibly, host–parasite coevolution weakens or eliminates fitness costs of parasitism.
Parasite-induced anorexia in a free-ranging mammalian herbivore: an experimental test using Soay sheep
Authors: Jones O.R. , Anderson R.M. , Pilkington J.G.
Published: August 2006

Theory suggests that gastrointestinal parasites can influence herbivore population dynamics by increasing host mortality rates. In addition, parasites may have a non-lethal range of both physiological and behavioural effects on their hosts. Two potential behavioural effects are parasite-induced anorexia and the alteration of diet selection patterns — both of which may influence plant communities without necessarily causing herbivore mortality. We report here the results of an experiment carried out in August–September 2001 to examine herbivore response to parasitism using feral Soay sheep ( Ovis aries L., 1758) living on Hirta, St. Kilda (Scotland, UK), as a model system. The aim of the experiment was to determine whether the sheep exhibit significant parasite-induced anorexia and whether diet selectivity was also altered in response to parasitism. The n-alkane technique was used to estimate forage intake rates and diet composition. Overall, intake rate increased with body mass and the mean (±SE) over both sexes was 737 ± 40 g DM / day (range 458–1241 g DM / day). However, we found no effect of parasite burden upon intake rate or selection patterns. The results of a power analysis imply that any reduction in intake rate was less than 30%, which is less than the 30%–60% reduction in intake rate recorded for domestic sheep under moderate parasite burdens. This suggests that Soay sheep are more resilient to parasitism than domestic breeds. Despite evidence to the contrary from simple farm-based studies, the lack of any effect on selection patterns in this case suggests that parasites do not cause significant alterations to the selection patterns of herbivores in complex non-agricultural environments.
Changes in diel diving patterns accompany shifts between northern foraging and southward migration in leatherback turtles
Authors: James M.C. , Ottensmeyer C.A. , Eckert S.A. , Myers R.A.
Published: August 2006

Diel diving patterns have been widely documented among plankton-feeding marine vertebrates. In many cases, these patterns have been interpreted as a response to the diel vertical migrations of prey. The leatherback turtle, Dermochelys coriacea (Vandelli, 1761), is a large marine predator that exploits gelatinous plankton in disparate foraging areas. Individuals of this species spend extended periods at northern latitudes before moving southward through pelagic waters. To identify and compare potential diel patterns of diving behaviour in temperate areas, where foraging has been observed, versus during southward migration, 15 subadult and adult leatherbacks were equipped with satellite-linked time–depth recorders off Nova Scotia, Canada. We observed variation in nocturnal versus diurnal behaviour, both at northern latitudes and during migration; however, diel differences in both diving and surface activity were much less pronounced while leatherbacks were in the north. We interpret the difference in leatherback diel diving regimen to reflect a response to changing resource conditions at these times, with leatherbacks foraging throughout the day and night at high latitudes, then changing to a bimodal pattern of diving during southward migration, with generally longer, deeper diving occurring during the night versus during the day. By quantifying diel changes in leatherback behaviour, we provide the first surface time correction factors based on multiple individuals for use in estimating abundance from aerial surveys.
Diet shifts of lesser scaup are consistent with the spring condition hypothesis
Authors: Anteau Michael J. , Afton Alan D.
Published: August 2006

We compared diets of lesser scaup ( Aythya affinis (Eyton, 1838)) in the springs of 2000 and 2001 to those reported in the 1970s and the 1980s to determine whether forage quality has declined as predicted by the spring condition hypothesis. In Minnesota, we found that the current aggregate percentage of Amphipoda (an important food item) in lesser scaup diets was 94% lower than that reported from the same locations in the 1980s. Current mean individual prey mass of Amphipoda and Bivalvia in Minnesota were 86.6% and 85.1% lower than historical levels, respectively. In Manitoba, current aggregate percentages of Trichoptera and Chaoboridae in lesser scaup diets (1% and 0%, respectively) were lower than those reported from the same location in the 1970s (14% and 2%, respectively), whereas the percentage of Chironomidae (40%) was higher than that of historical levels (19%). Current mean individual prey mass of all insects, seeds,Chironomidae, and Zygoptera in Manitoba were 63.5%, 65.4%, 44.1%, and 44.9% lower than those of historical levels, respectively. The observed dietary shift from Amphipoda to less nutritious prey in Minnesota, coupled with lower mean individual prey mass in both locations, likely constitutes lower forage quality in lesser scaup diets, which is consistent with the spring condition hypothesis.
Isotopic reconstruction of marine food webs using cephalopod beaks: new insight from captively raised Sepia officinalis
Authors: Hobson K.A. , Cherel Y.
Published: August 2006

Cephalopod beaks are a valuable source of material for stable isotope analysis to reconstruct the feeding ecology of cephalopods and their predators. We conducted a controlled captive-rearing experiment on the cuttlefish Sepia officinalis L., 1758 to 10 months of age. During the first and second months of life, animals were fed mysids ( Mysidopsis sp.) and shrimp ( Palaemonetes pugio Holthuis, 1949), but after 2 months, they were fed a homogeneous diet of shrimp ( Farfantepenaeus aztecus (Ives, 1891) and Litopenaeus setiferus (L., 1767)) until sampling. Soft tissues such as buccal mass, arm, and mantle were enriched in 15N over the shrimp diet by about 3.3‰, with little change in 13C, a result in keeping with previous findings for other marine predators. However, beaks showed little isotopic enrichment over the diets at the time of beak formation, with the beak rostral tips representing the neonatal diet and the remaining beak material representing the adult (shrimp) diet. Additionally, for four wild cephalopod species ( Todaropsis eblanae (Ball, 1841), Illex coindetii (Verany, 1839), Loligo vulgaris (Lamarck, 1798), and S. officinalis) obtained commercially in France, we measured δ13C and δ15N values in lower beaks and soft tissues. Similar to the results of our captive study, soft tissues were consistently enriched in 15N over beaks by an average of 4.8‰ (range 3.9‰–6.1‰) but were slightly depleted in 13C by 0.8‰ (0.7‰–1.2‰). The isotopic measurement of cephalopod beaks can thus be used to directly trace the isotopic composition of cephalopod diets and will be a powerful tool in the reconstruction of higher-trophic-level predators of cephalopods, since beaks are often the only material remaining for analysis from field samples.
Morphology of trophic eggs and ovarian dynamics in the subsocial bug Adomerus triguttulus (Heteroptera: Cydnidae)
Authors: Kudo Shin-ichi , Nakahira Taichi , Saito Yutaka
Published: August 2006

In the subsocial burrower bug, Adomerus triguttulus (Motschulsky, 1886), females produce trophic eggs, which are inviable and serve as a food supply for hatched nymphs, and add them onto egg masses during maternal care. Trophic eggs are expected to be less costly for females to produce and for offspring to consume than viable eggs. Such specialization may be reflected in the size, structure, and developmental process of the eggs. Inviable trophic eggs were smaller than viable eggs, and the intraclutch size variation of the former was larger than that of the latter. The viable eggs always had approximately five micropylar processes at a pole, whereas the trophic eggs mostly lacked them. Active oogenesis was maintained during the maternal egg care period; oocyte development continued after the deposition of viable eggs and declined close to the hatching time of the clutches. Mature chorionated eggs were consistently observed in ovaries. It is strongly suggested that at least some trophic eggs contained in clutches at hatching are those that have matured and been deposited during the maternal care of eggs. We discuss possible selective factors leading to the specialization of these unusual heteropteran trophic eggs and the ecological significance of their ovarian dynamics.
Do the sexes tend to segregate in roe deer in agricultural environments? An analysis of group composition
Authors: Villerette Nicolas , Marchal Carole , Pays Olivier , Delorme Daniel , Gerard Jean-François
Published: August 2006

We studied the composition of European roe deer, Capreolus capreolus (L., 1758), groupings in agricultural fields in northern France throughout an annual cycle to examine whether adult males and adult females tended to live in separate groups as is usually reported for gregarious ruminants. In April, shortly after the beginning of territoriality in mature males, single-sex groups were more frequent than expected by chance, evoking the grouping pattern reported in many territorial antelope species living in open landscapes. In contrast, mixed-sex groups were more frequent than expected by chance from October to January when adult males were no longer territorial and when large groups were formed. In addition, during this last period, females with attendant young were less sociable towards adult conspecifics than were males. Females with attendant young are known to be less sociable than adult males in several other deer species of the subfamily Odocoileinae. We hypothesize that this “sex-biased sociability” explains both the over-frequency of mixed-sex groups recorded in our roe deer population and the grouping patterns exhibited by sexually segregating Odocoileinae species.
The Harderian gland of two species of skink (Tiliqua rugosa and Hemiergis decresiensis): a discussion of the significance of lymphatic tissue in the squamate Harderian gland
Authors: Rehorek Susan J. , Baker Jeremy J. , Hutchinson Mark N. , Firth Bruce T.
Published: August 2006

The Harderian gland is an orbital structure ubiquitous in reptiles. Numerous functions have been ascribed to this gland, including osmoregulation, chemoreception, and immunity. The anatomical, histological, histochemical, and ultrastructural characteristics of the Harderian gland of two species of skink, Tiliqua rugosa (Gray, 1825) and Hemiergis decresiensis (Cuvier, 1829), were examined. Mucous and serous secretory cells were observed in both species. In T. rugosa, mucous cells are located in a small anterior region, while serous cells occupy most of the gland. In contrast, the Harderian gland of H. decresiensis contains mainly serous cells, with a few anteriorly located mucous cells. In both species, the serous granules exhibit internal compartmentalization. There is no evidence of either lipid secretions or salt secreting cells. However, there were either a few plasma cells (H. decresiensis) or several lymphatic aggregations (T. rugosa) in the serous portion of the gland. The presence of such lymphatic tissue may suggest a role in either the head-associated lymphatic tissue (HALT) system or the eye-associated lymphatic tissue (EALT). The difference between these two is based upon terminology, the consolidation of which would allow meaningful comparative analyses. The presence of lymphatic tissue implies that the Harderian gland could play a role in ocular immunity.
Ontogenetic and interspecific variation in timing of movement and responses to climatic factors during migrations by pond-breeding amphibians
Authors: Todd Brian D. , Winne Christopher T.
Published: August 2006

Pond-breeding amphibians from temperate regions undertake overland migrations to reproduce in aquatic habitats. In turn, their offspring metamorphose and emigrate to upland, terrestrial habitats. We examined the diel patterns and daily variability of migrations of adult and juvenile amphibians in response to climatic cues. Of the eight species ( Ambystoma talpoideum (Holbrook, 1838), Ambystoma tigrinum (Green, 1825), Bufo terrestris (Bonnaterre, 1789), Hyla gratiosa LeConte, 1856, Pseudacris crucifer (Wied-Neuwid, 1838), Pseudacris ornata (Holbrook, 1836), Rana sphenocephala Cope, 1886, and Scaphiopus holbrookii (Harlan, 1935)) that we observed, all migrated almost exclusively at night except for the recently metamorphosed B. terrestris, which frequently migrated diurnally (>50% of captures). Additionally, we correlated daily captures of adult and juvenile A. talpoideum, A. tigrinum, B. terrestris, and R. sphenocephala to maximum and minimum daily temperatures, number of previous days without rain, total rainfall during the previous 24 h, and interactions of these variables. Rain was often the most important predictor of amphibian movements. However, species differed in their response to climatic factors, with some species and age classes being more dependent on rain for migrations than others. Rapid changes in regional weather patterns may affect species’ migrations differently, possibly altering arrival times of reproductive adults or affecting the likelihood of successful migrations.
Vocal individuality as a potential long-term monitoring tool for Western Screech-owls, Megascops kennicottii
Authors: Tripp T.M. , Otter K.A.
Published: August 2006

Recent studies suggest that individually distinctive vocalizations found in many avian species can be used in population monitoring. In this study we assessed whether vocal identification of male Western Screech-owls ( Megascops kennicottii (Elliot, 1867)) was possible, and if it could be applied as a long-term monitoring tool. Recordings were collected between 2001 and 2003 from 28 territories on southern and central Vancouver Island. As a quantitative descriptor of the calls, a total of 17 variables were measured from each of 1125 calls. A discriminant function analysis resulted in 92.3% of calls being correctly classified to individual territories within one season and 87.3% of calls in a cross-validation of the model. Variables that showed the greatest discriminant ability included length of call, internote distance between first note and second note, and number of notes per call. Of the 14 territories that had owl calls recorded over 2 years, 4 appeared to be occupied by a different individual in the 2nd year, 7 had calls that were consistent between years, and 3 had calls that were ambiguously classified between years. Our results suggest that Western Screech-owl calls have enough individually recognizable characteristics to aid in the tracking of individuals both within and between years, allowing for long-term monitoring of individuals.
Consequences of forest fragmentation for juvenile survival in spotted (Ambystoma maculatum) and marbled (Ambystoma opacum) salamanders
Authors: Rothermel B.B. , Semlitsch R.D.
Published: August 2006

We compared demographic traits of postmetamorphic salamanders among old fields, forest interior, and edge habitats over 2 years. Recently metamorphosed spotted salamanders ( Ambystoma maculatum (Shaw, 1802)) and marbled salamanders ( Ambystoma opacum (Gravenhorst, 1807)) were individually marked, added to terrestrial enclosures, and recaptured in pitfall traps. Proportion known alive in the fields was <5% by the first fall and declined to 0% for both species in the 2nd year. In forested enclosures, significantly more A. opacum (mean 38.5%) and A. maculatum (mean 16.7%) survived until the first fall and several individuals of each species attained sexual maturity. Mean proportion known alive was approximately two times higher in A. opacum than in A. maculatum, perhaps because of an advantage of earlier metamorphosis in A. opacum. Our results indicate that the first few months in the terrestrial environment is a critical period which determines survival between metamorphosis and first reproduction. Juveniles that weighed more initially had greater chances of surviving this period. We found no evidence that proximity to forest edges incurred fitness costs in terms of reduced growth or survival for juvenile ambystomatids. Because no juveniles survived to maturity in fields, breeding sites surrounded by non-forested habitat may be population sinks for these species.
Habitat difference in food abundance possibly causes within-population variation in the timing of breeding in the Madagascar paradise flycatcher (Terpsiphone mutata)
Authors: Mizuta T.
Published: August 2006

Within-population variation in the timing of breeding in the insectivorous Madagascar paradise flycatcher, Terpsiphone mutata (L., 1766), was investigated in a dry forest of northwestern Madagascar. The study area was divided into two sites (namely, A and B) based on the distance from the waterside. An examination was conducted to determine whether the date of egg laying varies between the two sites, and if it does vary, what are the environmental factors that affect the variation. The females started egg laying significantly earlier at site B than at site A. The two sites are located in a continuous forest; hence, photoperiod and precipitation would not differ between them. The number of insects was higher at site B than at site A. The difference in the temperature was not considered to be the cause of the variation in the date of egg laying. Age structure of the females was not likely to differ between the sites. Therefore, the variation in the date of egg laying is considered to be caused by the difference in food abundance that is associated with the relative distance from the waterside.
Population structure of breeding Harlequin Ducks and the influence of predation risk
Authors: Heath J.P. , Robertson G.J. , Montevecchi W.A.
Published: August 2006

Landscape features can have an important influence on the characteristics of populations, often resulting in heterogeneity in demographic processes. Therefore, local measurements of population parameters may not reflect regional characteristics. We studied populations of Harlequin Ducks ( Histrionicus histrionicus L., 1758) breeding in 11 river canyons in northern Labrador in relation to biophysical habitat characteristics and abundance of avian predators. Density and stability of Harlequin Duck populations varied among river canyons and were positively related (mean of 4.7 survey years per river). Both density and stability were negatively related to densities of raptorial birds. Raptor density was related to availability of suitable cliff ledges for nesting. Comparison of rivers with stable, high-density Harlequin Duck populations and those with variable, low-density populations revealed no detectable differences in habitat or prey availability. In a high-density population, observed stability but positive projected growth suggested the system was at carrying capacity and a source of emigrants. In contrast, unstable, low-density populations approached local extinction in some years, while large increases in subsequent years were suggestive of immigration. These findings demonstrate that breeding aggregations in different river canyons could represent an important unit of demographic structure. The abundance of raptors appears to be an important factor influencing local characteristics of Harlequin Duck populations. We discuss the potential influence of local demographic differences on regional population dynamics and their importance for conservation management strategies for migratory species.
Influence of temperature on maternity roost selection by noctule bats (Nyctalus noctula) and Leisler’s bats (N. leisleri) in Białowieża Primeval Forest, Poland
Authors: Ruczyński Ireneusz
Published: August 2006

This study tests whether the temperature of tree cavities determines their selection by bats in Białowieża Primeval Forest (BPF), eastern Poland. Using a data logger, I simultaneously measured the temperature in cavities selected by bats as roosts and the temperature in available but unselected cavities. The maternity roosts chosen by noctule bats, Nyctalus noctula (Schreber, 1774), and Leisler’s bats, N. leisleri (Kuhl, 1817), during late pregnancy and lactation were warmer than unoccupied cavities, but temperature ranges in the two types of cavity did not differ. A logistic regression model showed that the mean cavity temperature during the night (2200–0400) and the minimum cavity temperature over a 24 h period were crucial for roost selection. This suggests that female noctule and Leisler’s bats selected roosts that promoted juvenile growth and used tree cavities that could save them energy while they were active because the cavity temperatures were close to the lower critical temperature of their thermoneutral zone. I also suggest that selection of warmer cavities minimized the bats' energy expenditure prior to emergence from the roost and that passive rewarming inside the cavity was an important factor in minimizing energetic costs of roosting by bats in BPF. Mean and maximum temperatures recorded near tree trunks increased with the height at which the temperature was measured (ground level, 10, 20, and 30 m), suggesting that bats can gain thermal benefits from insolation of the trunk by selecting highly placed cavities, as was observed in BPF.
Monitoring planktivorous seabird populations: validating surface counts of crevice-nesting auklets using mark–resight techniques
Authors: Sheffield Lisa M. , Gall Adrian E. , Roby Daniel D. , Irons David B. , Dugger Katie M.
Published: August 2006

Least Auklets ( Aethia pusilla (Pallas, 1811)) are the most abundant species of seabird in the Bering Sea and offer a relatively efficient means of monitoring secondary productivity in the marine environment. Counting auklets on surface plots is the primary method used to track changes in numbers of these crevice-nesters, but counts can be highly variable and may not be representative of the number of nesting individuals. We compared average maximum counts of Least Auklets on surface plots with density estimates based on mark–resight data at a colony on St. Lawrence Island, Alaska, during 2001–2004. Estimates of breeding auklet abundance from mark–resight averaged 8 times greater than those from maximum surface counts. Our results also indicate that average maximum surface counts are poor indicators of breeding auklet abundance and do not vary consistently with auklet nesting density across the breeding colony. Estimates of Least Auklet abundance from mark–resight were sufficiently precise to meet management goals for tracking changes in seabird populations. We recommend establishing multiple permanent banding plots for mark–resight studies on colonies selected for intensive long-term monitoring. Mark–resight is more likely to detect biologically significant changes in size of auklet breeding colonies than traditional surface count techniques.