bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of type-1 diabetes mellitus on the regulation of insulin and endothelin-1 receptors in rat hearts
Authors: Nuwayri-Salti Nuha , Karam Chehade N. , Al Jaroudi Wael A. , Usta Julnar A. , Maharsy Wael M. , Bitar Khalil M. , Bikhazi Anwar B.
Published: May 2007

This project assesses the treatment role with insulin and (or) angiotensin II receptor subtype-1 (AT1-R) blocker (ARB) on insulin receptor and endothelin-1 receptor subtype (ETA-R and ETB-R) regulation in rat hearts suffering from insulin-dependent diabetes mellitus (IDDM). Animals were divided into 6 groups: groups 1, 3, and 5 were controls consisting of normal, diabetic (streptozotocin-treated, once at 0 time), and diabetic supplemented daily with insulin, respectively, whereas groups 2, 4, and 6 were the controls treated daily with losartan. One month after enrollment, rats were sacrificed and samples of cardiac tissue were snapped frozen for immunostaining and Western blotting. Insulin receptor density was observed to be upregulated in the cardiomyocytes of diabetic animals, but downregulated with insulin supplementation alone. Cotreatment with insulin and an ARB resulted in drastic increase in insulin-receptor density in the diabetic rats. In addition, expression of ETA-R in cardiomyocytes was upregulated and was consistently maintained within the various treatment modalities. However, ETB-R expression was significantly reduced in the diabetic group treated with both insulin and an ARB. The changes in the expression of the insulin, the ETA-Rs, and the ETB-Rs at the various sites of the myocardium and the effect of both insulin treatment and blockade of the AT1-R explain the new benefits related to the halting of myocardial remodeling in IDDM rats.
Non-genomic effects of aldosterone on intracellular ion regulation and cell volume in rat ventricular myocytes
Authors: Matsui Saori , Satoh Hiroshi , Kawashima Hirotaka , Nagasaka Shiro , Niu Chen  Fung , Urushida Tsuyoshi , Katoh Hideki , Watanabe Yasuhide , Hayashi Hideharu
Published: May 2007

Aldosterone has non-genomic effects that express within minutes and modulate intracellular ion milieu and cellular function. However, it is still undefined whether aldosterone actually alters intracellular ion concentrations or cellular contractility. To clarify the non-genomic effects of aldosterone, we measured [Na+]i, Ca2+ transient (CaT), and cell volume in dye-loaded rat ventricular myocytes, and we also evaluated myocardial contractility. We found the following: (i) aldosterone increased [Na+]i at the concentrations of 100 nmol/L to 10 μmol/L; (ii) aldosterone (up to 10 μmol/L) did not alter CaT and cell shortening in isolated myocytes, developed tension in papillary muscles, or left ventricular developed pressure in Langendorff-perfused hearts; (iii) aldosterone (100 nmol/L) increased the cell volume from 47.5 ± 3.6 pL to 49.8 ± 3.7 pL (n = 8, p < 0.05); (iv) both the increases in [Na+]i and cell volume were blocked by a Na+–K+–2Cl– co-transporter (NKCCl) inhibitor, bumetanide, or by a Na+/H+ exchange (NHE) inhibitor, 5-(N-ethyl-N-isopropyl) amiloride; and (v) spironolactone by itself increased in [Na+]i and cell volume. In conclusion, aldosterone rapidly increased [Na+]i and cell volume via NKCC1 and NHE, whereas there were no changes in CaT or myocardial contractility. Hence the non-genomic effects of aldosterone may be related to cell swelling rather than the increase in contractility.
Bone mass, bone strength, and their relationship in developing CD-1 mice
Authors: Ward Wendy E. , Piekarz Ana V. , Fonseca Debbie
Published: May 2007

Optimizing nutrition during development may provide effective prevention strategies to protect against osteoporosis during later life. Because the mouse model is commonly used to test nutritional interventions on bone health, the overall objective of this study was to determine how bone develops during the first 4 months of life by assessing bone mass (bone mineral content (BMC) and bone mineral density (BMD)) and biomechanical strength properties such as peak load in male and female CD-1 mice. Bone outcomes were assessed at 1 month intervals from 1 to 4 months of age. Femur and spine BMC and BMD at 3 months were similar to 4 months, indicating that the accumulation of bone mass occurs primarily during the first 3 months of life. In contrast, the timing of changes in peak load, a measure of bone strength, varied by skeletal site. Regression analyses demonstrated that femur BMC is a significant predictor of femur peak load at the femur midpoint and neck. The study findings suggest that nutritional interventions aimed at optimizing peak bone mass to prevent osteoporosis may be most effective during pubertal growth.
Developmental changes in threshold, conduction velocity, and depressive action of lignocaine on dorsal root potentials from neonatal rats are associated with maturation of myelination
Authors: Lizarraga I. , Chambers J.P. , Johnson C.B.
Published: May 2007

Conduction velocity of primary afferent fibres and blocking actions of local anaesthetics seem to be developmentally regulated. The current work investigated physiological (threshold, conduction velocity, and myelination) and pharmacological (lignocaine (0.0625 to 2 mmol/L) and capsaicin (2 μmol/L)) ontogenic changes on in vitro sciatic nerve-dorsal root preparations from 0- to 12-day-old rats. As rats aged, stimulus intensities necessary to evoke A-fibre thresholds significantly decreased and A-fibre conduction velocities significantly increased. For C-fibres, thresholds significantly increased and conduction velocities significantly varied with age. The blocking potency of lignocaine varied with age: A-fibres from 4-day-old rats and younger were significantly more resistant than those from older rats, and C-fibres were blocked more uniformly amongst ages. Capsaicin significantly depressed C-fibres irrespective of age, and A-fibres were significantly reduced during the first postnatal week only. Myelination significantly increased as rats aged. A-fibre physiological parameters were significantly correlated with both other A-fibre physiological and pharmacological parameters, but C-fibre parameters were not. Peripheral A-fibre transduction mechanisms seem to require time to acquire their full stimulus-response sensitivity, which coincides with development of myelination. In contrast, peripheral C-fibres seem to have mature transduction mechanisms from the first days of postnatal life.
The significance of hydroperiod and stand maturity for pool-breeding amphibians in forested landscapes
Authors: Baldwin R.F. , Calhoun A.J.K. , deMaynadier P.G.
Published: May 2007

The loss of small seasonal wetlands and adjacent forested habitat is a major threat to pool-breeding amphibians in North America. Identifying environmental correlates of breeding effort (and success) in remaining intact landscapes is a critical first step in conservation planning. Little is known about how pool-breeding amphibian populations respond to fine-scale variations in hydroperiod or neighboring forest structure and composition. We studied these associations for wood frogs ( Rana sylvatica LeConte, 1825) and spotted salamanders ( Ambystoma maculatum (Shaw, 1802)) in a forested New England landscape (southern Maine, USA). We conducted egg mass counts across two seasons at 87 strictly seasonal pools. The influence of hydroperiod and landscape (150 and 500 m scales) habitat characteristics on breeding effort were investigated. Pools with longer hydroperiods (≥18 weeks post breeding) that were relatively isolated from other breeding wetlands (<13 neighboring pools within 150 m and <19 within 500 m) supported larger breeding populations of both wood frogs and spotted salamanders. Salamander breeding populations were largest in relatively mature forests. Naturalized, anthropogenic pools supported comparable levels of breeding effort with that of natural pools. Conservation planning for wood frogs and spotted salamanders should incorporate pools at the longer end of the seasonal hydroperiod gradient.
Feeding habits and trophic niche overlap between sympatric golden jackal (Canis aureus) and red fox (Vulpes vulpes) in the Pannonian ecoregion (Hungary)
Authors: Lanszki J. , Heltai M. , Szabó L.
Published: May 2007

The feeding ecology of the golden jackal ( Canis aureus L., 1758) and its interspecific trophic relationship with the sympatric red fox (Vulpes vulpes (L., 1758)) was investigated in an area of recent range expansion of the golden jackal in Hungary, central Europe. Diet composition was determined by scat analysis (over 4 years: jackal 814 scats; fox 894 scats). Compared with jackals, foxes consumed more small mammals (mean biomass consumed: jackal 77%; fox 68%) and to a lesser extent plant matter (6% and 18%, respectively). The importance of other prey, such as wild boar ( Sus scrofa L., 1758), cervids, brown hare ( Lepus europaeus Pallas, 1778), birds, reptiles, fish, invertebrates, and domestic animals, was minimal. Both mesocarnivores consumed primarily small animals (<50 g: 92% and 87%, respectively); this implies a typical searching and solitary hunting strategy. The trophic niche breadth of both species was very narrow and the fox proved to be more of a generalist. The food overlap index between the two canids was high (mean, 73%) and varied with the decreasing availability and consumption of small mammals. Based on prey remains found in scats, small-mammal specialization over a 2-year period and seasonal predation upon wild boar piglets (mainly by the jackal), seasonal fruit eating (mainly by the fox), and scavenging on wild or domestic ungulates (both predators) were found.
Asymmetric impact of piscivorous birds on size-structured fish populations
Authors: Beckmann Christa , Biro Peter A. , Post John R.
Published: May 2007

Fish are frequently considered the top predator in freshwater food web models despite evidence that predatory birds can impact fish populations. In this study, we quantified bird predation rates on experimental populations of rainbow trout ( Oncorhynchus mykiss (Walbaum, 1792)) created by stocking nine small lakes in British Columbia, Canada. Combining estimates of fish mortality with estimated bird predation rates allowed us to partition fish mortality into that due to birds versus cannibalism. Our results indicated that bird predators had significant impacts on age-1 trout populations, but little impact on age-0 trout. Common loons ( Gavia immer Brunnich, 1764) were the principle predator among eight predatory bird species present, apparently consuming nearly 50% of all stocked age-1 trout and explaining almost 50% of variation in mortality rates. Age-1 trout mortality did not differ significantly from zero in lakes without loons. Birds consumed a small proportion of age-0 trout, and estimated consumption explained none of the variation in age-0 trout mortality among lakes. We conclude that birds affect fish populations by asymmetric predation on different age (size) classes and can be important top predators that should not be ignored when characterizing freshwater food webs in lakes.
Yolk hormone levels in the synchronously developing eggs ofParoedura picta, a gecko with genetic sex determination
Authors: Kratochvíl Lukáš , Kubička Lukáš , Landová Eva
Published: May 2007

Sex steroid hormones of presumably maternal origin have been found in yolk of many oviparous vertebrates. Their effects on behavioural or physiological traits are well documented in birds, but until now are largely unknown in reptiles. The investigations of yolk steroids in reptiles have been focused mainly on species with temperature-dependent sex determination, where steroid levels are suggested to determine the sex of progeny. Here we report initial oestradiol (E2) and testosterone (T) levels in the yolk of the Madagascar ground gecko, Paroedura picta (Peters, 1854), a species with genetic sex determination. The yolk concentration was 0.39 ± 0.02 ng/g (mean ± SE) in E2, whereas the concentration of T was much higher (1.48 ± 0.06 ng/g, mean ± SE). Geckos usually lay two exceptionally large eggs per clutch; vitellogenesis and ovulation of both eggs proceed in phase. Individual two-egg clutches differed considerably in E2 and T levels. A clutch mean of E2 levels varied from 0.22 to 0.53 ng/g, whereas T levels varied from a clutch mean of 1.02 to 1.99 ng/g. Both eggs in a clutch possessed very similar levels of E2 and T. Initial yolk steroid levels thus presumably reflect maternal conditions during egg formation rather than differential allocation of hormones according to offspring sex.
Using n-alkane markers to estimate forage intake of mule deer
Authors: Kuzyk G.W. , Hudson R.J.
Published: May 2007

Dry matter intake (DMI) of free-ranging mule deer ( Odocoileus hemionus (Rafinesque, 1817)) in the aspen parkland of east-central Alberta was estimated using the double n-alkane ratio and bite count methods. Eleven female mule deer were given an intraruminal capsule containing synthetic n-alkanes and released into 4–8 ha paddocks. Known concentration of even-chained carbon (C32) was released from the capsules and recovered 7–10 days later from freshly voided faeces. Odd carbon chains of adjacent length (C31:C33) were extracted from vegetation samples gathered during behavioural observations of four tame deer. Calculations from the pairings (C31:C32; C33:C32) provided estimates of DMI that ranged from 1.29 to 2.73 kg/day. DMI was highest during autumn, possibly to prepare for increased energy demands for the upcoming winter. No differences were found in seasonal or annual comparisons of bite rates, but bite sizes differed in all comparisons, suggesting bite size was a critical factor affecting consumption rates for mule deer on northern ranges. Maximum bite sizes rose from 49 ± 5 mg/bite in July to 213 ± 58 mg/bite in October. Maximum consumption rates were in October of both years (3.6–4.4 g/min) and occasionally approached theoretical maxima (14.3–15.6 g/min).
Geographic variation in nesting behavior and reproductive biology of an insular iguana (Cyclura cychlura)
Authors: Knapp C.R. , Iverson J.B. , Owens A.K.
Published: May 2007

Intraspecific comparisons among geographically separated populations of wide-ranging species are particularly useful in elucidating variation in behavioral and reproductive life histories resulting from proximate and ultimate causes. From 2001 to 2004, we investigated geographic variation in nesting behavior and reproductive biology of a large-bodied Bahamian iguana ( Cyclura cychlura Cuvier, 1829) inhabiting two distinct island systems varying in area, topography, and rainfall. Studies of C. cychlura cychlura were conducted on Andros Island (approx. 6000 km2; annual rainfall 1100 to 1300 mm) and the results were compared with those for C. cychlura inornata Barbour and Noble, 1916 inhabiting two cays (each <4 ha; annual rainfall <600 mm) in the northern Exuma Island chain (approx. 140 km distant). Female iguanas from Andros Island initiated oviposition 5 to 6 weeks earlier than females from the Exumas. The Andros Island population deposited eggs primarily in termitaria, whereas the lizards in the Exumas deposited eggs in subterranean sand chambers. Female iguanas from Andros deposited significantly more eggs per clutch, heavier total clutches, and wider eggs than conspecifics from the Exumas. Despite egg size differences, hatchling snout–vent length and body mass per clutch did not differ significantly between the Andros and Exuma populations. Our results support the hypothesis that proximate environmental factors play an important role in determining geographic variation associated with not only reproductive output but also reproductive behavior.
On the efficacy of anti-parasite behaviour: a case study of tadpole susceptibility to cercariae of Echinostoma trivolvis
Authors: Koprivnikar Janet , Forbes Mark R. , Baker Robert L.
Published: May 2007

Many animals respond behaviourally to the infective stages of parasites, but the efficacy of such responses in reducing risk of parasitism often is not established. It was found that tadpoles of Rana clamitans Latr., 1801 (green frogs) and R. sylvatica LeConte, 1825 (wood frogs) increased their activity when exposed to live infective stages (cercariae) of the trematode Echinostoma trivolvis Rudolphi, 1809. The susceptibility to parasitism for green frog tadpoles subjected to three different treatments was compared. Tadpoles were housed at 20 °C and allowed to respond to cercariae, held at 6–8 °C and showing reduced behavioural responses, or anesthetized and showing no responses. Low levels of parasitism were found for tadpoles that responded behaviourally to cercariae; such responses are expected to occur under normal field conditions in the absence of factors suppressing activity of tadpoles. We also demonstrate that infectivity of E. trivolvis cercariae to non-responding (anesthetized) wood frog tadpoles was higher at warm than at cool temperatures. Thus, lowered parasitism at warm temperatures in the first experiment likely resulted from host behavioural responses and not from low infectivity of cercariae. These results have implications for observing effects of environmental factors on susceptibility to parasitism where susceptibility is thought or known to be mediated by host behaviour.
Risk-sensitive foraging by juvenile signal crayfish (Pacifastacus leniusculus)
Authors: Bondar C.A. , Zeron K. , Richardson John S.
Published: May 2007

Feeding behavior of carnivorous and herbivorous organisms is commonly explained in terms of nutritional requirements. However, feeding behavior of omnivorous organisms is difficult to predict and may not be based on nutritional requirements alone. To assess the plasticity of feeding behaviors exhibited by an omnivore, we conducted a feeding experiment using juvenile signal crayfish ( Pacifastacus leniusculus (Dana, 1852)), both alone and in the presence of conspecifics and predators. Crayfish were presented with three types of food (chironomids, mayflies, and woody debris) in experimental enclosures, and the food type consumed and time to consumption were recorded. Although the same overall food choice (chironomid larvae) was made in all trials, the time it took for the juvenile crayfish to make a food selection was longer in the presence of adult conspecifics (both male and female) and adult cutthroat trout ( Oncorhynchus clarkii (Richardson, 1836)). Food selection also took longer, although not significantly, in the presence of conspecific juvenile crayfish, and no changes in behavior were noted in the presence of young-of-the-year (YOY) cutthroat trout. The altered behavior of the juvenile crayfish observed in the presence of adult fish and crayfish can lead to context-dependent effects of this omnivore on its community. Ecologists must be increasingly aware that the feeding of omnivores may not be solely based on nutritional criteria.
Comparative branchial plume biometry between two extreme ecotypes of the hydrothermal vent tubeworm Ridgeia piscesae
Authors: Andersen A.C. , Flores J.F. , Hourdez S.
Published: May 2007

The vestimentiferan tubeworm Ridgeia piscesae Jones, 1985 from the Juan de Fuca Ridge is a morphologically plastic species with two contrasted ecotypes. The “chimney-dwelling” ecotype lives along the sides of active hydrothermal chimneys, where temperature and sulfide concentrations are high, but oxygen concentrations are low. Its morphology corresponds to the “short-fat” morphotype. The “basalt-dwelling” ecotype lives on rock outcrops in surrounding basaltic fields, where temperature and sulfide concentrations are low, but oxygen is readily available. Its morphology corresponds to the “long-skinny” morphotype. We compared the ultrastructure and biometry of their branchial plumes, the essential organ for respiration and nutrition in this symbiotic tubeworm. The branchial epidermis of both ecotypes contains electron-dense organelles, which may be related to the presence of sulfides in their environment. The diffusion distance across the gill epidermis is about 20% shorter in the short-fat R. piscesae. For tubeworms of the same mass, specific branchial surface areas (SBSA) are similar in both ecotypes (mean 24 cm2/g for worms of 1–2 g body mass), which is comparable with the SBSA in the vestimentiferan vent tubeworm Riftia pachyptila Jones, 1981 . The SBSA of R. piscesae follows a power curve that is negatively correlated with total body mass. The implications for gas uptake efficiency between these two ecotypes are discussed.
Impact of diet-index selection and the digestion of prey hard remains on determining the diet of the Steller sea lion (Eumetopias jubatus)
Authors: Tollit D.J. , Heaslip S.G. , Barrick R.L. , Trites A.W.
Published: May 2007

Nine prey species (n = 7431) were fed to four captive female Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) in 11 feeding trials over 75 days to investigate the effectiveness of different methods used to determine diet from prey hard remains. Trials aimed to replicate short (1–2 days) and long feeding bouts, and consisted of single species and mixed daily diets. Overall, 25.2% ± 22.2% (mean ± SD, range 0%–83%) otoliths were recovered, but recovery rates varied by species (ANOVA, P = 0.01) and were linearly related to otolith robustness (R2 = 0.88). Squid beaks were recovered at higher frequencies (mean 96%) than the otoliths of all species. Enumerating both non-otolith skeletal structures and otoliths (together termed bones) increased species recovery rates by twofold, on average (P < 0.001), with increases up to 2.5 times for Pacific herring ( Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847) and 3–4 times for salmonids. Using bones reduced interspecific differences (P = 0.08), but recovery varied among sea lions. Bones were distributed over more scats per meal (mean 2.9 scats, range 0–5) than otoliths (mean 1.9 scats, range 0–4). In three different 15-day mixed diet trials, biomass reconstruction (BR) indices performed better than frequency of occurrence indices in predicting diet fed. Applying our experimentally derived numerical correction factors (to account for species differences in complete prey digestion) further improved BR estimates, resulting in all 12 unweighted comparisons within 5% (for otoliths) and 12% (for bones) of the actual diet fed.
Nest-site selection in the barn swallow, Hirundo rustica: What predicts seasonal reproductive success?
Authors: Safran Rebecca Jo
Published: May 2007

Despite hundreds of studies, we know very little about the causes and fitness-related consequences of nest-site selection. For example, it is not typically known whether the rarely reported fitness consequences of site selection are the result of nest, individual, or nest-site variables or combinations of these factors. Reuse of previously constructed nest sites is a prevalent behavior in many animals and offers the opportunity to experimentally tease apart whether seasonal reproductive success is a function of nest, individual, or nest-site characteristics. I used observational and experimental data to test three hypotheses related to these factors in association with barn swallow ( Hirundo rustica L., 1758) nest reuse. While both nest and individual characteristics explain variation in seasonal reproductive success, nest location per se is not an important factor defining the outcome of nest-site selection. Whereas traits related to habitat and individual characteristics are likely confounded in correlational studies, my experiments demonstrate a causal relationship between seasonal reproductive success and aspects of the nest and individual, the latter explaining more variation in the model than nest characteristics. Knowledge of the relative roles of individual, nest, and nest-site attributes are important for understanding the causes and consequences of habitat selection behavior.
Influence of intraclutch egg-mass variation and hatching asynchrony on relative offspring performance within broods of an altricial bird
Authors: Bitton Pierre-Paul , Dawson Russell D. , O’Brien Erin L.
Published: May 2007

Rates of growth and size of nestlings at fledging have important consequences for future survival and reproductive success in many passerine birds. Within broods of altricial species, these characteristics are often influenced by size hierarchies established early in the nesting period due to hatching asynchrony and within-clutch variation in egg mass, but the concurrent effect of these factors is poorly understood. We investigated the relative influence of these variables on nestling performance within broods of tree swallows, Tachycineta bicolor (Vieillot, 1808). Nestlings that hatched earlier within nests were heavier and larger than their later-hatched siblings at 4 days of age. Similarly, earlier-hatched nestlings grew their ninth primary flight feathers faster and had longer ninth primaries just prior to fledging than did later-hatched siblings. Differences in egg mass of siblings also contributed to mass and size hierarchies at 4 days of age, but did not affect any other difference in sibling performance. We conclude that within-clutch variation in performance of offspring is determined primarily by size hierarchies resulting from asynchronous hatching. Intraclutch egg-mass variation appears to have little effect on performance of siblings and may be best explained by proximate constraints on females.
Influence of female-biased sexual size dimorphism on dominance of female Townsend’s chipmunks
Authors: Edelman A.J. , Koprowski J.L.
Published: May 2007

Female-biased sexual size dimorphism (SSD), a condition common in North American chipmunks, occurs when females are larger than males in a species. We examined the influence of body size on dominance of captive female Townsend’s chipmunks ( Tamias townsendii Bachman, 1839), a species that exhibits female-biased SSD, in all-female and mixed-sex dyadic encounters. In all-female dyads, large female chipmunks were more frequently dominant over small female opponents. In mixed-sex dyads, large females were always dominant over small males. Female-biased SSD in Townsend’s chipmunks appears to indirectly allow large females to more frequently dominate small female and male conspecifics. Greater dominance could increase reproductive success of large female chipmunks by increasing access to resources.
Winter habitat selection by female moose in western interior montane forests
Authors: Poole Kim G. , Stuart-Smith Kari
Published: May 2007

Winter range has been identified as an important component of moose ( Alces alces (L., 1758)) conservation in managed forests, yet there have been few studies on habitat associations in montane ecosystems. We investigated habitat selection by moose at landscape and stand scales during late winter in southeastern British Columbia using global positioning system (GPS) collars on 24 adult moose cows in each of two winters. The strongest determinant of late-winter range at the landscape scale was decreasing elevation, while moose also selected for areas of gentler slopes and higher solar insolation. Elevation likely is a surrogate for snow depth, which is probably the primary causative factor influencing late-winter distribution of moose. Within late-winter range, topographic variables had little influence on moose habitat selection. Lower crown closure was the strongest determinant of stand-scale selection, although the resultant model was weak. We found no disproportionate selection for stands with high crown closure, and there was little evidence for greater use of cover stands with increasing snow as winter progressed. Within late-winter range, moose selected forage habitats (42% use vs. 30% availability) over cover habitats (22% use vs. 37% availability). The delineation of late-winter moose range can be based on snow depth, or elevation as its surrogate.
Between-population differences in egg composition in Blue Tits (Cyanistes caeruleus)
Authors: Bourgault Patrice , Thomas Donald W. , Blondel Jacques , Perret Philippe , Lambrechts Marcel M.
Published: May 2007

Egg production may be influenced by environmental conditions such as local climate or food availability, which may impose physiological constraints on the acquisition and mobilization of egg constituents. We analyzed egg composition of free-ranging female Blue Tits ( Cyanistes caeruleus (L., 1758)) in both deciduous and evergreen oak habitats, which showed large differences in temperature and food availability. We found marked interhabitat differences in yolk mass, shell mass, protein content, and the abundance of linolenic (18:3) and palmitoleic (16:1) fatty acids. A weak but significant decline in total lipid content, as well as 14:0, 16:0, and 18:0 fatty acids, through the laying sequence was also detected. To our knowledge, this is the first evidence of between-population differences in nutrient allocation in eggs for a wild passerine. These differences in egg composition could be viewed as evidence of habitat-specific physiological and nutritional constraints, which in turn may contribute to the contrasting differences in timing of breeding and clutch size that we observed between both habitats. Our results point out the importance of habitat differences in our understanding of the causes and consequences of interhabitat phenotypic variation in breeding traits (timing of egg laying, clutch size) and variation in nestling traits such as growth and development.
Having a big nose: structure, ontogeny, and function of the elephant seal proboscis
Authors: Sanvito Simona , Galimberti Filippo , Miller Edward H.
Published: May 2007

The proboscis of male elephant seals ( Mirounga Gray, 1827) has been suggested as an example of a secondary sexual trait since Darwin. There has been much speculation about its social function (e.g., optical signal of breeding status, amplification of vocalizations, cue for female choice). However, it has never been studied in detail, probably because its fleshy nature makes measurement difficult. In this paper, we employ photogrammetry to measure the proboscis and facial morphology of a large sample of wild, unrestrained, displaying male southern elephant seals ( Mirounga leonina (L., 1758)). We describe ontogeny and allometry of the proboscis and analyze current phenotypic selection pressures on proboscis traits. We discuss the potential role of the proboscis in optical and acoustic signaling of male resource-holding potential and status. We demonstrate that proboscis size is positively correlated with age and body size independently, and that it is currently under a positive sexual selection pressure when the effect of selection on body size is removed. We suggest that selection on proboscis size is functionally related to the emission of agonistic vocalizations.
Foraging segregation in a breeding bird guild declines following nesting
Authors: Mills Alexander M.
Published: May 2007

Ecological communities appear to have structure, and exploitation of food resources have commonly been implicated in contributing to that apparent structure. Avian communities are frequently used in foraging research, but such studies do not usually document within-landscape patterns of change over seasonal time. I studied a guild of twelve small, foliage-gleaning, insectivorous songbirds in their breeding landscape in central Ontario, Canada. By focussing on foraging preferences indicated by tree species, foraging height, and foraging maneuvers, I compared patterns among the breeding period (June), midsummer (late July and early August), and early autumn (late August to mid September) within the one landscape. Correspondence analysis indicates that each species foraged in a distinct manner, yet there was substantial foraging overlap at all times in preferred (i) foraging tree species, (ii) foraging height, and (iii) foraging maneuvers. As the season progressed, patterns related to preferred foraging height and foraging maneuvers did not change dramatically. However, patterns of preferred foraging tree species did change progressively from breeding to autumn. During the breeding period, the guild tended to exploit different tree species in a manner correlated with the relative availabilities of those species, but this was not the case in midsummer or autumn. By autumn, foraging tree preferences among species were much more homogeneous, especially among wood-warblers of the genus Dendroica Gray, 1842. Consequently, based on preferred foraging tree species, whatever segregation existed during breeding was largely disassembled by autumn.
Is it risky to be a father? Survival assessment depending on sex and parental status in the water bug Abedus breviceps using multistate modelling
Authors: Munguía-Steyer R. , Macías-Ordóñez R.
Published: May 2007

We carried out a capture–recapture multistate modelling approach to estimate survival and recapture probabilities and transition rates between parental and nonparental status in an adult wild population of the water bug Abedus breviceps Stål, 1862 (Hemiptera: Belostomatidae). The global model included the following parameters: sex, male parental status (brooding or not), and transience (individual’s permanent movement from the site after first capture). Models were selected by means of the information-theory paradigm. The best supported model shows no difference in survival between males and females regardless of male parental status. Thus, the frequently assumed cost of parental care in terms of survival is not supported by our data. Furthermore, during the study, male expected adult life span in the wild was lower than the time needed to brood a batch of eggs from oviposition to hatching. We discuss potential consequences of such a short male expected adult life span in terms of parental behaviour decision rules related to fitness maximization.
Effect of oral suction and other friction-enhancing behaviors on the station-holding performance of suckermouth catfish (Hypostomusspp.)
Authors: Gerstner C.L.
Published: May 2007

Effect of oral suction and other friction-enhancing behaviors on the ability to maintain position in a current (station-holding) was determined for the suckermouth catfish (genus Hypostomus Lacépède, 1803). Fish were tested using an increasing velocity test on three substrata (smooth Lucite®, rough Lucite®, and wire grid). On the smooth substratum, use of oral suction and other behaviors delayed the need to swim continuously out of ground contact from 9.1 ± 0.3 cm/s (uslip) to 89.2 ± 7.9 cm/s (uswim). Trials on the wire grid showed that oral suction was ineffective as predicted; however, fish were able to use other friction-enhancing behaviors instead to improve station-holding performance. Behaviors that increased friction by hooking the fish to the substrate via the odontodes and pectoral fin spines were very effective at delaying the need for steady swimming from 12.9 to 145.0 cm/s. On the rough substratum, fish were able to use both oral suction and the odontodes or fin spines to increase friction, and station-holding performance was similar to values on the wire substratum. Thus, while use of the oral suction disk was shown to improve station-holding performance, use of other morphological features such as the odontodes and fin spines may be equally important.
Utilization of stored energy reserves during fasting varies by age and season in Steller sea lions
Authors: Rea L.D. , Rosen D.A.S. , Trites A.W.
Published: May 2007

Nine captive Steller sea lions ( Eumetopias jubatus (Schreber, 1776), 1.75–6 years of age) were fasted for 7–14 d to test the effect of short-term fasting on changes in body mass and body condition. Trials were repeated during both the summer breeding season and the nonbreeding season in seven animals to elucidate whether there was a seasonal component to the ability of Steller sea lions to adapt to limited food resources. Mean percent mass loss per day was higher during the breeding season in juveniles (1.8% ± 0.2%·d–1) than in subadults (1.2% ± 0.1%·d–1), but there were no significant age-related differences during the nonbreeding season (juveniles, 1.5% ± 0.3%·d–1; subadults, 1.7% ± 0.3%·d–1). A decrease in the rate of mass loss occurred after the first 3 d of fasting only in subadults during the breeding season. Percent total body lipid ranged from 11% to 28% of total body mass at the initiation of fasting trials. Animals with lower initial percent total body lipid exhibited higher subsequent rates of mass loss and a lower percentage of tissue catabolism derived from lipid reserves. There was no evidence of metabolic adaptation to fasting in juveniles, which suggests that juvenile sea lions would be more negatively impacted by food limitation during the breeding season than would subadults.
Ultrastructure of the mesonotal mycangium of Xylosandrus mutilatus (Coleoptera: Curculionidae)
Authors: Stone W.D. , Nebeker T.E. , Monroe W.A. , MacGown J.A.
Published: May 2007

Mycangial structures of female Xylosandrus mutilatus (Blandford, 1894), an Asian ambrosia beetle recently introduced and now established in the southeastern United States, were examined. In addition to the glandular (secretory) mesonotal mycangium located below the scutellum, nonglandular pit mycangia containing fungal propagules were discovered to occur externally on the scutellum. The ultrastructure of the glandular mesonotal mycangium, which consisted of an outer secretory layer covering an inner paired cuticular sac, is described and illustrated. Both secretory and cuticular layers of the mesonotal mycangium were highly tracheolated. Tracheae and tracheoles in association with a Xyleborine mycangium are reported here for the first time. Type 1 secretory cells were identified and observed passing electron-dense material into the glandular mycangium via efferent cuticular ductules, although type 2 secretory cells were not observed. Secretory cells were not observed in association with the nonglandular pit mycangia.
Resource partitioning and asymmetric competition between sympatric freshwater and Omono types of ninespine stickleback,Pungitius pungitius
Authors: Tsuruta Tetsuya , Goto Akira
Published: May 2007

The freshwater and Omono types of ninespine stickleback, Pungitius pungitius (L., 1758), coexist in several ponds and a stream in the Omono River system, Japan. We tested the hypothesis that coexistence of the two types is accomplished by resource partitioning through interspecific competition. First, the stomach contents of the two types were compared between sympatric and allopatric populations: the stomach contents of the sympatric freshwater type consisted of almost all Copepoda, whereas those of the sympatric Omono type consisted of not only Copepoda, but also many large benthic invertebrates; the stomach contents of both allopatric types were similar, consisting of Copepoda and large benthic invertebrates. Second, behaviour related to resource use in a sympatric pond was observed in the nonbreeding season: the freshwater type showed little aggressive behaviour, but the Omono type had a high frequency of aggressive behaviour. These results indicate that the sympatric freshwater type does not hold a feeding territory and its food resource is almost all Copepoda, whereas the Omono type has a feeding territory and its food resources are various. This suggests that asymmetric interference competition causes a diet shift of the sympatric freshwater type, allowing the two types to coexist by their resource partitioning.
Habitat structure, climatic factors, and habitat use by European bison (Bison bonasus) in Polish and Belarusian parts of the Białowieża Forest, Poland
Authors: Daleszczyk K. , Krasińska M. , Krasiński Z.A. , Bunevich A.N.
Published: May 2007

Białowieża Forest is divided into Polish and Belarusian parts that differ in habitat structure and degree of protection. The forest supports two European bison, Bison bonasus (L., 1758), populations that are isolated from each other. We analysed bison habitat use from relocations of 34 radio-collared bison from both populations collected in 1993–2003. The two bison populations differed considerably in habitat use, but home-range sizes were similar. The habitat structure in the Polish part is more advantageous for bison (deciduous forests prevail) than in the Belarusian part; however, open areas form a rich source of forage for ungulates in the Belarusian part, which presumably helped to eliminate the difference between the two parts. In 1977–2003, the annual temperature in this area rose and the total precipitation diminished. As a result, the habitat use by bison changed in both populations when compared with those in earlier studies; use of coniferous forests decreased, while use of deciduous forests and alderwoods increased. Generalized linear models on relationships among climatic factors and habitat use showed that the amount of water accessible in the period up to 4 years ago was the main factor affecting the use of various forest types. Habitat preferences differed between adult bulls and groups that included cows, but were similar in both populations irrespective of the differences in habitat composition.
Seasonal migration and home range of roe deer (Capreolus capreolus) in the Italian eastern Alps
Authors: Ramanzin M. , Sturaro E. , Zanon D.
Published: May 2007

Although it has been demonstrated that European roe deer ( Capreolus capreolus (L. 1758)) may migrate seasonally in areas with snow gradients, this behaviour remains scarcely understood. From 1999 to 2002, radio-tracking techniques in an Italian alpine area showed that 40% of the 32 monitored roe deer migrated (12.0 ± 6.2 km, mean ± SD) from the high-elevation summer ranges to the low-elevation winter ranges. Proportions of migratory deer were similar for fawns and adults and for males and females. We documented a mixed migration strategy, with most deer migrating once to the winter range in years of heavy snowfalls, but many deer migrating inconsistently or only for a short period to the winter range in one year with very scarce snowfalls. Seasonal home-range sizes were similar for migratory and stationary deer, except in a winter with very shallow snow when migrators used unusually large home ranges. In all seasons, migrators showed a lower within home range site fidelity than did stationary deer. Our results indicate that seasonal migrations may be a common strategy exhibited by roe deer living in mountain areas to avoid deep snow, and that variability in climatic conditions might be responsible for the development of variable spatial strategies.
Patterns of winter locomotion and foraging in two sympatric marten species:Martes martesandMartes foina
Authors: Goszczyński Jacek , Posłuszny Maciej , Pilot Małgorzata , Gralak Barbara
Published: May 2007

Modes of area searching and exploratory behaviour of the sympatric pine marten, Martes martes (L., 1758), and stone marten, Martes foina (Erxleben, 1777), were studied by snow-tracking in two regions of Poland. The accuracy of identifications of the two species on the basis of their snow tracks was assessed by DNA analysis of their faeces, as collected on the tracks; identifications were found to be correct in 88% of cases. Although most activities of the two species were concentrated on the forest floor, pine martens climbed trees, moved in tree crowns, and searched the bases of tree trunks and tree hollows more frequently than stone martens. In contrast, stone martens were more inclined to search for food in brushwood and piles of wood, and visited logged areas and garbage dumps more frequently. Pine martens avoided man-made objects and barriers such as roads and passed through open areas with reluctance. Such behavioural traits make this species particularly vulnerable to forest fragmentation and human activity in forests. Stone martens often explored woodless areas and inhabited buildings, which allowed them to use habitats substantially transformed and intensively explored by humans. The future coexistence and relative numbers of the two martens in forest habitats will depend on the mode of forest management and on the existence of effective migratory corridors connecting forest patches.
Litter size, sex ratio, and age structure of gray wolves, Canis lupus, in relation to population fluctuations in northern Belarus
Authors: Sidorovich V.E. , Stolyarov V.P. , Vorobei N.N. , Ivanova N.V. , Jędrzejewska B.
Published: May 2007

Gray wolf ( Canis lupus L., 1758) population fluctuations in northern Belarus (Vitebsk region) between 1990 and 2003 were significantly affected by hunting pressure by humans. Mean litter size was inversely density dependent and varied from 4.8 to 7.7 pups (range 2–10). The increase in litter size with declining density of wolf population concerned only female pups, whereas the number of male pups in a litter was not related to population density. The sex ratio of pups varied significantly: the proportion of females reached 70% in a low-density wolf population and declined to 40%–50% in a high-density population. The age structure also varied. In years following heavy hunting pressure, 55% of individuals shot were juveniles <1 year old (with a strong predominance of females that constituted 69% of juveniles shot), and only 11% of wolves were older than 4 years. The mean age of all wolves shot was 1.5 years. In years following low hunting pressure, 34% of animals shot were juveniles and 20% exceeded 4 years. The mean age was 2.8 years. A female-biased sex ratio of wolf pups conforms to Hiraiwa-Hasegawa’s hypothesis of the advantaged daughter, proposed for species in which mothers are able to influence the reproductive success of their daughters through transmission of rank.
Proximate constraints on reproductive output in a northern population of painted turtles: an empirical test of the bet-hedging paradigm
Authors: Rollinson N. , Brooks R.J.
Published: May 2007

For long-lived, iteroparous organisms whose annual reproductive success is low and unpredictable, the “bet-hedging” life-history paradigm predicts that an increase in resource acquisition should result in an increase in stored lipids and not an increase in reproductive output. We tested whether reproductive patterns in a population of midland painted turtles ( Chrysemys picta marginata Agassiz, 1857) are consistent with this prediction. Assuming that annual temperature variation is a proxy for variation in resource acquisition, we hypothesized that if harvested resources are generally sequestered for future reproduction, then there should be no relationship between clutch frequency (the number of clutches laid per season) and the temperature experienced when no follicular growth occurred. We hypothesized further that if temperature constrains clutch frequency by limiting the amount of energy that can be allocated to reproduction, then clutch frequency would be related only to the temperature experienced during the period in which follicular growth occurred (fall temperature). We found that clutch frequency was primarily related to fall temperature, which suggests that the amount of thermal energy experienced during periods of follicular development limits the amount of stored energy that can be allocated to developing follicles. This pattern of reproductive allocation is consistent with the bet-hedging paradigm.