bluuebunny/crossref_metadata_2025 huggingface dataset:
Habitat selection by muskrats in experimental marshes undergoing succession
Authors: Clark William R.
Published: July 2008

I analyzed habitat selection by muskrats (Ondatra zibethicus) in relation to density and plant succession in an experimental wetland complex flooded to three different levels: normal (long-term average elevation), medium (30 cm above normal), and high (60 cm above normal) at Delta, Manitoba. Locations where muskrats were trapped or built lodges were superimposed on vegetation types and water depth, in a geographic information system, to determine habitat selection. More than 60% of all individuals were captured in stands of Scirpus, Scolochloa, or Typha, and muskrats significantly avoided areas with water < 1 cm that were dominated by annuals and Hordeum. Muskrats preferred Typha and Scirpus stands for lodges, although some lodges were built in Scolochloa and Phragmites. Water depth at lodges averaged 38 cm, and > 90% of lodges were located in water ≥ 10 cm. Tall dense emergent growth trapped the most snow, resulting in the ice being less thick. Muskrats first captured in Typha or Scirpus stands gained significantly more mass during winter than did those captured in all other habitat types. As emergent vegetation changed and muskrat population density increased, the selection of habitat such as Typha in moderately deep water changed less than did the selection of habitat in shallow water or of those dominated by Scolochloa or sparse Scirpus. These data confirm density-dependent habitat selection by muskrats and suggest that spatial complexity induced by wetland succession is important in muskrat population dynamics.
Ultrastructural study of frontal glands in Bothromesostoma personatum (Platyhelminthes, Typhloplanoida)
Authors: Martínez-Alós S. , García-Corrales P. , Cifrian B.
Published: July 2008

The frontal glands of Bothromesostoma personatum were examined using transmission electron microscopy. These glands have two types of rhabdoid gland cells; one type produces rhabdites and the other a different type of rod secretion (rhabdoids). The ultrastructure of the latter type is described, together with their origin. Long necks containing the rhabdoids emerge from the rhabdoid gland cell bodies and extend to the anterior end of the animal, where they release the rhabdoids. The rhabdoids are compared with the rhammites of other rhabditophoran species on the basis of their dye affinities, formation mechanism, and ultrastructure.
Lung use and development in Xenopus laevis tadpoles
Authors: Pronych Scott , Wassersug Richard
Published: July 2008

Shortly after hatching, Xenopus laevis tadpoles fill their lungs with air. We examined the role played by early lung use in these organisms, since they are able to respire with both their lungs and their gills. We investigated the effect on X. laevis development when the larvae were prevented from inflating their lungs, and whether early lung use influenced the size of the lungs or the tadpole's ability to metamorphose. Tadpoles that were denied access to air had lungs one-half the size of those of controls. This difference in lung size was too large to be explained merely by a stretching of the lung due to inflation. The longer tadpoles were denied access to air, the longer they took to metamorphose, and their probability of completing metamorphosis diminished. One tadpole raised throughout its larval life without access to air successfully metamorphosed but had abnormal, solidified lungs and an enlarged heart. Collectively, these experiments demonstrate that early lung use in tadpoles is important in determining both ultimate lung size and the probability of successfully metamorphosing. Lung use during early larval development in X. laevis is not absolutely necessary for survival through metamorphosis, but its absence severely handicaps growth.
Spatial and social behaviour of Nearctic warblers wintering in Venezuelan mangroves
Authors: Lefebvre Gaetan , Poulin Brigitte , McNeil Raymond
Published: July 2008

The winter ecology of the Northern Waterthrush (Seiurus noveboracensis), the Prothonotary Warbler (Protonotaria citrea), and the American Redstart (Setophaga ruticilla) was studied in tropical mangroves of northeastern Venezuela. The birds' spatial and social behaviours were assessed through intensive mist-netting and observation sessions over two complete annual cycles. In all three species, transients corresponded to half of the migrant populations. Although many birds were observed more than once within a range of 50 m, most of them also moved considerably. Home ranges of individuals overlapped greatly in both Northern Waterthrushes and Prothonotary Warblers. Birds stayed in the mangroves for an average 2-month period, irrespective of their date of arrival, whereas new individuals were observed during most of the wintering period. Winter site fidelity characterized both transient and site-attached individuals. Although many birds showed some kind of site attachment, none of the three species can be considered territorial in the mangroves.
Changes in diets of river otters in Prince William Sound, Alaska: effects of the Exxon Valdez oil spill
Authors: Bowyer R. Terry , Testa J. Ward , Faro James B. , Schwartz Charles C. , Browning James B.
Published: July 2008

We studied the effects of the Exxon Valdez oil spill on the diets of river otters (Lutra canadensis) from oiled and nonoiled areas of Prince William Sound, Alaska, U.S.A., in 1989 and 1990. On the basis of identification of prey remains in their feces, otters fed principally on marine, bottom-dwelling fishes. Marine gastropods, bivalves, and crustaceans composed most of the invertebrates in the diet of otters; freshwater and terrestrial food items seldom occurred in their feces. The diets of otters included 149 different taxa, most of which rarely occurred in their feces. Sixty-five taxa occurred ≥ 5 times in our combined data set. Species richness and diversity of prey remains in otter feces were similar on oiled and nonoiled study areas in late winter (April) 1989 (before the oil spill) and during summer (June–October) 1989 following the spill. By summer (July–September) 1990, however, there were significant declines in the richness and diversity of species (mostly bony fish, molluscs, and bivalves) in otter diets on the oiled area. Likewise, the relative abundance of prey remains in otter feces showed strong differences between areas and years, and an area by year interaction. Members of the Perciformes and Archaeo-gastropoda declined from 1989 to 1990 on the oiled area while they increased on the nonoiled site; Malacostraca exhibited the opposite pattern. These outcomes, when considered with other data on body mass and blood chemistry, strongly suggest that some effects of the oil spill on otters were delayed.
Ultrastructural analysis of the invasion of tick cells by Lyme disease spirochetes (Borrelia burgdorferi) in vitro
Authors: Kurtti T. J. , Munderloh U. G. , Hayes S. F. , Krueger D. E. , Ahlstrand G. G.
Published: July 2008

The association of Lyme disease spirochetes, Borrelia burgdorferi, with tick cell cultures was characterized by electron microscopy. These cells were active in endocytosis and intracellular digestion, containing coated vesicles, pits, and phagosomes. Borrelia burgdorferi in tick cell cultures resembled those described in tick tissues. In RAE25 cultures, isolated from Rhipicephalus appendiculatus embryos, invasion of cells was mediated by coated pits, indicating active host cell participation. The invading, tapered end of B. burgdorferi contained an electron-dense body that persisted throughout invasion. A host-derived membrane surrounded invading and intracellular borreliae as observed by transmission electron microscopy of cross and longitudinal sections, whereas degenerating ones lay inside secondary lysosomes. Borrelia burgdorferi cocultivated with cell lines from Ixodes scapularis were mainly found at the cell surface or within lysosomes. The differences seen in invasion of these cell lines are interpreted to reflect differences in cell types rather than species. Gemmae, indicative of degenerative changes in the spirochetes, were observed extra- and intra-cellularly. Membrane blebs were liberated by the spirochetes into the medium and onto the cells, and were avidly endocytosed. Tick cell cultures are a useful tool to elucidate spirochete – vector cell interactions that may be obscured in vivo.
Patterns of intraspecific nest parasitism in the High Arctic common eider (Somateria mollissima borealis)
Authors: Bjørn Tor Harry , Erikstad Kjell Einar
Published: July 2008

Intraspecific nest parasitism was studied during two breeding seasons at two common eider (Somateria mollissima borealis) colonies in Kongsfjord, Svalbard (79°55′N, 12°10′E). The density of breeding eiders differed considerably from year to year and also among colonies. Parasitic eggs were identified through deviations from a normal laying pattern. Parasitic eggs (8%) were laid in 16% of the clutches at the dense colony. The corresponding values on the island with low breeding density were 1.6 and 2% in 1989 and 1990, respectively. Parasitic eggs were laid in clutches of all sizes according to their availability. The parasitizing females laid 70% of their eggs during the host's laying period. Parasitic laying occurred despite the constant availability of suitable nest sites. The hosts did not reduce their clutch size in response to egg parasitism. The rate of egg predation was significantly higher in parasitized than in nonparasitized nests. Parasitic eggs were laid late in the breeding period, suggesting that birds which were immature, in poor body condition, or had previously failed are salvaging some reproductive effort.
Jaw dimensions and torsion resistance during canine biting in the Carnivora
Authors: Covey Doreen S. G. , Greaves Walter S.
Published: July 2008

Carnivoran skulls can be functionally modelled as intricate half-cylinders. When a single canine meets resistance during biting, the jaw becomes asymmetrically loaded and the maximum torsional strains lie along helices on the surface of the skull that are positioned at 45° to the twisting forces. The integrity of the skull as a whole is conserved by the innate stability of its overall tubular shape. Strengthening structures, if needed, are expected to be concentrated along these helices. Our analysis predicts that the amount of bone needed to form the skull can be significantly reduced if the dimensions of the jaw are restricted such that the length to width ratio is less than or equal to π/2. Measurements of a sample that includes most of the modern genera of the Carnivora, as well as some extinct forms, all conform to this prediction.
Context-specific alarm calls of the eastern chipmunk, Tamias striatus
Authors: Silva Karen Burke da , Kramer Donald L. , Weary Daniel M.
Published: July 2008

The structure and context of alarm calls produced by chipmunks (Tamias striatus) at a field site in southern Quebec were recorded during opportunistic field observations and experimentally simulated hawk attacks. Chipmunks produced three call types in the presence of predators. Chipping consisted of a series of high frequency notes with a rapid downward frequency slope (9.6 to 2.8 kHz) and was given in the presence of mammalian predators by chipmunks perched on a raised vantage point. Chucking consisted of a series of lower frequency notes also sloping downwards (2.5 to 0.4 kHz), given in the presence of avian predators by perched animals. The trill was a lower amplitude, multi-note call usually given only once by animals before reaching a refuge while fleeing from either type of predator. The average trill contained 6–11 downward sloping notes (7.3 to 0.8 kHz). The alarm call types of eastern chipmunks appear to be similar to those reported for western chipmunks. However, they differ in the clear separation of the calls for aerial and terrestrial predators. Chipmunks differ from most other terrestrial sciurids in giving repeated calls for aerial as well as terrestrial predators and in using a call just before reaching a secure refuge.
Development of the germ cells and reproductive primordia in male and female embryos of Rhodnius prolixus Stål (Hemiptera: Reduviidae)
Authors: Heming B. S. , Huebner E.
Published: July 2008

Newly deposited eggs of Rhodnius prolixus lack a visible pole plasm and require 14 days to develop at 27 °C and 70% RH. The first germ cells originate at 9% of embryogenesis by asynchronous mitosis of blastodermal cells behind the germ Anlage at the posterior pole of the egg. From 9 to 17%, these proliferate to a mean of 270 cells and, from 13 to 18%, migrate forward over the dorsal surface of the mesoderm and lodge in abdominal segments 3–7. Between 22 and 30%, they shift laterally and segregate into three or four paired clumps between segments 3 and 4, 4 and 5, 5 and 6, and, sometimes, 6 and 7 and, from 30 to 37%, gradually assemble into a continuous longitudinal mass on either side of segments 3–6, where they begin to associate with mesodermal cells. Between 37 and 46%, these collect between (males) and around the germ cells to form the rudiments of the terminal filaments (females), inner and outer gonadal sheaths, interstitial cells (males), and primary exit ducts. Dorsally situated sheath cells then invaginate ventrally into each gonadal rudiment, partitioning it into seven compartments, each containing a mean of 15 oogonia or 16 spermatogonia. These seem to fuse into a rosette, at least in females, but do not begin to divide again until after hatch. Excluded germ cells lodge within the rudiments of one or both exit ducts. The evolutionary and functional aspects of our findings are addressed and new observations are presented on the mechanism of anatrepsis.
Hydrostatic stability of fish with swim bladders: not all fish are unstable
Authors: Webb Paul W. , Weihs D.
Published: July 2008

The center of mass and the center of buoyancy were found to occur at the same relative longitudinal location along the body of the elongate-bodied European eel (Anguilla anguilla), the fusiform yellow perch (Perca flavescens), and two gibbose species, rock bass (Ambloplites rupestris) and bluegill (Lepomis macrochirus). The locations of these centers were not affected by fish size. Therefore the fish were neutral in hydrostatic pitching equilibrium. The vertical location of the centers of mass and buoyancy were the same for bluegill, but the center of mass was dorsal to the center of buoyancy in yellow perch. The observations on bluegill show that neutral hydrostatic rolling equilibrium is possible. Our conclusions on similarity or separation between the locations of the centers of mass and buoyancy derive from tests of significance and differ from conclusions reported elsewhere on the basis of mean values only. In general, fish with swim bladders can be at or close to neutral hydrostatic equilibrium but any disturbance will be destabilizing. This probably explains continuous fin-beating of fish in apparently still water.
Milk production and milk consumption in polar bears during the ice-free period in western Hudson Bay
Authors: Arnould J. P. Y. , Ramsay M. A.
Published: July 2008

Milk yield and milk consumption were measured in polar bears (Ursus maritimus) during the summer ice-free period in western Hudson Bay, a period of severe nutritional restriction. The transfer of milk between adult and dependent offspring was measured for five females with cubs (aged 8 months) and four with yearlings (aged 20 months) by a hydrogen isotope dilution–transfer method. Females with cubs produced significantly more milk energy (10.9 MJ∙day−1) than females with yearlings (2.6 MJ∙day−1). Daily milk production represented a greater proportion of body mass for females with cubs than females with yearlings but milk production was not correlated with maternal mass or litter mass in either group. Milk energy consumption was correlated with body mass in cubs but not in yearlings. Cubs consumed significantly more milk energy (7.8 MJ∙day−1), and displayed a higher relative growth rate, than yearlings (1.5 MJ∙day−1). However, both age groups lost proportionally the same amount of mass during the study period, suggesting that cubs are less able to survive nutritional restrictions and are more dependent on milk for survival than yearlings.
Étude de l'inhibition sexuelle acquise chez un mutant neurologique, no-bridgeKS49, appartenant à l'espèce Drosophila melanogaster
Authors: Bouhouche A. , Choulli M. K.
Published: July 2008

The conditioned inhibition of courtship in male was quantitatively and sequentially studied in the Drosophila melanogaster neurological mutant no-bridgeKS49 (nob). After being paired first with a previously fertilized (unreceptive) female, wild-type Berlin males court virgin, receptive females less vigorously (if not at all) then naive wild-type males do. This conditioned inhibition is characterized by the latency of the first contact, the frequency and duration of the courtship acts, and the sequential organization of the kinetograph. In contrast, when presented with the same sequence, the nob males were not inhibited, as reflected in all courtship parameters; their courtship performance with virgin females was similar to that of naive nob males. This behavior pattern could be due to the disorganization of their protocerebral bridge interrupting inhibitory interactions between the two brain hemispheres, thereby causing uncoordinated descending inhibition of the motor behavior. The results suggest that the central complex could be the high brain center controlling this kind of learning.
Branchial chloride cell proliferation in the rainbow trout, Oncorhynchus mykiss: implications for gas transfer
Authors: Bindon Shawn D. , Fenwick James C. , Perry Steve F.
Published: July 2008

The effects of branchial chloride cell proliferation on ion transport capability and gill morphometry were evaluated in the rainbow trout, Oncorhynchus mykiss, to test the hypothesis that chloride cell (CC) proliferation benefits ionic regulation at the expense of efficient gas transfer. The extent of hormone-induced CC proliferation (using ovine growth hormone (oGH), cortisol, or a combination of both) on the gill filament epithelium was assessed by determining the fractional surface area of exposed cells using scanning electron microscopy. Cortisol and oGH were equally effective in increasing CC fractional surface area (~2×), owing to the enlargement of individual CCs. The combined cortisol/oGH treatment resulted in an even greater increase in CC fractional area (~6×), as both the size and number of CCs increased. Sham injections were without effect on CC surface area or number. Significant increases in Na+ (Jin Na+) and Cl− uptake (Jin Cl−) were observed after all hormone treatments and were correlated positively with the increases in the CC fractional surface area. These findings support the view that CC proliferation enhances branchial ion transport capability. Lamellar epithelial thickness (measured by transmission electron microscopy) was increased in hormone-treated fish, while lamellar surface area (measured using light microscopy) was unaffected. The area of the interlamellar water channels (calculated from light micrographs) was significantly reduced in hormone-treated fish. These results suggest that, in trout, a compromise is made between the efficiency of ion regulation and gas transfer in which the enlargement/proliferation of CCs may impede gas transfer.
The in vitro respiratory and acid–base properties of blood and tissue from the Kemp's ridley sea turtle, Lepidochelys kempi
Authors: Stabenau Erich K. , Heming Thomas A.
Published: July 2008

We determined the in vitro respiratory and acid–base properties of blood and tissue from Kemp's ridley sea turtles (Lepidochelys kempi). Blood O2 dissociation curves of ridley turtles were sigmoid, with a P50 of 31.2 ± 0.3 (mean ± SD) torr at 25 °C and pH 7.51. Increments in temperature or [Formula: see text] were associated with a shift of the O2 dissociation curves to the right and, hence, a reduction in haemoglobin–O2 binding affinity. The apparent heat of oxygenation, which is a measure of the temperature sensitivity of haemoglobin–O2 affinity, was −10.5 kcal/mol O2. The degree of cooperativity of O2 for hemoglobin binding sites, as measured by the Hill coefficient, increased at higher temperatures (20–30 °C at a [Formula: see text] of 37 torr), but was unaffected by changes in [Formula: see text] (37–52 torr at 25 °C). The CO2-Bohr effect was −0.34 torr/pH unit. The CO2 capacitance coefficient of whole blood and plasma declined as a function of increased [Formula: see text] (22 °C). Non-bicarbonate buffer capacities (22 °C) were 19.7, 18.5, and 6.4 slykes for whole blood, true plasma, and separated plasma, respectively. The skeletal muscle myoglobin content was 3.1 ± 0.84 mg∙g−1 of tissue. The respiratory and acid–base properties of blood and tissue from Kemp's ridley sea turtles are consistent with those of species that utilize lung O2 stores during long-term aerobic dives. The enhanced haemoglobin–O2 temperature sensitivity exhibited by the ridley turtle could be a physiological adaptation for life in coastal environments that typically undergo substantial fluctuations in temperature.
Estimating energy intake of free-ranging moose cows and calves through collection of feces
Authors: Hjeljord Olav , Sæther Bernt-Erik , Andersen Reidar
Published: July 2008

We calculated the daily energy intake of wintering cow and calf moose from a series of 24-h feces collections and from estimates of the digestibility and energy content of forages from four different habitats in Norway during a 3-year period (1984–1986). Habitats varied in condition from good to poor. In early winter, the estimated energy intake of cows ranged from 803 kJ∙kg−0.75∙day−1 in the good- and average-quality habitats to 573 kJ∙kg−0.75∙day−1 in the poor habitat. Estimated energy intake decreased by 15–30% from early to late winter. The estimated energy intake of calves ranged from 920 kJ∙kg−0.75∙day−1 in the good habitat to 414 kJ∙kg−0.75∙day−1 in the poor habitat; a significant decrease over winter was not evident. The estimates of daily energy intake correspond to a browse wet mass of 8–17 kg for cows and 4–10 kg for calves. In the good- and medium-quality habitats the average energy deficiency of adult cows over winter was estimated at 25–30%.
Responses to simulated grazing and browsing of vegetation available to caribou in the Arctic
Authors: Ouellet Jean-Pierre , Boutin Stan , Heard Doug C.
Published: July 2008

We investigated the consequences of simulated grazing and browsing on net primary production and chemical composition (nutrients, fiber, and total nonstructural carbohydrates) of some plant types available to caribou on Southampton Island, Northwest Territories, Canada. Clipping experiments were conducted in three large exclosures (22 × 22 m) on one deciduous (Salix lanata), one evergreen (Cassiope tetragona), and one semi-evergreen (Dryas integrifolia) shrub species and two types of sedges (Carex scirpoidea and wet-meadow sedges). The impact of various clipping regimes was analyzed in the growing season during which the treatments were applied and at the end of the following growing season. Clipping, for the most part, reduced plant net production. Responses differed among and within plant types according to the timing and intensity of clipping. In some cases maximum net production of plants was not restored during the recovery year, although grazing and browsing pressure was lifted. Clipping modified the chemical composition of S. lanata, D. integrifolia, and the two types of sedges investigated. In clipped sedges, nitrogen, magnesium, potassium, and phosphorus levels in regrowth were above the maximum obtained from controls at any point during the growing season. These chemical changes possibly enhanced the quality of these plants as food for herbivores. Because plant types that showed a high degree of compensatory growth also showed an increase in quality following clipping, herbivores might benefit if they reselect these plants over the course of the growing season. Growth of S. lanata is negatively affected by clipping and represents an important component of the caribou's summer diet, therefore willows are expected to decrease in abundance as the caribou population increases. The decrease in abundance of deciduous shrubs may have important consequences for the caribou's range use and population dynamics.
Growth of moose calves (Alces alces americana) infested and uninfested with winter ticks (Dermacentor albipictus)
Authors: Addison Edward M. , McLaughlin Robert F. , Broadfoot Jim D.
Published: July 2008

Captive moose calves (Alces alces americana) in Algonquin Provincial Park, Ontario, were similar in size to most calves of the same age from other regions and of other subspecies. Their general patterns of growth were comparable to those observed for other northern cervids with an active growth phase throughout the summer and early autumn followed by a period of slow growth in winter. Maximum average daily mass gains (1.1 kg) were achieved in mid-September and were similar to those observed in other studies. Male calves were larger than females at any given age but males and females showed similar growth rates. Infestation with winter ticks (Dermacentor albipictus) may have caused a reduction in the mass gain of moose in autumn. If this occurs in the wild, heavy autumn tick infestation may predispose calves to reduced physical fitness and likelihood of survival during winter. Total length, chest girth, and shoulder height were all strongly correlated with live mass and may be valuable for estimating the live mass of moose calves under field conditions.
Comparative fine structure of sperm of Verutus volvingentis and Meloidodera floridensis (Heteroderinae, Nematoda)
Authors: Cares J. E. , Baldwin J. G.
Published: July 2008

The fine structure of sperm of one representative species each of Verutus and Meloidodera was compared through development from the pre-adult male as a starting point for the discovery of new phylogenetically informative characters for Heteroderinae. Males of both V. volvingentis and M. floridensis have a single tubular genital tract, including a telogonic testis and a wall consisting of a single layer of epithelial cells enclosing conspicuous vesicles believed to be secretory. As in other nematodes, the sperm lack a flagellum, acrosome, and axoneme, and the nuclear envelope is lost during spermatogenesis. Nevertheless, the sperm are highly divergent between the two representative species. Those of V. volvingentis are about twice the size of those of M. floridensis, and the former can also be distinguished from the latter by the asymmetrical distribution of their filopodia and the relative lack of change in condensation of chromatin after insemination. In addition, fibrous bodies are less persistent in sperm of V. volvingentis than in those of M. floridensis. Since both representative species lack cortical microtubules, which are present in other Heteroderinae, examination of additional out-groups may support this loss as a synapomorphy between Verutus and Meloidodera.
Multivariate analysis of geographic covariance between phenotypes and environments in the threespine stickleback,Gasterosteus aculeatus, from the Cook Inlet area, Alaska
Authors: Bourgeois J. F. , Blouw D. M. , Koenings J. P. , Bell M. A.
Published: July 2008

Widely distributed freshwater populations of Gasterosteus aculeatus exhibit reduction in the bones of the pelvis and the numbers of lateral plates and dorsal spines. We investigated the relationship between skeletal reduction and the characteristics of the environments in which it occurs. A combination of environmental factors, including environmental ion composition – lake productivity, geographic position, opportunity for gene flow, and the presence of other fishes, is associated with skeletal reduction. The principal correlates of reduction in all skeletal traits are low concentrations of calcium, magnesium, silicon, H+, and reactive phosphorus. We hypothesize that the ion composition of lake water is the main selective agent promoting skeletal reduction in sticklebacks in the Cook Inlet area, Alaska, and that other fishes and local gene flow may modify its extent. Our results show that a suite of skeletal traits responds in common to the interacting effects of at least three environmental factors (ion composition of lake water, presence of other fishes, local gene flow), and they emphasize that unitary explanations of the evolution of skeletal reduction are unlikely to be adequate.
Isoforms of apolipoprotein A-I in the serum of brown bullheads (Ameiurus nebulosus) with liver cancer
Authors: Denslow Nancy D. , Chow Ming M. , Folmar Leroy C.
Published: July 2008

Brown bullheads (Ameiurus nebulosus) express two different isoforms of apolipoprotein A-I in the serum, a predominant form characterized by a pI of 6.9 and a more acidic isoform with a pI of 6.65. The two proteins were identified by N-terminal amino acid sequencing, with 50 residues for the pI 6.9 isoform and 20 residues for the pI 6.65 isoform. Sequences for the two proteins were identical for the first 20 amino acids; however, differences in their primary sequences were deduced by analysis of peptide maps obtained through proteolytic digestion. The ratio of the isoforms changes from 75% pI 6.9/25% pI 6.65 (no tumors) to equal amounts of both isoforms in bullheads with hepato- or cholangio-cellular carcinomas. This is the first report of these serum isoforms in feral fish showing that the expression of these proteins is directly related to both cholangio- and hepato-cellular carcinomas. The potential use of these proteins as tumor biomarkers is discussed.
Geographic variation in size and sexual dimorphism across a hybrid zone between Carrion Crows (Corvus corone corone) and Hooded Crows (C. c. cornix)
Authors: Saino Nicola , Bernardi Fiorenza De
Published: July 2008

Sexual size dimorphism was analysed across a hybrid zone existing between allopatric populations of Carrion Crows and Hooded Crows (Corvus corone corone and C. c. cornix) in northwestern Italy. Twenty-five morphological (osteological and plumage) variables were measured in a sample of 1599 specimens obtained from allopatric parental areas and from the hybrid zone. For each morphological variable considered, sexual size dimorphism was measured as the ratio of males/females or the absolute difference between mean sizes of males and females within each subpopulation studied. Overall sexual size dimorphism was described by discriminant function analysis. All the sexual size dimorphism measures adopted showed variation across the hybrid zone according to elevation. Male/female ratios and male–female differences significantly differed between the parental allopatric "operational taxonomic units," Carrion Crows being more dimorphic than Hooded Crows. Across the hybrid zone, sexual size dimorphism was correlated with the phenotypic composition of the crow subpopulations and with size of males but not size of females. The data presented show that sexual size dimorphism is correlated with an ecological gradient and that its geographical variation is determined by variation in size of males only.
A study of the Malpighian tubules of the plecopteran nymph Paragnetina media (Walker) (Plecoptera: Perlidae) by light, scanning electron, and transmission electron microscopy
Authors: Kapoor N. N.
Published: July 2008

The present study concerns the structural details of the Malpighian tubules in the nymph of the stonefly Paragnetina media. There is no external segmentation except for a distal short hyaline segment. The tubules are composed of two cell types: primary and stellate. Primary cells in the proximal and middle portions of the tubule have short infoldings of the basal membrane and the cytosol is packed with laminate spheres. Cells of the distal segment possess long and tightly packed membrane folds but are devoid of laminate spheres. The stellate cells are sparsely distributed in the middle region and make up 12% of the total cell population in the Malpighian tubule; they lack laminate spheres. Long processes of the stellate cells extend between adjacent primary cells to the luminal and outer surfaces of the tubule.
Moderate water restriction differentially constrains reproduction in two species of dwarf hamster (Phodopus)
Authors: Scribner Stephen J. , Wynne-Edwards Katherine E.
Published: July 2008

The dwarf hamsters Phodopus campbelli and P. sungorus are found in semi-arid areas of Siberia and northern Mongolia, but habitat and diet differences suggest species differences in water regulatory efficiency. These differences were investigated by examining the effect of moderate water restriction (50% of ad libitum consumption) on solitary dams and on their reproductive success. In response to water restriction, P. sungorus dams lost less body mass than P. campbelli dams, and despite similar litter sizes, P. sungorus produced heavier litters and pups than P. campbelli, indicating that P. sungorus pups were larger. These results suggest that P. sungorus is more tolerant of water restriction than P. campbelli. In a second experiment the possibility that paternal care may mitigate the effects of water restriction was examined by leaving the mated pair together throughout lactation. Pairing reduced mass loss by P. campbelli dams and increased the proportion of large P. campbelli pups at weaning, but had no effect on these measures in P. sungorus, eliminating interspecific differences in responses to water restriction. Results suggest that biparental care may be a facultative response to environmental stress in P. campbelli.
The ultrastructure of the spermatozoon of the northern water snake, Nerodia sipedon (Colubridae, Serpentes), with phylogenetic considerations
Authors: Jamieson B. G. M. , Koehler L.
Published: July 2008

The ultrastructure of the spermatozoon of Nerodia sipedon conforms closely to that of other described snake sperm: it is filiform; the acrosome vesicle is in the form of a hollow, concentrically zoned cone that basally overlies a subacrosomal cone which invests the tapered anterior end of the nucleus; the putative perforatorium is a slender rod extending anteriorly from the subacrosomal cone; the midpiece contains dense bodies and mitochondria; the axonemal fibrous sheath extends anteriorly into the midpiece (squamate autapomorphy); 9 peripheral dense fibres surround the distal centriole and the axoneme in the midpiece, of which fibres adjacent to 3 and 8 are enlarged; and the endpiece lacks peripheral fibres and the fibrous sheath. The midpiece is very long (a synapomorphy of the Serpentes) and is surrounded by a multilaminar membrane (an autapomorphy). In the squamates, only snakes, including N. sipedon, retain microtubules external to the plasma membrane of the mature spermatozoon. Helically arranged zigzag mitochondria are shared (probably homoplasically) with iguanid sperm. A poorly developed "stopperlike" putative perforatorial base plate in N. sipedon, unknown in other snakes, is questionably homologous with that of gekkonids. An electron-lucent space caps the nuclear point, as in the snakes Boiga irregularis and Stegonotus cucullatus and in some other squamate orders.
Nesting dispersion of a Black Kite population in relation to location of rabbit warrens
Authors: Viñuela Javier , Villafuerte Rafael , Court Claudine De Le
Published: July 2008

Previous studies have shown that the rabbit (Oryctolagus cuniculus) is the main prey of the Black Kite (Milvus migrans) in Matasgordas (Doñana National Park, southwestern Spain), and that the reproductive success of pairs is enhanced with increasing rabbit consumption. In our study area, rabbits live mainly in large warrens patchily distributed across the breeding area of Black Kites. Rabbit consumption was higher for Black Kite pairs having warren entrances close to their nests. During the 3 years of the study, this population of Black Kites suffered a considerable increase. New pairs in the area selected nesting trees inside areas with a high density of rabbits. The pattern of Black Kite aggregation in our study area, where they breed in a "colony" with a population density among the highest recorded, can be explained, at least partially, by rabbit aggregation. Defense of feeding resources could help to explain the territorial behavior of Black Kites. Coloniality and feeding territoriality are not mutually exclusive.
Presence of rodlet cells in the intrahepatic biliary ducts of the brown trout, Salmo trutta fario Linnaeus, 1758 (Teleostei, Salmonidae)
Authors: Rocha Eduardo , Monteiro Rogério A. F. , Pereira Carlos A.
Published: July 2008

We report for the first time rodlet cells in the epithelium of intrahepatic biliary ducts of the brown trout (Salmo trutta fario Linnaeus 1758). Such cells have not been described in the liver of any salmonid. Several developmental stages of the rodlet cells were found, including mature, discharging elements. The number of rodlet cells decreased from June to April. Intra-epithelial macrophages were found in close proximity to rodlet cells, suggesting a mild pathological reaction.
Feeding behaviour of predatory larvae of Atherix lantha Webb (Diptera: Athericidae)
Authors: Hunter Fiona F. , Maier Astrid K.
Published: July 2008

Larvae of Atherix lantha Webb (Diptera: Athericidae) are piercing – sucking predators. Predator–prey experiments were conducted in beakers containing gravel substrates and airstone-oxygenated water. The predator:prey ratio used in all experiments was 5:5. One prey type was tested at a time. Prey tested included large and small heptageniid mayflies, hyalellid amphipods, and hydropsychid caddisflies. The effect of predator size was examined using two size classes of A. lantha larvae. Large A. lantha consumed more mayflies than did small A. lantha. However, amphipod mortality was the same with large as with small A. lantha. The effect of prey size on predation success was tested using two size classes of mayflies. Statistically, small A. lantha fed on equal numbers of small and large mayflies, whereas large A. lantha consumed more large than small mayflies. Data for species-wise comparisons are only available for small A. lantha; according to our results, hydropsychid caddisflies (average mortality (m) = 0.5346) are more vulnerable to predation than are hyalellid amphipods (m = 0.2041) and heptageniid mayflies (m = 0.1135–0.1813). However, the mortality of large mayflies caused by large A. lantha larvae (m = 0.5375) is the same as that of caddisflies caused by small A. lantha larvae. Thus, the vulnerability of prey species depends, in part, on predator size.
Effect of water on retention time and food consumption in deer mice
Authors: Reid Edward D. , Brooks Ronald J.
Published: July 2008

Experiments were conducted to assess the effect of water on food consumption and retention time in deer mice (Peromyscus maniculatus). We tested whether increased intake of water, preformed in food or free drinking water, affects mean retention time and consumption of food. Mean retention times for diets of sunflower seeds (Helianthus annuus), commercial rat chow, and insect–seed mixtures were estimated by using 2-mm red thread markers. For all diets, mean retention time and food intake were negatively and positively correlated, respectively, with water intake. Mean retention times decreased more rapidly with increased water content for sunflower seeds than for rat chow, suggesting that food type also may be important. Granivorous rodents may consume wet food items during periods of low water availability to increase energy intake rather than to satisfy water requirements.
Spacing behaviour and habitat use of axis deer (Axis axis) in lowland Nepal
Authors: Moe Stein R. , Wegge Per
Published: July 2008

A total of 17 axis deer (Axis axis) (12 females, 5 males) were radio-instrumented in Bardia National Park in lowland Nepal, and 1921 locations of females and 605 locations of males were obtained during the 2-year study period. Both the annual home ranges (135 ± 33 and 204 ± 38 (SD) ha for females and males, respectively) and the seasonal home ranges were quite small compared with those reported in another study in Nepal. We present evidence that this difference is due to a more fine-grained habitat mosaic in Bardia. Males used larger areas than females in the monsoon and the hot part of the dry season. The deer were sedentary, with a mean seasonal home range overlap between 49 and 86%, and seasonal occupancy centres were all located less than 1300 m apart. Mean seasonal home range size (68 and 110 ha for females and males, respectively) was smallest in the cool part of the dry season. The rutting period did not seem to have any major effect on the ranging behaviour, as neither males nor females increased home range size from the pre-rut to the rutting period. The deer used riverine forest preferentially during the cool-dry and hot-dry seasons, whereas sal forest was the preferred habitat during the monsoon and the cool-dry season. Grasslands were preferentially utilized by females at night during the hot-dry season, presumably because of improved forage quality following cutting and burning. Males were more associated with riverine and sal forest than were females, while females used grassland areas more than males did.
Seasonal variations in intertidal density of invertebrate prey in a tropical lagoon and effects of shorebird predation
Authors: Mercier Francine , McNeil Raymond
Published: July 2008

We analyzed the relationship between the abundance of shorebirds and that of their intertidal invertebrate prey, and attempted to determine if shorebird predation significantly affects prey density. The study was conducted at three sites in the Chacopata Lagoon complex in northeastern Venezuela between January 1985 and September 1986, using shorebird census data, monthly sampling of intertidal invertebrates, and exclosure experiments. The invertebrates collected were divided into three groups: (i) polychaetes (≤50 mm in length), (ii) small bivalves (2 – 3 mm in length), and (iii) other species. The overall density of shorebirds foraging in the Chacopata Lagoon complex was very high, exceeding the densities reported for most other staging and overwintering areas by a wide margin. The abundance of shorebirds in the study area was related primarily to the density of polychaetes, their main prey. At two of the study sites, the arrival of fall migrants followed a significant increase in polychaete numbers. The increase in shorebird numbers in autumn was negligible at the third site, where polychaete density was lower than at the other sites. The impact of shorebird predation on their invertebrate prey varied seasonally, as did the extent of the foraging area available to them. The exclosure experiment revealed significant differences in the density of polychaetes inside and outside the exclosures only during, or shortly after, the fall migration period. The variability in the conclusions drawn from other studies examining prey depletion by shorebirds in tropical environments may be explained by differences in the length of sampling periods and seasonal variations in the numbers of foraging shorebirds, the energy demands of moult, fat deposition, and the intertidal surface area available for feeding. The impact of seasonal variables such as these should be taken into consideration when designing studies to measure prey depletion by shorebirds; such objectives may necessitate long-term studies.
Seasonal movement patterns in a subalpine population of the tiger salamander, Ambystoma tigrinum nebulosum
Authors: Whiteman Howard H. , Wissinger Scott A. , Bohonak Andrew J.
Published: July 2008

Seasonal movements of a subalpine population of metamorphic tiger salamanders, Ambystoma tigrinum nebulosum, were explored from 1990 to 1992. Metamorphic adults bred in permanent and semipermanent habitats during June of each year. After breeding, soma individuals returned to the terrestrial environment, but many remained and congregated in nonpermanent ponds. Metamorphic adults in nonpermanent ponds included those that moved from permanent ponds, those that bred and remained in semipermanent ponds, and those that did not breed but migrated from the terrestrial environment after the breeding season. Dietary analyses indicated that metamorphic adults in nonpermanent ponds have significantly greater numbers, biomass, and calories of prey in their gut than the few metamorphic adults remaining in permanent ponds. This difference was due to the presence of fairy shrimp (Branchinecta coloradensis), which composed 91 % of metamorphic adult diets in nonpermanent ponds and accounted for three times the average caloric value of all prey in gut samples from metamorphic adults in permanent ponds. Intraspecific competition also may have contributed to movement into nonpermanent ponds: post-breeding densities of metamorphic adults in permanent ponds were inversely related to the densities of other morphs (paedo-morphic adults and large larvae). We conclude that metamorphic A. t. nebulosum in this population utilize nonpermanent ponds after the breeding season because of the abundance of high-quality aquatic prey and reduced competition from con-specific morphs.
Comparison of capture–recapture estimators of snowshoe hare populations
Authors: Boulanger John , Krebs Charles J.
Published: July 2008

We used two island populations of snowshoe hares (Lepus americanus) in the Kluane Lake area of the Yukon Territory of Canada to evaluate capture – recapture estimators. These islands were intensively sampled, allowing us to enumerate the actual population size. Population size estimates were calculated using the programs CAPTURE and JOLLY, and estimators were compared for bias characteristics. Results from both islands suggest that the CAPTURE heterogeneity models Mh (jackknife), Mh (Chao), and Mth (time – heterogeneity) and the Jolly – Seber model were approximately unbiased. All other CAPTURE models displayed a negative bias. The CAPTURE model selection routine picked estimation models of different biases for each trapping period, an undesirable result. We conclude that it is best to use one robust estimator such as the Mh (jackknife) with snowshoe hare data.
A taxonomic reevaluation of North American Bosminidae
Authors: Melo Rita De , Hebert Paul D. N.
Published: July 2008

Prior morphological studies have led to the recognition of six species in the genus Bosmina from North America. The present study employed allozymic and morphological analyses to ascertain the taxonomic diversity of bosminids from 72 North American habitats. The results suggest the occurrence of 10 species, including representatives from four recognized subgenera. Populations assignable to Bosmina (Bosmina) longirostris s.l. were rare, but two newly described species in the subgenus Sinobosmina were common in the eastern half of the continent. Four species of the subgenus Eubosmina were detected, one of which is newly described, while a second species new to North America apparently represents a recent invasion from Eurasia. Two species of the subgenus Neobosmina were found in lakes from the northeastern portion of the continent, while a third species was restricted to southern sites.