bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative productivity of American black ducks and mallards nesting on Chesapeake Bay islands
Authors: Krementz David G. , Stotts Daniel B. , Pendleton Grey W. , Hines James E. , Stotts Vernon
Published: July 2008

We estimated laying dates, clutch sizes, and nest success rates of sympatrically breeding populations of American black ducks (Anas rubripes) and mallards (Anas platyrhynchos) on Chesapeake Bay islands between 1986 and 1989. Neither average laying date nor clutch size differed between black ducks and mallards. Nest success rates were higher for mallards in 2 of 4 years, but were area dependent.
Site specificity of Gyrodactylus salaris Malmberg, 1957 (Monogenea) on Atlantic salmon (Salmo salar L.) in the River Lakselva, northern Norway
Authors: Jensen Arne Johan , Johnsen Bjørn Ove
Published: July 2008

Site specificity of Gyrodactylus salaris on 853 Atlantic salmon (Salmo salar) parr infected with 1 – 10 625 parasites was studied in the River Lakselva in northern Norway. At low intensities (< 100), the dorsal fin was the principal site of attachment, followed by the pectoral and anal fins. However, the distribution of parasites on the fish, and their crowding, varied with infection intensity. When the intensity increased to more than 100, more parasites were located on the caudal fin, and when it exceeded 1000, the body of the fish was also heavily infected.
Fine structure of the body wall cuticle of females of Bellodera utahensis and Ekphymatodera thomasoni (Sarisoderini, Heteroderinae)
Authors: Baldwin J. G. , Eddleman C. D.
Published: July 2008

The female body wall cuticle of Bellodera utahensis and Ekphymatodera thomasoni (Heteroderinae) has an external sub-crystalline layer and four concentric layers, A, B, C, and D. Surface striae of the cuticle of B. utahensis are transverse, whereas those of E. thomasoni are longitudinal. The surface patterns are reflected in the A layer, which is thickest in the elevated regions between striae. The B layer consists of vertical columns and is continuous in young females but is broken into discontinuous patches as the female increases in girth. The C layer and adjacent D layer tend to merge at an intermediate zone in B. utahensis and E. thomasoni. The D layer is composed of fibrils about 31 nm in diameter arranged in a helicoidal pattern. An E layer adjacent to the hypodermis is present only in B. utahensis. The D layer is not resolved in newly molted females of B. utahensis, contrary to E. thomasoni. The presence of a D layer is a phylogenetic character shared with most other Sarisoderini. Although further investigation of Rhizonema and Hylonema is needed, existing knowledge of the body wall cuticle in females strengthens hypotheses of the monophyly of Sarisoderini.
Effect of temperature on egg hatching and survival of larvae of Anisakis simplex B (Nematoda: Ascaridoidea)
Authors: Brattey John , Clark Kirsten J.
Published: July 2008

Eggs of the parasitic nematode Anisakis simplex B, obtained from a white-beaked dolphin (Lagenorhynchus albirostris Gray), were incubated in seawater at constant temperatures from −0.7 to 24.3 °C and hatching times determined. Eggs hatched at all temperatures except −0.7 °C. The number of days until hatching ranged from 3 at 24.3 °C to 74–81 at 1.9 °C. There was a declining curvilinear relationship between temperature and both hatching time and duration of the hatching period. The hatching period increased and became more variable with decreasing temperature and ranged from 5 days at 24.3 °C to 55–72 days at 3.8 °C. The percentage of eggs that hatched at each temperature was variable but generally fell in the range 30–60% and was not correlated with temperature. Survival times of hatched larvae peaked at 75–105 days at 8.6 °C, with a minimum of 3–8 days at 24.3 °C. Dimensions of eggs (length, width, volume) differed significantly among individual worms but were not correlated with worm size (wet weight). Egg hatching and larval survival characteristics indicate a species adapted to cold-temperate waters and are consistent with the known distribution of A. simplex B. Preliminary experiments indicated that harpacticoid copepods will ingest newly hatched larvae of A. simplex B and become infected, suggesting that these microcrustaceans may be involved in the life cycle of the nematode.
Seasonal changes in the neutral and polar lipid fatty acid content of female northern pike (Esox lucius L.)
Authors: Schwalme Karl , Mackay William C.
Published: July 2008

We quantified seasonal changes in the total fatty acid content and the content of major fatty acid classes (i.e., saturates, polyunsaturates, etc.) in the neutral lipids and polar lipids of ovaries, liver, white muscle, and adipopancreatic tissue of female northern pike in central Alberta. Concentrations (percent wet weight) of polar lipid fatty acids (PLFAs) increased during fall and winter in all the organs and tissues examined. As the ovaries were recrudescing between July and March, ovary PLFA content increased from 0.03 to 4.60 g and the combined PLFA content of the three somatic tissues increased from 1.87 to 2.68 g (quantities are expressed per kilogram carcass weight of pike). During this period the quantity of neutral lipid fatty acids (NLFAs) (per kilogram of carcass weight) in the ovary increased from 0.01 to 1.95 g and liver NLFA content decreased from 0.60 to 0.14 g. The NLFA content of adipopancreatic tissue was 3.5–5.5 g/kg carcass weight and that in muscle was 2–4 g/kg carcass weight, but neither showed significant seasonal variation. There were no significant seasonal changes in either the total fatty acid content or the content of any fatty acid class in the combined neutral lipids or combined total lipids (neutral lipids plus polar lipids) of the three somatic tissues. Thus, there do not appear to be large seasonal transfers of fatty acids from somatic to ovarian tissues or from neutral to polar lipids in female pike.
Chemically mediated avoidance behavior in wild brook trout, Salvelinus fontinalis: the response to familiar and unfamiliar predaceous fishes and the influence of fish diet
Authors: Keefe MaryLouise
Published: July 2008

Choice experiments were used to determine whether juvenile wild brook trout would avoid chemical traces of predaceous fishes found in their native stream; the fishes used were the red fin pickerel (Esox americanus) and American eel (Anguilla rostrata), and a predaceous fish with which the trout had no prior experience, the Atlantic salmon (Salmo salar). Juvenile trout avoided pickerel odors but did not avoid water conditioned by American eels. They also avoided water conditioned with Atlantic salmon. A second experiment using trout from two wild populations demonstrated that the brook trout's avoidance of Atlantic salmon was a response to the salmon's piscivorous diet. These results suggest that brook trout do not avoid odors of all predaceous fishes and are capable of altering their behavior patterns in response to a change in the diet of a predatory fish.
Invertebrate abundance on Potamogeton nodosus: effects of plant surface area and condition
Authors: Beckett David C. , Aartila Thomas P. , Miller Andrew C.
Published: July 2008

Using the macrophyte Potamogeton nodosus, we investigated variability in abundance of plant-dwelling invertebrates among individual plants. Plants were collected from three Potamogeton beds in Eau Galle Lake, Wisconsin, in June and August 1987. Invertebrate abundance on P. nodosus and the amount of plant surface area were positively correlated in both June and August. In August the amount of leaf damage (plant condition) was another important predictor of invertebrate abundance. Plant surface area and plant condition were responsible for most to almost all of the variability in invertebrate abundance on P. nodosus (R2 = 0.66 in June; R2 = 0.83 in August). The correlation between invertebrate abundance and plant condition in August and the lack of such a correlation in June indicated that plant age, rather than plant condition per se, was a causal mechanism for increased invertebrate abundance. Some plants were heavily colonized by invertebrates; a single plant collected in June held a total of 555 invertebrates, which included 177 chironomid larvae and 143 naidid worms. We estimate that the P. nodosus in a 20 × 60 m Potamogeton bed supported about 33 million invertebrates in June and approximately 30 million invertebrates in August. The use of lake management techniques in which plants are eliminated would therefore markedly reduce invertebrate abundance in the littoral zone, and would, in turn, deny fishes and waterfowl an important and abundant food resource.
Cuticular repair in the mature male snow crab, Chionoecetes opilio (Majidae; Crustacea): relation to ecdysteroids
Authors: Halcrow K. , Steel C. G. H.
Published: July 2008

Morphometrically mature male snow crabs, Chionoecetes opilio, are not known to molt; they are believed to lack functional Y-organs and hence molting hormones. Small regions of the dorsal surface of crabs were damaged and the ensuing repair of the cuticle was followed by light microscopy at intervals of up to 60 days. Events within the limb base after forced autotomy of a single pereiopod were also investigated and compared with cuticle deposition in limb bases of pereiopods autotomized before the crabs' arrival in the laboratory. Circulating ecdysteroids were assayed by radioimmunoassay at intervals throughout the experiments. New cuticle was deposited in response to all types of injury and in a manner similar to that described previously. New cuticle was deposited across the breakage plane of autotomized limb bases; a complete and substantial layer was present in many of the bases of previously autotomized legs. Neither basal growth nor premolt growth was detected in the base of any autotomized limb. Ecdysteroids were detectable in the hemolymph of most crabs but at low titers, ranging from 6.0 to 11.6 ng/mL.
Maternal aggression in the South American fur seal in Peru
Authors: Harcourt Robert
Published: July 2008

Maternal aggression was examined with regard to its role in maternal defense of offspring in the South American fur seal (Arctocephalus australis) at Punta San Juan, Peru (15°22′S, 75°12′W). Female fur seals' responses to conspecifics and to predatory southern sea lions (Otaria byronia) were examined pre- and post-partum. Although the defense of offspring from predators may be expected to be a major component of maternal care, mothers rarely defended their offspring from raiding sea lions, possibly due to the high risks involved in attacking a large and potentially very dangerous predator. The costs of defending the pup from sea lions appeared to outweigh the potential benefit of increased survival of the pup, due to the already high pup mortality at the site. Maternal defense from conspecifics may also be a possible function of female aggression. Females with newborn pups were more aggressive towards other females than were females without pups, particularly during the perinatal attendance period. They threatened a higher proportion of approaching females and won more aggressive encounters postpartum. However, mothers of surviving pups did not appear to be any more aggressive, their pups did not receive any fewer threats from unrelated females, nor did they reside in areas of less aggression, than mothers whose pups died. Aggression towards male conspecifics appeared to serve a further purpose, as females threatened approaching adult and subadult males regardless of whether the females had a pup. Unlike colonially breeding phocid pinnipeds, there seems to be no correlation between increased maternal aggression and neonate survival in the South American fur seal. This may be because females have to leave their offspring to forage when the offspring are still vulnerable to attack by unrelated conspecifics. Alternatively, maternal aggression may have been subjected to such intense selection that although it is responsible for increased pup mortality at the site, there is insufficient variability to measure differential consequences.
The anatomy, chemical composition, and metabolism of adipose tissue in wild polar bears (Ursus maritimus)
Authors: Pond Caroline M. , Mattacks Christine A. , Colby Richard H. , Ramsay Malcolm A.
Published: July 2008

Adipose tissue was dissected completely from 14 polar bears (Ursus maritimus) killed in the southeastern Northwest Territories and northern Manitoba in November 1988. Mean adipocyte volume, collagen content, the activities of hexokinase and phosphofructokinase, and the fatty acid composition of the triacylglycerols were measured in samples of adipose tissue from several superficial, intra-abdominal, and inter-muscular depots homologous to those of other terrestrial mammals. The total adipocyte complement was calculated from the mass of each depot and its site-specific adipocyte volume. All the adipose depots found in other Carnivora and most other mammals are present in polar bears. The superficial layer of adipose tissue in polar bears arises from thickening and lateral expansion of depots that are discrete in most other mammals. All depots except the cardiac adipose tissue expand with increasing fatness, but the superficial depots expand faster than any of the internal depots, almost entirely by adipocyte proliferation. The gross anatomy of the superficial adipose tissue is determined mainly by the effect of body mass on the ratio of the surface area of the body to its volume. The superficial depots account for a greater proportion of the total adipose tissue in larger bears and in fatter specimens. The total adipocyte complement is about two to three times greater than that predicted from allometric equations relating adipocyte complement to body mass in non-arctic carnivores. The fatty acid composition of the triacylglycerols in the adipose tissue of polar bears is similar to that of the milk and the serum, but there were fewer long-chain polyunsaturated fatty acids than in their principal prey, ringed seals. There was no clearcut biochemical evidence for the existence of a thermal gradient between the inner and outer sides of the superficial adipose tissue. We conclude that in spite of their arctic habitat, neither the gross distribution of adipose tissue of polar bears nor its biochemical properties are adapted to thermal insulation. The enlarged superficial layer of adipose tissue is primarily an adaptation to increased energy storage.
Allometry of the distribution of adipose tissue in Carnivora
Authors: Pond Caroline M. , Ramsay Malcolm A.
Published: July 2008

The gross masses of intra-abdominal viscera and superficial and intra-abdominal adipose tissue are compared in 41 randomly obtained Carnivora. The mass of the intra-abdominal viscera scales as (lean body mass)0.76. In a sample of 28 Carnivora native to the tropics or the temperate zone, in which dissectible adipose tissue is more than 8.4% of the total body mass, superficial adipose tissue scales isometrically to lean body mass, but intra-abdominal adipose tissue increases as (lean body mass)0.74. Comparable measurements from 13 adult and subadult wild polar bears (Ursus maritimus) fit these allometric equations, indicating that the partitioning of adipose tissue between internal and superficial depots can be fully explained by the fact that these animals are larger and more obese than most other Carnivora. There is no evidence for adaptation of the gross anatomy of the adipose tissue of polar bears to their semi-aquatic habits or arctic habitat.
Spongilla heterosclerifera Smith, 1918 is an interspecific freshwater sponge mixture (Porifera, Spongillidae)
Authors: Ricciardi Anthony , Reiswig Henry M.
Published: July 2008

A freshwater sponge classified as Spongilla heterosclerifera Smith, 1918 and reported only from Oneida Lake, New York, was considered to be an endangered species. Examination of the holotype specimen reveals that it is actually an interspecific mixture of two widely distributed sponges, Ephydatia muelleri (Lieberkühn) and Eunapius fragilis (Leidy). Spongilla heterosclerifera is therefore a junior synonym, in part, of both of these distinct species. Similar erroneous taxonomic interpretations of species mixtures have been documented and illustrate the importance of recognizing the possibility of species mixing when identifying freshwater sponge taxa.
Effects of predation risk on foraging behavior of juvenile rainbow trout (Oncorhynchus mykiss)
Authors: Angradi Ted R.
Published: July 2008

The effects of a simulated avian predator attack on the food intake and foraging behavior of wild juvenile rainbow trout, Oncorhynchus mykiss, were examined in laboratory streams. Exposure to a simulated predator attack reduced the amount of food eaten for several minutes after an attack. The percent reduction in foraging rate was not related to the base-line foraging rate of the fry, a measure of feeding motivation, indicating that fry were not balancing risk and hunger. Fry at risk responded differently from safe fry to individually presented food items. Following exposure to a simulated attack, fry initially ate fewer items than did nonattacked fry, but over the course of the 10-min experiment, fry at risk ate as much as safe fry, which suggests a degree of compensation for lost foraging opportunities. I hypothesized that fry at risk from overhead avian predators should avoid risk by temporarily suspending foraging, since the risk is acute, short-term suspension of foraging has low energetic costs, and compensation is often possible. Fry at risk from piscivorous fish should be sensitive to predator behavior and should balance risk and energy intake, since risk is more likely to be sustained, and prolonged suspension of foraging has a high energetic cost.
Postemergence development in Lycosa carbonelli Costa and Capocasale, L. thorelli (Keyserling), and their hybrid progeny (Araneae, Lycosidae): a comparative laboratory study
Authors: Francescoli Gabriel , Costa Fernando G.
Published: July 2008

Twenty-six juvenile wolf spiders belonging to each of three groups, Lycosa carbonelli and L. thorelli and their experimentally obtained hybrids, were raised; 11, 7, and 17, respectively, survived to the adult stage. Lycosa carbonelli averaged 8.1 moults to reach the adult stage, L. thorelli 9.7, and hybrids 8.6; no significant differences were observed between the sexes. Lycosa carbonelli required more time than the other groups between emergence from the egg sac and the first moult. The durations of the intermoult periods and total development were not significantly different among groups. In L. carbonelli and the hybrids, the duration of the intermoult periods increased during development. In L. thorelli the duration of the intermoult periods was fundamentally modified in relation (inverse) to temperature. The life-span of the adults was similar in the three groups: females generally lived longer than males. The initial delay in the development of L. carbonelli would contribute to a decrease in competition of small juveniles with those of L. thorelli, although adults would compete more. The characteristics of hybrids tended to be intermediate, though closer to those of L. carbonelli.
Annual variation in reproductive traits in the lizard Acanthodactylus erythrurus
Authors: Castilla Aurora M. , Barbadillo L. Javier , Bauwens Dirk
Published: July 2008

During a 2-year period we studied the reproductive and fat body cycles and reproductive characteristics (clutch size, egg size) of the oviparous lizard Acanthodactylus erythrurus in central Spain. Testes exhibited their maximal volume during April–June and decreased in size throughout the summer. Fat bodies of males were smallest during the spring mating period. Vitellogenesis started in May or June, with oviposition occurring during June–July. Female fat bodies declined in size during the period of yolk deposition. A delay in the timing of reproductive events in 1 year was associated with adverse weather conditions during early spring. During the "good" year, reproduction was initiated early enough to allow some females to produce a second clutch. Both clutch size and egg size increased with female body length, but did not vary between years. Environmental factors that induced temporal variation in the timing of reproduction and clutch frequency did not affect clutch characteristics.
Brood amalgamation and alloparental care in the Least Sandpiper, Calidris minutilla
Authors: Cooper John M. , Miller Edward H.
Published: July 2008

Least Sandpipers (Calidris minutila) were studied on the Queen Charlotte Islands, British Columbia, over five breeding seasons. Brood amalgamation and care of foreign chicks occur regularly, though at low incidence, among the approximately 90 breeding pairs there. Such behavior is probably important to chick survival and has little impact on adult fitness. Brood amalgamation and alloparental care appear to be widespread in calidridine sandpipers.
A fluorine-19 nuclear magnetic resonance study of 5-fluorouracil metabolism in Mesocestoides corti tetrathyridia
Authors: Novak Marie M. A. , Shimizu Katherine , Blackburn Barry J.
Published: July 2008

Fluorine-19 nuclear magnetic resonance spectra of live tetrathyridia of Mesocestoides corti incubated in 10 mM 5-fluorouracil (5-FU) showed that these larvae metabolize 5-FU to α-fluoro-β-ureidopropionic acid (FUPA), α-fluoro-β-alanine (FBA1) and fluoronucleotides (FNuct). This metabolism is predominantly catabolic, since as time progressed (up to 7 h) the 5-FU signal continuously decreased while the FBA1 signal correspondingly increased and the composite FNuct peak remained small. Similar spectra were obtained from acid extracts of tetrathyridia, except that an additional, very small fluoronucleoside (FNuc) composite peak could be detected. We found 5-FU to be unsuccessful in inhibiting the growth of M. corti tetrathyridia in mice; it is postulated that this was due to the failure of the larvae to effectively anabolize 5-FU.
In vitro evidence for sodium-dependent pH regulation in sea lamprey (Petromyzon marinus) red blood cells
Authors: Tufts Bruce L.
Published: July 2008

Factors influencing the pH of sea lamprey (Petromyzon marinus) erythrocytes were examined in vitro. The absence of extracellular Na+ caused a significant reduction in the erythrocyte pH. In addition, the protonophore 2,4-dinitrophenol was capable of reducing the erythrocyte pH when it was dissolved in dimethyl sulfoxide. In the presence of ouabain, a step increase in the carbon dioxide tension caused a large increase in the intracellular Na+ concentration, but the rate of increase was considerably reduced after the 1st hour. Even in the absence of ouabain, however, the intracellular Na+ concentration in erythrocytes equilibrated with 3% CO2 is much greater than that in erythrocytes equilibrated with 0.2% CO2. Together, these results suggest that Na+-dependent H+ movements, possibly Na+–H+ exchange, may have an important role in erythrocyte pH regulation in P. marinus. Moreover, the mechanism appears to be stimulated by the decrease in extracellular or erythrocyte pH associated with the increase in [Formula: see text]. Extracellular Na+ also has a significant impact on the CO2-transport properties of P. marinus blood. In the absence of extracellular Na+, the intracellular total CO2 concentration was significantly reduced, whereas extracellular total CO2 concentration, [Formula: see text], was significantly increased. Furthermore, in the no-Na+ saline, [Formula: see text] became dependent on the hematocrit; an increase in the number of erythrocytes resulted in an increase in [Formula: see text]. This result suggests that the erythrocyte membrane of P. marinus may be permeable to [Formula: see text].
The role of temperature in microhabitat selection by northern water snakes (Nerodia sipedon)
Authors: Robertson Ian C. , Weatherhead Patrick J.
Published: July 2008

Using field observations and laboratory experiments we examined the role of temperature in microhabitat selection by an eastern Ontario population of northern water snakes (Nerodia sipedon). From 1349 random transects through a marsh we found that basking activity peaked at 09:00 and then declined steadily until 14:00 before increasing again. Our ability to detect snakes depended upon the microhabitat they occupied, and to the time of day when the snakes were encountered in water. In the field, temperatures of basking snakes averaged (±SE) 26.3 ± 0.7 °C (n = 36), while captive snakes in a thermal gradient showed a narrower selectivity, averaging 27.7 ± 0.4 °C (n = 21). The temperatures of basking snakes never exceeded 33 °C, even though a model snake placed in the sun reached 48 °C, suggesting that the snakes were thermoregulating to prevent overheating. In both the field and enclosures, water snakes basked more frequently as the temperature of the air increased relative to the water. Experimental manipulation of water temperature relative to air temperature revealed that temperature influenced microhabitat selection independently of circadian patterns. Finally, when in water, snakes tended to frequent habitats where leopard frogs (Rana pipiens), a common prey species, were most abundant, suggesting that prey distribution may also be an important component of water snake habitat selection.
Brook trout (Salvelinus fontinalis) embryo habitat and timing of alevin emergence in a lake and a stream
Authors: Snucins E. J. , Curry R. Allen , Gunn J. M.
Published: July 2008

We assessed redd characteristics of brook trout in a lake and a stream and alevin emergence in the lake. Both populations spawned over upwelling groundwater. In the lake site fish deposited eggs 7–19 cm in the sediment in an egg pocket that contained large-particle substrate. A similar vertical distribution of eggs (16–20 cm) and substrate occurred in the stream; however, in addition to the digging action of the female, the flow conditions in the stream appeared to produce coarser surface sediment conditions. Groundwater offered a high concentration of dissolved oxygen and, relative to lake water, less variable temperature and pH regimes for incubating eggs. Alevin emergence extended over a 71-day period, coinciding with the spring thaw and an episodic pH depression.
Dose-dependent effect of testosterone on the induction of eclipse coloration in castrated wild mallard drakes (Anas platyrhynchos L.)
Authors: Haase Eberhard , Schmedemann Reiner
Published: July 2008

Four groups of adult wild mallard drakes that had been previously castrated were injected daily with 5, 1, or 0.2 mg testosterone dissolved in propanediol or with the vehicle alone. The injections started on February 29 and continued for 64 days during the natural breeding season of the species. The birds were kept in outdoor aviaries in a seminatural environment in Kiel (54°N). By the end of the postnuptial molt in mid-July the groups differed markedly in coloration. The vehicle-injected control group had regained an almost typical nuptial plumage, whereas the castrates that had received the highest daily dose of testosterone exhibited an almost complete eclipse plumage. The two other groups showed an intermediate pattern, with about 40% eclipse coloration in the group injected with 1 mg testosterone/day and about 10% eclipse coloration in the group that had received 0.2 mg testosterone/day. The possible role of the aromatization of testosterone to estrogens in the induction of the eclipse coloration is discussed.
Examining hypotheses about feeding strategies of white-tailed deer
Authors: Weckerly Floyd W. , Kennedy Michael L.
Published: July 2008

We examined whether the forage abundance hypothesis or the selective quality hypothesis could explain the feeding strategies of white-tailed deer (Odocoileus virginianus) on Hatchie National Wildlife Refuge in Haywood County and the Ames Plantation in Fayette and Hardeman counties, Tennessee (from autumn 1983 to summer 1986). The botanical composition of the diets on Ames was characterized by agricultural crops, browse, and acorns in autumn and winter, and browse, forbs, and agricultural crops in spring and summer. Acorns were common in autumn and winter diets on Hatchie, as were browse and agricultural crops. Spring and summer diets were high in browse and forbs and, to a lesser extent, agricultural crops. Diets were lower in crude fat, crude protein, and fiber in spring and higher in most nutritional parameters in autumn and winter at both sites. Neither the nutritional value nor the abundance of forages had a strong impact on diet in any of the seasons and years of the study as predicted by the forage abundance hypothesis. Spearman's correlation coefficients of forage consumption and abundance in spring and summer were positive and much higher than in autumn and winter at both sites. Deer are apparently less selective during seasons of lower dietary fiber and higher forage abundance. Our data support the selective quality hypothesis as a more appropriate model of feeding strategies for white-tailed deer.
The carabid fauna (Coleoptera: Carabidae) during postfire regeneration of boreal forest: properties and dynamics of species assemblages
Authors: Holliday N. J.
Published: July 2008

Following an intense forest fire, carabid beetles were sampled by pitfall trapping in a burned site that had been dominated before the fire by aspen, Populus tremuloides, in a second burned site that had been dominated by conifers (Picea spp.), and in matching unburned sites. In principal-components ordination, carabid species assemblages in burned sites were initially distinct, but at the end of the study were similar to those in the unburned aspen site. The assemblage in the burned aspen site approached its final position more rapidly than that in the burned conifer site. There were fewer individuals and fewer species in burned sites, but the logarithmic series α and the evenness were unaffected by burning. Species gain and species loss were used as indices of colonization rate and extinction rate, respectively. Species loss did not differ significantly between burned and unburned sites. In unburned sites, species gain was related to previous numbers of species caught in the way expected if gain was limited by the pool of potential colonist species. In burned sites, species gain was initially similar to that in unburned sites, but later gain was less than expected. Low species gain, coupled with ongoing species loss, was responsible for the small number of species caught in burned sites. It is suggested that domination of the burned sites by aspen saplings limited the establishment of arriving colonist species and so depressed species gain in the later stages of the study.
Phenotypic and genetic variation in the stridulatory organs of male decorated crickets, Gryllodes sigillatus (Orthoptera: Gryllidae)
Authors: Sakaluk Scott K. , Burpee Dianne M. , Smith Robert L.
Published: July 2008

Cricket songs are produced by a file–scraper mechanism, present only on the modified forewings of males, which causes a thickened membrane on each wing (the harp) to resonate and radiate sound. We examined the pattern of phenotypic variation and covariation in male body size, file tooth number, and harp area in decorated crickets, Gryllodes sigillatus, and obtained preliminary estimates of the additive genetic variance underlying these traits. Male body mass and harp area were positively correlated, and neither trait showed any appreciable evidence of genetic variance. We attribute the lack of genetic variance in harp area to selection that favours larger harps because of their enhanced signalling properties and, indirectly, to sexual selection for large male body size. In contrast, the number of file teeth did not covary with male body mass, and variation in file tooth number had a strong genetic component as indicated by a full-sib analysis and parent–offspring regression.
Oxygen stores and aerobic dive limit of ringed seals (Phoca hispida)
Authors: Lydersen Christian , Ryg Morten Skrede , Hammill Mike Osborne , O'Brien Peter James
Published: July 2008

In this paper we measured total lung capacity, myoglobin content of muscle tissue, and hemoglobin content of the blood of ringed seals (Phoca hispida). Based on this information and body composition analysis we estimated the total available oxygen stores of a diving average adult ringed seal (standard length 129 cm, body mass 73.7 kg) to be 4.5 L. The aerobic dive limit for a ringed seal of this size was estimated to be 8.9 min. Diving data from previous studies show that less than 4% of the dives of adult free-living ringed seals exceed this aerobic dive limit. Based on information from the literature on maximum breathhold capacity and observed maximum dive times of ringed and Weddell seals (Leptonychotes weddellii), the maximum breathhold capacity of adult ringed seals was suggested to be 26.1 min.
Body size, age distribution, and reproduction in a northern population of wood turtles (Clemmys insculpta)
Authors: Brooks Ronald J. , Shilton Cathy M. , Brown Gregory P. , Quinn Norman W. S.
Published: July 2008

A population of the wood turtle (Clemmys insculpta) was studied on the east side of Algonquin Provincial Park, Ontario, from 1987 to 1990. A total of 77 adults (56 females, 21 males) and 13 juveniles were captured, measured, and individually marked. Age at maturity was 17–18 years at a minimum carapace length of 185 mm for females and 199 mm for males. Our data supported the hypothesis that turtles in northern populations are larger and older at maturity than are those in southern populations. For 21 nests, mean clutch size was 8.8 eggs and egg mass was 96 g. Predators destroyed 15 of 17 nests in 1990, and had injured 60% of adult turtles observed. Therefore, our population had low recruitment, few juveniles, and high levels of predation on nests and adults. Comparisons among females refuted two predictions from optimal egg size theory. Mean width and mass, but not length, of eggs correlated positively with female size, and correlated positively with clutch size, even after effects of body size were removed by partial correlation. However, smaller females in the population had relatively longer eggs than did larger females, whereas the Algonquin females have absolutely smaller eggs than do much smaller females in a New Jersey population.
Rhabdochona rotundicaudatum n.sp. and a redescription of R. cascadilla Wigdor, 1918 (Nematoda: Thelazioidea) from minnows in southern Ontario, Canada
Authors: Byrne Philip J.
Published: July 2008

Rhabdochona rotundicaudatum n.sp. is described from hornyhead chub (Nocomis biguttatus (Kirtland, 1841)), and a redescription of R. cascadilla Wigdor, 1918 from common shiner (Notropis cornutus Mitchill, 1817) is provided. Rhabdochona rotundicaudatum n.sp. most closely resembles Rhabdochona cascadilla, but is distinguished by the size and form of the right spicule and the form of the tail in both sexes. Rhabdochona rotundicaudatum n.sp. has a rounded tail tip whereas R. cascadilla has a pointed tail tip. Females of both species produce ovoidal eggs without filaments or floats. No other Rhabdochona species from North America have both a rounded tail tip and smooth eggs. Adult R. rotundicaudatum n.sp. were also recovered from a mayfly (Ephemeroptera). The occurrence of an adult spirurid nematode in an invertebrate is rare; adult spirurids are normally found only in vertebrate (definitive) hosts.
On the biology of Rhabdochona rotundicaudatum and R. cascadilla (Nematoda: Thelazioidea) in stream fishes from southern Ontario, Canada
Authors: Byrne Philip J.
Published: July 2008

The seasonal pattern of parasite acquisition, maturation, and loss of Rhabdochona cascadilla Wigdor, 1918 and Rhabdochona rotundicaudatum Byrne, 1992 collected in common shiners (Notropis cornutus Mitchill, 1817) from the Eramosa River in southern Ontario, Canada, was followed. Adult R. cascadilla and R. rotundicaudatum appeared in large numbers in late spring. Females of both species matured quickly and contained embryonated eggs in June and July. Prevalence and intensity of R. cascadilla tapered off throughout the summer but never reached zero. Prevalence and intensity of R. rotundicaudatum decreased rapidly through the summer and only one adult was recovered after August 1. Rapid acquisition of worms by fish in late spring seems to be facilitated by the convergence of the intermediate and definitive hosts in space and time. Convergence with common shiner and the intermediate host of R. rotundicaudatum, Ephemera simulans Walker, 1853 (Ephemeroptera), occurs in the stream riffle areas during late May and early June. Results suggest that the intermediate host of R. cascadilla and the common shiner also converge during the spring, but because the intermediate host of R. cascadilla was not found, this could not be confirmed. Also, the presence and rapid maturation of adult R. rotundicaudatum are probably related to their acquisition as adults from the mayfly intermediate host. These findings support the hypothesis that the presence of precocial nematode parasites in the intermediate host represents a transmission strategy that accelerates gametogenesis in the final host in order to take advantage of the limited time and space available for transmission.
Body weight and population dynamics: cyclic demography in a noncyclic population of the field vole (Microtus agrestis)
Authors: Agrell J. , Erlinge S. , Nelson J. , Sandell M.
Published: July 2008

Differences in body weight, individual growth rate, survival, and recruitment of young between years were analysed in a noncyclic population of field voles (Microtus agrestis) to determine the respects in which this population differed from cyclic ones. Large differences in body weight, survival of both sexes, and recruitment of young existed between years. Over 4 years, body weight was positively related to population growth (measured as the change in density over the reproductive season). Also, the recruitment of young was higher in years when female voles were heavier and survived longer. Thus, the occurrence of high body weights in years when density is increasing or high is not a unique feature of populations showing cyclic density changes. Our findings indicate that survival is the primary factor connecting body weight to population growth. Neither genotypic changes nor variable predation pressure were likely to account for the between-years differences in body weight, survival, and recruitment. Instead food quality and (or) quantity, possibly affected by density, seem to be the primary extrinsic factors influencing individual quality, thereby influencing population growth. We propose that this population of field voles does in fact carry the potential for cyclic density changes, although predation prevents the manifestation of such a pattern.
Effects of the insecticide Bacillus thuringiensis on Sorex cinereus (masked shrew) populations, diet, and prey selection in a jack pine plantation in northern Ontario
Authors: Bellocq M. I. , Bendell J. F. , Cadogan B. L.
Published: July 2008

A simulated operational spray with Bacillus thuringiensis in a jack pine (Pinus banksiana) plantation near Gogama, Ontario, showed effects of the insecticide on the population structure, diet, and prey selection of the masked shrew, Sorex cinereus. During the pretreatment period, the abundance and population structure of S. cinereus were similar in the control and experimental areas. Although the total abundance of shrews was also similar after spraying, there were fewer adult males and more juveniles in the treated area than in the control. The emigration of adult males was apparently increased after spraying. Lepidopteran larvae and Araneae were the most abundant items in the diet. After spraying, more lepidopteran larvae were eaten on the control than on the treated area. Juveniles and adult females but not adult males shifted from lepidoptran larvae to alternative prey in the treated area. Generalist insectivores such as S. cinereus are more likely to control the abundance of arthropods and less likely to be impacted negatively by selective insecticides such as B. thuringiensis.
Morphological and functional aspects of the female gonad of the conchostracan Leptestheria dahalacensis Rüppel, 1837 (Crustacea, Branchiopoda), and a comparison with the gonads of other Branchiopoda
Authors: Tommasini Stefano , Sabelli Franca Scanabissi
Published: July 2008

The structure of the female gonad of the conchostracan Leptestheria dahalacensis Rüppel, 1837 was studied. The ovary consists of a pair of cellular cords that undergo cyclical changes from an almost straight, compact form to one that is heavily branched, then having a ductlike appearance each time the eggs mature and are spawned. The latter are uniformly distributed in the gonadal stroma and are mixed with somatic cells, largely of a glandular type. The material produced by the glandular cells envelops the eggs during their descent towards the oviducts, and has the sole function of keeping the spawn together. A comparative analysis of the branchiopod female gonad has led us to reconsider their phylogeny, and to hypothesise a polyphyletic origin of the Conchostraca.
Microsporidian hyperparasites and bacteria associated with Pseudodiplorchis americanus (Monogenea: Polystomatidae)
Authors: Cable J. , Tinsley R. C.
Published: July 2008

This is the first report of a microsporidian hyperparasite in a monogenean. Every stage in the life cycle of the polystomatid Pseudodiplorchis americanus was infected (prevalence 11%). Ultrastructural examination revealed microsporidians within most tissues, but the heaviest aggregations occurred in the external surface layer of the larvae, especially the tegumental ciliated cells where they may interfere with exciliation. Adult worms also harboured a bacterium (prevalence 55%) that was largely restricted to the gut lumen and therefore probably ingested. Transmission of the microsporidian may occur via ingestion of host tissue, but infection within the germ cells and encapsulated embryos in utero demonstrates transovarian and trans-uterine transfer. The oncomiracidia can be already infected at the time of transmission, carrying the microsporidians to newly invaded vertebrate hosts. Heavy microsporidian infections are associated with cellular damage in developing and adult monogeneans and may have a direct effect on the population biology of P. americanus.
Sex ratio of hatchling loggerhead sea turtles: data and estimates from a 5-year study
Authors: Mrosovsky N. , Provancha Jane
Published: July 2008

Hatchling loggerhead sea turtles (Caretta caretta) were collected over three nesting seasons from a rookery at Cape Canaveral, Florida. From data on the distribution of nests over the season, we estimated that 92.6–96.7, 94.7–99.9, and 87.0–89.0% of the hatchlings produced on this beach in 1986, 1987, and 1988, respectively, were females. These skewed sex ratios were consistent with the fact that for most of the season, sand temperatures were above the pivotal level for loggerhead turtles. The present results show that the female-biased sex ratio reported previously by these authors for the 1986 nesting season at this site was not an isolated, atypical event. In addition to a total of 3 years of sampling for sex ratio, measurements of beach temperatures at the depth of turtle nests were extended to cover 5 years. These temperatures were commonly above the pivotal level. The strongly female-biased hatchling sex ratio found in this population of loggerhead turtles poses theoretical challenges. It may also complicate conservation efforts, since global warming might be expected to skew the sex ratio still further toward females.
Genetic divergence and the Pleistocene history of the alpine butterflies Boloria improba (Nymphalidae) and the endangered Boloria acrocnema (Nymphalidae) in western North America
Authors: Britten Hugh B. , Brussard Peter F.
Published: July 2008

Allozymes were assayed at 20 presumptive loci in increasingly isolated populations of alpine butterflies in the Boloria improba species-group including the endangered Boloria acrocnema. Populations of this Holarctic group were sampled along the Rocky Mountain Cordillera from the Yukon Territory to Colorado. Samples from a more widely distributed and generalist butterfly, Boloria titania, were assayed at 18 presumptive loci for comparative purposes. Estimates of heterozygosity, percent polymorphic loci, mean number of alleles per locus, genetic identity, and distribution of regional and private alleles indicated that the current distribution of butterflies in the B. improba group is the result of a vicariance event. During the last Wisconsin glacial maximum (20 000 to 18 000 years BP) the range of ancestral B. improba was split into Alaskan refugial populations and southern glacial-margin populations. Subsequent dispersal into an ice-free corridor 12 000 to 10 000 years BP from the Alaskan refugial populations gave rise to British Columbia and Alberta B. improba populations. Results from B. titania support these findings.
Pregnancy rates and serum progesterone levels of polar bears in western Hudson Bay
Authors: Derocher Andrew E. , Stirling Ian , Andriashek Dennis
Published: July 2008

Blood samples were collected from 354 female polar bears (Ursus maritimus) on 476 occasions between 1982 and 1990. Serum progesterone concentrations were determined to evaluate reproductive status. Progesterone levels greater than 2.5 ng/mL were considered indicative of pregnancy in autumn. Of 85 females classified as pregnant that were seen the following year, 67% were with cubs and 33% were without cubs. Possible explanations for the large proportion of females with apparent reproductive failure include neonatal mortality, failure to implant, or abortion. The minimum weight of a confirmed pregnant female in autumn was 189 kg, but approximately 10% of the suspected pregnant females were below this and may have had insufficient fat stores to fast through the winter and produce cubs. Based on progesterone levels, implantation appeared to occur between mid-September and mid-October, likely followed by parturition from mid-November to mid-December. The annual pregnancy rate of solitary females, as determined by progesterone concentrations, varied between 82.4 and 100%, but the differences were not significant. Females bred for the first time between 3 and 5 years of age, at an average of 4.1 years. The age-specific pregnancy rates of 3- to 4-year-old females and females 21 years and older were lower than those of other age-classes. However, some older females appear to retain reproductive competency throughout their life.