bluuebunny/crossref_metadata_2025 huggingface dataset:
Ovary development in bumble bee queens: the influence of abdominal temperature and food availability
Authors: Vogt F Daniel , Heinrich Bernd , Plowright Catherine
Published: April 2011

The influence of abdominal temperature (Tab) on ovary development was determined for queen bumble bees (Bombus impatiens) recently aroused from hibernation. Ovary growth was accelerated in queens with high Tab: after 6 days, laboratory-reared queens with mean Tab = 24°C showed negligible ovary growth (compared with the ovaries of queens sacrificed before arousal from hibernation), whereas queens with mean Tab = 27 and 32°C exhibited near 35 and 135% increases, respectively. The presence of pollen and honey in the diet also had a pronounced effect on ovary development. Queens provided with pollen and honey ad libitum nearly tripled the mass of their ovaries in 8 days, whereas bees fed pollen alone or honey alone showed about a 50% increase. Queens provided with neither pollen nor honey exhibited about a 25% increase in ovary mass during the same period (all queens presumably can gain sustenance for ovary development from the reserve of food left in their honey crop when they emerge from hibernation). These results show that ovary growth can be rapid when queens maintain a high Tab with access to ample pollen and nectar, thereby enabling them to potentially accelerate colony founding. High Tab and nearly continuous access to food are factors that enable bumble bees to successfully rear colonies in a short growing season.
Broad-frequency modulation in cricket (Orthoptera, Grylloidea) calling songs: two convergent cases and a functional hypothesis
Authors: Desutter-Grandcolas L
Published: April 2011

Broad-frequency modulations in the calling songs of two cricket species (Eneoptera guyanensis and Lerneca fuscipennis) are documented. Such modulations were considered improbable in cricket songs, owing to the functioning mode of the cricket stridulum. Some species were known to emit sounds at frequencies that differed according to ambient temperature (thermometer crickets (Oecanthus spp.) among others), and small frequency modulations usually occur in the calling songs of many species at the beginning and at the end of each acoustic pulse. This is the first time, however, that broad-frequency modulations have been documented in the same burst of song and under constant ambient conditions. Stridulum analyses show that both studied species are characterised by a heterogeneous stridulatory file in which the teeth are either irregularly distributed or have an unusual structure: in L. fuscipennis the teeth are very close together in one part of the file and very widely separated in another, whereas in E. guyanensis, half of the teeth are divided by a median furrow into two crests. Such features of the stridulatory file have never been observed in crickets before. A functional hypothesis that could explain these frequency modulations is that each file section, when dropped by the plectrum, would set into vibration a different area of the stridulum characterised by a particular resonance frequency. This hypothesis is corroborated by the ultrastructure of the stridulum of the two studied species. The evolutionary and biological significance of frequency modulations in cricket calls is briefly discussed.
Cellular organization and fine structure of type II microtrich sensilla in gammaridean amphipods (Crustacea)
Authors: Steele V J , Steele D H
Published: April 2011

The cellular organization of type II microtrich sensilla was studied in male Anonyx lilljeborgi Boeck, 1871 (Lysianassoidea) by light and transmission electron microscopy. The sensillum consists of two bipolar sensory neurons and three concentric sheath cells. The sensory cell bodies are subepidermal. In each sensillum both dendrites are enclosed by the thecogen cell process. The inner dendritic segments are filled with mitochondria and lucent vesicles and expand in the epidermis into a spindle-shaped swelling. One of the neurons gives rise to two cilia and the second to a single cilium. These three outer dendritic segments lie in the receptorlymph cavity. The dendritic sheath, secreted by the thecogen cell process, completely ensheaths the outer dendritic segments. The trichogen (middle) cell and the tormogen (outer) cell incompletely enclose the thecogen cell, but their processes form autojunctions around the dendritic sheath in the apical epidermis. In premolt, the trichogen cell processes project into the exuvial space. The cytoplasm of the tormogen cell and the bordering epidermal cells contains coarse osmiophilic inclusions. All the cells of the sensillum are joined by desmosomes. The sensilla structurally resemble chemosensory (gustatory) insect sensilla.
Prolonged storage of spermatozoa in the genital tract of female Mexican big-eared bats (Corynorhinus mexicanus): the role of lipid peroxidation
Authors: León-Galvan Miguel Angel , Fonseca Teresa , López-Wilchis Ricardo , Rosado Adolfo
Published: April 2011

The results of this work support the existence of sperm storage in Corynorhinus mexicanus, a vespertilionid bat endemic to Mexico, and evidence is presented that modulation of peroxidative toxicity plays a role in the mechanism of prolonged sperm storage in Chiroptera. Spermatozoa were obtained from C. mexicanus by retrograde perfusion of the cauda epididymis, and from genital washings from previously inseminated females captured during reproductive activity. Ejaculated pig spermatozoa were simultaneously studied as controls. Lipid peroxidation was determined in both the presence and absence of genital secretions obtained from previously inseminated female C. mexicanus by measuring malondialdehyde generated during aerobic incubation of spermatozoa suspensions. The number of spermatozoa recovered from the cauda epididymis decreased steadily from November through January. Corpora lutea were observed in January. None of the female bats captured between October and January were pregnant, but some females captured in mid-February were already pregnant. Spermatozoa of C. mexicanus showed substantial lipid peroxidation activity (0.64 ± 0.11 nmol malondialdehyde was produced by 108 spermatozoa per 22 h), about half of that observed in ejaculated pig spermatozoa. Incubation of pig and C. mexicanus spermatozoa in the presence of bat female genital tract washings induced highly significant concentration-dependent inhibition of lipid peroxidation.
Fine structure of antennal sensilla of the female sphinx moth, Manduca sexta (Lepidoptera: Sphingidae). I. Trichoid and basiconic sensilla
Authors: Shields VDC , Hildebrand J G
Published: April 2011

Olfaction is the principal sensory modality through which insects locate their food sources, mates, and oviposition sites. Insects offer certain advantages as experimental models for the study of mechanisms of olfaction, and a thorough knowledge of the antennal olfactory sensory cells is essential for such studies. While the sphinx moth, Manduca sexta, has proved to be an especially favorable experimental model in studies of pheromone processing in males, little is known about the female olfactory system, including the antennal olfactory sensilla. In this and another paper in this series, we present the first thorough investigation of the structure, innervation, number, and distribution of sensilla on the antennal flagellum of female M. sexta. The flagellum of the female moth bears eight morphological types of sensilla: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex. In this paper, we describe the two types of trichoid and two types of basiconic sensilla. The first type of trichoid sensillum, a long hairlike sensillum averaging 34 µm in length, is innervated by two bipolar sensory cells, and the second type, a shorter hairlike sensillum averaging 26 µm in length, is innervated by either one or three bipolar sensory cells. The first type of basiconic sensillum is a long peg, averaging 22 µm in length, and the second is a shorter peg, averaging 15 µm in length. Both types of basiconic sensilla are innervated by three bipolar sensory cells. These trichoid and basiconic sensilla have structural features characteristic of insect olfactory sensilla.
Variation in the echolocation calls of the hoary bat (Lasiurus cinereus): influence of body size, habitat structure, and geographic location
Authors: Barclay Robert MR , Fullard James H , Jacobs David S
Published: April 2011

The echolocation calls of bats vary according to the task being undertaken by the individual. Within species, there is evidence for geographic, habitat, and individual variation, although it is often difficult to separate these factors and rule out variation in recording or analysis techniques. We studied the variation in echolocation call design of the hoary bat (Lasiurus cinereus) by analyzing calls, recorded in the same manner, from free-flying bats at one site in Manitoba and at four sites in the Hawaiian islands. Sites varied in terms of the proximity of the bats to vegetation. As predicted, individuals from the larger subspecies (Lasiurus cinereus cinereus; Manitoba) used lower frequency calls than did the smaller individuals in Hawaii. Within the same habitat type (open or closed), there was evidence for differences in echolocation call design between populations on different islands. On the island of Hawaii, bats at a single site used shorter higher frequency calls when foraging within the vegetation than when foraging in the open, again as predicted. However, bats foraging in different sites used calls with the opposite characteristics to those predicted on the basis of the openness of the site. Although there are several possible explanations for this, we suggest that prey encounter rate and the ability of bats to augment acoustic prey detection with visual information may be important.
Anoxic cardiac performance in Amazonian and north-temperate-zone teleosts
Authors: Bailey J R , Val A L , Almeida-Val VMF , Driedzic W R
Published: April 2011

Amazonian fish face periodic conditions of hypoxic water not commonly encountered by most other species. We examined the impact of simulated anoxia on cardiac performance of Amazonian species relative to north-temperate-zone species to assess whether the ability to maintain anoxic heart performance is related to either respiratory strategy or geographic location. Four Amazonian species (acará-açu (Astronotus ocellatus), acari-bodó (Lipossarcus pardalis), tambaqui (Colossoma macropomum), and tamoatá (Hoplosternum littorale)) and four north-temperate-zone species (American eel (Anguilla rostrata), bullhead (Ictalurus punctatus), yellow perch (Perca flavescens), and rainbow trout (Oncorhynchus mykiss)) were studied. The Amazonian species display a range of respiratory modes from obligate gill-breather to facultative air-breather. The performance of isolated ventricular strips under conditions of impaired oxidative phosphorylation was monitored under the same conditions of temperature (25°C) and contraction frequency (30 bpm) for all species. In all cases, ventricular strips showed a decrease in the force of contraction with sodium cyanide (NaCN) treatment. Ventricular strips from two Amazonian and one north-temperate-zone species showed signs of recovery from NaCN treatment. There was considerable diversity in the ability of ventricular strips to develop force under conditions of impaired oxidative phosphorylation that was not related to the ability to obtain oxygen from the air or to geographic location. However, there was a major difference between Amazonian and north-temperate-zone species in the ability of ventricular strips to maintain resting tension under NaCN treatment. Resting tension increased under conditions of simulated anoxia in ventricular strips from all north-temperate-zone species, but there was no change in resting tension in ventricular strips from Amazonian species. We propose that hearts from the Amazonian species are better able to reduce cytoplasmic calcium levels, possibly through a more highly developed sarcoplasmic reticulum.
Latitudinal variation in the life cycle of allodapine bees (Hymenoptera; Apidae)
Authors: Cronin Adam L , Schwarz Michael P
Published: April 2011

The life cycles of Exoneura robusta and Exoneura angophorae are examined in four populations along the eastern seaboard of Australia, where climate ranged from temperate in the south to subtropical in the north over a latitudinal range of approximately 10°. These species were univoltine throughout the range examined and most colonies produced a single brood. Timing and duration of brood development in E. robusta varied between sites, with brood development being more rapid in northern populations; there was only weak evidence of any effect of latitude in E. angophorae. All populations of E. angophorae exhibited a small proportion of doubly brooded colonies, but doubly brooded colonies were found only in northernmost populations of E. robusta. Two-brooded colonies can give rise to opportunities for sib rearing, which can alter the indirect fitness benefits for alloparental care. Our results indicate that there is an effect of climate on sociality in E. robusta but no, or very little, such effect in E. angophorae.
Genetics of the tsetse fly Glossina morsitans submorsitans Newstead (Diptera: Glossinidae): further mapping of linkage groups I, II, and III
Authors: Gooding R H , Challoner C M
Published: April 2011

Standard mapping procedures were used to map four loci in linkage group I (the X chromosome), two loci in linkage group II, and two loci in linkage group III of Glossina morsitans submorsitans. In the presence of the allele Srd (the distorter allele favoring production of female offspring), no recombination occurred between any of the following loci: Pgm (phosphoglucomutase), wht (white eye color), Est-X (a thoracic esterase), and Sr (sex-ratio distortion). However, in the absence of Srd (i.e., in females homozygous for Srn, the allele that permits males to sire both female and male offspring in approximately equal numbers), the loci Pgm and wht were separated by 23 ± 4.0% recombination (map distance). These results indicate that ourG. m. submorsitans strains carry two forms of the X chromosome, designated XA and XB. In support of this interpretation, two lines of G. m. submorsitans were established: in both lines, males with wild-type eyes sired families that were almost exclusively female, while males with white eyes sired families having males and females in approximately equal numbers. Two loci, Ao (aldehyde oxidase) and Est-1 (a thoracic esterase) were separated by 6.1 ± 2.3% recombination in linkage group II, and two loci, Mdh (malate dehydrogenase) and Pgi (phosphoglucose isomerase), showed 51.9 ± 4.9% recombination in linkage group III.
Profiling the peptides in two neurohemal organs, the sinus gland and lateral nervous plexus of terrestrial isopods (Crustacea), by mass spectrometry
Authors: Martin G , Sorokine O , Moniatte M , Juchault P , Dorsselaer A Van
Published: April 2011

A comparison was made of the ultrastructure of two neurohemal organs: the sinus gland and the lateral nervous plexus of the Oniscidea (Crustacea). Reverse-phase chromatography clearly showed that the two organs contain different neuropeptides. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry proved to be an efficient tool for detecting the molecules stored in a single freshly dissected neurohemal organ. All the results combined lead us to emphasize that the sinus gland of Oniscidea stores mainly crustacean hyperglycemic hormone (CHH) and vitellogenin-inhibiting hormone; these two hormones were not characterized in the lateral nervous plexus (LNP). Smaller peptides and other molecules of the CHH family might be released by the LNP in the vicinity of the Y-organ (the ecdysteroid-producing gland).
Habitat fragmentation and the distribution of amphibians: patch and landscape correlates in farmland
Authors: Kolozsvary Mary B , Swihart Robert K
Published: April 2011

We studied the effects of agriculturally induced fragmentation of forests and wetlands on amphibian assemblages and their distribution in a landscape of the midwestern United States. Potential breeding pools and upland areas in 30 forest patches of various sizes and degrees of isolation were intensively sampled for amphibians during April through August 1996 and March through August 1997 in Indiana. Species presence was documented using pitfall traps, anuran vocalization surveys, and cover-board sampling for adults and minnow traps and dip nets for larvae. Amphibian, anuran, and salamander assemblages were nonrandomly distributed across the landscape. American toads (Bufo americanus) and gray treefrogs (Hyla versicolor) were ubiquitous, whereas the distributions of several other species were ordered in a predictable manner. Logistic regression was used to develop predictive models of probabilities of occurrence for species in response to forest and wetland patch and landscape variables. Occurrence of redback salamanders (Plethodon cinereus) was positively associated with the area of a forest patch. Occurrence of ranid frogs was positively associated with proximity of wetlands for three of four species, and occurrences of smallmouth salamanders (Ambystoma texanum), spring peepers (Pseudacris crucifer), and western chorus frogs (Pseudacris triseriata) were related to the degree of wetland permanency. Multiple linear regression revealed that species richness was greatest for wetlands with intermediate degrees of permanency. The observed nonrandom distribution exhibited by several amphibians suggests that they respond to landscape-level attributes. Moreover, species differed substantially in the nature of their responses to fragmentation, consistent with differences in their life history and ecology.
Metabolism of [3-13C]alanine in liver of mice infected with cysticerci ofTaenia crassiceps
Authors: Corbin I , Blackburn B J , Novak M
Published: April 2011

Carbon-13-decoupled proton spin-echo nuclear magnetic resonance (NMR) spectroscopy, with and without13C population inversion, was used to study carbon flow between the host and the parasite in the mouse - Taenia crassiceps system. This NMR analysis revealed that 2 h after intraduodenal injection of [3-13C]alanine, livers from both uninfected mice and those infected with cysticerci of T. crassiceps contained13C label in glycogen, glucose, succinate, glutamate, alanine, and lactate. Livers of infected animals had a lower percentage of13C in alanine, indicating increased utilization of the substrate. In addition, infected mice had a lower concentration of total hepatic glucose and glutamate. The data are consistent with an increased rate of gluconeogenesis in the liver of infected animals. Cysticerci possessed13C label in glucose, acetate, alanine, and lactate. Since these metacestodes are unable to make glucose de novo from pyruvate, labelled glucose found in cysticerci had to be newly synthesized via the host gluconeogenic pathway and then siphoned off by the parasite.
Effects of food abundance and wind on the use of tree lines by an insectivorous bat, Pipistrellus pipistrellus
Authors: Verboom B , Spoelstra K
Published: April 2011

We tested the hypotheses that the distance bats fly from tree lines depend on food abundance and protection from wind. We monitored the activity of pipistrelle bats (Pipistrellus pipistrellus) and measured insect abundance and wind speed and direction at fixed distances up to 50 m from tree lines. We compared bat behaviour in different situations: with and without wind and with low and high insect abundances in adjacent open areas. In all situations, pipistrelle bats' activity decreased with increasing distance from the tree line. Within nights, we found no effect of wind speed on bat activity (sound recorded per 5 min) on the leeward side of the tree lines. Between nights, however, bats concentrated their activities closer to the tree lines at high wind speeds or angles of incidence of wind from 45° to 90°. A significant relationship between bat and insect abundances was found only when the tree line was bordered by insect-rich grassland. Since wind and insect abundance only partly explained the distances bats flew from tree lines, two alternative explanations, namely predator avoidance and the use of tree lines as acoustic landmarks, are discussed. Pipistrelle bats using a double row of trees as a commuting route at dusk flew mainly between the tree lines, regardless of insect abundance or wind speed. It is argued that predator avoidance explains this behaviour, being a constraint on movements of bats at relatively high light levels. At high wind speeds and angles of incidence greater than 45°, the proportion of pipistrelle bats commuting on the leeward side of the tree lines increased.
Experimental infections of muskoxen (Ovibos moschatus) and domestic sheep with Umingmakstrongylus pallikuukensis (Nematoda: Protostrongylidae): parasite development, population structure, and pathology
Authors: Kutz S J , Hoberg E P , Polley L
Published: April 2011

Three captive muskoxen (Ovibos moschatus) were successfully infected with third-stage larvae of Umingmakstrongylus pallikuukensis digested or emerged from the slugs Deroceras reticulatum and D. laeve, for the first time completing the life cycle of this parasite under experimental conditions. The course of parasite development and patency was followed for 26 months post infection (p.i.) using fecal examinations and radiography. The prepatent periods in two of the muskoxen were 91 and 95 days and the patent period in one extended for 23 months. Larval production peaked 13-14 months p.i. On postmortem of two of the muskoxen at months 14 and 26 p.i., adult parasites were found only within pulmonary cysts and cysts were randomly distributed between left and right lungs. Cyst dimensions were positively correlated with the number of adult parasites they contained. On postmortem of the third muskox at day 97 p.i., not all adult parasites were within typical cysts; two were found free in interlobular septa. First-stage larvae were recovered from lung cysts of this animal but not from feces. Lung pathology in all three muskoxen appeared localized and associated with the adult nematodes. Infection of two sheep with third-stage larvae of U. pallikuukensis did not result in parasite establishment.
Colonization of high-elevation lakes by long-toed salamanders (Ambystoma macrodactylum) after the extinction of introduced trout populations
Authors: Funk W Chris , Dunlap William W
Published: April 2011

We surveyed high-elevation lakes for long-toed salamander (Ambystoma macrodactylum) larvae and trout in the northern Bitterroot Mountains of Montana, U.S.A., in 1978, 1997, and 1998. Our objectives were to (i) test whether trout exclude salamander populations; (ii) determine whether lakes in which trout have gone extinct have since been colonized by salamanders; and (iii) estimate the rates of population extinction and colonization in lakes never stocked with trout. In agreement with previous work on the interactions between trout and long-toed salamanders, trout effectively excluded salamander populations from lakes. Somewhat surprisingly, however, salamanders managed to colonize lakes after the extinction of trout populations despite evidence of low levels of interpopulation dispersal in these salamander populations. In lakes never stocked with trout there was no evidence of a decline in salamander populations; 2 of these lakes were colonized and no populations went extinct.
Factors influencing the escape response of an arboreal agamid lizard of tropical Australia (Lophognathus temporalis) in an urban environment
Authors: Blamires S J
Published: April 2011

The escape response of the agamid lizard Lophognathus temporalis in an urban population was examined during the dry season. Two measurements of escape response were made: the distance an observer can approach before the lizard flees (approach distance) and the distance the lizard flees to refuge (flight distance). The relationship between approach distance and flight distance was examined, as was the relationship between air temperature and both approach distance and flight distance. The influence of time of day, the lizard's perch (in a tree or on the ground), and year (1996 or 1998) on the escape response was determined. Approach distance and flight distance had no relationship with each other. Air temperature had a positive relationship with approach distance, so variations in temperature between the two years might explain variations in approach distance between them. The lizard's perch had the greatest influence on flight distance. Lizards in trees fled shorter distances, usually to the opposite side of the tree trunk or branch to the observer. Lizards on the ground always fled to the nearest refuge.
Ontogeny of swimming and diving in northern fur seal (Callorhinus ursinus) pups
Authors: Baker Jason D , Donohue Mary J
Published: April 2011

Time spent in the water and diving behavior of northern fur seal (Callorhinus ursinus) pups were monitored between birth and weaning at St. Paul Island, Alaska. The median age when pups began swimming was 26 days, but prior to 40 days of age they spent virtually all their time on shore and only rarely took brief (15-20 min) swims. Pups began spending substantial time in the water at approximately 40-50 days of age, coinciding both with the early growth of insulating underfur and a seasonal peak in sea surface temperature. This suggests that pups had earlier been constrained to remain on shore by their undeveloped thermoregulatory capabilities. Time in the water increased up to approximately 100 days of age, when molted pups spent about 35% of their time in the water and swim bouts were several hours in duration. Moreover, the presence of a pup's mother on shore, photoperiod, and precipitation also influenced the amount of time pups spent in the water. Pups (mean age = 100 days) dove to very shallow depths (mean = 3 m) for short durations (mean = 11 s). Because pups did not gain mass unless suckled by their mothers, it is unlikely that they fed extensively while diving prior to migration. The pattern of development of swimming and diving in northern fur seals is intermediate between typical phocid and otariid patterns, as is the maternal strategy.
Ageing the eggs and embryos of the pig-nosed turtle, Carettochelys insculpta (Chelonia: Carettochelydidae), from northern Australia
Authors: Beggs Kerry , Young Jeanne , Georges Arthur , West Peter
Published: April 2011

Standard series of embryonic stages are the primary basis for organising information in embryological studies and for ageing eggs and embryos in field studies. In this paper we calibrate the developmental series for the pig-nosed turtle, Carettochelys insculpta, from northern Australia against an established series for Chelydra serpentina, carefully noting unique attributes of C. insculpta. We also extend existing non-destructive approaches to staging embryos by identifying several additional specific embryological attributes visible externally or by candling. A chronological sequence of attributes visible by candling is established as a viable alternative to the destructive approaches requiring direct examination of embryos.
Influence of cell type and mandibular dentition on the ability of captive honey bee workers and drones (Apis cerana indica Fabr. and Apis mellifera L.) to uncap brood cells: biological implications for parasitic mites (Varroa spp.)
Authors: Davis A R , Prabhuswamy H P
Published: April 2011

Experiments to study the ability of adults (workers and drones) of the eastern honey bee, Apis cerana indica Fabr., and the western honey bee, Apis mellifera L., to uncap brood cells were undertaken in Bangalore, India. Using halved gelatin capsules, individual adults were confined opposite the intact cap that sealed vacant, isolated brood cells. From inside the cell, workers and drones of both species penetrated the drone-cell cap of A. mellifera with regularity. When placed outside the cell, workers of both species were successful in perforating the same cap. Similarly, A. c. indica workers easily perforated the cap of A. c. indica worker cells from inside. However, significant caste-specific differences in success at perforating the cap of A. c. indica drone cells were observed; whereas drones did so regularly, A. c. indica workers usually perished when so challenged. When held facing the cap while inside or outside the drone cell, none or only 10% of workers, respectively, managed to chew a hole in it. Even when two workers faced the same drone-cell cap, one from each side, only 20% of caps were perforated. These results are consistent with the hypothesis that the tough apex of the drone cocoon of A. cerana is typically impervious to uncapping from outside, and hence has provided an opportunity for the uninterrupted reproduction of invading parasitic mites (Varroa spp.). The mandibles of drones of both species possess a diminutive apical tooth along the distal margins that is absent in workers. The lack of mandibular teeth in workers may explain the disparity in ability to penetrate the tough cocoon of A. c. indica drones. The mandibles of both castes suffer wear.
Dispersal pattern and effective population size of the beaver
Authors: Sun Lixing , Müller-Schwarze Dietland , Schulte Bruce A
Published: April 2011

The dispersal pattern of the beaver (Castor canadensis) was studied by intensive livetrapping, tagging, and observation in Allegany State Park and its vicinity in New York from 1984 to 1996. The majority (74%) of dispersing beavers (n = 46) initiated dispersal in a downstream direction after spring ice-out. Females dispersed significantly farther away from their natal colonies than males (10.15 ± 2.42 (SE) km vs. 3.49 ± 0.86 km). Movements to neighboring sites were common (16 of 46 dispersers), indicating that beavers, especially males, may prefer to disperse to the nearest available sites. Most (64%) natal dispersers were 2-year-olds. Three-year-olds also constituted a considerable proportion (21%) of the dispersers, but 1-year-old dispersers were relatively rare (14%). Many adults underwent secondary dispersal after successful natal dispersal in our study area. Male secondary dispersers were more inclined to take over neighboring sites than were male natal dispersers (10 of 13 vs. 3 of 13). The effective population size in a 250-km2area was estimated to be 161-228 individuals by the areal method and 267-378 individuals by the 85th percentile method.
Implantation date, growth rate, and allometric relationships in foetal Northwest Atlantic harp seals (Phoca groenlandica)
Authors: Chabot Denis , Stenson Garry B
Published: April 2011

Using a sample of 150 female and 141 male foetal Northwest Atlantic harp seals (Phoca groenlandica) collected between October and February of 1980-1995, we determined that the allometric relationship between total body mass and standard length did not differ between sexes and did not differ from the relationship calculated for foetal harp seals from the study of Stewart and co-workers (R.E.A. Stewart, B.E. Stewart, D.M. Lavigne, and G.W. Miller. 1989. Can. J. Zool. 67: 2147-2157). Combining the data for foetuses from both studies, the exponent of the mass-length relationship was 2.75, significantly different from 3. Except for very small foetuses (<20 cm) standard length and mass1/2.75 increased linearly as gestation progressed. Equations are provided to estimate standard length and total mass of foetuses in the period August-February and to estimate sculp mass, core mass, and axillary girth from length for the period October-February. The most reliable estimate of implantation date (day 223, 11 August) was obtained by regressing sampling date1/2 on mass1/2.75.
Ontogeny of the responses of European rabbits (Oryctolagus cuniculus) to aerial and ground predators
Authors: Pongrácz Péter , Altbäcker Vilmos
Published: April 2011

The responses of adult (6-9 months old) and young (5-8 weeks old) rabbits (Oryctolagus cuniculus) to their natural predators were tested. The aims of our experiments were to investigate whether (i) inexperienced rabbits would avoid a stuffed goshawk but not a non-bird-like control object and (ii) adult rabbits would behave differently toward an aerial and a terrestrial predator model on their first encounter, and (iii) to compare the inherited antipredator behaviour of adult and young rabbits toward the two types of predators. We tested only naïve rabbits and used a stuffed goshawk and fox as predators. Our results showed that under controlled laboratory conditions (i) a stuffed predator could elicit avoidance behaviour in rabbits without previous experience with predators; (ii) adult rabbits behaved differently toward the stuffed fox and goshawk; (iii) the behaviour of young rabbits was less differentiated, and their "quantitative" response developed into the adults' well-structured defensive behaviour without any experience with predators.
The effects of heating on the behaviour ofOxytricha bifaria(Ciliophora, Hypotrichida)
Authors: Barbanera F , Erra F , Ricci N
Published: April 2011

Experimental populations of the ciliate Oxytricha bifaria grown at 24°C were exposed to progressively higher temperatures in a thermally isotropic environment. Their behaviour was monitored and an ethogram was drawn for each step of the warming process (24, 29, and 34°C), as well as for three further periods of time after the temperature was brought back to the initial 24°C. As the temperature increased, (i) the percentage of mobile cells decreased (significantly at 34°C), (ii) their periods of immobilisation were more frequent; (iii) their average creeping velocity did not change; (iv) the radius of the arcs and the length of both the linear segments and the arcs decreased; (v) the frequency of the "side-stepping reaction" increased progressively, and (vi) it was often performed as bursts of reactions. Moreover, (vii) a new behavioural pattern, the "maximum-rotation reaction," was performed. When the ciliates were brought back to 24°C, their behavioural parameters, except for general mobility, did not return to normal values during the first 90 min. Linear heating of the experimental populations of O. bifaria induced nonlinear and time-stable effects on their behaviour (12 out of 17 parameters actually changed at 34°C).
Can an orbital gland function in the vomeronasal sense? A study of the pygopodid Harderian gland
Authors: Rehorek S J , Firth B T , Hutchinson M N
Published: April 2011

The Harderian gland occurs in the orbit of most tetrapod vertebrates. A growing body of evidence suggests that this gland is associated with the chemoreceptive function of the vomeronasal organ. In the present study, the morphology of the Harderian gland in two species of pygopodids was examined, and the results were contrasted with those from both geckos and snakes. The results show that the pygopodid Harderian gland shares histochemical and ultrastructural features with that of the geckos. However, in several gross morphological features, the pygopodid Harderian gland more closely resemble that of snakes than that of geckos. In both pygopodids and snakes, the nasolacrimal duct forms a direct link between the Harderian gland and the vomeronasal organ, which indicates that this specialized connection between the Harderian gland and vomeronasal organ is a convergent evolutionary attribute of these two groups.
Effects of methylparaben on the development and chemosensitivity of the blow fly Protophormia terraenovae Rob.-Desv. (Diptera: Calliphoridae)
Authors: Voss Michael
Published: April 2011

Maggots of the blow fly Protophormia terraenovae were divided into three groups; one group was reared on beef liver and the other two groups were reared on an artificial diet in which the fungicide methylparaben (methyl 4-hydroxybenzoate, Nipagin®-M) at a concentration of 0.6% was present or absent. Development of maggots reared on the diet containing methylparaben was prolonged, and the pupae were smaller and pupal mortality increased from 17 to 26%. Gustatory tests showed that the threshold for adults to respond to sucrose solution at different concentrations increased more than threefold when the flies were exposed to methylparaben as larvae.
The response of yellow warblers to brown-headed cowbird models in Prince Edward Island
Authors: Teather Kevin , Cronin Shannon
Published: April 2011

The negative impact of brown-headed cowbird parasitism (Molothrus ater) on the reproductive success of many songbirds has led to the evolution of host defensive behaviours that may reduce the chance of being parasitized. Populations of songbirds that have only recently experienced cowbird parasitism, however, may have had insufficient time to develop such behaviours. We examined the response of nesting yellow warblers (Dendroica petechia), a host species, to cowbird models on Prince Edward Island, where cowbirds have been present for less than 50 years. Yellow warblers gave more alarm calls and remained closer to their nests when presented with a cowbird model than when presented with a model of a white-throated sparrow (Zonotrichia albicollis), a nonthreatening local species. Our results suggest that yellow warblers recognize brown-headed cowbirds as greater threats to their nests and respond in a way that is similar to other populations which have been exposed to cowbirds for a much longer period of time.
Population dynamics of northern white-tailed deer during mild winters: evidence of regulation by food competition
Authors: Dumont André , Crête Michel , Ouellet Jean-Pierre , Huot Jean , Lamoureux Jean
Published: April 2011

We studied white-tailed deer (Odocoileus virginianus borealis) at the northeastern limit of their range after their density had decreased as a result of harsh winters aggravated by coyote predation. We compared two populations wintering in adjacent areas. In the Lac Témiscouata wintering area (LTWA), deer and browse density averaged 10 animals/km2 and 127 000 deciduous twigs/ha compared with 20 deer/km2 and 68 000 twigs/ha, respectively, at the Pohénégamook wintering area (PWA). For 75 radio-collared deer, the probability of death was highest during the short spring migration and remained elevated in winter, whereas fewer deaths occurred in summer and none during autumn migration. PWA deer had a higher mortality rate than did LTWA animals and died mostly in winter, from predation, starvation, and collision equally. Based on observed survival rates, we estimated that the finite rate of increase averaged [Formula: see text]1.25 and [Formula: see text]1.00 for LTWA and PWA populations, respectively. At PWA, we examined 129 carcasses to determine the mortality pattern of deer. Among adults, we did not detect significant differences related to sex. Starvation and predation affected more fawns and old deer than prime animals, whereas collision appeared to be nonselective. Most cases of starvation occurred after the beginning of March, when body reserves dropped to low levels. We conclude that competition for winter forage regulated PWA deer during the study.
Endovascular Treatment of Tandem Extracranial/Intracranial Anterior Circulation Occlusions
Authors: Malik Amer M. , Vora Nirav A. , Lin Ridwan , Zaidi Syed F. , Aleu Aitziber , Jankowitz Brian T. , Jumaa Mouhammad A. , Reddy Vivek K. , Hammer Maxim D. , Wechsler Lawrence R. , Horowitz Michael B. , Jovin Tudor G.
Published: April 2011

Background and Purpose—

Acute ischemic stroke due to tandem occlusions of the extracranial internal carotid artery and intracranial arteries has a poor natural history. We aimed to evaluate our single-center experience with endovascular treatment of this unique stroke population.

Methods—

Consecutive patients with tandem occlusions of the internal carotid artery origin and an intracranial artery (ie, internal carotid artery terminus, M1 middle cerebral artery, or M2 middle cerebral artery) were studied retrospectively. Treatment consisted of proximal revascularization with angioplasty and stenting followed by intracranial intervention. Endpoints were recanalization of both extracranial and intracranial vessels (Thrombolysis In Myocardial Ischemia ≥2), parenchymal hematoma, and good clinical outcome (modified Rankin Scale ≤2) at 3 months.

Results—

We identified 77 patients with tandem occlusions. Recanalization occurred in 58 cases (75.3%) and parenchymal hematoma occurred in 8 cases (10.4%). Distal embolization occurred in 3 cases (3.9%). In 18 of 77 patients (23.4%), distal (ie, intracranial) recanalization was observed after proximal recanalization, obviating the need for distal intervention. Good clinical outcomes were achieved in 32 patients (41.6%). In multivariate analysis, Thrombolysis In Myocardial Ischemia ≥2 recanalization, baseline National Institutes of Health Stroke Scale score, baseline Alberta Stroke Programme Early CT score, and age were significantly associated with good outcome.

Conclusions—

Endovascular therapy of tandem occlusions using extracranial internal carotid artery revascularization as the first step is technically feasible, has a high recanalization rate, and results in an acceptable rate of good clinical outcome. Future randomized, prospective studies should clarify the role of this approach.
Hemorrhage Risk of Cerebral Arteriovenous Malformations Before and During the Latency Period After Gamma Knife Radiosurgery
Authors: Yen Chun-Po , Sheehan Jason P. , Schwyzer Lucia , Schlesinger David
Published: April 2011

Background and Purpose—

To evaluate the hemorrhage rates of cerebral arteriovenous malformations (AVM) and the risk factors of hemorrhage before and after Gamma Knife radiosurgery (GKS).

Methods—

The annual hemorrhage rate was calculated as the number of hemorrhages divided by the patient-years at risk. Characteristics of patients and AVM related to hemorrhagic or nonhemorrhagic presentation were evaluated by logistic regression. Risk factors predicting AVM hemorrhage during the period from the diagnosis to GKS of AVM and during the latency period after radiosurgery were evaluated using Cox regression hazards model.

Results—

The annual hemorrhage rate before GKS was 2.0% assuming patients were at risk for hemorrhage since their birth. The hemorrhage rate calculated between the diagnosis and GKS of AVM was 6.6% and reduced to 2.5% after GKS until obliteration of the AVM. Although small and deep nidi and those with deep and single draining veins tended to present themselves with hemorrhage, only nidi with single draining veins and those ruptured before were more likely to bleed once the AVM had been diagnosed. These factors no longer predisposed the nidus to a rupture after radiosurgery and the only predicting factor for hemorrhage was a low radiosurgical prescription dose to the margin of nidus.

Conclusions—

The AVM hemorrhage rate seems to reduce after GKS. After radiosurgery, none of the patients or nidus-related risk factors remained relevant to the occurrence of hemorrhage. The nidus treated with a high radiosurgical dose is less likely to bleed.
Association of Early National Institutes of Health Stroke Scale Improvement With Vessel Recanalization and Functional Outcome After Intravenous Thrombolysis in Ischemic Stroke
Authors: Kharitonova Tatiana , Mikulik Robert , Roine Risto O. , Soinne Lauri , Ahmed Niaz , Wahlgren Nils ,   for the Safe Implementation of Thrombolysis in Stroke (SITS) Investigators
Published: April 2011

Background and Purpose—

Early neurological improvement (ENI) after thrombolytic therapy of acute stroke has been linked with recanalization and favorable outcome, although its definition shows considerable variation. We tested the ability of ENI, as defined in previous publications, to predict vessel recanalization and 3-month functional outcome after intravenous thrombolysis recorded in an extensive patient cohort in the Safe Implementation of Thrombolysis in Stroke–International Stroke Thrombolysis Register (SITS-ISTR).

Methods—

Of 21 534 patients registered between December 2002 and December 2008, 798 patients (3.7%) had CT- or MR angiography-documented baseline vessel occlusion and also angiography data at 22 to 36 hours post-treatment. ENI definitions assessed at 2 hours and 24 hours post-treatment were (1) National Institutes of Health Stroke Scale (NIHSS) score improvement ≥4 points from baseline; (2) NIHSS 0, 1, or improvement ≥8; (3) NIHSS ≤3 or improvement ≥10; (4) improvement by 20%; (5) 40% from baseline; or (6) NIHSS score 0 to 1. Receiver operating curve analysis and multiple logistic regression were performed to evaluate the association of ENI with vessel recanalization and favorable functional outcome (modified Rankin Scale score 0 to 2 at 3 months).

Results—

ENI at 2 hours had fair accuracy to diagnose recanalization as derived from receiver operating curve analysis. Definitions of improvement based on percent of NIHSS score change from baseline demonstrate better accuracy to diagnose recanalization at 2 hours and 24 hours than the definitions based on NIHSS cutoffs (the best performance at 2 hours was area under the curve 0.633, sensitivity 58%, specificity 69%, positive predictive value 68%, and negative predictive value 59% for 20% improvement; and area under the curve 0.692, sensitivity 69%, specificity 70%, positive predictive value 70%, and negative predictive value 62% for 40% improvement at 24 hours). ENI-predicted functional outcome with OR 2.8 to 6.0 independently from recanalization in the angiography cohort (n=695) and with OR of 6.9 to 9.7 in the whole cohort (n=18 181).

Conclusions—

Early 20% neurological improvement at 2 hours was the best predictor of 3-month functional outcome and recanalization after thrombolysis, although fairly accurate, and may serve as a surrogate marker of recanalization if only imaging evaluation of vessel status is not available. If recanalization status is required after intravenous thrombolysis, vascular imaging is recommended despite ENI.
Predicting Infarction Within the Diffusion-Weighted Imaging Lesion
Authors: Carrera Emmanuel , Jones P. Simon , Alawneh Josef A. , Klærke Mikkelsen Irene , Cho Tae-Hee , Siemonsen Suzanne , Guadagno Joseph V. , Mouridsen Kim , Ribe Lars , Hjort Niels , Fryer Tim D. , Carpenter T. Adrian , Aigbirhio Franklin I. , Fiehler Jens , Nighoghossian Norbert , Warburton Elizabeth A. , Ostergaard Leif , Baron Jean-Claude
Published: April 2011

Background and Purpose—

There is ample evidence that in anterior circulation stroke, the diffusion-weighted imaging (DWI) lesion may escape infarction and thus is not a reliable infarct predictor. In this study, we assessed the predictive value of the mean transit time (MTT) for final infarction within the DWI lesion, first in patients scanned back-to-back with
15
O-positron emission tomography and MR (DWI and perfusion-weighted imaging; “Cambridge sample”) within 7 to 21 hours of clinical onset, then in a large sample of patients with anterior circulation stroke receiving DWI and perfusion-weighted imaging within 12 hours (85% within 6 hours; “I-KNOW sample”).

Methods—

Both samples underwent structural MRI at approximately 1 month to map final infarcts. For both imaging modalities, MTT was calculated as cerebral blood volume/cerebral blood flow. After image coregistration and matrix resampling, the MTT values between voxels of interest that later infarcted or not were compared separately within and outside DWI lesions (DWI+ and DWI−, respectively) both within and across patients. In the I-KNOW sample, receiver operating characteristic curves were calculated for these voxel of interest populations and areas under the curve and optimal thresholds calculated.

Results—

In the Cambridge data set (n=4), there was good concordance between predictive values of MTT
positron emission tomography
and MTT
perfusion-weighted imaging
for both DWI+ and DWI− voxels of interest indicating adequate reliability of MTT
perfusion-weighted imaging
for this purpose. In the I-KNOW data set (N=42), the MTT significantly added to the DWI lesion to predict infarction in both DWI− and DWI+ voxels of interest with areas under the curve approximately 0.78 and 0.64 (both
P
<0.001) and optimal thresholds approximately 8 seconds and 11 seconds, respectively.

Conclusions—

Despite the relatively small samples, this study suggests that adding MTT
perfusion-weighted imaging
may improve infarct prediction not only as already known outside, but also within, DWI lesions.