bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal components of genetic variation in migrating and wintering American wigeon
Authors: Rhodes Jr. Olin E. , Smith Loren M. , Chesser Ronald K.
Published: July 2008

Data from allele frequencies of wintering American wigeon (Anas americana) from the Southern High Plains (SHP) of Texas were used to monitor changes in genetic characteristics of the wintering population through time, and to estimate the average proportion of total genetic variation partitioned among parent breeding populations. Wigeon were surveyed electrophoretically for genetic variation at 25 biochemical loci. Changes in total gene diversity were observed throughout the study period (5 October 1988 to 15 March 1989) at numerous loci. Significant temporal changes in the genetic composition of the wintering population were detected, and a minimum of 7% of the total genetic variation in these wigeon was thought to be partitioned among the breeding populations represented on the SHP. A new influx of migrating wigeon, weather-related movements of wigeon, or spatial subdivision of breeding populations on the SHP may be responsible for shifts observed in the genetic characteristics of the wintering population. Significant heterozygote deficiencies in the sample of wintering wigeon suggest that this species maintains some degree of genetic structure on the breeding grounds. Genetic data collected from wintering waterfowl may provide minimum expectations of the degree of genetic subdivision among breeding populations and may help waterfowl biologists to detect changes in the composition of wintering waterfowl populations through time.
Diet selection by a ruminant generalist browser in relation to plant chemistry
Authors: McArthur C. , Robbins C. T. , Hagerman A. E. , Hanley T. A.
Published: July 2008

Captive mule deer (Odocoileus hemionus hemionus) and black-tailed deer (O. h. sitkensis) were used in cafeteria-type, two choice feeding trials to test the hypothesis that digestible dry matter (energy) and nontannin phenolics of tree, shrub, and forb leaves are major determinants of diet preference. Deer selected plants in relation to a trade-off between the benefit derived from digestible dry matter and the cost of nontannin phenolics presumably associated with toxicity when absorbed. When one of the forages contained both the highest digestible dry matter and lowest nontannin phenolics, the deer always preferred that plant. When one forage had the highest digestible dry matter but the other plant had the lowest nontannin phenolics, the deer selected the high-energy plant when the difference in nontannin phenolics was relatively small, but they preferred the low-energy plant when the other forage had much higher levels of nontannin phenolics. Tannins influenced diet choice only as one of the factors reducing digestible dry matter in these forages. Apparently total dry-matter intake was constrained by the nontannin phenolic fraction but not by tannins. Tannins and nontannin phenolics both contribute to defending plants against browsers.
Sampling protocols for estimating time budgets of roosting bats
Authors: Winchell Jane M. , Kunz Thomas H.
Published: July 2008

This study was designed to evaluate sampling protocols for estimating time-activity budgets of colonial roosting bats during the day-roosting period, based on data collected from roosting activities of adult eastern pipistrelles (Pipistrellus subflavus) at a maternity colony in eastern Massachussetts. A comparison of three different scan-sampling protocols was used to quantify day-roosting activities (LONG, 72 scans at 60-min intervals; SHORT, 20 scans at 15-min intervals; and BRIEF, 10 scans at 15-min intervals) relative to a standardized protocol (HOUR, continuous replicate scans over a 60-min session). These analyses indicate that day-roosting activity is most reliably quantified using the SHORT and BRIEF sampling protocols (those with the highest sampling frequencies). The rarity of some activities (e.g., crawling) may not warrant an increased frequency of sampling to quantify daily time budgets of roosting bats. Comparisons of an intensive version of SHORT (20 scans at 10-min intervals) and focal sampling protocols used during the two most active periods of day-roosting (immediately following return to the roost before dawn and just prior to departure before dusk) suggest that these sampling methods provide comparable estimates of roosting activity. We suggest that frequent short scan-sampling protocols may be used to reliably quantify day-roosting activities of bats both during active and inactive periods, although focal sampling may be more appropriate if individual behavior is of interest during intense periods of activity (postfeeding return and pre-emergence periods).
Directions of arrivals of Great Blue Herons (Ardea herodias) at nests with large chicks near Montréal, Quebec
Authors: Benoit Réjean , DesGranges Jean-Luc , McNeil Raymond
Published: July 2008

We studied the arrivals of Great Blue Herons (Ardea herodias) breeding at the Ile Saint-Bernard heronry near Montréal, Quebec. A total of 42 nests were monitored during the daytime. Overall (i.e., for all flight directions), the distance separating the colony from the potential feeding areas seems to have been the single most important factor in the herons' choice of feeding sectors. Date, wind direction, and water level had a slight influence on the use of feeding areas in this riverine system. Flight directions varied slightly according to these variables during the sampling period. Other variables such as wind speed, time of day, cloud cover, and rain had less influence on the distribution of flight directions. Many breeding pairs used only one or two sectors in particular while feeding their brood. We suggest that in natural environment contamination studies, the faithfulness of certain pairs to specific feeding sectors could help to identify the origin of the contaminants found in the tissues of sampled birds.
Population structure and changes in body mass and composition of mallards (Anas platyrhynchos) wintering in Edmonton, Alberta
Authors: Pawlina Iwona M. , Boag David A. , Robinson Frank E.
Published: July 2008

The population structure and changes in body mass and body composition of mallards wintering on the North Saskatchewan River in Edmonton, Alberta, were investigated from November 20, 1989 to March 15, 1990. The age composition of the population was biased in favor of juveniles (84%) and in favor of males (71%), possibly because of differential emigration at the onset of winter. Ducks in the wild population lost 22–30% of their live mass over winter. On average, males lost 75–76% of body lipids and 24–29% of proteins. Females lost between 66 and 92% of body lipids and between 18 and 23% of proteins. These losses suggested that mallards wintering in Edmonton in 1989–1990 were insufficiently prepared to meet the energy demands of spring migration and reproduction. Moreover, neither sex was able to maintain the level of protein intake needed to meet the protein costs of molt.
Corneal anatomy of marine mammals
Authors: Pardue M. T. , Sivak J. G. , Kovacs K. M.
Published: July 2008

The corneal anatomy of fin whales (Balaenoptera physalus), minke whales (Balaenoptera acutorostrata), harp seals (Phoca groenlandica), ringed seals (Phoca hispida), and bearded seals (Eriganthus barbatus) was examined to determine if marine mammals have evolved specialized corneas for life in a marine habitat. One to seven eyes of each species were analyzed: paraffin sections stained with haematoxylin and eosin for light microscopy; and ultrathin sections for transmission electron microscopy. All corneas contain the five typical mammalian layers: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. The corneas of these marine mammals are thicker than human corneas because of a thicker stromal layer. The other layers are thinner than those found in humans, except for the epithelial layer in the bearded seal and the cetaceans where it may provide extra protection for the eye during feeding behaviour. The epithelial cells in all corneas studied have an abundance of tonofilaments, which may strengthen the cells and distribute force across the corneal surface. No special organization of collagen fibrils was found in the stroma that would offer protection from ultraviolet radiation or glare for pinnipeds when on ice. The thickness of the sclera in the cetaceans may serve to hold the inner globe of the eye in an elliptical shape, while the thinning of the sclera in the equatorial region in pinnipeds may flatten the eye in air to reduce aerial myopia.
Regulation of a large herd of migratory caribou: summer nutrition affects calf growth and body reserves of dams
Authors: Crête Michel , Huot Jean
Published: July 2008

The range used for calving and for the first month of lactation by the Rivière George Caribou Herd (RGH), which peaked at over 600 000 individuals in the mid-eighties, showed signs of overgrazing, in contrast to that used by the adjacent Rivière aux Feuilles Herd. Density of females in the tundra habitat below 600 m asl averaged 11.2 animals/km2 on the overgrazed range in 1988, in comparison with ≈0.5/km2 on the other range. Inadequate foraging conditions during the first month of lactation caused complete exhaustion of fat reserves in females on the poor range; milk production was seemingly insufficient, as calves were lighter and grew at a slower rate than calves born on the better summer range or born in captivity from dams fed ad libitum. Moreover, females on the poor range were shorter and lighter than their counterparts on the good range, illustrating that priority goes to reproduction rather than to growth under suboptimal foraging conditions. Accretion of body fat and protein in RGH females was rapid in autumn, but individuals with a calf at yield accumulated smaller fat reserves than nonreproductive adult females. Condition did not affect ovulation. However, interruption of gestation was suspected in females that were unable to accumulate enough body reserves in autumn or early winter, judging from the progressive decline in the pregnancy rate and in the autumn cow:calf ratio observed for the RGH since 1984, concomitant with the levelling off of the herd. Summer nutrition seemingly regulated the RGH through a combination of decreased fecundity and survival.
Mating behavior of a parajulid millipede, Aniulus bollmani
Authors: Mathews Patrick L. , Bultman Thomas L.
Published: July 2008

The mating behavior of a North American parajulid millipede, Aniulus bollmani, was examined. Pairs of mature A. bollmani collected from a small woodlot in northern Missouri were placed into chambers to allow mating to be observed through a dissecting microscope. Five complete matings were observed out of 10 pairings. Males used their enlarged first leg pair to grasp females before and during copulation, and their anterior and posterior gonopods articulated to transfer sperm to the females. Information on age distribution over a 10-month sampling period indicated multiple mating seasons and long maturation times for this millipede.
Evoked chirping in the weakly electric fish Apteronotus leptorhynchus: a quantitative biophysical analysis
Authors: Zupanc Günther K. H. , Maler Leonard
Published: July 2008

Apteronotus leptorhynchus, a gymnotiform fish, produces highly regular electric organ discharges of 600–1000 Hz. Short-term modulations of the electric organ discharge ("chirps") were elicited by imitating the discharges of neighboring fish. Chirps displayed an increase in frequency of approximately 100 Hz, a duration of about 15 ms, and an absolute amplitude of 0.5–2 mV. Since, similar to natural conditions, chirps summated with the beat caused by interference of the fish's own electric organ discharge and the imitating discharge, the size and shape of the chirp's amplitude envelope varied greatly according to its phase relative to the beat cycle; however, the frequency of the chirp amplitude modulation was always 50–100 Hz. All 21 males examined chirped, but their rate of chirping varied considerably (range 2–59 chirps/30 s; mean 22 chirps/30 s). In contrast, only one out of nine females chirped (mean 0.25 chirps/30 s). The latency between stimulus onset and first chirp was variable and often long (range 1.0–25.0 s; median 3.3 s). We propose that chirps are not a sensory reflex but a communicatory behavior regulated by hypothalamic peptidergic input.
Associations among photographically identified Hector's dolphins
Authors: Slooten Elisabeth , Dawson Stephen M. , Whitehead Hal
Published: July 2008

Associations among Hector's dolphins photographically identified in the waters off Banks Peninsula, New Zealand, were studied using cluster analyses of simple and half-weight association indices. In addition, we carried out a temporal analysis of association patterns, plotting changes in the standardized reassociation rate over time. Some individually identified Hector's dolphins were photographed in the study area in successive seasons and years, and appeared to be resident in the area. Social organization was characterized by relatively fluid association patterns, with little stability over periods longer than a few days. Both male and female Hector's dolphins interacted with a large number of other individuals, males more so than females. Association patterns and other evidence support the hypothesis that Hector's dolphins have a promiscuous mating system.
The effect of size on the kinematics and performance of angelfish (Pterophyllum eimekei) escape responses
Authors: Domenici Paolo , Blake Robert W.
Published: July 2008

Angelfish (Pterophyllum eimekei) employ two types of fast-starts, single bend (SB) and double bend (DB). Higher performance (distance travelled, velocity, acceleration) and smaller angles of turn are found in DB responses than in SB responses. The percentage of DB responses is inversely related to body size. Small fish employ DB responses for all escape angles, whereas larger fish commonly show SB responses. This is due to a decrease in maximum DB escape angles for larger fish. Escape angles for pooled SB and DB responses are size-independent. Distance covered within a given time, maximum velocity, and maximum acceleration for pooled SB and DB responses are size-independent. With the exception of the smallest fish, angelfish show submaximal performance when making large turns. We suggest that angelfish employ a particular type of response depending on their predators' strike angle. Extremely small and large fish use principally DB and SB responses, respectively. The employment of SB and DB responses in small and large fish, respectively, may be restricted to a narrow range of predator strike angles.
Effectiveness of several androgens in stimulating kidney hypertrophy, a secondary sexual character, in castrated male three-spined sticklebacks, Gasterosteus aculeatus
Authors: Borg Bertil , Antonopoulou Efthimia , Andersson Eva , Carlberg Tomas , Mayer Ian
Published: July 2008

The effectiveness of different androgens in stimulating hypertrophy of the kidney tubules, a male secondary sexual character, was studied by injecting castrated male sticklebacks with androgens at doses of 0.008–25 μg∙g body weight−1∙day−1 (or control injections were given) for 3 weeks. The doses (μg/g) needed to give 50% stimulation of the kidney epithelium height were as follows: 11-ketotestosterone (OT), 0.047; 11β-hydroxyandrostenedione, 0.070; 11-ketoandrostenedione, 0.11; 5α-androstane-3,11,17-trione, 1.1; 5α-dihydrotestosterone, 1.8; 17β-hydroxy-5α-androstane-3,11-dione, 3.0; and testosterone, 15.2. Androstenedione and 5β-androstane-3,11,17-trione did not reach half-effectiveness at the dose tested (5 μg/g). It is suggested that OT is the physiologically relevant androgen in this case.
Occurrence of Salmincola siscowet (Copepoda: Lernaeopodidae) on lake trout (Salvelinus namaycush) and lake trout backcross (S. namaycush × S. fontinalis) in Lake Huron
Authors: Anderson David M.
Published: July 2008

Examination of 1524 lake trout (Salvelinus namaycush) and 1254 lake trout backcross (S. namaycush × S. fontinalis) from 2 locations in Lake Huron revealed the presence of a parasitic copepod, Salmincola siscowet, previously undescribed in Lake Huron waters. The prevalence and intensity of S. siscowet on trout increased between 1990 and 1992. All copepods detected were sexually mature females. There was no clear relationship between copepod prevalence and host length.
Growth and reproduction of the northern right whale dolphin, Lissodelphis borealis, in the offshore waters of the North Pacific Ocean
Authors: Ferrero Richard C. , Walker William A.
Published: July 2008

Biological samples and data were obtained from 229 northern right whale dolphins, Lissodelphis borealis (99 males and 130 females), taken in Japanese squid driftnets in the central North Pacific Ocean, May – November of 1990 and 1991. Length and sex were recorded for an additional 188 males and 272 females. Ages were determined by counting dentinal growth layer groups. Female reproductive status was determined by macroscopic examination of ovaries; 67 were mature. Sixteen percent were pregnant, 3% were pregnant and lactating, 33% were post partum, 24% were lactating (no recent pregnancy), 10% were resting, and 14% were of unknown condition. Testis and epididymis were examined for evidence of spermatogenesis; 28 were mature. Three estimates of length at birth were 99.7, 100.6, and 103.8 cm. The gestation period was 12.1 – 12.3 months. The sex ratio at birth was not significantly different from 1.0; the male component decreased with age. Estimates of the average age at sexual maturation among males were 9.9 and 10.1 years; average length at sexual maturation was estimated at 215.1 and 214.7 cm. Mature testis masses ranged from 117.4 to 1300 g. Estimates of the average age at sexual maturation among females were 9.7 and 10.4 years; the average length at sexual maturation was estimated at 201.1 and 199.8 cm. Males reach an asymptotic length of 265 cm, females 210 cm. Ovulation rates were < 1.0/year. Calving appeared to peak in July and August; the minimum calving interval was 2 years.
Energy allocation to reproduction and maintenance in mountain bluebirds (Sialia currucoides): a food supplementation experiment
Authors: Garcia Patrick F. J. , Merkle Marilyn S. , Barclay Robert M. R.
Published: July 2008

Mountain bluebirds (Sialia currucoides) were supplemented with food during the nestling period to assess the trade-off between allocation of energy to parental self-maintenance and investment in offspring. Three treatment groups were established, with pairs of birds receiving 0 (control), 9 (small), or 18% (large) of the estimated daily energy requirements of both parents and their brood. Unsupplemented adult females lost an average of 3 g during the nestling period, while both supplemented groups maintained their body mass at approximately 33 g. Adult males in all three groups maintained their mass at approximately 30.5 g. Nestlings in both supplemented groups fledged with heavier masses than did those in the control group. Those receiving the large supplement also grew faster. Food appears to limit the lifetime reproductive success of mountain bluebirds. Adult females allocated additional energy to self-maintenance rather than to increased investment in current offspring. This result was not seen in males. We conclude that our results demonstrate a trade-off between investment in current versus future components of reproductive success.
Aggressive behaviour among convict cichlid (Cichlasoma nigrofasciatum) fry of different sizes and its importance to brood adoption
Authors: Fraser Shannon A. , Wisenden Brian D. , Keenleyside Miles H. A.
Published: July 2008

Convict cichlids (Cichlasoma nigrofasciatum) exhibit extended biparental care of their young. Parents will adopt unrelated (foreign) conspecific young of similar size to or smaller than their own but reject larger foreign young. Adoption of smaller foreign young may benefit the parents by reducing loss of their own young to predators by the dilution effect, which may be enhanced by differential predation on the smaller young. Another factor influencing adoption is that larger foreign young may pose a direct predatory threat to the host parents' young. Measures of aggression among free-swimming young of different sizes showed that there was at least a 1 mm (standard length) size difference before larger young attacked smaller, a 3 mm difference before injury occurred, and a 4–5 mm difference before predation occurred. Parents were initially more discriminating than their young with respect to the size of foreign young accepted. As their young grew and became stronger swimmers, parents less actively rejected larger foreign young; however, they continued to reject them before they were large enough to pose a direct predatory threat. Parental rejection of relatively large foreign young is therefore based more on protecting their own young from differential predation than from aggression by larger adoptees.
Ecology of the whiptail lizard Cnemidophorus deppii on a tropical beach
Authors: Vitt Laurie J. , Zani Peter A. , Caldwell Janalee P. , Durtsche Richard D.
Published: July 2008

The whiptail lizard Cnemidophorus deppii was studied during late dry season on a tropical beach on the Pacific coast of Nicaragua. Most aspects of the ecology of this species are similar to those of other active foraging lizard species studied. Individual C. deppii spend most of a typical daily activity period on sand moving from vegetation patch to vegetation patch, presumably in search of food. The amount of time spent in the sun is greatest in early morning and at its lowest level at midday. The average rate of movement was 0.048 ± 0.004 m/s. Body temperatures of active lizards averaged 40.0 ± 0.25 °C, and most activity occurred during morning and late afternoon. Body temperatures were significantly lower in whiptails active during the morning than later in the day. Forty-two types of prey were identified in stomachs, with termites, spiders, and various orthopterans accounting for most of the diet volumetrically. There was no correlation between lizard size and prey size. There was a significant negative relationship between prey width and the number of prey in stomachs. Snout–vent length (SVL) at sexual maturity was 60 mm for females and 58 mm for males. Mature females averaged 63.8 ± 0.7 mm SVL and produced clutches varying from 1 to 3 eggs ([Formula: see text]). Oviductal eggs averaged 13.6 ± 0.64 × 7.7 ± 0.21 mm in size. There was no significant relationship between female SVL and clutch size. Relative clutch mass was similar to that for other active foraging lizard species. Sexual dimorphism was apparent in coloration (males brightly colored), body size (males larger), and relative head size (male heads larger independent of body size differences). These differences presumably are due to sexual selection.
Microhabitat selection by the lotic amphipod Gammarus pseudolimnaeus Bousfield: mechanisms for evaluating local substrate and current suitability
Authors: Olyslager N. John , Williams D. Dudley
Published: July 2008

This study examined key environmental cues used by Gammarus pseudolimnaeus during microhabitat selection, and cues and mechanisms used to evaluate and react to changing current conditions. Thigmotactic cues for complexity and texture were used independently during microhabitat selection. Neither the external leg sensilla nor the antennae appeared to detect these cues. Neither hydromechanical cues detected by either the antennae or type II microtrich sensilla nor visual cues appear to play a key role. The amphipods showed no ability to compensate when deprived of individual cues. These results suggest that internal proprioceptors were involved, that current is not a major proximal factor, and that the presence of substrate interstices is the critical factor considered during microhabitat selection, not substrate size. Animals displayed a mechanical capability to turn into the flow, probably owing to differential inertial forces resulting from the centre of gravity being located forward and above the physical midpoint. During a field experiment, animals displayed no preference for maintaining their position after disturbance, or for moving upstream or downstream. However, they were less able to move upstream when their microtrich sensilla were masked. Excessively displaced animals did not show a preferred mechanism for returning to the substrate.
The coccidia (Apicomplexa: Eimeriidae) of Caudata (Amphibia), with descriptions of two new species from North America
Authors: Upton Steve J. , McAllister Chris T. , Trauth Stanley E.
Published: July 2008

Over 300 caudate Amphibia were surveyed for coccidia in North America. Two new species of coccidia (Apicomplexa: Eimeriidae) are described. Oocysts of Eimeria opacum sp.nov. from Ambystoma opacum are spherical to subspherical, rarely ellipsoidal, 29.5 × 28.1 (27–32 × 22–31) μm, and have a shape index (length/width) of 1.05 (1.0–1.4). A micropyle, oocyst residuum, and polar granule are absent. Sporocysts are ellipsoidal to kidney-bean shaped, 17.4 × 9.1 (16–21 × 8–11) μm, with a shape index of 1.92 (1.6–2.3). Sporocysts are unusual in that they are encased in a second, more fragile wall that thins to form membranes at the poles; Stieda and substieda bodies are absent. Oocysts of Isospora hightoni sp.nov. from Plethodon albagula are spherical, rarely subspherical, 22.9 × 22.8 (21–24 × 21–24) μm, with a shape index of 1.0 (1.0–1.04). A micropyle and polar granule are absent, but a delicate oocyst residuum was noted in 13/40 (33%) of the oocysts. Sporocysts are ellipsoidal, 16.6 × 11.1 (14.5–17.5 × 10.5–12) μm, with a shape index of 1.5 (1.4–1.6); Stieda and substieda bodies are present. In addition to the species described herein, a taxonomic summary is provided of the known coccidia from Caudata, with the species E. nipponensis sp.nov., E. pyrrhogaster sp.nov., and E. saitamaensis sp.nov. assigned to previously reported coccidia erroneously assigned to named species.
The effects of suspended sediment on rainbow smelt (Osmerus mordax): a laboratory investigation
Authors: Chiasson Alyre G.
Published: July 2008

The swimming behavior of rainbow smelt (Osmerus mordax) was evaluated at 4 concentrations of suspended sediment: 0, 10, 20, and 40 mg∙L−1 in a current gradient of 0.18–1.22 m∙s−1. Fish were significantly more active at suspended sediment concentrations equal to and greater than 10 mg∙L−1, swimming repeatedly back and forth through areas of differing current velocity. Repeated exposure of smelt to suspended sediments at 24-h intervals produced significantly more active fish only upon the third exposure. Increased swimming behavior is interpreted as an alarm response. The need for further field and laboratory research is discussed.
Sphaerospora oncorhynchi n.sp. (Myxosporea: Sphaerosporidae) from the kidney of sockeye salmon (Oncorhynchus nerka) in British Columbia and its possible relationship to the myxosporean causing proliferative kidney disease in salmonid fishes
Authors: Kent M. L. , Whitaker D. J. , Margolis L.
Published: July 2008

Sphaerospora oncorhynchi n.sp. is described from sockeye salmon (Oncorhynchus nerka) from Great Central Lake, Vancouver Island, British Columbia, Canada. Subspherical spores and monosporous pseudoplasmodia were observed in the lumen of renal tubules. Pseudoplasmodia are oval or elongate and range from 5 to 15 μm in the greatest dimension. Spores are 8.2–10.2 μm (length) × 7.8–9.2 μm (width, in sutural plane) × 10.2–11.2 μm (thickness, perpendicular to sutural plane), with two spherical polar capsules of equal size measuring 2.9–3.3 μm in diameter and containing polar filaments with 4–5 coils. The spore contains two uninucleate sporoplasms and is usually surrounded by a degenerated pseudoplasmodium. The type locality for S. oncorhynchi is enzootic for proliferative kidney disease of salmonid fishes. This disease is caused by the PKX organisms, the extrasporogonic stage of an unidentified myxosporean similar to species of Sphaerospora. Sphaerospora oncorhynchi and the PKX organism are similar in that monosporous sporogenesis occurs within the lumen of renal tubules, and the trophozoites and pseudoplasmodia in early sporogenesis of the two parasites are indistinguishable. Furthermore, Sphaerospora spores very similar to those of S. oncorhynchi have been observed in salmonids from two localities in the U.S.A. that are enzootic for proliferative kidney disease. Therefore, the PKX myxosporean in North America may be an extrasporogonic form of S. oncorhynchi n.sp.
The effect of multiple mating on female reproductive success in the simultaneously hermaphroditic land snail Arianta arbustorum
Authors: Chen Xiaofeng , Baur Bruno
Published: July 2008

The simultaneously hermaphroditic land snail Arianta arbustorum mates several times in the course of a reproductive season. Repeated matings might be adaptive for the male function of A. arbustorum to inseminate several "females." We designed an experiment to evaluate the effects of repeated mating on the female reproductive success of this hermaphrodite. Reproductive traits and survival were examined over 2 years in individuals that copulated several times per year (snails were kept in pairs), in individuals that copulated twice (once at the beginning of each year) or once (at the beginning of the first year only), and in individuals prevented from copulating (they were kept isolated). Copulations were not always reciprocally successful: 3 of 57 snails (5.3%) failed to produce fertile eggs, although their mates reproduced successfully. Similarly, 2 of 15 pairs (13.3%) failed to reproduce successfully. Snails allowed to mate repeatedly within each season tended to lay more eggs than snails that mated once per year. However, the numbers of hatchlings did not differ significantly between the two treatment groups, because eggs laid by snails allowed to mate repeatedly had a lower hatching success. Snails that remated in the second year laid more eggs that had higher hatching success, and thus produced more hatchlings than snails that mated once at the beginning of the first year only. Snails that were prevented from mating produced a few hatchlings (by self-fertilization) in the second year; their reproductive success was less than 1% of that of mated snails. Our results suggest that multiple mating is also adaptive for the female function of A. arbustorum by increasing female fecundity and fertility and serving as a hedge against unsuccessful copulations.
Genital mechanics and sexual selection in the spider Nesticus cellulanus (Araneae: Nesticidae)
Authors: Huber Bernhard A.
Published: July 2008

The spider Nesticus cellulanus (Clerck, 1758) was investigated with respect to the functional morphology of its genital organs, using for the first time the method of freeze-fixation of the spiders in copula by liquid nitrogen and subsequent preparation of serial sections of the copulatory organs in functional contact. Use of this method provides new and detailed insights into the function of complex genitalia. Previous ideas, based on artificial expansion of the male copulatory bulbs and simulation experiments, must be rejected or doubted. The role of female choice as a universal cause of species specificity and complexity in genitalia, proposed by Eberhard, is discussed. The total absence of sensilla in the contact zones of the female copulatory organs indicates that the female is not stimulated by the copulatory organs of the male, nor can she evaluate their mechanical fit. "Female choice" can therefore act only indirectly, by influencing the number of offspring, which is assumed to be correlated with the fitting of the male genitalia, thus determining the number of sperm transferred. This postmating "choice" is absolutely independent of the female nervous system and is seen to be at least an important additional mechanism of sexual selection.
Latitudinal variation in egg and clutch size in turtles
Authors: Iverson John B. , Balgooyen Christine P. , Byrd Kathy K. , Lyddan Kelly K.
Published: July 2008

Reproductive and body size data from 169 populations of 146 species (56% of those recognized), 65 genera (75%), and 11 families (92%) of turtles were tabulated to test for latitudinal variation in egg and clutch size. Body-size-adjusted correlation analysis of all populations (as well as within most families) revealed (i) a significant negative relationship (r2 = 0.26) between latitude and egg size, (ii) a significant positive relationship (r2 = 0.21) between latitude and clutch size, and (iii) no relationship between latitude and clutch mass. Phylogenetic contrast analyses corroborated these patterns. Clutch size was also negatively correlated with egg size across all populations as well as within most families. We evaluate the applicability to turtles of hypotheses postulated to explain such latitudinal patterns for other vertebrate groups. The observed pattern may be the result of latitudinal variation in selection on egg size and (or) clutch size, as well as on the optimal trade-off between these two traits.
Diving depths, diet, and underwater foraging of Rhinoceros Auklets in British Columbia
Authors: Burger Alan E. , Wilson Rory P. , Garnier Don , Wilson Marie-Pierre T.
Published: July 2008

Rhinoceros Auklets (Cerorhinca monocerata) were studied at Triangle Island, Cleland Island, and Seabird Rocks, British Columbia, in 1986–1989. Epipelagic schooling fish were consistently the most common prey delivered to auklet chicks at all three localities. Pacific sand lance (Ammodytes hexapterus), Pacific herring (Clupea harengus), juvenile salmon (Onchorhyncus spp.), Pacific saury (Cololabis saura), and juvenile rockfish (Sebastes spp.) were important prey. Bite marks on the fish showed that 73% were attacked from below. The mean deepest depth recorded for 16 auklets was 30 m (range 12–60 m). Eleven time-at-depth records showed that the auklets were epipelagic foragers: 90% of the mean underwater time was spent in the upper 10 m, although most birds had a few deeper dives of 20–60 m. Shipboard transects showed that Rhinoceros Auklets usually foraged in water considerably deeper than 15 m. A model of diving efficiency indicated that a relatively large proportion (> 40%) of the average dive cycle was spent foraging rather than travelling or resting, and prolonged dives invoking anaerobic glycolysis were avoided. We discuss the implications of diving limitations on foraging behaviour and the use of Rhinoceros Auklets as indicators of prey availability.
Sexual size dimorphism and food requirements of nestling birds
Authors: Anderson David J. , Reeve Jo , Gomez Juan E. Martinez , Weathers Wesley W. , Hutson Siobhan , Cunningham Heather V. , Bird David M.
Published: July 2008

The food requirements of dependent sons and daughters have important implications for evolution of the sex ratio, according to current sex allocation theory. We studied food requirements of nestling American kestrels (Falco sparverius), a moderately size-dimorphic falcon, by hand-feeding 61 birds from hatching to fledging. Daughters, the larger gender, consumed 6.99% more food than did sons. Sons did not have higher energy expenditure from higher effort during sibling competition than daughters did, so parents must supply more food to satisfy daughters' needs than to satisfy sons'. A review of all related studies shows a strong positive association between the degree of sexual size dimorphism and gender difference in food requirements.
Noise generated by the jaw actions of feeding fin whales
Authors: Brodie Paul F.
Published: July 2008

The fin whale (Balaenoptera physalus) is representative of baleen whales, which feed by engulfing up to 70 t of seawater in an elastic throat pouch, prior to filtering. This represents (i) the greatest biomechanical action in the animal kingdom, and (ii) a deviation from the flowthrough design of fishing trawls, most filter-feeders, and sampling devices. Based upon observations of fresh carcasses, it is proposed that during the brief period at full gape agile prey may be startled and retained within the pouch by noise: a synovial joint-crack generated during realignment of the tips of the mandibles. It is argued that the previous detection of nonvocal sounds, attributed to the body movements of feeding fin whales, may also include noise resulting from this action.
A retrospective evaluation of the effects of parelaphostrongylosis on moose populations
Authors: Whitlaw Heather A. , Lankester Murray W.
Published: July 2008

Long-term historical data were examined for associations between moose (Alces alces) population declines, white-tailed deer (Odocoileus virginianus) densities, and reports of parelaphostrongylosis as a test of the hypothesis that Parelaphostrongylus tenuis causes moose declines. Moose declines over the past 80 years were associated with deer densities greater than 5/km2. This observation may be useful to managers but did not allow any effects of P. tenuis to be separated from other possible causes of moose declines. Whether moose numbers were stable, increasing, or decreasing was independent of the occurrence of reports of sick moose. The best test of causality that could be constructed, namely an increase in the reporting rate of observed sick animals concurrent with moose population declines, did not support the hypothesis. Although we doubt that reporting rates are representative, a reasonable test of the hypothesis has been possible, and the suggestion that P. tenuis has caused declines in moose populations is not supported by the historical information available. However, this question, and the ways and extent to which the disease may instead limit moose populations cohabiting with infected deer, remain in need of research.
The effect of maternal age and other factors on birth mass in the harbour seal
Authors: Bowen W. D. , Oftedal O. T. , Boness D. J. , Iverson S. J.
Published: July 2008

We studied the effects of maternal age, maternal body mass at parturition, year of birth, birth date, pup sex, and developmental stage (as indicated by the presence of a foetal pelage called lanugo) on the birth mass of harbour seals (Phoca vitulina) on Sable Island, Nova Scotia, Canada. Between 1987 and 1992, mass was obtained on 330 newborns and 259 of their mothers. Birth mass was significantly correlated with maternal mass (r = 0.42 for male pups; r = 0.32 for female pups). Among pups that had shed their lanugo, males were significantly heavier at birth (11.4 ± 0.09 kg, n = 107) than females (10.9 ± 0.09, n = 99). Birth mass increased significantly with maternal age (n = 71, range 4–12 years) even after the effects of maternal mass and pup sex were statistically removed. Mean birth mass varied significantly among years, from 10.5 to 11.5 kg. Newborns averaged 12.8% of maternal mass at parturition (84.8 ± 0.49 kg). Most (84%) pups had shed their lanugo before birth. Pups born with extensive lanugo were born earlier in the season and weighed about 20% less than pups born without lanugo. These data suggest that pups born with lanugo may be less developed than pups that had shed their foetal coat. Young mothers (4 and 5 years old) produced most of the underweight, lanugo-covered pups.
Mountain goat recruitment: kid production and survival to breeding age
Authors: Festa-Bianchet Marco , Urquhart Martin , Smith Kirby G.
Published: July 2008

During a 5-year study of a marked population of mountain goats (Oreamnos americanus) in west-central Alberta, 5 of 17 females produced their first kid at 4 years of age, while most females did not reproduce until 5 years of age. Twinning accounted for 2% of births. Survival of kids to 1 year averaged 60%, and survival of females from 1 to 4 years of age was 52%. Most deaths of kids occurred in September–November and appeared due to predation by wolves (Canis lupus), cougars (Felis concolor), and grizzly bears (Ursus arctos). At least half of the yearlings lost from the population were preyed upon, but losses of 2-year-olds were concentrated in the summer, suggesting emigration. Survival rates of young goats were not different according to sex. We suggest that nutrient availability limits the reproductive performance of the goats by retarding their growth, while predation on young goats is a major source of mortality.
Incubation conditions as potential factors limiting the northern distribution of snapping turtles, Chelydra serpentina
Authors: Bobyn Michele L. , Brooks Ronald J.
Published: July 2008

We incubated snapping turtle eggs at extreme levels of temperature and moisture to test the hypothesis that incubation conditions limit the species' range by affecting hatching success and posthatching survival and growth. We also tested for local adaptations to cold incubation conditions by comparing the responses of embryos and hatchlings from a population near the northern limit of the species' range with those from a population farther south. Eggs of 20 clutches from two Ontario populations were incubated at 21.1 or 25.3 °C at one of three substrate moisture levels (−150, −300, −800 kPa), and hatchling survival and growth were monitored in the laboratory for 23 months. Hatching success, hatchling survival, and posthatching growth were lowest among turtles from eggs incubated at 21.1 °C. They were also uncoordinated and had poor control of their buoyancy. Hatching success was reduced in the drier substrates, but posthatching survival and growth were not affected by substrate moisture. Embryo and hatchling survival were lower in turtles from the southern population (which may be related to contaminants in the eggs) but hatchlings from that population grew the fastest. Hatching success at 21.1 °C or in the driest substrate did not differ between the two populations, but embryos from the northern population did show a greater increase in mortality at 21.1 °C relative to 25.3 °C than embryos from the more southerly population. The effects of lower incubation temperatures may be the most important factor limiting the northern distribution of this species, because lower temperatures during incubation and a shorter growing season probably reduce both the quantity and quality of hatchling turtles produced at northern sites.
Natural variation in the temporal patterning of calling song structure in the field cricket Gryllus pennsylvanicus: effects of temperature, age, mass, time of day, and nearest neighbour
Authors: Ciceran Mark , Murray Anne-Marie , Rowell Gareth
Published: July 2008

Genetic and environmental sources of variation in the temporal patterning of song structure may be important variables influencing male field cricket reproductive success. Song structure in both field and laboratory populations of Gryllus pennsylvanicus was examined to assess possible sources of variation. Factors examined included temperature, male age, body mass, time of day, and male spacing patterns. Temperature was positively correlated with pulse rate and negatively correlated with interchirp interval for both field and laboratory populations. Temperature was negatively correlated with chirp duration only in the field population. Calling song structure did not vary with male age or mass. Time of day had a significant effect on the song parameters examined, even when data were corrected for temperature differences. Males calling in the morning had faster pulse rates and shorter chirp durations than males recorded at night time. Male spacing patterns also influenced calling; isolated males had longer intervals between consecutive chirps than clumped males. Data are discussed in terms of acoustical competition between males and female choice.
Costs to foraging bumble bees of switching plant species
Authors: Laverty Terence M.
Published: July 2008

Many pollinators tend to move between flowers of the same species of plant even when flowers of other species are available. Reasons for this behaviour (known as flower constancy) are unclear. One possible explanation (proposed by Darwin) is that flower handling methods learned on one plant species interfere with previously learned handling methods of other plant species. Darwin's hypothesis was tested by measuring the constancy of bumble bees (Bombus fervidus) foraging in the field and looking for evidence of interference (increased handling times and flower handling errors) when bees switched among four species with relatively simple flowers (Prunella vulgaris, Trifolium pratense, T. hybridum, and Vicia cracca) and two species with more complex flowers (Aconitum napellus and Impatiens capensis). Bees foraging on simple flowers showed no tendency towards flower constancy, and switching between species did not increase handling times or handling errors. Foragers displayed strong constancy when visiting the species with more complex flowers and there was also some evidence of increased handling times and error frequencies following switches. However, the time costs of switching were small (about 1 s over the first flower visit after a switch) and are unlikely to account for flower constancy by bumble bees foraging under natural conditions.
The biophysics of Bergmann's rule: a comparison of the effects of pelage and body size variation on metabolic rate
Authors: Steudel K. , Porter W. P. , Sher D.
Published: July 2008

Should an animal extending its range into a cooler climate rely most on pelage or on body size change to minimize its mass-specific metabolic rate? The various examples of animals following Bergmann's rule support the latter. The fact that an increase in size will result in an increase in total metabolic rate (though coupled to the decrease in the mass-specific metabolic rate) suggests that increases in the insulative value of the pelage would be the preferred strategy. We used a thermal simulation model to compare the relative effects of increasing body mass versus increasing pelage insulative properties on the mass-specific metabolic rate. We found that even the fur of summer-adapted small mammals from temperate climates is extremely dense compared with that of larger mammals and is near the point at which increases in density increase, rather than decrease, heat loss as a result of the high conductivity of individual hairs compared with the layer of still air that it encloses. Small mammals also have lower fur depths, presumably as a result of biomechanical constraints. Seasonal changes in pelage observed in small mammals have very modest effects on mass-specific metabolism. Summer-adapted temperate large mammals, however, are less heavily insulated and, consequently, have substantial latitude for increasing insulation as a means of minimizing mass-specific metabolism. Thus, Bergmann's rule should be more relevant to small mammals than to large ones.
Attachment of eggs by Lamellodiscus acanthopagri (Monogenea: Diplectanidae) to the gills of Acanthopagrus australis (Pisces: Sparidae), with evidence for auto-infection and postsettlement migration
Authors: Roubal Frank R.
Published: July 2008

The eggs of the diplectanid monogenean Lamellodiscus acanthopagri are T-shaped with a thornlike filament that is inserted into the epithelium between respiratory lamellae on the gills of the sparid fish Acanthopagrus australis. The resulting epithelial hyperplasia eventually sheds the egg. The most extensive hyperplasia is always associated with mature and hatched eggs. Few developing eggs are shed from the gills. Most eggs are attached in the basal third of the gill filament irrespective of infection intensity. Most adult and juvenile parasites are in this basal zone at low levels of infection, but predominate in the middle zone at higher infections. A ciliated oncomiracidium hatches from the egg and may attach nearby. As it develops, the parasite apparently moves distally on the gill filament. Only a few fish in the wild have high intensities of infection by L. acanthopagri compared with six other species of monogenean on, A. australis. Auto-infection occurs at all levels of infection but dispersal of larvae to the water column may limit population size on host individuals.