bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of current velocity on byssal-thread production in the zebra mussel (Dreissena polymorpha)
Authors: Clarke Michael , McMahon Robert F.
Published: May 2008

The effect of current velocity on byssal-thread production by adult zebra mussels (Dreissena polymorpha) was investigated. The number of threads produced by 20 individuals at currents of 0.10, 0.15, 0.20, 0.27 m/s was recorded daily over 21 consecutive days, after which individual shell length and dry tissue masses were measured and the byssal complex was removed. Increasing the current velocity from 0.10 to 0.20 m/s significantly elevated rates of byssal-thread production, but the rate was reduced at 0.27 m/s. Current-induced suppression of byssal-thread production may be due to mechanical disturbance of attached mussels, interfering with their ability to press the tip of the foot against the substratum as the thread cures. The mean thread number in a newly formed byssal complex after 21 days was 52.5, 63.8, 73.3 and 60.4 at currents of 0.10, 0.15, 0.20 and 0.27 m/s, respectively. Current velocity had no effect on thread width. The mean number of threads found in the byssal complex of individuals from the wild taken from the same population from which experimental subjects were drawn was 148.3/mussel. There was no correlation between thread number and shell length in the wild population. Results indicate that there are both similarities and differences in the response of byssal-thread production to variable current velocity in freshwater dreissenids and marine mytilids.
Intra- and inter-individual variation in reproductive effort in captive-breeding zebra finches (Taeniopygia guttata)
Authors: Williams Tony D.
Published: May 2008

Intraspecific variation in egg size, clutch size, and timing of laying was studied in captive-breeding zebra finches (Taeniopygia guttata) maintained under conditions of constant temperature, humidity, photoperiod (14 h light: 10 h dark), and ad libitum food supply. Individual variation was marked in the experimental population: egg size 0.915–1.342 g, clutch size 2–7 eggs, and laying interval 4–13 days; however, within individual females egg size (r = 0.742) and clutch size (r = 0.588) were highly repeatable between first and second clutches. Body condition explained only 8% of egg size variation, and clutch size and laying interval were independent of body condition. Clutch size was negatively related to laying interval: females laying later relative to pairing laid smaller clutches (b = −0.175 eggs/day). Body mass of breeding females decreased by 1.57 g (9% of initial mass) during laying of first clutches; mass loss was positively related to initial body condition (R2 = 27.8%) and total clutch mass (R2 = 7.6%). Mass loss was lower (0.47 g) during laying of second or replacement clutches than during laying of first clutches. Individual variation in reproductive effort in captive-breeding zebra finches is very similar to that in free-living avian populations. Laboratory studies on captive-breeding species can provide a valuable approach for the study of proximate physiological mechanisms underlying intraspecific variation in reproduction.
The proximate effects of food supply on intraclutch egg-size variation in American kestrels
Authors: Wiebe Karen L. , Bortolotti Gary R.
Published: May 2008

Egg size can be an important determinant of offspring survival in birds. We measured eggs from 275 clutches of wild American kestrels (Falco sparverius) to study the degree of intraclutch variability in egg size. We also performed two food-supplementation experiments to investigate the proximate role of food supply during laying in determining egg size. Females with relatively abundant food and those in good body condition did not lay eggs that were more uniform in size than those laid by control females. This result is contrary to hypotheses that propose an adaptive explanation for intraclutch egg-size variation and also to ideas of energy depletion during laying. Patterns of egg size versus laying order were different between years, suggesting that females did not adaptively manipulate laying order and egg size within a clutch. The food-supplementation experiments showed that laying female kestrels probably depend on both stored energy reserves and on daily energy surpluses to form eggs. It appears that slight intraclutch variations in egg size occur in response to short-term food shortages during laying, but that these variations are probably nonadaptive. This is in marked contrast to interclutch (among females) variation in egg size, which we have shown varies significantly with food supply.
Comparison of harbour seal diets in two inshore habitats of Atlantic Canada
Authors: Bowen W. D. , Harrison G. D.
Published: May 2008

We studied the composition of harbour seal (Phoca vitulina) diets in two areas, the lower Bay of Fundy and along the northeastern coast of Nova Scotia, that differ in prey species diversity, bottom type, and physical oceanography. Prey remains were found in 250 of 470 harbour seal stomachs collected mainly from May to September between 1988 and 1992. Although 23 taxa were identified, four species, Atlantic herring (Clupea harengus), Atlantic cod (Gadus morhua), pollock (Pollachius virens), and short-finned squid (Illex illecebrosus), accounted for 84% of the estimated biomass of prey consumed in the two areas combined. Species, such as herring and squid, that dominated the diets in both habitats, also tended to be abundant in both habitats during the summer. Atlantic cod was the principal gadoid in the Bay of Fundy, whereas pollock was most important along the Atlantic coast. Differences in prey distribution and abundance appeared to account for differences in the contribution of the alewife (Alosa pseudoharengus), winter flounder (Pseudopleuronectes americanus), hake (Urophycis spp.), and capelin (Mallotus villosus) in the diet. Pronounced interannual variation in the species composition of diets was evident in both habitats. This variation was associated with broad-scale changes in prey abundance in some cases (e.g., squid and capelin) but not in others (e.g., Atlantic cod and pollock).
Can shrub cover increase predation risk for a desert rodent?
Authors: Schooley Robert L. , Sharpe Peter B. , Horne Beatrice Van
Published: May 2008

Previous research indicates that predation risk may influence activity patterns, habitat partitioning, and community structure of nocturnal desert rodents. Shrub microhabitat is typically considered safer than open microhabitat for these small mammals. We investigated predation risk for Townsend's ground squirrels (Spermophilus townsendii), which are diurnal desert rodents that detect predators visually and use burrows for refuge. Our results suggested that shrub cover may increase risk for these squirrels by decreasing their ability to escape from predators. Our field experiment indicated that running speeds of juvenile squirrels were lower in shrub (Ceratoides lanata) habitat than in open areas. Shrub cover was also associated with shorter predator-detection distances (mammalian and avian) and fewer refuges (burrow entrances per hectare) than in open areas in one year but not in another. Our study demonstrated that the visual and locomotive obstruction of vegetative cover may increase predation risk for diurnal desert rodents and that elements of habitat-dependent risk may be temporally dynamic.
Nitrogen fertilization stimulates herbivory by snowshoe hares in the boreal forest
Authors: Nams Vilis O. , Folkard Nicholas F. G. , Smith James N. M.
Published: May 2008

We fertilized small plots in the boreal forest of the southwestern Yukon, Canada, to see how herbivory was affected. We assessed snowshoe hare (Lepus americanus) activity by counting pellets, and estimated grazing on grass as the proportion of blades eaten. After 2 years of fertilization, snowshoe hares spent more time on and near the test plots with more fertilizer. More grass was grazed on those plots but not near them. Thus, herbivores were attracted to the general area of the fertilized plots but only grazed directly on the plots.
Thermoregulation of juvenile grey seals,Halichoerus grypus, in air
Authors: Boily Patrice , Lavigne David M.
Published: May 2008

Metabolic rate, core temperature, and duration of sleep-related apnea events were monitored in three juvenile grey seals (Halichoerus grypus) aged 7–19 months (49–78 kg), at ambient air temperatures ranging from −18 °C to 35 °C. At low temperatures, only one seal increased its metabolic rate (at −18 °C), whereas at high temperatures (up to 35 °C) none of the three animals increased its metabolic rate. Nonetheless, seals usually became hyperthermic when they were subjected to air temperatures of 30 °C or higher. There was no indication that the duration of sleep-related apnea was greater at higher temperatures. The sleeping metabolic rate was significantly lower (20%) than the resting level. A metabolic depression associated with sleep may be advantageous at higher temperatures, reducing the internal heat load of the animal. These results suggest that cold-water adaptations of juvenile grey seals do not interfere with their ability to cope with higher air temperatures. Also, such animals should not be directly limited in their distribution by either high or low ambient air temperatures.
Cost of locomotion and daily energy expenditure by free-living swift foxes (Vulpes velox): a seasonal comparison
Authors: Covell Darrel F. , Miller David S. , Karasov William H.
Published: May 2008

We studied the daily energy expenditure of free-living nonreproductive carnivorous swift foxes (Vulpes velox, average mass 2.1 kg) on shortgrass prairie in southeastern Colorado in summer and winter in relation to air temperature, daily activity pattern, movement rate, and daily movement distance. The field metabolic rate (FMR) was measured with doubly labeled water, and activity and movements were monitored by radiotelemetry. During their nighttime activity period in winter, swift foxes traveled large distances (18.5 ± 0.6 km/d). Locomotion costs (estimated from daily movement distance in winter, using an allometric equation) accounted for at least 21% of total daily expenditure, the highest proportion reported for a mammal. During their nocturnal activity periods (winter vs. summer), swift foxes apparently traveled farther (ca. 13.0 vs. 5.7 km/night, using equal sampling intervals) and were active longer (ca. 12.9 vs. 11.3 h/night) in colder air. Nevertheless, FMR in winter (1488 kJ/d) was significantly lower than during summer (2079 kJ/d). We review available data for other free-living eutherians and show that low temperatures in winter are not necessarily associated with increases in FMR.
Growth and survival of juvenile yellow-bellied marmots (Marmota flaviventris)
Authors: Lenihan Colleen , Vuren Dirk Van
Published: May 2008

We compared patterns of growth in juvenile yellow-bellied marmots (Marmota flaviventris) between 2 years in which precipitation differed, and we determined if mass at entry into hibernation affects over-winter survival. Juveniles exhibited an asymptotic growth pattern with mass gain for a mean of 60.8 days, followed by stable mass until entry into hibernation. Growth ceased in early September, shortly after the end of the plant growing season. Juveniles born in 1991, a year of late snowmelt and low summer precipitation, entered into hibernation at significantly lower mass than juveniles born in 1992. Juveniles born in 1992 survived better despite experiencing a long winter during which they spent more days in hibernation and lost more mass. Overall, heavier juveniles were more likely to survive hibernation. Further, mass at entry into hibernation apparently had a greater effect on over-winter survival than did winter severity.
Three sibling species of didemnid ascidians from northern Norway: Didemnum albidum (Verrill, 1871), Didemnum polare (Hartmeyer, 1903), and Didemnum romssae sp.nov.
Authors: Marks Jessica A.
Published: May 2008

Recent advances in taxonomy have disclosed the prevalence of cryptic sibling species in marine systems. In didemnid ascidians, morphological variation between species is often slight, and many species may have been overlooked. Species boundaries within this group are often equivocal, and patterns among taxa are reminiscent of those formed by reticulate evolution in plants. Specimens of the sessile colonial ascidian Didemnum albidum (Verrill, 1871) were examined for life-history and morphological characters and found to constitute at least three sympatric sibling species. One of these, Didemnum romssae, is described here as a new species. Colonies were collected from hard-bottom assemblages in Troms and Finnmark counties in northern Norway. Zooid morphology in D. romssae is similar to that of D. albidum, but varies within each species, even for traits usually considered specific. Didemnum romssae is proposed as a distinct species on the basis of consistent differences in (i) the shape and size of calcium carbonate spicules within the common test; (ii) larval size and the number of lateral ampullae; (iii) timing of reproduction; and (iv) the absence of a seasonal nonfeeding, overwintering stage, which occurs in D. albidum. Examination of specimens from museum collections considered synonymous with D. albidum confirmed the presence of a third species, Didemnum polare (Hartmeyer, 1903), which differed from the other two species in zooid and larval morphology as well as spicule shape. Complexes of sibling species such as these provide a tractable system for studying the consequences of life-history variation among closely related taxa.
Stretch-induced release of atrial natriuretic factor from the heart of rainbow trout (Oncorhynchus mykiss)
Authors: Cousins K. L. , Farrell A. P.
Published: May 2008

We investigated the effect of both cardiac filling and after-load pressures on the release of atrial natriuretic factor (ANF) from rainbow trout hearts (Oncorhynchus mykiss). Our experimental approach was to perfuse hearts in situ and collect perfusate ejected from the heart in 1-min fractions and assay for immunoreactive ANF-(99-126) (human and canine). Increases in cardiac filling pressure produced repeatable and sustained increases in cardiac output. At the same time, there was an immediate and sustained increase in ANF secretion. ANF secretion increased sixfold from the control level of 30.68 ± 4.76 pg∙min−1∙g−1wet heart mass for a fourfold increase in cardiac output from 15.24 ± 0.73 mL∙min−1∙kg−1body mass. ANF secretion was unaffected by increases in after-load pressure. Measurement of immunoreactive ANF content in trout myocardial tissues revealed ANF in both the atrium and ventricle, but 92% of the total ANF store was contained within the atrium. This suggests that in rainbow trout, the atrium serves as the primary cardiac tissue for ANF release. These data are consistent with the mechanism of ANF release for mammalian hearts, and provide additional evidence that ANF secretion in vertebrates is mediated by atrial stretch and not ventricular stretch.
Day-roosting activity budgets of the eastern pipistrelle bat, Pipistrellus subflavus (Chiroptera: Vespertilionidae)
Authors: Winchell Jane M. , Kunz Thomas H.
Published: May 2008

Daily and seasonal activity budgets of adult female eastern pipistrelle bats, Pipistrellus subflavus, were quantified at a maternity colony in eastern Massachusetts. Ambient and roost temperatures were recorded. Activities of roosting bats were monitored using an infrared-sensitive video camera. Scan sampling was used to analyze video records taken at weekly intervals from mid-May to late July 1989. Analysis of day-roosting indicates that adult females spend an average of 77% of their time at rest, 16% alert, 7% grooming, and < 1% crawling. Bats were most active immediately following their morning return to the day-roost and just prior to their departure at dusk. Periodic bouts of activity throughout the day were usually associated with urination and (or) defecation, mother–pup interactions, and movements in response to changes in roost temperature. Females were significantly more active in mortise roosts than when roosting on the open ridgepole, probably because fluctuations in temperature in mortises were smaller. As the season progressed, the overall time that bats spent resting decreased from 86 to 70%, whereas time spent alert increased from 9 to 24%; weekly fluctuations in the incidence of grooming and crawling showed no consistent seasonal trends. Roost temperature, time of day, and date explained significant amounts of variation in both daily and seasonal activity budgets. Females rested significantly less and were more alert after young were born than before, although time spent grooming and crawling did not differ significantly between the pre- and post-partum periods. Our findings for P. subflavus generally corroborate activity budgets previously reported for the little brown bat (Myotis lucifugus).
Winter diet of marten during a snowshoe hare decline
Authors: Poole Kim G. , Graf Ron P.
Published: May 2008

We examined the winter diet of marten (Martes americana) from northern (65–67°N) and southern (60–62°N) regions of the western Northwest Territories from 1988–1989 to 1993–1994 during a decline in snowshoe hare (Lepus americanus) abundance that started in 1990. We used 4256 marten carcasses collected from trappers to examine changes in diet, productivity, age and sex structure of the harvest, and body and reproductive indices. Arvicoline rodents formed the greatest proportion (41–95% occurrence of total prey items) of the annual winter diet in both regions and snowshoe hares constituted 1–39% of prey items. Snowshoe hares constituted 3–64% of the diet when expressed as biomass. Dietary proportions of arvicolines increased and snowshoe hares decreased with time in the northern region but not in the southern region. Female marten took proportionately more arvicolines and males took more snowshoe hares. Juvenile marten took proportionately more snowshoe hares, while adults took more arvicolines. The proportion of juvenile marten in the harvest declined in both regions between 1991–1992 and 1993–1994. The ratio of juveniles to adult females in the harvest also declined with time in the southern region but not in the northern region. The amount of omental fat declined with time for most age and sex classes. Ovulation rates (as determined by counts of corpora lutea) declined with time among yearlings, and among adults from the southern region but not in the northern region. In utero litter size did not change. We suggest that the snowshoe hare population cycle has a significant impact on marten populations in the northern boreal forest.
Twin malformation induced in chum salmon eggs by elevated water temperature, with a suggestion as to its mechanism
Authors: Yamamoto Tadashi S. , Kobayashi Wataru , Kuramoto Tsutomu
Published: May 2008

Inseminated eggs of chum salmon, Oncorhynchus keta, were incubated at 18 °C. In batches of eggs from different females, we regularly observed twinning in a proportion of the eggs (0.5–4%) continuously incubated at this temperature, although no twins were obtained at 8 °C. Twinning was, however, observed at 8 °C when inseminated eggs had been previously treated at 18 °C until the 2- to 4-cell stage. In contrast, eggs attaining telophase in the second meiosis at 8 °C did not show the twin malformation, even when they continued embryonic development at 18 °C. In sections of eggs developed as twins, we detected accumulations of PAS-positive vesicular bodies in the ooplasm between the two embryos. A small number of eggs showing impaired exocytosis of cortical vesicles (alveoli) during egg activation developed into twins. A similar malformation was also induced after part of the ooplasm was dislodged in activated eggs. We propose that vesicular bodies interfere with the convergent migration of the axial determinant during the early phase of embryonic development, which leads to the formation of multiple morphogenetic centers in the eggs incubated at 18 °C.
Clutch frequency, egg and clutch characteristics, and nesting activity of spur-thighed tortoises,Testudo graeca, in southwestern Spain
Authors: Diaz-Paniagua C. , Keller C. , Andreu A. C.
Published: May 2008

Reproduction in female spur-thighed tortoises (Testudo graeca) in a population from southwestern Spain was studied by X-radiography of thread-trailed and radio-tagged individuals. Most females reproduce every year, laying one to four clutches from April to June with internesting intervals ranging from 21 to 29 days. Clutch size varied from 1 to 7 eggs and averaged 3.5 eggs. Carapace length and mass of females were positively correlated with the starting date and duration of the nesting season, while age was not correlated with any reproductive variable. Eggs averaged 33.87 × 27.97 mm in dimensions and 14.4 g in mass. Female mobility increased shortly before or after nesting, which resulted in wide dispersal of the various nests laid by an individual female.
A new species of the congrogadin genus Rusichthys from southern Oman (Perciformes; Pseudochromidae), with notes on its osteology
Authors: Winterbottom Richard
Published: May 2008

Three specimens of a distinctive new species of congrogadin belonging to the basal lineage (Rusichthys) of the subfamily are reported here. The new species differs from its congener in having more dorsal-fin and anal-fin rays and more gill rakers on the outer surface of the first gill arch, in colour pattern, and in various osteological details (especially of the caudal skeleton). Rusichthys explicitus n.sp. is presently known from a single collection taken from 27 m off southwest Oman, whereas R. plesiomorphus is presently known from two specimens trawled in 140 m on the Lamu Banks off northern Kenya.
Population structure of the sand dollar Echinarachnius parma in the subtidal zone of the northern Gulf of St. Lawrence, eastern Canada
Authors: Cabanac A. , Himmelman J. H.
Published: May 2008

We examined changes in populations of Echinarachnius parma with depth on subtidal sediment slopes in the Mingan Islands. Size distributions showed the presence of two major groups measuring 1–21 and 37–62 mm in length, respectively. Intermediate-sized sand dollars were rare. Juveniles (< 28 mm in length) were extremely abundant at 16 and 20 m depth (460–660/m2) and decreased in number with decreasing depth, whereas the density of adults was relatively stable at different depths. Juveniles were more frequently buried (95%) than adults (30%). Analysis of growth lines and of shifts in juvenile cohorts indicated that growth rate increased with size up to a maximum between 20 and 40 mm and then decreased sharply. The bimodal size structure is possibly due to the accelerated growth rate at intermediate sizes. We hypothesize that sand dollars move to shallower water with increasing size to take advantage of food resources, possibly benthic diatoms, which are more abundant there. Large individuals are probably better adapted than juveniles to exploiting shallower water because they are less likely to be transported by water turbulence.
Sexual dimorphism in wolves (Canis lupus) of the Keewatin District, Northwest Territories, Canada
Authors: Hillis Tracy L. , Mallory Frank F.
Published: May 2008

Twenty-two skeletal, visceral, and adipose parameters were compared in 425 wolves collected from the central Arctic between 1987 and 1989. Fifteen parameters differed significantly by sex. Males were usually larger than females; however, the degree of sexual dimorphism varied with structure. Male skeletal parameters ranged between 3 and 6% greater than those of females, and significant differences were largely associated with the anterior body region and the limbs. Male body mass was 18% and male visceral parameters ranged between 12 and 24% heavier than those of females. Patterns of adipose deposition were also significantly different. Sternum and inguinal fat depths and total external and mesentery fat indices were significantly greater in males (5–44%), while rump fat depth was significantly greater in females (1%). These results support the conclusion that sexual dimorphism in wolves has evolved primarily as a foraging strategy, owing to division of labour between the sexes, and males are more highly specialized for capturing and killing large ungulate prey, while females are more specialized for a nurtural role.
The evolution of body size in the Monogenea: the role of host size and latitude
Authors: Poulin Robert
Published: May 2008

Monogeneans form a diverse group of parasitic platyhelminths that show substantial interspecific variation in body size, though this variation remains largely unexplained. The relationships between monogenean body size and both host body size and latitude were examined in comparative analyses using data from 613 monogenean species. First, phylogenetically independent contrasts among 39 monogenean families revealed no relationship between host size and parasite size. However, large parasite size was consistently associated with high latitude, suggesting that larger body size in monogeneans may result more from external factors such as temperature than from host-related factors. The potential effects of other variables (site of attachment on the host, host taxonomy, and type of aquatic habitat) could not be assessed in the analysis. Second, analyses among genera within families failed to show any consistent relationships between monogenean body size and either host size or latitude. The results of this study suggest that latitude had an evolutionary influence on monogenean body size, though this may be only visible in comparisons among higher taxonomic levels, and that monogenean body size has not simply adjusted to host body size following host-switching events.
Foraging movements of female bushy-tailed wood rats (Neotoma cinerea)
Authors: Topping Michael G. , Millar John S.
Published: May 2008

Nocturnal foraging movements of female bushy-tailed wood rats (Neotoma cinerea) in the Canadian Rocky Mountains, Alberta, were monitored using radiotelemetry over two breeding seasons (1993–1994). Total distance moved and maximum foraging radius from the nest per night were calculated for individual females throughout the breeding season. Movements during pregnancy, lactation, and the postreproductive period did not differ significantly. Females moved much farther (up to 470 m) from the nest than previously reported for this species (60 m). Such long-distance movements may be related to the availability of an appropriate food supply.
Assessing the use of hard parts in faeces to identify harbour seal prey: results of captive-feeding trials
Authors: Cottrell Paul E. , Miller Edward H. , Trites Andrew W.
Published: May 2008

Faeces were collected from four captive harbour seals (Phoca vitulina) that consumed known amounts of herring (Clupea harengus), walleye pollock (Theragra chalcogramma), Pacific hake (Merluccius productus), surf smelt (Hypomesus pretiosus), and juvenile chinook salmon (Oncorhynchus tshawytscha). The goal was to determine which structures (hard parts) passed through the digestive tract (e.g., eye lenses, scales, vertebrae, otoliths), and which of these could be used to determine the type and number of fish consumed. Nearly 5000 fish were consumed, from which over 50 000 hard parts were recovered from seal faeces. Scales were the most numerous of the 23 structures recovered (>20 000), followed by vertebrae, eye lenses, and otoliths. Morphological distinctiveness and digestive erosion of the structures varied among fish taxa. Two to five structures accounted for over 90% of the taxon-specific elements recovered, depending upon the species of fish consumed. Otoliths, which are used routinely to characterize pinniped diets, accounted for only 17% of the identified taxon-specific hard parts. The variation in types of structures and rates of recovery across taxa underscores the importance of using several types of hard parts to identify prey. Identifying several different prey structures increases the likelihood of identifying a prey type.
Cytological evidence for cryptic speciation in MediterraneanOscarellaspecies (Porifera, Homoscleromorpha)
Authors: Muricy Guilherme , Boury-Esnault Nicole , Bézac Chantal , Vacelet Jean
Published: May 2008

Three new sponge species without a skeleton, Oscarella viridis, O. microlobata, and O. imperialis, were found in sublittoral caves and on vertical walls along the coast of Provence (western Mediterranean Sea, France). Their morphology, anatomy, and cytology are described and they are compared with the two other valid Mediterranean Oscarella species, O. lobularis and O. tuberculata. Reproductive and internal anatomical characters are uniform in the genus, but details of external morphology and especially cytological characters (mesohylar cells with inclusions) provide good diagnostic features at the species level. Careful observation of morphological and cytological characters is essential for clarifying the systematics of Oscarella and reveals an unexpected biodiversity of this genus in the Mediterranean Sea.
The aquatic oribatid mite genus Mucronothrus in Canada and the western U.S.A. (Acari: Trhypochthoniidae)
Authors: Norton Roy A. , Behan-Pelletier Valerie M. , Wang Hui-fu
Published: May 2008

The aquatic oribatid mite genus Mucronothrus (Trhypochthoniidae) is redescribed on the basis of characters of adults and immatures and its familial placement is reviewed. It is represented in North America by two species. Mucronothrus nasalis, a globally widespread species, is redescribed on the basis of all active instars. In Canada it is now known from Newfoundland, New Brunswick, Ontario, Quebec, Saskatchewan, Alberta, and British Columbia and in the U.S.A. from Oregon and Colorado. Ancillary new distribution records include England and Cape Horn. Misinterpretations of homologies of leg setae in the literature are corrected. A population near Toronto, Ontario, was examined for variation in genital and leg setation; this conforms well with previously described geographic patterns (J. Travé). This population exhibits previously unknown variation in cheliceral form. A second species, Mucronothrus willmanni n.sp., is proposed on the basis of adults and tritonymphs. Current records are from California, Oregon, and Montana, where it inhabits riffles in streams. Only females are known and, like M. nasalis, the species appears to be thelytokous.
Nematode diversity of native species of Vitis in California
Authors: Banna Luma Al , Gardner Scott Lyell
Published: May 2008

From 1990 through 1992, nematodes were extracted from soil samples taken from the rhizosphere of native species of grapes from four areas of northern California and two areas of southern California. For comparison, samples from domestic grapes as well as a putative hybrid of Vitis californica and V. vinifera were also taken. Rhizosoil from California native grapevine contained many more species of nematodes than did soil obtained from cultivated forms of V. vinifera. Taxonomic and trophic diversity was much higher in nematodes from sampling sites from native grapes than in those from grapes maintained in vineyard situations. Ordination methods using correspondence analysis showed both similarities and differences in the faunal assemblages of nematodes from the different sampling sites, based on indexes of species and trophic groups. Collected data indicate that nematode communities with high trophic and taxonomic diversity have a lower numerical density of plant parasites.
Breeding populations of northern pintails have similar mitochondrial DNA
Authors: Cronin Matthew A. , Grand J. Barry , Esler Daniel , Derksen Dirk V. , Scribner Kim T.
Published: May 2008

Northern pintails (Anas acuta) are highly nomadic, which may result in high levels of gene flow among nesting areas. To assess the extent of genetic differentiation among nesting areas, we analyzed mitochondrial DNA (mtDNA) variation in northern pintail females from three regions: Alaska, California, and midcontinent prairies and parklands. Abundant mtDNA variation was evident (20 genotypes among 289 birds), but there was no significant genetic differentiation of nesting areas within or among regions. Results indicate that pintails have had historically large breeding population sizes and a high rate of gene flow among North American nesting areas. Specific nesting areas are not independent units, but part of a larger continental population. High rates of gene flow suggest that over time, localized reductions in recruitment or survival may be compensated for by immigration.
Avian eggshell formation in calcium-rich and calcium-poor habitats: importance of snail shells and anthropogenic calcium sources
Authors: Graveland J.
Published: May 2008

Most passerines depend on the intake of calcium-rich material in addition to their normal food for proper eggshell formation and skeletal growth. A large proportion of Great Tits (Parus major) in forests on nutrient-poor soils in the Netherlands produce eggs with defective shells as a result of calcium deficiency. Eggshell defects are much scarcer near human settlements and do not occur on nutrient-rich soils. I investigated this variation in eggshell quality by examining the use of calcium-rich material by the birds. The results show that calcium-rich items in nest material and droppings can be used as a measure of calcium consumption. Snail shells were the main calcium source in forests where eggshell defects did not occur. In forests where the tits exhibited calcium deficiency, snail shells were rarely taken and birds used anthropogenic calcium sources such as chicken grit and chicken eggshells. It was demonstrated that the dependence on snail shells and the use of alternatives such as anthropogenic calcium sources in areas where snails are scarce are general features of calcium intake among birds. Thus, calcium limitation may be a common phenomenon in avian reproduction on poor soils in countries less populous than the Netherlands.
Dawn song repertoires of tree swallows (Tachycineta bicolor)
Authors: Horn Andrew G.
Published: May 2008

I describe the dawn songs of 38 male tree swallows (Tachycineta bicolor) recorded at five sites near Wolfville, Nova Scotia. Males deliver dawn song each morning during the hour before dawn, while flying elliptical paths above their nest sites. These dawn songs consist of syllables approximately 0.15 s long, delivered every 1.5 s. Each male has a recorded repertoire of one to seven discrete syllable types (average 2.6) and may repeat each syllable type an apparently random number of times before switching to the next. Most syllables could be classified on the basis of their structure into seven types, with much variation among renditions by different males of any given syllable type. Three of these syllable types were very similar to call notes that have specific uses at other times of day. Syllable types were randomly distributed among males and sites. In this species neither syllable type, the number of times each type is repeated (string length), nor the number of types a male sings (repertoire size) appears to carry particular messages or advertise male quality. Instead, syllable types may provide individual distinctiveness and variety in song sequences.
Diving performance of male and female Japanese Cormorants
Authors: Watanuki Yutaka , Kato Akiko , Naito Yasuhiko
Published: May 2008

Sexual differences in the diving behavior of the sexually dimorphic Japanese Cormorant, Phalacrocorax capillatus (males are 26% heavier than females), were studied at Teuri Island, Hokkaido, using time–depth recorders. A typical dive cycle involved a rapid descent phase, a bottom phase where they remained for a while, an ascent phase, and a postdive surface phase. Depth and duration across individual birds were greater for males (15.1 ± 3.7 (mean ± SD) m, 37 ± 5 s, respectively) than those for females (7.2 ± 2.4 m, 24 ± 4 s, respectively). While submerged, females spent a similar proportion of time during the bottom phase to males, hence foraging efficiency (proportion of time at the bottom to total dive cycle time) did not differ between the sexes. No sexual differences were found in descent and ascent rates, dive bout duration, or time spent underwater per day. No significant effects of dive duration on postdive surface time were observed for either sex, indicating that birds dived within an aerobic dive limit. However, mean dive durations and maximum dive durations for individual birds were a function of body mass to the power 1.49 and 1.87, respectively, suggesting that body mass partly constrains the diving behavior of this opportunistically feeding cormorant.
Population performance of generalist and specialist rodents along habitat gradients
Authors: Seamon Joshua O. , Adler Gregory H.
Published: May 2008

Population performance along habitat gradients is predicted to differ among species that differ in their degree of habitat specialization. We compared a specialized rodent (the eastern chipmunk, Tamias striatus) with a generalist (the white-footed mouse, Peromyscus leucopus) that occurs across a wider range of habitats. Populations were seasonally livetrapped on 10 small forested sites every 2 weeks for 4 years. Linear regressions were used to relate density, residency, and reproduction to microhabitat gradients developed by hierarchical factor analysis of vegetation variables. Densities of both species were related to a habitat complexity gradient. Density variability and duration of residency in P. leucopus were related to fewer habitat variables than in T. striatus. Associations of P. leucopus densities with habitat variables varied more among years than those of T. striatus. Over-winter survival and reproductive activity were related to microhabitat gradients for T. striatus only. Population performance of habitat generalists and specialists overlaps to a greater degree than predicted by a single continuum of specialization, since each species responded to habitat components in both a fine-grained and a coarse-grained manner. Species may partition variance in demography along different regions of macrohabitat gradients, leading to unique relationships with the same microhabitat in different environments.
Insect fossils in middle Eocene deposits from British Columbia and Washington State: faunal diversity and geological range extensions
Authors: Douglas Sheila D. , Stockey Ruth A.
Published: May 2008

Fossil insects in the orders Coleoptera, Hymenoptera, Diptera, and Lepidoptera were examined from nine middle Eocene localities in British Columbia, Canada, and Washington State, U.S.A. Twenty-five taxa are described, with the majority classified into families. Specimens belonging to Bibionidae and Ichneumonidae were the most common. Almost half of the coleopteran specimens were isolated elytra and identification was not possible. Three of the insect families (Cantharidae, Arctiidae, Noctuidae) represent the earliest known occurrence of the taxa in the world geological record and seven families (Lucanidae, Cantharidae, Scoliidae, Pompilidae, Rhagionidae, Arctiidae, Noctuidae) are the earliest records in North America. Eleven of the families identified are new records for the middle Eocene of British Columbia – Washington State, bringing the diversity of fossil insects in the region to 28 families. Significant for the study of anthecology are new records for lepidopterans.
Size-related changes in winter condition of female and male reindeer calves
Authors: Kojola I. , Helle T.
Published: May 2008

This study investigated how relationships between body size and back-fat depth develop in female and male reindeer (Rangifer tarandus tarandus) calves in winter. Back-fat depths did not differ between male and female calves, but depended more strongly on body size in female calves. Because no sex difference was found in the post-rut sample (October), differences were not attributed to male puberty and consequent sexual activity. Sex differences might be related to the fact that female calves feed more often than males from craters dug in the snow by their mother and that daughters of dominant mothers share feeding craters with their mother most often. In the last sample month, February, the fattest males were medium-sized, but mean back-fat depths did not differ between medium-sized and large calves. The decreasing trend in size dependence of fat reserves of male calves through the winter possibly weakens the link between maternal investment and reproductive success of sons.
The evolution of sexual dimorphism in the lizard Anolis polylepis (Iguania): evidence from intraspecific variation in foraging behavior and diet
Authors: Perry Gad
Published: May 2008

Two main explanations, intraspecific niche divergence and sexual selection, have been proposed to explain the origin of sexual size dimorphism. To test these competing hypotheses I studied the ecology, feeding behavior, and diet of the lizard Anolis polylepis in a Costa Rican rain forest. Male A. polylepis were significantly larger and heavier than females but ate smaller food items and had lower stomach volumes, despite possessing longer and wider heads. Males were more sedentary than females or juveniles, chose higher perches, and were more likely to be involved in agonistic interactions. Diets of males, females, and juveniles were also significantly different taxonomically. These data are consistent with the sexual selection origin theory but not with an ecological one. Thus, observed dietary differences probably evolved once dimorphism had been attained through sexual selection.
Parasite-induced changes in the behaviour of cestode-infected beetles: adaptation or simple pathology?
Authors: Robb Tonia , Reid Mary L.
Published: May 2008

Although the cause is often unclear, many parasites alter the behaviour of their intermediate hosts. The larval form of the rat tapeworm, Hymenolepis diminuta, has previously been shown to modify the behaviour of its intermediate host, the flour beetle, Tribolium confusum, in a manner that may be adaptive to the parasite. To test this explanation we observed host behaviours including activity, concealment, and the response to and production of pheromones. Infected female beetles examined both 4–5 and 11–12 days post infection were slower moving and slower to conceal themselves than uninfected conspecifics; however, they did not differ from uninfected individuals in staying concealed. Infection of T. confusum did not affect the production of pheromones by mated and virgin females or the response of females to male pheromones. A second hypothesis for altered behaviours may be that modified behaviours result from pathology. The survivorship of mated infected female beetles was significantly lower than that of infected virgin beetles and uninfected beetles. Thus, both mated status and infection were important factors in survivorship, but only infection had significant effects on the altered behaviours. In this system, therefore, the hypothesis that behavioural changes are due to adaptive manipulation of the host by the parasite is supported.
Recovery of Hesperodiaptomus arcticus populations from diapausing eggs following elimination by stocked salmonids
Authors: Parker Brian R. , Wilhelm Frank M. , Schindler David W.
Published: May 2008

Hesperodiaptomus arcticus, a predatory calanoid copepod, was eliminated from two alpine lakes within 6 years of stocking with salmonids. Using historical and contemporary Zooplankton and fish data, sediment analysis for diapausing eggs, and experiments on predation of Gammarus lacustris on diapausing eggs of H. arcticus, we assess the fate of these populations 35 years after fish stocking. In Pipit Lake, in which the trout introduction failed within 21 years, we propose that H. arcticus recovered as a result of hatching of diapausing eggs held in the sediments. In Snowflake Lake the diapausing egg bank was exhausted prior to the loss of the fish population 25 years after first stocking and H. arcticus recovery did not occur. Experimental studies indicate that G. lacustris predation on diapausing eggs probably occurs within the sediments. Combined with a 10-fold difference in G. lacustris density between Snowflake and Pipit lakes the results of the predation experiments imply that G. lacustris had a strong negative impact on the abundance of diapausing eggs held in Snowflake Lake sediments and therefore reduced the ability of the population to recover following perturbation.
Optimization of shock parameters in inducing mitotic gynogenesis in the carp Cyprinus carpio L.
Authors: Yousefian M. , Amirinia C. , Horváth L. , Bercsényi M.
Published: May 2008

The relative effects of heat-shock parameters on the induction of first-cleavage suppression of common carp (Cyprinus carpio L.) eggs were examined. Eggs of females with scattered scales were fertilized with sperm that had been irradiated with gamma-ray cobalt-60. Fertilized eggs were exposed to heat shock at different temperatures (39, 40, 41 °C) for periods of 1–3 min at 0.5-min intervals, initiated at 41, 44, or 47 min post fertilization in a factorial design. The use of three treatment factors made it possible to analyze the main effects and all possible combinations of the three factors. The highest percentage of mitotic gynogenetic diploids (mitotic-G2n) (up to 10.6% survival at the feeding larva stage relative to the total number of inseminated eggs) was obtained from the groups treated at 40 °C for 2 min at 44 min post fertilization (ambient temperature 21 °C). Optimum duration was observed to be 2.5–3 min at 39 °C and 1–1.5 min at 41 °C. The embryos were developed under hatchery condition, while larvae were reared in a flow-through system with natural feeding. Isozyme and scale pattern analysis performed on putative mitotic-G2n individuals both proved that their genome is of maternal origin.
Effects of the introduction of white sucker, Catostomus commersoni, on the parasite fauna of brook trout, Salvelinus fontinalis
Authors: Dubois Nicole , Magnan Pierre , Marcogliese David J.
Published: May 2008

White sucker, Catostomus commersoni, has been introduced in many brook trout, Salvelinus fontinalis, lakes of the Laurentian Shield, Quebec, Canada. The goal of this study was to assess the impact of these introductions on the parasite fauna of brook trout. Three lakes containing brook trout only and three lakes containing both brook trout and white sucker were studied. The objectives were (i) to determine if white sucker parasites were able to colonise the relatively oligotrophic lakes of the Laurentian Shield, (ii) to establish if parasites were exchanged between sucker and trout, and (iii) to study the effect of trout feeding habits on their parasite fauna, since this fish shifts its diet from zoobenthos to Zooplankton when living with white sucker. Eight of the 12 parasite species found on white sucker probably colonised the lakes with their host. Among the 11 parasite species identified from trout, it is unlikely that any were introduced by white sucker. Trout living with white sucker have more parasites transmitted by Zooplankton (Diphyllobothrium ditremum and Eubothrium salvelini) and fewer parasites transmitted by zoobenthos (Crepidostomum farionis and Sterliadochona ephemeridarum) than trout living in allopatry. Local factors such as lake morphometrics also seemed to play an important role in the composition of the trout parasite fauna.
Development of larvae of Chrysops nigripes Zetterstedt and Chrysops probably zinzalus Philip (Diptera: Tabanidae) in a subarctic Labrador peatland
Authors: McElligott Paul E. K. , Lewis David J.
Published: May 2008

A total of 476 tabanid larvae, including 108 Chrysops nigripes and 145 Chrysops probably zinzalus, were obtained from regular collections made from early June through late August 1990–1991 in Iron Arm Fen, a minerotrophic peatland located in subarctic Labrador near Schefferville, Quebec. Changes in head capsule and total body length-frequency distributions among successive sampling periods and years suggest very slow growth rates for Chrysops species at subarctic latitudes; life cycles may require 7–8 years to complete.