bluuebunny/crossref_metadata_2025 huggingface dataset:
Food of Double-crested Cormorants,Phalacrocorax auritus, in the Gulf and Estuary of the St. Lawrence River, Quebec, Canada
Authors: Rail Jean-François , Chapdelaine Gilles
Published: April 2011

Between 1994 and 1996, a total of 613 Double-crested Cormorant (Phalacrocorax auritus) regurgitations were collected at four colonies located in the St. Lawrence Estuary and one colony on the North Shore of the Gulf of St. Lawrence. The diet comprised a great variety of prey, with fishes well represented. Capelin (Mallotus villosus) and sand lance (Ammodytes sp.) together constituted most of the diet, (i.e., frequency of occurrence 66%, numerical frequency 68%, and volume 50%). Sand lance, which were nearly absent in regurgitations from the Estuary, were important in the diet of cormorants from the North Shore of the Gulf. At the North Shore colony, capelin were much more abundant in the diet in 1996 than in 1995, which correlates with independent fisheries data. In contrast to the results of previous studies of this cormorant's diet, our results show a preponderance of schooling fishes over benthic species. We suggest that this reflects a recent trend towards an increase in the abundance of schooling fishes in the St. Lawrence Estuary and Gulf. Overfishing of predatory fishes and oceanographic factors could be involved.
A technique for identifying the early-premolt stage in the male snow crab Chionoecetes opilio (Brachyura: Majidae) in Baie des Chaleurs, southern Gulf of St. Lawrence
Authors: Benhalima Khadra , Moriyasu Mikio , Hébert Marcel
Published: April 2011

New criteria for determining the early-premolt stage (D0) of the snow crab Chionoecetes opilio are described, based on histological observations. Identifying the early-premolt stage in snow crabs on the basis of observations of setagenesis poses difficulties for inexperienced observers. At the start of the premolt phase, numerous actively secreting cells beneath the epithelium and Leydig cells in the connective tissue can be observed using histological techniques. A semitransparent substance observed between the membranous layer and epithelium by histological means was further subjected to transmission electron microscope observations, which suggested that this was the molting fluid whose presence represents the beginning of the process of deposition of the epicuticle. At the time when the molting fluid is secreted in snow crabs, no morphological characteristics of premolt stage D1 are discernible, therefore these features can be used to identify D0. Using this technique, the molt stages of adolescent male crabs in the southern Gulf of St. Lawrence were examined, revealing the existence of two different types of molters that enter into the molting process in different times of the year. The majority of adolescent males go through the premolt stages in August-December and start to molt in March-April of the following year; another group of adolescent males with more epibionts on the carapace in the spring (adolescents that did not molt in the previous spring) are in the premolt stages in May-July and probably start to molt in December-January. The present study reveals that the molting patterns of snow crabs are far more flexible than the previous literature had suggested. The implications for long-term stock management are quite important, and further study on the structure and dynamics of molters is needed.
Effects of temperature on individual growth rate and body size of a freshwater amphipod
Authors: Panov Vadim E , McQueen Donald J
Published: April 2011

Individual growth rates of the freshwater amphipod Hyalella azteca (Saussure) were measured in the littoral zone oftwo small oligotrophic Ontario lakes and in growth experiments over a natural temperature gradient (10, 15, 20, and 238C).Field observations showed that a temperature of 208C is important for both the induction and termination of reproductiveresting stages in H. azteca. Growth rates were more affected by temperature in small than in large individuals. Growthparameters are related to rearing temperature by linear regressions, which can be used as a simple model for bioenergeticscalculations in crustaceans. A negative relationship between water temperature and maximum size attained by the amphipodswas found. The largest adults were absent in studied populations when summer temperatures were high, and this phenomenon,which has also been observed in other aquatic invertebrates, was bioenergetically determined. Energy-budget estimationsshowed negative net growth efficiency (K2) in the largest adults at temperatures above 208C. The relationship between K2andtemperature showed a dome-shaped pattern, K2values for larger amphipods being maximal at lower temperatures. Seasonalmigrations of adult H. azteca from shallow littoral to deeper cold habitats, observed in lakes during the warmest periods, appearto be temperature-induced and bioenergetically advantageous, despite probable increases in predation risk experienced inspatially simple deep-water habitats.
The relative positions of the jaw joint and the tooth row in mammals
Authors: Greaves Walter Stalker
Published: April 2011

The mammalian jaw joint almost always lies above the tooth row. A model is presented in which the moment arm ofthe resultant of jaw muscle force is held constant for a series of hypothetical jaw joints. Some of these joints lie above whileothers lie below the tooth row. The model initially considers the distance from the jaw joint to the last molar (J-M). This span islong when the joint is either high above or far below the tooth row. One can observe in the model that for animals with aposteriorly oriented muscle vector, J-M is shortest (i.e., perpendicular to the arrow representing the jaw muscle force) when thejaw joint is below the level of the tooth row. A short span might be expected in an animal if excess bone and its metabolic costare to be minimized. Yet the joint is usually above the level of the tooth row in mammals. Therefore, the distance from the jointto molar J-M is almost always longer than expected in the large number of animals with a posteriorly oriented muscle vector.Another measurement of some importance is the distance from the jaw joint to the origin, on the skull, of the head of the arrowrepresenting the muscle force (J-S). This distance is shorter when the joint is above and longer when the joint is below the toothrow. Minimizing the sum of J-M and J-S requires that the jaw joint be located at a point above the level of the tooth row. A highposition for the joint corresponds to the actual architecture of mammalian skulls, and permits an economical structure without
The energy cost of gestation in white-tailed deer
Authors: Pekins P J , Smith K S , Mautz W W
Published: April 2011

Gestation in white-tailed deer (Odocoileus virginianus) of northern regions occurs throughout winter, when foragequantity and quality are limited. Our objective was to measure the energy cost of gestation during winter and spring in order todetermine its impact on energy balance of deer. We used indirect respiration calorimetry to measure the metabolism of 21pregnant deer every 24 weeks during gestation (JanuaryMay). Fasting metabolic rates (FMR) were used to develop apredictive equation to evaluate temporal energy costs. A measurable increase in metabolism occurred on day 91 of gestation.FMR (kJ/kg body mass (BM)0.75 per day) of pregnant deer rose curvilinearly (FMR = 0.02(days)2  3.261(days) + 465.2), with92.2% of the increase occurring in the third trimester; costs were 45% greater in the last trimester for pregnant than fornonpregnant deer. Peak FMR of pregnant deer at 200 days gestation was 617 kJ/kg BM 0.75 per day, 84% above that ofnonpregnant deer (335 kJ/kg BM 0.75 per day). The total energy cost of gestation, in terms of FMR, was 78 004 kJ/kg BM 0.75 per200 days, a 16.4% increase above that of nonpregnant deer. The temporal increase in energy costs was correlated with springgreen-up, indicating important relationships between energy demands, food quality and availability, spring weather, andphysiological adaptations in deer.
Distinguishing small juvenile Atlantic cod ( Gadus morhua) from Greenland cod ( Gadusogac) by comparing meristic characters and discriminant function analyses of morphometric data
Authors: Methven David A , McGowan Colin
Published: April 2011

Two biochemical, 7 meristic, and 14 morphometric characters in addition to total body mass were examined to determine which characters best distinguish demersal Gadus ogac from Gadus morhua over the size range 87-135 mm standard length. These congeneric species of cod (Gadidae) remain difficult to distinguish where they co-occur in coastal habitats as recently settled juveniles. Consequently, surveys that target young demersal cod (G. morhua) in coastal nursery areas may be biased, owing to misidentifications. The electrophoretic mobilities of esterase and creatine kinase proteins unambiguously distinguished G. ogac from G. morhua. Of the 14 morphometric characters examined by means of discriminant function analyses, eye diameter and body depth at the origin of the second dorsal fin in addition to total body mass best separate G. ogac from G. morhua over the size range examined. In general, G. ogac has smaller eyes and is heavier and deeper bodied than G. morhua. Counts of vertebrae and of dorsal, anal, and caudal fin rays overlap between species. The shape of the lateral line and especially body coloration are additional characters that help to distinguish these species in the field. Gadus ogac are usually bottle green when freshly caught, whereas G. morhua are usually brownish in dorsal and lateral coloration. Gadus ogac also often have a more strongly arched lateral line than G. morhua of a similar size. All juvenile cod collected along the northeast coast of Newfoundland in this study were either G. ogac or G. morhua. Microgadus tomcod, another gadid common in coastal habitats, was not collected.
Aerial surveys of cetaceans in the Gulf of St. Lawrence in 1995 and 1996
Authors: Kingsley MCS , Reeves R R
Published: April 2011

Aerial line-transect surveys of cetaceans were flown in the Gulf of St. Lawrence in late August and early September of 1995 and in late July and early August of 1996. Systematic north-south transects were spaced 15prime of longitude apart. In 1995, the study area comprised the entire Gulf, divided into three strata for analysis; 69% was flown. In 1996, a single stratum covered only the north shore shelf; 75% of the design was flown. The survey platform was a light high-winged aircraft with bubble windows flown at 213 m (700 ft). Ten species were seen. Minke whales (Balaenoptera acutorostrata), Atlantic white-sided dolphins (Lagenorhynchus acutus), and harbour porpoises (Phocoena phocoena) yielded enough sightings to support good estimates, while fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), white-beaked dolphins (Lagenorhynchus albirostris), and long-finned pilot whales (Globicephala melas) yielded few sightings and unreliable estimates. Blue whales (Balaenoptera musculus) and belugas (Delphinapterus leucas) were seen too rarely to support any analysis. The tenth species was a small delphinid, not positively identified. Minke whales were ubiquitous, but more common in the northern strata. We estimated about 1000 in the whole Gulf in 1995 and about 600 in the northernmost stratum in 1996 (these numbers, and those following, are uncorrected for visibility bias). We estimated about 12 000 Atlantic white-sided dolphins in the Gulf in 1995, but in 1996 saw hardly any, perhaps because we flew the survey earlier. Harbour porpoises (12 000 in 1995 and 21 000 in 1996) were most numerous in the northern stratum, but were also widely distributed at lower densities in the central and southern Gulf. White-beaked dolphins (2500 in 1995 and 2500 in 1996) occurred only in the Strait of Belle Isle and the extreme northeastern Gulf. We estimated a few hundred fin whales in the northern and central strata and about 100 humpbacks, mostly in the northeast. Long-finned pilot whales were only seen in the southeastern Gulf, surveyed only in 1995 (about 1500).
Absorption of macromolecular proteins by the rectal epithelium of the Antarctic fish Notothenia neglecta
Authors: Hernandez-Blazquez Francisco Javier , Cunha da Silva José Roberto Machado
Published: April 2011

The absorption of intact proteins by Notothenia neglecta enterocytes was studied by both light and electron microscopy after administration of ferritin by the oral and anal routes. Intense pinocytosis of ferritin occurs in the second half of the preanal segment, located distal to the rectal valve, which is equivalent to 5% of the intestine length. The ferritin was identified after 48 h by light microscopy and was also observed in the interior of the electron-dense cytoplasmic vesicles of the rectal epithelium. Uptake and transport of protein macromolecules by the oral route are less marked than in other fishes studied. As ferritin uptake was more intense by the anal route, we conclude that the rectum of N. neglecta is the intestinal segment where endogenous or exogenous proteins are normally absorbed in great quantity by pinocytosis.
Microhabitat use by juvenile Atlantic salmon (Salmo salar ) sheltering during the day in summer
Authors: Gries Gabe , Juanes Francis
Published: April 2011

Daytime snorkeling surveys were conducted in the Wardsboro Branch, a tributary of the West River, Vermont, U.S.A., in July and August 1996. We documented microhabitat use by 245 juvenile Atlantic salmon (Salmo salar) sheltering (i.e., concealed beneath the stream substrate) at water temperatures ranging from 17 to 23°C, well above 10°C, the maximum temperature at which young salmon are thought to shelter during the day. The majority (92%) of sheltering salmon were young-of-the-year salmon (YOY). Of the YOY observed, 45% were sheltering, while 55% were in the water column. In comparison, only 10% of post-young-of-the-year salmon (PYOY; age 1 or older) observed were sheltering, while 90% were in the water column. Sheltering PYOY occupied greater water depths and were found under larger substrate stones than were YOY. Sheltering salmon (YOY and PYOY) were not distributed in proportion to the available microhabitat. Salmon only sheltered beneath unembedded cobble or boulder substrate, and sheltering salmon were found in pool habitats 43% of the time. Daytime sheltering suggests that the current interpretation of juvenile salmon habitat use and behavior during summer is incomplete. The availability of suitable sheltering habitats may be a factor affecting juvenile salmon production.
Effect of body size, body mass, and body condition on reproduction of female South African fur seals (Arctocephalus pusillus) in Namibia
Authors: Guinet Christophe , Roux Jean Paul , Bonnet Marielle , Mison Valérie
Published: April 2011

The relationships between female reproductive parameters (fertility, pregnancy, and lactation status) and body mass, body condition, and body length in South African fur seals (Arctocephalus pusillus) were investigated over 4 years. Ovulation rate in every year was 100% despite interannual differences in female body condition index (BCI). The overall pregnancy rate was 79%. The proportion of pregnant females was related to BCI but not to body mass or body length. In good years, BCI decreased through the first part of the reproductive cycle to a minimum at implantation and increased again through pregnancy. In 1989, BCI declined over the whole reproductive cycle, and there was a higher proportion of nonpregnant females and failures of lactation. Thus, poor nutritional conditions may affect reproductive success through failure to rear a pup, and pup production the following year may also be reduced. This lower rate of pregnancy is partly explained by an increase in the incidence of spontaneous abortions, but other parameters such as a lower implantation rate are also likely to be involved.
Capelin (Mallotus villosus) and herring (Clupea harengus) as paratenic hosts of Anisakis simplex, a parasite of beluga (Delphinapterus leucas) in the St. Lawrence estuary
Authors: Hays Réjean , Measures Lena N , Huot Jean
Published: April 2011

Capelin (Mallotus villosus) (N = 760) and herring (Clupea harengus) (N = 165) were collected in the St. Lawrence estuary during the summer of 1994 and 1995 to examine the importance of pelagic fish in transmission of Anisakis simplex to cetaceans. Larval A. simplex were removed from fish by means of a pepsin-digest solution or by dissection. Prevalence of A. simplex in dissected capelin was 5%, with a mean intensity of 1.2. Prevalences of A. simplex in herring were 95 and 99%, with mean intensities of 6.2 and 6.8 for pepsin digestion and dissection, respectively. Third-stage larval A. simplex found in capelin and herring were compared with third-stage larvae found in euphausiids and belugas (Delphinapterus leucas) from the St. Lawrence estuary and no differences in size or morphology of larvae from these four hosts were observed. Euphausiids, which harboured moulting second-stage and third-stage larvae, are intermediate hosts of A. simplex. As there was no apparent development of larvae in herring or capelin, these fish are considered to be paratenic hosts of A. simplex in the St. Lawrence estuary.
Molecular and historical evidence for the introduction of clouded salamanders (genusAneides) to Vancouver Island, British Columbia, Canada, from California
Authors: Jackman Todd R
Published: April 2011

Genetic evidence shows that Vancouver Island populations of clouded salamanders (genus Aneides) are nearly identical with some California populations, in both allozymes and mitochondrial DNA. Historical evidence suggests that salamanders were introduced to Vancouver Island during the nineteenth century. They were probably included in shipments of tan oak bark from California. Tan oak bark was used extensively in the tanning of leather at that time. The introduction to Vancouver Island provides an opportunity to study environmental effects in a species that can not be easily studied on a short-term basis. The California and Canadian populations differ strikingly from Oregon populations of clouded salamanders and are described as a new species, Aneides vagrans.
Neuroanatomy and neurochemistry: implications for the phylogeny of the lower Neoptera
Authors: Ali Declan W , Darling D Christopher
Published: April 2011

Physiologists and developmental biologists routinely collect data that, when analyzed from a phylogenetic perspective, may improve our understanding of the evolutionary relationships of many enigmatic groups of organisms. Immunohistochemical studies of the innervation of the salivary glands provide data that clarify the evolutionary relationships of the lower Neoptera, a major unresolved issue in our understanding of insect phylogeny. Support for the hypothesis that the Phasmatodea and Orthoptera are sister taxa is provided by the dorsal position of the cell body of salivary neuron 1 in the subesophageal ganglion and the presence of serotonin in salivary neuron 2.
Inferring age and growth from remains of fossil and predated Recent anurans: a test case using skeletochronology
Authors: Esteban Marisa , Castanet Jacques , Sanchiz Borja
Published: April 2011

Large amounts of vertebrate remains regurgitated by owls are potentially available for continuous monitoring of predated populations, without human interference or the need to sacrifice any specimens. Presumably, Pleistocene and Holocene fossil microvertebrate assemblages found in caves or shelters are also principally the result of predation by nocturnal birds. Our study tests, for the first time, the standard skeletochronological technique on such prey remains. We analyse two Spanish samples from the genus Discoglossus (Amphibia, Anura, Discoglossidae), a living population of D. galganoi (n = 65 individuals) predated by the European Barn Owl, Tyto alba, and a Pliocene-Pleistocene sample of an extinct species (n = 22) presumably predated by Tyto balearica, a closely related ancestor of T. alba. The histological peculiarities and alterations found in bones of both samples are described, but the results indicate that, in general, this type of material is suitable for skeletochronological applications. In the living population, both size and longevity were greater than previously recorded for the species. For both samples, size and age are positively, though weakly, correlated. Comparisons by age-class show that the extinct species is larger than the living one, particularly for 4- and 5-year-old individuals. Growth rates in juveniles (or larvae) of the extinct species should have been slightly higher than in the living species, with similar growth rates after the third year. Recorded longevity is higher in the extinct species. All these life-history traits support a distinct taxonomic status for the extinct Balearic Discoglossus species.
Feeding suppression in the tobacco hornworm, Manduca sexta: costs and benefits to the parasitic wasp Cotesia congregata
Authors: Adamo Shelley A
Published: April 2011

While the larvae of the parasitic wasp Cotesia congregata developed inside the tobacco hornworm, Manduca sexta, the host's behaviour was similar to that of unparasitized M. sexta. However, once the wasps had exited the host to spin their cocoons, M. sexta stopped feeding. Unparasitized M. sexta ate C. congregata cocoons, which suggests that cessation of feeding by parasitized M. sexta prevented them from consuming the wasps' cocoons. However, suppression of host feeding might be expected to lead to increased host mortality. Host mortality decreased wasp survival. Few cocoons (18%, n = 43) attached to dead hosts produced adult wasps, while 90% of cocoons on live hosts successfully produced adults (n = 20). In the field there was no significant increase in host mortality during wasp pupal development. Cotesia congregata appeared to benefit from the lack of feeding by M. sexta without incurring the increase in mortality that would result if the host died from its lack of feeding. Although cocoons that were detached from the host were more successful (55% produced adults, n = 20) than those attached to a dead host, there was no evidence that wasps emerging from dying M. sexta were more likely to form cocoons away from the host.
Excretion of citrate by metacestodes of Mesocestoides vogae
Authors: Corbin I , Payette J , Blackburn B J , Novak M
Published: April 2011

When metacestodes of Mesocestoides vogae were incubated with oxaloacetate, the 1H NMR spectra of the incubation media established the presence of citrate in addition to the usual worm excretory products succinate, acetate, alanine, and lactate. Given the known impermeability of the inner mitochondrial membrane to multiply charged matrix metabolites, the finding strongly suggests the presence of a transporter to convey citrate from the mitochondria to the cytosol. It is proposed that some of the extramitochondrial citrate serves as a source of cytosolic acetyl-CoA, via the citrate lyase reaction, for conversion to malonyl-CoA and subsequent fatty acid chain elongation. The data demonstrate that because citrate is excreted, further forward steps in the tricarboxylic acid cycle are either very slow or not operating.
Geographical ecology of the gymnophthalmid lizard Neusticurus ecpleopus in the Amazon rain forest
Authors: Vitt Laurie J , Zani Peter A , Avila-Pires Teresa Cristina , Espósito Maria Cristina
Published: April 2011

Lizards in four distantly separated populations of the gymnophthalmid lizard Neusticurus ecpleopus in the Amazon region of South America were strikingly specific in habitat and microhabitat use, being restricted to streams and swamps and living between the water line and the bank-forest interface. They were as likely to be active during cloudy periods as during sunny periods, but most individuals were not exposed to direct insolation while active. Activity occurred through much of the day, with most activity at two sites during between 11:00 and 14:30. Body temperatures were 27.0 ± 0.02°C and were correlated with substrate temperatures. Body temperatures were higher than substrate temperatures, indicating behavioral or possibly physiological thermoregulation. These lizards ate a variety of prey, but eight prey categories accounted for a major proportion of the total diet at all sites. There were differences among sites in prey type, prey size, relative prey size, and total stomach fullness. Even though there was some size variation among sites, variation in other morphological characters was more striking. Even withstanding the differences among populations in ecological and morphological characteristics, it appears that much of the ecology of N. ecpleopus is constrained by fidelity to specific habitat patches (stream banks) distributed linearly through lowland tropical forest.
Characteristics of first-antler growth in reindeer and their association with seasonal fluctuations in steroid and insulin-like growth factor 1 levels
Authors: Blake J E , Rowell J E , Suttie J M
Published: April 2011

Growth and development of the pedicles and first antlers were monitored in seven reindeer (Rangifer tarandus tarandus) calves (three males, four females) from birth to 1 year of age. Calves were weighed, blood was sampled, and antler observations and (or) measurements were taken on the day of birth and days 2, 4, and 7 and then at weekly intervals for the remainder of the year. Prior to measurable growth, the frontal lateral crest was carefully palpated for evidence of pedicle initiation, starting on the day of birth. Calves were born between April 8 and 26, 1994. Pedicle initiation occurred in all reindeer by day 7. Velvet skin first appeared when calves were 4-6 weeks old, when estimated pedicle height was 3.5 ± 0.9 cm (mean ± SD). Antler growth in both sexes followed a sigmoidal pattern, producing a mean antler length of 33.5 ± 4.2 and 46.7 ± 13.8 cm in females and males, respectively. Antler growth was complete by week 18 in females and week 21 in males. Velvet cleaning was associated with a significant increase in plasma testosterone levels in males and estradiol-17beta (but not testosterone) levels in females. Insulin-like growth factor 1 levels were significantly higher in males than in females and were positively correlated with the period of most rapid antler growth in both sexes. Casting occurred between March 14 and April 17, when steroid levels were at a minimum, and was immediately followed by growth of the second antler.
Altitudinal variation in size and composition of eggs in the land snail Arianta arbustorum
Authors: Baur A , Baur B
Published: April 2011

Egg size and egg provisioning are crucial for the survival of offspring in invertebrates without postlaying egg care. The effects of elevation and size of the mother on egg size and on nitrogen and carbon concentrations in eggs were examined in eight populations of the land snail Arianta arbustorum over an altitudinal gradient from 370 to 2340 m in Switzerland. The dry mass of single eggs ranged from 1.48 to 2.79 mg and decreased with increasing altitude. Adult snail size (shell volume) also decreased with increasing elevation as did clutch size and reproductive investment (clutch size x egg dry mass) of mothers. Hatching success of eggs varied among populations, but showed no altitudinal pattern. When differences in parental shell size were taken into account, correlations between altitude and egg size, clutch size, and reproductive investment disappeared. Thus, the altitudinal decreases in egg size, clutch size, and reproductive investment were mainly due to smaller snail sizes at higher elevations. The nitrogen concentration in eggs ranged from 3.4 to 4.5% and decreased with increasing elevation. In contrast to egg and clutch size, the altitudinal variation in nitrogen concentration of eggs cannot be explained by differences in snail size. The carbon concentration in eggs ranged from 31.1 to 33.1%, but showed no altitudinal variation. Nitrogen and carbon concentrations in the eggshell and egg fluid in eggs from four populations were examined separately. The nitrogen concentration in the eggshell ranged from 0.7 to 1.8% and was lower than that of the egg fluid (5.1-5.8%). Similarly, the carbon concentration in the eggshell was lower (20.2-22.8%) than that in the egg fluid (35.8-0.2%). Interpopulation differences in egg composition may affect growth, size, and survival of hatchlings and the extent of egg cannibalism in A. arbustorum.
Seasonal and depth variations in gametogenesis and spawning of Dreissena polymorpha and Dreissena bugensis in eastern Lake Erie
Authors: Claxton W Trevor , Mackie Gerry L
Published: April 2011

Dreissena polymorpha and Dreissena bugensis are two exotic species of dreissenid mussels introduced into the Great Lakes within the past decade. Dreissena bugensis profunda is a morphologically distinct dreissenid taxon, representing either a third species or a phenotype of D. bugensis. In in situ mussels, D. polymorpha and D. bugensis from the wave zone spawned simultaneously, approximately 1 week before D. bugensis profunda from the epilimnion and hypolimnion.Dreissena bugensis profunda from the hypolimnion spawned at 9°C, which is below the previously accepted minimum dreissenid spawning temperature (12°C), and may explain why D. bugensis profunda is proliferating in the hypolimnion. The gametogenic index of all taxa was significantly correlated with temperature at all sites. The gametogenic index of D. bugensis profunda from the epilimnion and hypolimnion was significantly correlated with water protein and chlorophyll a content, respectively. In mussels transplanted to the epilimnion, D. bugensis and D. bugensis profunda spawned simultaneously between August 18 and 28, approximately 2 weeks before D. polymorpha. In mussels transplanted to the hypolimnion, D. bugensis and D. bugensis profunda spawned between July 27 and August 18 at a temperature of 9-10°C. Dreissena polymorpha neither spawned nor showed significant gametogenic development, which suggests that this taxon cannot successfully colonize hypolimnial waters.
Histochemical and electrophoretic analysis of the primary flight muscle of several phyllostomid bats
Authors: Hermanson John W , Ryan James M , Cobb Matthew A , Bentley Jacqueline , Schutts, Jr. William A
Published: April 2011

We identify a novel histochemical fibre type that is correlated with a unique myosin heavy chain isoform in the pectoralis muscle of the two bats Artibeus lituratus and Carollia perspicillata (Phyllostomidae). Pectoralis muscles sampled from four other species (Phyllostomus hastatus, Platyrrhinus helleri, Glossophaga soricina, and Diaemus youngi) exhibited myosin heavy chain isoforms with electrophoretic properties identical with those of A. lituratus andC. perspicillata. The pectoralis muscles of A. lituratus and C. perspicillata consisted mainly of the newly described type IIe fibre. Diaemus youngi differed from the other species studied by having an FM5 native myosin isoform, a feature shared with Desmodus rotundus. We hypothesize that the two-fibre-type composition of the pectoralis muscle in the phyllostomid bats may be related to a "two-gear" locomotor strategy and represents a synapomorphy. The distribution of fibre types and myosin isoforms correlated with family-level phylogenetic affinity rather than with functional characteristics. One of the fibre types was identical with type IIa of terrestrial mammals and a correlated IIa isoform pattern upon electrophoretic analysis. The IIa fibres had high oxidative and glycolytic potential. The second fibre type, which we call type IIe, had a histochemical and immunocytochemical pattern inconsistent with interpretation as a type IIb muscle fibre. Electrophoretic analysis confirmed that isoforms correlated with IIe fibres migrated at different rates from type I, IIa, IIb, and IIx isoforms. The IIe fibres had a fast oxidative metabolic pattern and were at least twice as numerous as IIa fibres. Thus, a novel type IIe fibre is predominant in the pectoralis of six phyllostomid species that exhibit highly divergent body sizes and (or) flight styles.
Phenology and social biology of two sibling species of Halictus in an area of sympatry
Authors: Dunn Melanie , Mitchell Paula Levin , Packer Laurence
Published: April 2011

Fortnightly samples of foragers of Halictus ligatus Say and its recently distinguished sibling species Halictus poeyi Lepeletier were collected in an area of sympatry. Both species were active from late April until autumn, although H. ligatus ceased foraging about 1 month earlier than H. poeyi. Phenological differences were minor and insufficient to preclude hybridization opportunities between the species. The two had a similar proportion of ovarially developed workers, but the proportion that mated in H. poeyi was double that found in H. ligatus, and size dimorphism between castes was greater in H. poeyi than in H. ligatus. When these data are compared with data from other populations, in sympatry the two species appear to be more similar to each other in several sociobiological parameters than each does to allopatric conspecific populations. This suggests a prime role for ecological factors in determining details of social organization in halictine bees.
Genetic population structure of the fairy shrimp Branchinecta coloradensis (Anostraca) in the Rocky Mountains of Colorado
Authors: Bohonak Andrew J
Published: April 2011

Dispersal rates for freshwater invertebrates are often inferred from population genetic data. Although genetic approaches can indicate the amount of isolation in natural populations, departures from an equilibrium between drift and gene flow often lead to biased gene flow estimates. I investigated the genetic population structure of the pond-dwelling fairy shrimp Branchinecta coloradensis in the Rocky Mountains of Colorado, U.S.A., using allozymes. Glaciation in this area and the availability of direct dispersal estimates from previous work permit inferences regarding the relative impacts of history and contemporary gene flow on population structure. Hierarchical F statistics were used to quantify differentiation within and between valleys (thetaSV and thetaVT, respectively). Between valleys separated by 5-10 km, a high degree of differentiation (thetaVT = 0.77) corresponds to biologically reasonable gene flow estimates of 0.07 individuals per generation, although it is possible that this value represents founder effects and nonequilibrium conditions. On a local scale (<=110 m), populations are genetically similar (thetaSV = 0.13) and gene flow is estimated to be 1.7 individuals exchanged between ponds each generation. This is very close to an ecological estimate of dispersal for B. coloradensis via salamanders. Gene flow estimates from previous studies on other Anostraca are also similar on comparable geographic scales. Thus, population structure in B. coloradensis appears to be at or near equilibrium on a local scale, and possibly on a regional scale as well.
Zoogeography of the parasites of Pacific halibut (Hippoglossus stenolepis) in the northeast Pacific
Authors: Blaylock R B , Margolis L , Holmes J C
Published: April 2011

The parasite fauna of 336 adult Pacific halibut (Hippoglossus stenolepis) from 15 geographic localities along the North American coast, ranging from northern California to the northern Bering Sea, was examined to assess zoogeographic and latitudinal zonation of Pacific halibut parasites in the eastern North Pacific. Results show the existence of three zoogeographic zones in the northeast Pacific with boundaries near the southern Queen Charlotte Islands and in the vicinity of Kodiak Island. "Fuzziness" around these boundaries probably reflects small-scale fish movement and the complexity of parasite life cycles. These boundaries roughly correspond to those previously established using the fish and invertebrate faunas. Parasite species richness appears to be more directly correlated with halibut abundance than with latitude; parasite abundance appears to be correlated with temperature and therefore negatively correlated with latitude.
Terrestrial burrowing ecology of newly metamorphosed frogs (Rana pipiens complex)
Authors: Parris Matthew J
Published: April 2011

I examined the burrowing performance of newly metamorphosed Rana areolata, Rana blairi, and Rana sphenocephala in laboratory aquaria. Three treatments were used to determine whether metamorphs, when deprived of a water source, actively dig their own burrows, and if they utilize natural irregularities in substrate profiles or preexisting burrows as shelter from evaporative desiccation. Analysis of covariance (initial body mass covariate) revealed that individuals of all three species actively burrowed and passively utilized preexisting experimental burrows, but active burrowing, which consisted of substrate excavation using only the hind limbs, took much longer. Metamorphs that used preexisting burrows conserved water more efficiently than those that actively dug their own burrows. Rana blairi experienced the highest percent water loss across all treatments and was the only species to suffer mortality during the experiment. These data suggest that burrowing, by minimizing evaporative water loss, may be a critical adaptive behavior for metamorphic frogs in semi-arid environments.
Evidence for birth-site tenacity in breeding Common Black-headed Gulls, Larus ridibundus
Authors: Prévot-Julliard Anne-Caroline , Pradel Roger , Lebreton Jean-Dominique , Cézilly Frank
Published: April 2011

We show that in a large colony of Common Black-headed Gulls (Larus ridibundus) in an unstable aquatic habitat, adults that return to their natal colony tend to breed in close proximity to their natal site. We discuss this finding in relation to potential benefits from colonial nesting.
Natal dispersal and demography of a subsocial Anelosimus species and its implications for the evolution of sociality in spiders
Authors: Avilés L , Gelsey G
Published: April 2011

The transition to permanent-sociality in spiders is thought to have involved the suppression of the dispersal phase characteristic of hypothetical subsocial or periodic-social ancestral species. Extant periodic-social species may provide insights into this transition. The periodic-social Anelosimus jucundus in southern Arizona was found to form mother-offspring and sibling associations that disintegrate prior to the mating season. Following the breakdown of the social phase, more than twice as many females as males became established within a few metres of the natal nest. Given that the predispersal sex ratio was 1:1, a fraction of the males may have dispersed beyond the local area. The short dispersal distances of at least a fraction of individuals of both sexes, the clustering of nests in local areas, and at least two possible cases of sibling mating suggest, however, that dispersal may not eliminate the possibility of close inbreeding in this species. Estimated transition probabilities between life-history stages show that the heaviest loss of individuals occurs during dispersal. Once established, 41% of the females that reached maturity succeeded in producing grown progeny. We discuss the implications of these findings in terms of the transition from periodic to permanent sociality in spiders and of current models that consider the interplay between competition and inbreeding avoidance in the evolution of dispersal.
Tests of estimation of age from tooth wear on roe deer of known age: variation within and among populations
Authors: Hewison AJM , Vincent J P , Angibault J M , Delorme D , Laere G Van , Gaillard J M
Published: April 2011

The rate of wear of ruminant teeth may vary according to diet, habitat, and individual tooth characteristics. This variation may cause error in estimating the age of wild ungulates from patterns of tooth wear. We tested the ability of 10 observers to accurately estimate age from observation of tooth wear in a large sample of jaws of known-age roe deer (Capreolus capreolus) from three populations. Although the average error was not large (±1.02 years), maximum error ranged from -5 to +6 years for jaws of animals between 1 and 7 years old, with observers generally overestimating the age of young animals and underestimating the age of old animals. We found significant differences among observers in estimation error. When a "jaw-board" of known-age reference specimens was provided, this observer effect was largely controlled for, but accuracy was not improved. Error was partly due to variation in tooth wear, both within and among populations. Initial cusp height of the first molar was lower, but tooth wear tended to be slower in one population than in the other two populations, possibly reflecting differences in diet and (or) habitat. Individual variation in tooth wear within populations was observed, possibly reflecting variation in tooth characteristics (e.g., enamel mineralisation), which was a source of error in age estimation from observation. Observers tended to underestimate the age of jaws with a relatively low degree of wear and vice versa. These results show that estimating the age of roe deer from observation of tooth wear produces biased results, severely limiting its application in population studies of this species.
Mass-dependent reproduction or reproduction-dependent mass? A comment on body mass and first-time reproduction in female sciurids
Authors: Humphries Murray M , Boutin Stan
Published: April 2011

We question the validity of Svendsen and White's conclusion that body mass affects the timing of primiparity in eastern chipmunks (Tamias striatus) (G.E. Svendsen and M.M. White. Can. J. Zool. 75: 1891-1895. 1997). Because the masses of reproductive and non-reproductive females were measured during the postpartum period only, the differences reported by Svendsen and White may be due to reproductive females gaining more mass than non-reproductive females between the premating and postpartum periods. We evaluated the plausibility of this alternative explanation by comparing the body mass of reproductive and non-reproductive female red squirrels (Tamiasciurus hudsonicus). Like Svendsen and White, we found that postpartum reproductive females were significantly heavier than non-reproductive females, but contrary to their interpretation, these differences did not exist during the premating period. We conclude that primiparity in female sciurids may not be mass-dependent, but rather that postpartum mass differences may occur because reproductive females augment their energy reserves to help sustain reproductive demands during late lactation.
Measurement of heritability of hatching date and chick condition in parasitic jaegers
Authors: Phillips R A , Furness R W
Published: April 2011

There are few published studies of heritability of reproductive traits in long-lived birds. In parasitic jaegers (Stercorarius parasiticus) breeding on Foula, Shetland, there was no significant heritability in calendar hatching date or relative hatching date, using either mother-offspring, father-offspring, or pooled mother/father - offspring regressions. By contrast, chick body condition (mass corrected for size) was highly heritable. Both traits were important determinants of chick survival from banding until recruitment. High heritability of chick condition was therefore surprising, as characters closely related to fitness are generally assumed to have low heritability. However, chick condition may include a component of structural size, and morphological traits tend to have high heritabilities despite frequently having an important influence on fecundity or viability in birds.
Microanatomy of the bell rim ofAurelia aurita(Cnidaria: Scyphozoa)
Authors: Chapman David M
Published: April 2011

The bell rim of Aurelia aurita is described in detail. This medusa has usually eight marginal sensory complexes and many tentacle chambers, the latter made up of a roof, sides (lappets), and a floor. The sole contents of a tentacle chamber are a few bladelike tentacle bases. The distal tentacle is narrow and moniliform and grooved on the adoral side with a folded sheet of muscle fibers on the deep side. Between the underside of the tentacle chamber's floor and a more adoral circumferential flange (pseudovelarium) lies a ciliated food groove lined with a thick amuscular epithelium containing ordinary surface cells, mucous cells, and presumed digestive cells. The subumbrella is bilayered, with an outer epithelial layer that sends thin cytoplasmic sheets to the mesoglea; deeper is a layer of myocytes each with a striated circular myofibril. Towards the periphery, and before the pseudovelarium, is a rim of smooth radial myocytes overlaid with an epithelial layer. The adoral side of the pseudovelarium has smooth radial epitheliomuscular cells. Where the pseudovelarium attaches to the subumbrella, neuromuscular cords traverse the mesoglea to join the adoral side of the tentacles. Along the food groove and midway between rhopalia is a pocket in the pseudovelarium, the food pouch, which collects plankton. The pararhopalial region of the rim is different in that the floor of the tentacle chamber is short or absent; a modified intertentacular partition can sometimes form a protuberance on the aboral side of the pseudovelarium; and the pseudovelarium takes a right-angled turn outwards near the rhopalium to form the thin part of the rhopalial hood. This type of rim is specialized for the concentration and, perhaps, the early digestion of plankton.
Molecular systematics of gadid fishes: implications for the biogeographic origins of Pacific species
Authors: Carr Steven M , Kivlichan David S , Pepin Pierre , Crutcher Dorothy C
Published: April 2011

Phylogenetic relationships among 14 species of gadid fishes were investigated with portions of two mitochondrial DNA (mtDNA) genes, a 401 base pair (bp) segment of the cytochrome b gene, and a 495 bp segment of the cytochrome oxidase I gene. The molecular data indicate that the three species of gadids endemic to the Pacific Basin represent simultaneous invasions by separate phylogenetic lineages. The Alaskan or walleye pollock (Theragra chalcogramma) is about as closely related to the Atlantic cod (Gadus morhua) as is the Pacific cod (Gadus macrocephalus), which suggests that T. chalcogramma and G. macrocephalus represent separate invasions of the Pacific Basin. The Pacific tomcod (Microgadus proximus) is more closely related to the Barents Sea navaga (Eleginus navaga) than to the congeneric Atlantic tomcod (Microgadus tomcod), which suggests that the Pacific species is derived from the Eleginus lineage and that Eleginus should be synonymized with Microgadus. Molecular divergences between each of the three endemic Pacific species and their respective closest relatives are similar and consistent with contemporaneous speciation events following the reopening of the Bering Strait ca. 3.0-3.5 million years BP. In contrast, the Greenland cod (Gadus ogac) and the Pacific cod have essentially identical mtDNA sequences; differences between them are less than those found within G. morhua. The Greenland cod appears to represent a contemporary northward and eastward range extension of the Pacific cod, and should be synonymized with it as G. macrocephalus.
Bat attacks and moth defensive behaviour around street lights
Authors: Acharya Lalita , Fenton M Brock
Published: April 2011

The defensive behaviour of moths around street lights was examined at a site where bats feed heavily on moths. The lights had a negative effect on moth defensive behaviour, but a combination of observational techniques (recording the outcome of naturally occurring bat-moth interactions) and experimental techniques (deafening moths by puncturing the tympanal organs) indicated that ultrasound-detecting ears still afforded the moths some protection from bat predation. On average, bats captured 69% of the moths they attacked. Moths that exhibited evasive behaviour were caught significantly less often than those that did not (52 vs. 2%). Moths whose tympanic organs had been punctured were significantly easier to catch (requiring fewer attempts) than moths with intact ears, reflecting the fact that significantly more of the eared than the deafened moths showed evasive behaviour (48 vs. 0%). Overall, the number of captures of deafened moths was higher, though not significantly, than the number of captures of eared moths.