bluuebunny/crossref_metadata_2025 huggingface dataset:
A study of the variability of the return migration route of Fraser River sockeye salmon (Oncorhynchus nerka)
Authors: Hamilton Kevin
Published: January 2008

This paper discusses the interannual variability observed in the fraction of the Fraser River sockeye spawning run that returns around the north end of Vancouver Island and then through Johnstone Strait (the so-called "northern diversion"). Estimates of the northern diversion have been produced by the International Pacific Salmon Fisheries Commission for each year from 1953 through 1983. In the present study commercial catch data were used to estimate the diversion rates for the years 1906–1952. The extended time series 1906–1983 was then employed in an examination of the relation between the diversion rates in each year and (i) the phase of the familiar 4-year cycle of the Fraser sockeye, (ii) the size and timing of the spawning run, and (iii) environmental factors such as ocean temperature and Fraser River discharge. The results obtained suggest that there is at most a weak relationship between the diversion rates and the 4-year cycle. There is a strong correlation between the northern diversion and the duration of the spawning run; the sockeye run tends to be spread out over a longer period in years with anomalously large returns through Johnstone Strait. A very significant correlation was found between the diversion rate and the temperature change in the coastal waters off Vancouver Island over the last 18 months of the salmon's ocean residence. Strong, persistent warming trends in these coastal waters are known to accompany most large tropical El Niño events; thus it often happens that large northern diversions of the Fraser sockeye occur after major Los Niños (most notably in 1915, 1926, 1958, and 1983).
Neural fold abnormalities induced in newt embryos by a carcinogen
Authors: Tsonis Panagiotis A.
Published: January 2008

The effects of a carcinogen, N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), on newt embryonic development were studied. When embryos are treated with MNNG before the blastula stage, abnormal development occurs. The most prominent effect is that the hinder region of the egg–embryo (vegetal pole) does not participate in the development; thus, only one hemisphere (animal pole) of the egg develops. This phenomenon is evident at the gastrula stage and becomes even more apparent during the neurula stage.
Nest sites of the threespine stickleback: Can site characters alone protect the nest against egg predators and are nest sites a limiting resource?
Authors: Whoriskey F. G. , FitzGerald G. J.
Published: January 2008

In a field population of Gasterosteus aculeatus, analysis of the patterns of nest destruction following removal of males indicated that nest site variables per se offered little protection against egg predation in the absence of paternal defense. These experiments also indicated that male breeding densities were not limited by a lack of space for territories. We suggest that site quality and male quality, which is determined in part by the quality of parental defense, interact to determine the number of eggs a male can hatch.
Effects of vitamin A and other retinoids on the differentiation and morphogenesis of the integument and limbs of vertebrates
Authors: Johnson Keith J. , Scadding Steven R.
Published: January 2008

Exogenous vitamin A is a well-known teratogen and modifies the course of cell differentiation, embryonic development, and morphogenesis. Recent evidence has shown that vitamin A and related compounds (the "retinoids") are likely natural morphogens, carrying out important roles in such processes as limb development and epithelial differentiation. Retinoids can modify the differentiation of individual cells and can induce specific modifications of morphogenesis in such structures as epithelial appendages, developing limbs, and regenerating limbs. Evidence is accumulating that there may be a common mechanism of action underlying these diverse phenomena. Retinoids may enter cells and induce changes in gene transcription in a manner similar to that reported for steroid and thyroid hormones and their receptors. Retinoids are particularly useful probes in the study of cell differentiation and morphogenesis because an understanding of their action can provide clues to the mechanisms involved in the complex processes of normal differentiation, morphogenesis, and pattern regulation.
Effect of snow depth on wolf activity and prey selection in north central Minnesota
Authors: Fuller Todd K.
Published: January 2008

Wolf (Canis lupus) activity and interactions with white-tailed deer (Odocoileus virginianus) were monitored in north central Minnesota during six winters in which mean January–February snow depth alternated between shallow (19–26 cm) and relatively deep (40–47 cm) and winters (winter severity index; L. J. Verme. 1968. J. Wildl. Manage. 32: 566–574) alternated between mild (71–98) and moderately severe (126–137). Wolves traveled farther and more often and spent less time with other pack members in mild than in severe winters. Radio-marked wolves and deer used conifer cover less, and fewer deer were killed there, when snow was shallow. Similarly, fewer wolf-killed deer were found in and near deer concentration areas during mild winters. Of the 74 deer killed by wolves, the proportion that were fawns (54%) differed from the proportion of fawns in the winter population (27%), but neither varied with winter severity. Few deer killed by wolves appeared debilitated. Carcass consumption was high in all winters, regardless of their severity, but wolves scavenged less in mild than in severe winters (10 vs. 29% of deer carcasses observed). Thus, wolves changed winter activity, movement patterns, sociality, and feeding behavior in response to snow-induced changes in deer distribution and mobility.
Effects of food availability on intraspecific aggression in salamanders of the genus Ambystoma
Authors: Ducey Peter K. , Heuer Jonathan
Published: January 2008

Although intraspecific aggression is widespread in salamanders, distinguishing among hypotheses concerning the functions of this aggression has proved difficult. Because salamanders of the genus Ambystoma mate and lay eggs in water but spend the rest of the year on land, their terrestrial aggression may function in defense of refuge tunnels, feeding areas, or both. Defense of feeding areas was examined by testing the effects of changes in food availability on the aggressive behavior of four species of Ambystoma (A. maculatum, A. opacum, A. talpoideum, and A. tremblayi). Residents of each species behaved aggressively toward, and bit, intruding conspecifics. Aggression level, measured as either mean number of bites per encounter or percentage of residents that bite, was significantly reduced following increased food availability. Despite interspecific differences in habitat and morphology, all four species were similarly affected by food levels. These results suggest that a function of intraspecific aggression in Ambystoma is repulsion of conspecifics from feeding areas.
Structure of shells from eggs of the Australian lizard Amphibolurus barbatus
Authors: Packard Mary J. , Hirsch Karl F. , Packard Gary C. , Miller Jeffrey D. , Jones Menna E.
Published: January 2008

Eggshells of the Australian bearded dragon consist of a layer of calcite overlying a multilayered, fibrous shell membrane. Some layers of the shell membrane are comprised of tightly woven feltworks of fibers, whereas other layers consist of more open mats of fibers with numerous spaces among the fibers. The shell membrane is organized into a series of shallow crests and troughs with furrows delimiting the irregular plaques of crystal that cover the shell membrane. The morphology of the outer crystalline layer varies from compact calcareous rosettes to coarsely granular aggregations of crystals. Numerous porelike areas and fissures fenestrate the crystalline material. These openings presumably provide for exchange of gases and water between the egg and its environment. The calcareous layer is organized into columns of loosely aggregated crystals extending deep into the fibrous shell membrane and enclosing fibers of the membrane. The bearded dragon represents only the second lepidosaurian found to produce a flexible-shelled egg consisting of crystalline columns that extend into the shell membrane.
The parasite–host relationship of glochidia (Mollusca: Margaritiferidae) on the gills of young-of-the-year Atlantic salmon (Salmo salar)
Authors: Cunjak R. A. , McGladdery S. E.
Published: January 2008

The relationship between condition of overwintering young-of-the-year salmon (Salmo salar) and levels of infection by glochidia of the freshwater mussel Margaritifera margaritifera was investigated at two sites in South River, Nova Scotia, which contained significantly different concentrations of adult M. margaritifera. Although the salmon at site A (which had 5.1 times fewer freshwater mussels than site B) were significantly larger than the salmon at site B, there was no correlation between size of salmon and abundance of glochidia. Mean condition factor (K) was lower at site B. There was a significant increase in K in spring, which was most likely due to spring growth as there was no significant decrease in glochidia abundance. Significant, negative regressions were found only in January and February, when 24 and 66% of the variation in K, respectively, could be explained by the abundance of glochidia on the gills. Abundance and prevalence of infection did not change significantly between October and March. There was, however, a 45% decrease in infections of over 300 glochidia after December, which may have been due to host mortality. The mean size of glochidia increased between October and November, levelled off between December and March, and increased again in April. In May there was no further increase in growth, which is believed to be due to the loss of larger glochidia from the gills at that time. The data suggest an increasingly detrimental impact to juvenile salmon over winter as a function of the time and degree of infection (i.e., intensity, abundance) with mussel glochidia.
A phylogenetic analysis of the Tubificinae (Oligochaeta, Tubificidae)
Authors: Brinkhurst R. O.
Published: January 2008

The Tubificinae is a monophyletic taxon in relation to the outgroup Rhyacodrilus. A hypothetical ancestor with almost completely plesiomorphic character states was included in the analyses. It appears at the base of the taxon as expected when the outgroup is used for rooting, but is unresolved in relation to the genera Lymphachaeta and Peipsidrilus. The genera with elongate atria form a monophyletic group, as do all the papillate taxa with the exception of Tubificoides. The generic and subgeneric rankings of the papillate taxa that constituted the bulk of the former genus Peloscolex require cladistic evaluation. The separation of Ilyodrilus, Teneridrilus, and perhaps even Tubificoides also needs to be investigated. Clitelloides and Lycodrilides are potential synonyms of Clitellio and Lycodrilus, respectively.
Sublethal parasites in white-footed mice: impact on survival and reproduction
Authors: Munger James C. , Karasov William H.
Published: January 2008

The potential impact of two parasites on the population density of host white-footed mice (Peromyscus leucopus) was assessed by measuring effects on survival and reproduction in field populations. Thirty-eight mice infected with larvae of the bot fly Cuterebra angustifrons had their larvae removed, another 41 mice remained infected, and 46 other mice were naturally uninfected during the experiment. No effect of bot larvae removal was detected on either survival (measured as attrition) or reproduction (measured as end of reproductive season). However, contrary to expectation, naturally infected mice had lower attrition and a marginally longer reproductive season than naturally uninfected mice. This latter result is probably an artifact, due to underlying differences between naturally infected and uninfected mice. Sixty-seven mice were experimentally infected with the tapeworm Hymenolepis citelli (64 mice were controls), but no effect was detected on attrition from the trappable population nor on the cessation of the reproductive season. Our results indicate that (i) these parasites are unlikely to have any effect on population density of white-footed mice, and (ii) it is potentially misleading to use "natural experiments" (comparison of naturally infected hosts with uninfected hosts) to study the impact of parasitic infection.
Adaptational changes in the venous system of diving mammals
Authors: Galantsev V. P.
Published: January 2008

The venous system of diving mammals has changed during the course of evolution. The common adaptational change in the venous system of animals that have been investigated is an increase in its volume. Venous collectors and plexuses are observed, where blood is stored during the complex haemodynamic changes that occur underwater. Comparative studies of diving animals have shown that in different species, changes in the venous system aimed at increasing its volume have followed different routes. Hence, the shapes, sizes, and locations of venous collectors were dissimilar in the various species. A certain amount of similarity in the development of the venous system is observed, however, in some diving rodents and carnivores. Still, the prominence of venous collectors, which is directly linked to the species' ecological specialization, varies. The development of morphological adaptations of the cardiovascular system in diving mammals during ontogenesis follows a certain species-specific path. During heterochronous development in some species, the most important features of this system are observed in new born pups, whereas in others they appear later in postnatal life. Adaptational changes in the arterial system are found only in the most skilled divers.
Separation of two populations of fish hepatocytes by digitonin infusion: some metabolic patterns and hormonal responsiveness
Authors: Ottolenghi C. , Ricci D. , Gavioli M. E. , Puviani A. C. , Fabbri E. , Capuzzo A. , Brighenti L. , Plisetskaya E. M.
Published: January 2008

Two pools of liver cells, enriched either in periportal or in perivenous hepatocytes, were obtained from the catfish Ictalurus melas by the selective destruction of the liver by digitonin infusion. Following digitonin pulses directed either orthograde via the portal vein or retrograde via the hepatic vein, hepatocytes from undamaged perivenous and periportal zones, respectively, were isolated by the conventional collagenase perfusion procedure. Eluates from either periportal or perivenous zones were collected for a total of 9 min before, during, and immediately following the digitonin pulse. The eluates were assayed for protein, glycogen, glucose, and activities of lactate dehydrogenase and alanine aminotransferase, and their yield ("recovery") was estimated as a percentage of the total hepatic content. The aforementioned metabolic compounds and enzyme activities were measured also in periportal and perivenous liver cells. No significant differences were obtained between these cells. Both pools of hepatocytes were more than 90% viable and remained hormone responsive. Epinephrine (3 × 10−8 M) or salmon glucagon (3 × 10−8 M) elevated cAMP content, and stimulated glycogen phosphorylase a activity, glycogen depletion, and glucose release in periportal and perivenous liver cells. No differences were observed between periportal and perivenous cells in their metabolic responsiveness to either hormone.
Mechanisms that elevate the glucose concentration of muscle and liver in yellow perch (Perca flavescens Mitchill) after exercise–handling stress
Authors: Schwalme Karl , Mackay William C.
Published: January 2008

To identify the mechanisms that elevate the glucose concentration of muscle and liver in yellow perch after exercise–handling, we exercised–handled perch for 10 min and measured subsequent changes in the glucose, glycogen, lactate, and pyruvate content of liver and muscle. By 15 min after the start of exercise–handling, the average glucose concentration had increased from 40 to 200 mg/100 g in liver, from about 6 to 18 mg/100 g in muscle, and in one of two experiments the average liver glycogen level declined from 4.0 to 2.2% wet weight. The increases in liver and muscle glucose content within 15 min were too large to be accounted for by the disappearance of muscle lactate (via the Cori cycle) and likely resulted from glycogenolysis or gluconeogenesis (from nonlactate substrates) in the liver. However, the Cori cycle, gluconeogenesis from glycerol and amino acids, and inhibition of glucose catabolism by preferential oxidation of lactate could all have contributed to prolonging hyperglycemia in muscle and liver, which lasted more than 12 h. Perch excreted about 7% of the total muscle lactate burden produced during exercise–handling stress.
On sex-specific foraging behaviour in the Willow Warbler, Phylloscopus trochilus
Authors: Nyström K. G. Kenneth
Published: January 2008

The foraging behaviour of Willow Warblers (Phylloscopus trochilus) in relation to the availability of their insect prey was studied at the Tovetorp Field Station and at the Royal Park of Djurgården, Stockholm, Sweden, from 1985 through 1989. The numbers and types of arthropods available to Willow Warblers fluctuated throughout the breeding season. In general, most arthropods were found on the underside of the leaves. Males spent more time gleaning and less time hovering and fly catching when preying chiefly on aphid nymphs then when foraging on other arthropods on birch before budbreak. They performed more fly-catching behaviour and tended to forage in taller trees than did females. Dissimilarities in foraging behaviour between the sexes were attributed to differences in wing length and wing shape. Because females are smaller and have less pointed wings they are better adapted for hovering than males. Consequently, females were better at capturing prey on the underside of birch and willow leaves, which was abundant during the egg-laying and brood-rearing periods. Thus, in birch and willow, females hovered more frequently than males, but there was no difference between males and females foraging in spruce, pine, and oak.
Structure and ontogeny of dominance relationships among bighorn rams
Authors: Hass Christine C. , Jenni Donald A.
Published: January 2008

Dominance relationships among bighorn rams (Ovis canadensis) were studied over a 2-year period to quantify structure and development. Rams exhibited a stable, linear hierarchy that was strongly correlated with age. Dominance relationships were not evident until rams were at least 1 year old. Individuals gained in rank as they grew older and by fighting their way up the rank order. Rams aged 4–7 years interacted at the highest rates. After 10 years of age rams declined rapidly in condition, spent more time alone, and interacted less frequently with other rams.
Influence de la croissance et de facteurs du milieu sur l'alimentation du crabe des neiges, Chionoecetes opilio (O. Fabricius), dans le sud-ouest du golfe du Saint-Laurent
Authors: Lefebvre L. , Brêthes J.-C. F.
Published: January 2008

The stomach contents of snow crabs (Chionoecetes opilio) of carapace width >0.6 cm and <7.3 cm were examined in 650 specimens collected at the entrance of the Chaleur Bay, in the southwestern region of the Gulf of St. Lawrence. Individuals were collected with a beam trawl at depths of 70–120 m, on gravelly–muddy and muddy substrates, during the summers of 1986 and 1987. A repletion iridex (RI) was estimated and the daily feeding rhythm of early benthic stages (carapace width <3.0 cm) was determined while considering four classes of RI on 246 crabs. A significant difference between day and night in RI was observed, indicating nocturnal feeding activity in early benthic stages of snow crab, as is the case in the older stages. The mineral content of stomachs, as determined by burning, increases proportionally with the size of the crab. Diet is dominated by crustacea (85% of stomachs), followed by polychaeta (83%) and mollusca (19%). A correspondence analysis conducted on preys and variables (depth, substratum, and size of crab) showed common feeding preferences for crabs of the same size in spite of environmental disparity.
Étude cinématique de la palette natatoire antérieure de la tortue Luth, Dermochelys coriacea (Vandelli, 1761), au cours de sa locomotion terrestre
Authors: Renous Sabine , Bels Vincent
Published: January 2008

The leatherback turtle, Dermochelys coriacea, which is particularly well adapted to marine life, uses a mode of terrestrial locomotion that does not involve raising the entire body; it drags itself instead, which is unique to heavy animals. The primary pattern of tetrapods, using alternate movements and a diagonal sequence of the limbs, is replaced by a specific repertory of periodic and synchronous movements of the fore- and hind-limbs. The forelimbs, which have evolved into large paddles, produce lifting and forward movements of the body as if the turtle were "walking on crutches." During terrestrial locomotion, the forelimb movement, derived from swimming, is rather similar to that used during vigorous swimming, except for a reduction of the upstroke.
Ecology and life history of the scansorial arboreal lizard Plica plica (Iguanidae) in Amazonian Brazil
Authors: Vitt Laurie J.
Published: January 2008

A field study on two populations of the tropical iguanid lizard Plica plica in the Brazilian Amazon revealed that this lowland forest species is diurnal, occurs on vertical smooth-barked trunks of the largest trees in the forest, and feeds mostly on ants. Comparisons between rainy season samples from Pará and dry season samples from Rondonia show that even though lizards ate, on average, the same number of prey, prey were larger in Rondonia and prey diversity was greater in Pará. Lizards sleep on tree trunks or similar surfaces when available, apparently leaving the trees only to deposit eggs. Clutches are deposited in palm litter and inside rotted palm trunks. Clutch size averages 2.9 ± 0.1 eggs and is significantly correlated with female snout–vent length. The reproductive season appears to be extended in that females produce at least two clutches. Relative clutch mass of females is low compared with that of other sit-and-wait foraging lizard species, and this, coupled with the flattened morphology, presumably reflects adaptations for maintaining the center of gravity near vertical smooth tree trunks.
Using exotic antigens to measure reproduction and dispersal in Peromyscus leucopus
Authors: Glass Gregory E. , Korch George W. , Gomez James E. , Childs James E.
Published: January 2008

Free-ranging female white-footed mice, Peromyscus leucopus, were inoculated with a series of exotic (not encountered in the environment) antigens to evaluate the utility of maternally transferred antibodies in identifying offspring under field conditions. Inoculated females suffered no apparent effects from the antigens, and their survival, growth, and reproductive success did not differ from those of uninoculated, control females. Six of nine marked females produced seven offspring. These offspring dispersed an average of 64 m from their mothers' centers of activity. Recruitment rates per adult female were similar to those reported for nest box studies. The exotic antigen technique appears to be a feasible method for studying the population biology of secretive small mammals.
Intentional stranding apprenticeship and social play in killer whales (Orcinus orca)
Authors: Guinet Christophe
Published: January 2008

Over three hunting seasons, killer whales (Orcinus orca) from two pods were observed stranding intentionally on the beaches of Possession Island, Crozet Archipelago. Intentional stranding was performed principally by adult females to catch elephant seals on shore and during social play. Within a pod significant differences existed in the number of intentional strandings performed by individual females during hunting and also during "social beaching play." During intentional stranding, calves were associated with an adult female. Two calves were systematically associated with their mother, but one calf was associated significantly more with the two other pod females. This calf s mother stranded intentionally significantly less than the two other females. This suggests that alloparental "teaching" may occur within a pod according to the specific skills of the pod members.
Insulin binding to liver plasma membranes in salmonids with modified plasma insulin levels
Authors: Gutiérrez Joaquim , Plisetskaya Erika M.
Published: January 2008

Insulin binding to the liver plasma membranes was assessed in coho salmon (Oncorhynchus kisutch) injected intraperitoneally with 6.6 μmol arginine/g body weight, and in rainbow trout (Oncorhynchus mykiss) fasted for 40 days and then refed for 15 days. Corresponding control groups of fish were injected with saline (coho salmon) or fed regularly (trout). Arginine injection was followed by a substantial elevation of plasma insulin titres from 12.5 to 76.8 ng/mL, an increase in the binding capacity and, consequently, an increase in specific binding of insulin to the liver plasma membranes from 3.4 to 5.5%. The binding affinity remained unchanged. Food deprivation lowered plasma insulin titres from 13.2 to 3.0 ng/mL, increased the binding capacity, but decreased the binding affinity, so the specific binding remained essentially unchanged (5.6% in fed versus 5.1% in fasted fish). Refeeding of fasted fish resulted in restoration of insulin levels and an increase in binding affinity relative to both control and fasted groups of fish. This led to a substantial elevation of the specific binding of insulin up to 7.1%. The binding of insulin to liver plasma membranes in salmonids depends both on the number of binding sites (binding capactity) and on the binding affinity. Long-term treatment, such as food deprivation, resulted in altered affinity and capacity of binding, whereas short-term treatment, such as arginine injection, affected mostly the binding capacity. Modulation of the number of binding sites in liver plasma membrane according to the insulin level was observed only in experiments on trout conducted at a higher (15 °C) water temperature.
The function of the wishbone
Authors: Bailey Jason P. , Demont M. Edwin
Published: January 2008

The furcula of birds has traditionally been thought to have a static function. In recent studies it has been hypothesized that the furcula may be acting as a spring in a secondary respiratory mechanism that functions during flight. We tested this hypothesis by comparing the wingbeat frequency and the predicted natural frequency of this secondary respiratory system in 17 avian species, and found a correspondence of nearly 1:1 between these frequencies. Thus, the thoraco-abdominal complex in those birds that couple wingbeat with respiration in a 1:1 ratio may operate as a resonant oscillator during flight. Others have hypothesized that the furcula may function as a spring by assisting in the upstroke phase of the wingbeat cycle. We found that the furculas of 16 of the 17 bird species did not store a functionally important quantity of elastic strain energy compared with the kinetic energy of the wings. We further hypothesized that the furcula may be acting as a spring in a resonant panting system. However, the panting frequencies of three bird species were found to be different from the predicted natural frequencies of their thoraco-abdominal complex. Thus, the furcula does not appear to be functionally important in panting.
Parturition and clutch characteristics of short-horned lizards (Phrynosoma douglassii brevirostre) from Alberta
Authors: Powell G. Lawrence , Russell Anthony P.
Published: January 2008

Field capture records and observation of wild-caught females indicate that parturition in Alberta populations of Phrynosoma douglassii brevirostre, a viviparous lizard, is synchronized among females, taking place during a short period around the end of July, and generally around noon. Relative clutch mass appears to decrease with female age, and clutch size varies between 6 and 11 neonates, with an overall sex ratio of 1.0. Female behaviour during parturition consists of four distinct phases, involving straddling of the hind legs, abdominal contractions, and pelvic movements. After parturition, the female moves away from the neonate. Neonate behaviour is associated chiefly with escaping from the extraembryonic membranes. Male neonates have a greater snout–vent length than females, but neonate mass is similar. Gravidity appears to impose a great physiological cost upon reproducing females.
Ecology and life history of the wide-foraging lizard Kentropyx calcarata (Teiidae) in Amazonian Brazil
Authors: Vitt Laurie J.
Published: January 2008

Kentropyx calcarata is a widely foraging terrestrial lizard that is most common in edge situations (riparian, tree falls) in tropical lowland rain forest of South America. Various microhabitats are used, and lizards often forage in vegetation off the ground in a leaf-gleaning fashion. Body temperatures during activity average 37.6 °C in sun and 35.7 °C in shade, body temperature always being higher than that of the substrate or air. Daily activity appears to be associated with availability of direct sunlight. Differences in lizard body size (reflecting age), activity times, prey composition, and prey size are apparent between Rondônia (dry season) and Pará (wet season) populations. Sexual dimorphism is evident in head size, males having longer and wider heads than females, presumably due to sexual selection. Clutch size varies from 4 to 10, and the reproductive season appears to be prolonged. Natural nests occurred in sandy areas exposed to full sun along stream banks. Overall, K. calcarata in the Amazon region is more similar in ecology to other teiid lizards studied in drastically different environments than to sympatric lizards in other families.
Analysis of morphogenetic determinants in ascidian eggs and embryos by cytoplasmic deletion and microinjection
Authors: Bates William R.
Published: January 2008

The determination of cell fates in ascidian embryos is thought to be mediated primarily by factors localized in the cytoplasm. Morphogenetic factors were studied in ascidian eggs and early cleavage stage embryos by the partial deletion of blastomeres and by microinjection of sperm cells into anucleate, myoplasm-deficient egg fragments. In the first series of experiments, regions of blastomeres comprised of 20–30% of the volume of one blastomere were deleted from two- and four-celled embryos. Most of the embryos exhibited regulative capabilities, in that normal tadpole larvae developed from the operated embryos, irrespective of the deletion site. In a second series of experiments, the expression of endodermal alkaline phosphatase (AP) and muscle acetylcholinesterase (AchE) were tested in myoplasm-deficient egg fragments that were injected with sperm cells. After the unoperated controls had developed into tadpoles, myoplasm-deficient fragments injected with sperm cells were scored for their ability to express AP and AchE activity. Many of the myoplasm-deficient fragments that contained injected sperm cells expressed AP activity, whereas uninjected myoplasm-deficient fragments did not exhibit AP activity. When myoplasm-deficient fragments injected with sperm cells were tested for their ability to express AchE activity, none of the fragments expressed this muscle cell marker. Similar results were obtained using two species, Halocynthia roretzi and Styelaplicata. These results suggest that nuclear events are required for the expression of AP and that the myoplasmic region of the fertilized egg contains muscle cell determinants.
Assessment of DNA fingerprinting for studies of small-mammal populations
Authors: Cummings Shawn A. , Hallett James G.
Published: January 2008

We examined the use of DNA fingerprinting for determining degree of genetic relatedness and kin relationships of small mammals. We examined the utility of three DNA probes: a "mouse" probe, a repeat sequence from a Mus musculus genomic library; (CAC)5, a synthesized probe consisting of cytosine–adenine–cytosine repeated five times; and the SNAP probe, a synthesized probe containing a 22 base pair sequence. All three probes provided DNA fingerprints for montane voles (Microtus montanus), although the number of bands per individual varied among probes. We could obtain bands only with the snap probe for deer mice (Peromyscus maniculatus) and pocket mice (Perognathus parvus). Successful modifications of protocols for DNA extraction from small blood samples and for nonradioactive detection of bands suggest that DNA fingerprinting should be useful for in situ studies of natural populations by many research laboratories. To determine genetic similarity we calculated the probability of band sharing between individuals. The average probability varied among probes for the same unrelated M. montanus individuals and among species for the snap probe. For all probes the average probability of band sharing was significantly greater for related than for unrelated individuals of M. montanus. Unrelated individuals usually share an unpredictable number of bands, and the probability of band sharing may reach that of related individuals. Average band sharing for related M. montanus individuals was greater than the expected 0.5 only for (CAC)5. Average probability of band sharing between unrelated and related individuals and the variance of this value must be known before an attempt is made to determine general relationships in field populations. When maternity was known, paternity could be determined with a low probability of misassignment by identifying obligate paternal bands.
Mechanics of the startle response in the northern pike, Esox lucius
Authors: Frith H. R. , Blake R. W.
Published: January 2008

The thrust produced during an escape response (C-start) of a northern pike, Esox lucius (0.41 m total length, 0.398 kg), an acceleration specialist, is estimated using the Weihs model for fish fast-starts. High-speed cine film records (250 Hz) of pike C-starts were digitized and the angle of attack and displacement of all body sections determined. These parameters were incorporated into the model and thrust was calculated. A comparison of model predictions with values predicted from required forces found six of eight performance parameters to be within 22% for three fast-starts. A lack of significant difference between model estimates and required forces suggests that lift and acceleration forces are the major components of total thrust during C-type fast-starts. The caudal region, including the caudal, anal, and dorsal fins, contributes the most (>90%) to positive total thrust during the propulsive stage (stage 2). High velocities, large angles of attack, and large surface areas of these sections account for this. Approximately 77% of the positive total thrust during the propulsive stage is generated by the caudal fin and 28% by the anal and dorsal fins. Lift forces averaged over the fast-start are greater than average acceleration forces, but when positive acceleration forces of the propulsive stage only are considered, average lift and acceleration forces are similar (60 and 43% of total positive forces, respectively). Also, acceleration forces peak earlier than lift forces and contribute to an earlier escape response.
Characteristics of wild turkey nest sites in a mixed-grass prairie–oak–woodland mosaic in the northern great plains, South Dakota
Authors: Day Keith S. , Flake Lester D. , Tucker W. Lee
Published: January 2008

Habitat characteristics potentially important to nest site selection were measured at 44 wild turkey (Meleagris gallopavo) nests in a mixed-grass prairie–oak–woodland mosaic in south-central South Dakota during 1986 and 1987. Characteristics were compared between nest sites within woodland and grassland communities and with those of random sites within these respective communities by means of a median scores test (nonparametric). Almost all nests initiated in April were in woodland communities, whereas nests started after the 1 st week in May were primarily in grassland communities. Hens in woodlands and grasslands selected nest sites with concealing vegetation immediately above the nest and placed their nests in habitats associated with high interspersion. Shrubs were strongly selected for as nesting cover in grassland communities. Hens in grasslands selected sites with high visual obstruction (0–60 cm and 60–180 cm) immediately around the nest site when compared with random sites; nests in grasslands were also associated with higher than expected visual obstruction (0–60 cm) in the 10- to 40-m peripheral area. Nests in grasslands had better concealment from above (1.5 m) and higher visual obstruction readings under 60 cm (at nest site) than did nests in woodlands. We detected no association of nests with water sources in grasslands or woodlands.
Discordant phenotypic variation in sympatric resident and anadromous Atlantic salmon (Salmo salar) populations
Authors: Claytor R. R. , Verspoor E.
Published: January 2008

Sympatric but electrophoretically distinguishable resident and anadromous Atlantic salmon (Salmo salar) populations from Little Gull Lake, Newfoundland, were compared for meristic and morphometric variation. No morphometric differentiation was detected. As the two populations have similar juvenile rearing habitats, this result is consistent with the hypothesis that local water-flow conditions are important in determining morphometry. Meristic divergence is as great as that between regional North American stocks, and the Little Gull Lake resident population is significantly different from all other Newfoundland–Labrador populations. With our data we cannot separate environmental from genetic contributions to the mersitic divergences because spatially separate spawning locations coincide with temperature differences. Our results suggest that meristic, morphometric, and electrophoretic variation are likely to be congruent only by coincidence among Atlantic salmon populations and that these characteristics likely evolve independently.
Seasonal patterns of prey availability and the foraging behavior of arctic foxes (Alopex lagopus) in a waterfowl nesting area
Authors: Stickney Alice
Published: January 2008

The foraging behavior of arctic foxes was observed in a waterfowl nesting area on the Yukon–Kuskokwim Delta of Alaska in 1985–1986. Observations were made during peak fox activity from two towers, 3 m high, located in different community types. Data were collected continuously for individual foxes on specific activities, the community in which activities occurred, and the type of food obtained. After migratory birds started nesting in the area, the food potentially available to foxes changed from microtines, old caches, and carrion to include eggs and birds. This change was reflected in the foraging behavior of the foxes as they switched to predation on eggs. After nesting began, the search success rate of foxes increased (from <30% to >50%) and search duration decreased (mean 19.7 s before nest initiation versus mean 9.4 s in mid-incubation) as the rate of food acquisition increased. Over 80% of the eggs taken by foxes were cached rather than eaten immediately, which extended the availability of this temporally limited resource to foxes. Eggs were the primary prey of arctic foxes during the nesting stages in both years, even though microtine populations were high in one year (1985) and low in the other (1986).
Body mass, volume, and buoyancy of some aquatic birds, and their relation to locomotor strategies
Authors: Lovvorn James R. , Jones David R.
Published: January 2008

Body mass, volume, and buoyancy of diving ducks, surface-feeding ducks, auklets, cormorants, and gulls were measured by means of water displacement. Relations of volume and buoyancy to body mass in surface-feeding ducks were linear and did not differ from those of diving ducks if scoters and eiders were excluded. These large-bodied sea ducks (scoters and eiders) had buoyancies 22–28% above values predicted by the common linear regression for surface-feeding ducks and smaller diving ducks. Thus, scoters and eiders have larger respiratory or plumage air volumes relative to body mass. Although relations of volume and buoyancy to body mass were similar among most ducks, volumes and buoyancies of gulls were much higher, and those of cormorants much lower, than those of ducks. Volumes and buoyancies of auklets were the same as those of ducks of similar mass. The significance to locomotion of the buoyancy of restrained birds depends on predive expiration and ptilosuppression, and reduced buoyancy from compression of air spaces at foraging depths typical for the species.
Molecular evolution and morphological speciation in North Atlantic brachiopods (Terebratulina spp.)
Authors: Cohen Bernard L. , Balfe Peter , Cohen Moyra , Curry Gordon B.
Published: January 2008

Morphological and molecular differentiation of western and eastern North Atlantic brachiopods were examined by morphometric analysis of six shell characters (n = 144), allozyme electrophoresis at six nuclear gene loci (n = 485), and estimation of nucleotide difference by digestion of mitochondrial DNA (mtDNA) with nine restriction endonucleases (n = 96). Principal components analysis associated 16.1% of morphometric variation with shape differences, resulting in clear morphometric discrimination. Allozyme genotype frequencies indicated sampling of large populations in genetic equilibrium. Heterozygosity was 0.174 and 0.141 for the Canadian and Scottish samples, respectively. Mitochondrial DNA nucleon (haplotype) diversity, ĥ, was 0.53 and 0.99 for the Canadian and Scottish samples, respectively. Allozyme genetic distance (0.318) and mtDNA net nucleotide difference [Formula: see text] were both high. The samples shared only 9 of 31 allozyme electromorphs, 13 of 132 restriction fragments, 1 or 2 of 67 restriction fragment patterns ("mitomorphs"), and none of 42 composite nine-enzyme mtDNA phenotypes ("mitotypes"). Canadian mtDNAs varied in size (modal size 15.83 kilobase pairs (kbp), range 15.2–16.7 kbp) but quasi-continuous and discrete variation were not distinguished. Scottish mtDNAs did not vary in size (mean size, 15.72 ± 0.13 kbp). Overall results are consistent with the classical assignment of Canadian and Scottish Terebratulina to separate morphospecies, T. septentrianalis and T. retusa, and suggest divergence at least 11–18 million years ago. There is no evidence of genetic exchange between the populations sampled. These conclusions are consistent with the known biogeography and life history of these articulate brachiopods.
Evolutionary attributes of headfirst prey manipulation and swallowing in piscivores
Authors: Reimchen T. E.
Published: January 2008

Headfirst swallowing of fish prey is a common attribute of gape-limited predators, conferring the presumed advantage of reduced esophageal abrasion. I evaluate swallowing orientation using cutthroat trout (Oncorhynchus clarki) as predator and three-spine stickleback (Gasterosteus aculeatus) as prey. Field data indicate that orientation is random when prey diameter is less than one-half the gape of the predator, but this increases to 90% headfirst orientation as prey diameter approaches and exceeds the maximum gape, consistent with the suspected reduction in abrasion. Experimental data show two additional advantages to headfirst orientation. Following capture, there is a 2- to 5-fold reduction in escape rate of the prey, and among prey that were swallowed, the manipulation period is substantially reduced (mean 29 vs. 81 s for headfirst and tailfirst orientation, respectively), the differences being most accentuated at large prey sizes.
Burrowing behavior and soil manipulation by a tarantula, Rhechostica hentzi (Girard, 1853) (Araneida: Theraphosidae)
Authors: Formanowicz Jr. Daniel R. , Ducey Peter K.
Published: January 2008

The Texas brown tarantula, Rhechostica hentzi, uses silk during burrow construction to manipulate, remove, and transport soil. Soil adheres to the silk desposited on the soil surface, and the strands are pulled together to form soil–silk masses. The spiders pick up the masses in the chelicerae and carry them away from the developing burrow. We suggest that this specialized use of silk for burrowing may have evolved from a combination of existing behavior patterns.
Comparative ultrastructural study of the lemnisci in larvae and adults of Centrorhynchus milvus Ward, 1956 (Acanthocephala, Centrorhynchidae)
Authors: Marchand Bernard , Grita-Timoulali Zohra
Published: January 2008

The lemnisci of acanthocephalans are enigmatic organs which, except for those of adult Moniliformis dubius and Octospinifer macilentus, have not been described on the basis of examination by electron microscopy. We were able to study them in cystacanths, juveniles, and adults of Centrorhynchus milvus. They show a fibrous outer layer covering an amorphous layer; the latter is in close contact with a lining plasma membrane perforated by numerous pores which communicate with an equal number of small vesicles in cystacanths, with endocytotic vacuoles in juveniles, and with canaliculi in adults. In the center of each lemniscus are large nuclei surrounded by a common cytoplasm containing large protein granules. Only the lemnisci of cystacanths encysted in wood lice exhibit a large network of microfilaments at their center.
Changes in masked thresholds of a harbour seal (Phoca vitulina) associated with angular separation of signal and noise sources
Authors: Turnbull S. D.
Published: January 2008

The masked pure tone thresholds of a harbour seal (Phoca vitulina) were measured at various angles using a white noise masker. The white noise source was placed at 0°, 30°, 60°, and 90° relative to the midline of the seal's head (0°). The masked pure tone thresholds for each angle were determined at 2, 4, 8, and 16 kHz. As the angle separating the signal and noise sources increased from 0° to 90°, the critical ratios of the harbour seal decreased by 1–4 dB. This shift in masked thresholds from a reference point of 0° azimuth was significant (H = 10.374, df = 3,16, p < 0.05). No significant difference was found in masked thresholds between 0° and 30° or between 60° and 90°. This indicates that if a noise source is separated by more than 30° relative to the location of a vocalizing seal, signal detection thresholds will be enhanced and communication distances increased.