bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of the life-cycle stages of Goussia janae (Apicomplexa, Eimeriidae), with X-ray microanalysis of accompanying precipitates
Authors: Lukeš Julius , Starý Vladimír
Published: July 2008

The ultrastructural features of the life-cycle stages of Goussia janae from the intestinal epithelium of the dace Leuciscus leuciscus and chub L. cephalus are described. All merogonial, gamogonial, and early sporogonial stages were localized in the microvillar region in an intracellular and extracytoplasmic position, covered by closely apposed enterocyte and parasitophorous vacuole membranes. Two types of location in the host cell were observed: (i) a more frequent "monopodial" type with a single zone of attachment to the host-cell cytoplasm, and (ii) a "spider-like" type with several isolated zones of attachment. Merozoites were formed by either ecto- or endo-merogony. Microgamonts produced elongated biflagellate microgametes at their periphery. The oocyst wall, produced exclusively by the parasite, was formed at the end of the intracellular phase of the life cycle. Exogenous sporulation resulted in the formation of elongated sporocysts with a thin sporocyst wall bearing a longitudinal suture accompanied by a narrow membranaceous veil. In the cytoplasm and cytoplasmic and parasitophorous vacuoles of the parasite, fine, dense precipitates were present. X-ray microanalysis of these precipitates from osmicated and non-osmicated samples revealed high levels of Ca and P, indicating the possible presence of hydroxyapatite.
Foraging behaviour of oystercatchers Haematopus ostralegus specializing on different species of prey
Authors: Boates J. Sherman , Goss-Custard John D.
Published: July 2008

Adult oystercatchers Haematopus ostralegus specializing on four prey species, the mussel Mytilus edulis, the winkle Littorina littorea, the ragworm Nereis diversicolor, and the clam Scrobicularia plana, were compared. Some clear trends from mussels to winkles to clams to worms were identified. First, mean biomass (size) of prey decreased but more prey were attacked per unit time and, since fewer attacks were aborted, more prey were actually captured per unit time. Second, handling time decreased, and birds raised their heads less often while handling a prey item and carried prey less frequently. Third, foraging density, attack rate, and avoidance rate all decreased. However, average rates of food intake did not follow the same order and were inconsistent with the expected preference for prey. The greatest intake rate was achieved by birds specializing on clams, the least preferred prey. The rate of intake of mussels, the most preferred prey, was significantly lower. Alternatives to the energy rate maximization model to explain prey preference are discussed and dismissed. The results of this study contrast with those from several studies on prey-size selection within a single prey species, which show that oystercatchers prefer prey that maximize their intake rates. We suggest that the basis for selecting a prey species and for selecting different size classes within one prey species may be quite different.
Rubbing behaviour of belugas, Delphinapterus leucas, in a high Arctic estuary
Authors: Smith Thomas G. , St. Aubin David J. , Hammill Michael O.
Published: July 2008

From about mid-July to mid-August belugas (Delphinapterus leucas) over five seasons spent from 27 to 38 days at Cunningham Inlet (74°05′N, 93°45′W), where maximum numbers in each of eight seasons varied from 762 to 1741. While in the estuary, whales actively rub all their skin surface on the mud, pebble, and sharp limestone substrate near shore. Rubbing behaviour is more frequent early in the period of estuarine occupation and is exhibited by all age-classes with the exception of neonates and their dams. Remains of skin found in the area are proof that the epidermal surface is cut and shed from the whales in the shallow areas of the inlet. Active abrasion of skin surfaces softened by exposure to warm fresh water is thought to accelerate the moult, which is linked to a seasonal endocrine cycle and synchronized to meet the energetic demands imposed by their environment.
Low pH alters response to food in the crayfish Cambarus bartoni
Authors: Allison Vanessa , Dunham David W. , Harvey Harold H.
Published: July 2008

In a relatively acid-tolerant crayfish, Cambarus bartoni, locomotory response to food, and associated antennular flicking, were tested at both a circumneutral and a sublethal acid pH. Crayfish were run through a Y maze at pH 7.5, 4.5, and again at 7.5. One arm of the Y maze contained food; the other did not. The time to complete the maze at pH 4.5 increased significantly compared with the time taken at pH 7.5 (P < 0.001). Once pH was restored to 7.5, the time to complete the maze was greater than the initial control at pH 7.5 (P < 0.001) but less than pH 4.5 (P < 0.05). At pH 7.5, 73% of the crayfish chose the food arm; at pH 4.5, 33% chose the food arm; and when pH was returned to 7.5, 46% chose the food arm. Antennular flicking frequency was greatest at pH 7.5 and significantly less at 4.0 (P < 0.0001). Once pH was restored to 7.5, flicking rates were significantly lower than those in the first trial at pH 7.5 (P < 0.01), but significantly greater than those at pH 4.0. Decreased antennular flicking and possible avoidance of food at a sublethal pH (4.0) imply that either chemoreception of food cues or normal central processing of chemical input is seriously impaired.
Nestling growth and fledging success in manipulated American kestrel broods
Authors: Gard Nicholas W. , Bird David M.
Published: July 2008

To study factors regulating clutch size in American Kestrels (Falco sparverius), brood manipulation experiments were performed on captive and wild birds in southwestern Quebec during 1986 and 1987. The largest normally occurring brood size was 5 young. Manipulations enlarged or decreased broods to 7 or 2 young, respectively. Significantly more young fledged from wild control and enlarged broods in 1987 than from comparable groups in 1986. The average number of young fledging from enlarged wild broods in 1987 was slightly higher than for control broods, but fledging weight was significantly depressed in enlarged broods. Growth rates and tarsal and antebrachial length at fledging were not affected by brood size, but development of primary feathers was slower in enlarged wild broods. Parental ability to adequately feed all young appears to be the major factor limiting brood size in American Kestrels.
In vivo protein synthesis rates in larval nase (Chondrostoma nasus L.)
Authors: Houlihan D. F. , Wieser W. , Foster A. , Brechin J.
Published: July 2008

In vivo protein synthesis rates were determined in larvae of nase (Chondrostoma nasus (L.)) by bathing the fish in [3H]phenylalanine. After a delay of about 1 h the rate of labelling of the larval protein was linear. A significant relationship was found between specific growth rate (kg) and fractional rate of protein synthesis (ks) when animals from low and high ration groups and starved animals are included, which can be described by ks = 8.5 + 1.45 kg (both variables in %∙day−1). The efficiency of retention of synthesised protein (kg∙100/ks) was 45% at a growth rate of 10%∙day−1 and 50% at 15%∙day−1. The metabolic costs of total protein synthesis were estimated by comparing the protein synthesis rates of C. nasus with levels of oxygen consumption in similarly treated larvae of the related species Rutilus rutilus. At growth rates below 10%∙day−1, oxygen consumption above maintenance (FIT, food induced thermogenesis, μmol O2∙g fresh weight−1∙h−1) is related to protein synthesis (Ps, mg protein synthesised∙g fresh weight−1∙h−1) by FIT = 24.7 Ps − 3.3. This relationship provides an estimate of the cost of protein synthesis of 24.7 μmol O2 ∙ mg protein synthesised−1 which is 3 times higher than minimal theoretical costs.
Spinal flexion and locomotor energetics in kangaroo, monkey, and tiger
Authors: Gál Julianna M.
Published: July 2008

It has been suggested that galloping is the most economical gait for mammals to use in high-speed locomotion, because galloping makes it possible for kinetic energy associated with leg movements to be stored briefly as strain energy in elastic structures in the back. When this strain energy is returned in elastic recoil, it reduces the total amount of work done by the muscles. This hypothesis was tested in the context of the passive mechanical properties of mammalian intervertebral joints in sagittal bending. The specific strain energies absorbed (EIN/mass) were expressed as power functions of the changes in intervertebral angle (Δθiv) from the unloaded excised states: EIN/mass = C(Δθiv)D, where C and D are constants for each species. Observed changes in spinal deformation were used to estimate changes in intervertebral angles and corresponding changes in specific strain and recoil energies for a hopping kangaroo (Macropus rufus) and a galloping monkey and tiger (Cercopithecus aethiops and Panthera tigris). The specific recoil energies were compared with the energies associated with limb swing during galloping and hopping. The percent contributions of spinal recoil energy to limb kinetic energy were about 2, 5.5, and 0.2 for kangaroo, monkey, and tiger, respectively. The results are discussed in terms of galloping and hopping energetics.
The use of space by yearling Columbian ground squirrels before male dispersal
Authors: Waterman Jane
Published: July 2008

The development of spatial patterns relevant to natal philopatry and dispersal was examined in yearling Columbian ground squirrels, Spermophilus columbianus. Observations using scan and all-occurrence sampling recorded the activities and locations of 56 yearlings in a population in southwestern Alberta. Yearling males moved greater distances from spring emergence to the time of dispersal from the colony. Females were more restricted in their movements, with no increase in the maximum distance moved over the summer. Early movement patterns of males reflected patterns of later dispersal, whereas females appeared to centre their activities on the natal area. These differences are discussed in light of the proximate causes of dispersal in the Columbian ground squirrel.
Coyote coexistence with wolves on the Kenai Peninsula, Alaska
Authors: Thurber Joanne M. , Peterson Rolf O. , Woolington James D. , Vucetich John A.
Published: July 2008

Coyote food habits, home range, and interactions with wolves were examined on the Kenai Peninsula, Alaska (1976–1980), to determine mechanisms of competition between the two species. Scat analyses (percent frequency occurrence) indicated coyotes relied primarily on snowshoe hare, porcupine, and small mammals. Coyote home ranges overlapped those of wolves and averaged 104.0 ± 44.6 (SE) and 70.2 ± 10.4 km2 for males and females, respectively. The ratio of coyotes to wolves captured on public roads was 10:1, while the ratio on roads closed to vehicle access was 0.71:1. Eight instances of wolves killing coyotes are reported. Lack of or minimal exploitation competition appears to allow coexistence of wolves and coyotes, while interference competition is believed to account for the difference in canid abundance near the two road types.
Is nest predation density dependent? A test using artificial nests
Authors: Reitsma Leonard
Published: July 2008

Experiments using artificial nests to test whether predation varies with nest density were conducted in a northern hardwood forest in New Hampshire in June 1989. Nests were baited with quail eggs and placed at densities similar to and substantially higher than the range of natural nest densities. There was no statistically significant difference in predation levels among densities, but there was a trend for higher predation at the highest density.
Parapatric lake and stream sticklebacks on northern Vancouver Island: disjunct distribution or parallel evolution?
Authors: Lavin P. A. , Mcphail J. D.
Published: July 2008

Morphological analysis of sticklebacks from Misty Lake and its inlet stream (Keogh River system, northern Vancouver Island) reveals two forms of Gasterosteus. Sticklebacks from the lake are large and slender bodied with a black back and sides, while sticklebacks from the inlet stream are smaller with a stockier body and mottled brown back and sides. Lake fish also have shorter jaws, longer spines, and more gill rakers than the stream fish. These differences in body shape, trophic structures, and colour are inherited, and the two forms breed true in the laboratory. This implies that they are independent gene pools rather than a single gene pool containing some complex polymorphism. The pair from Misty lake and stream is compared with ecologically similar pairs from Graham Island in the Queen Charlotte Archipelago. The lake–stream pairs on the two islands are strikingly similar. Two hypotheses are examined that might explain the origins and remarkable resemblance of these widely disjunct lake–stream pairs. One hypothesis is historically based and argues that the lake–stream pairs on northern Vancouver Island and the Queen Charlotte Islands share a common origin. The other hypothesis argues that the similarities between the lake–stream pairs on the two islands are the result of parallel evolution (i.e., independent evolution of similar phenotypes in response to similar selection regimes). The available data do not allow a distinction to be made between the hypotheses. The historical hypothesis, however, argues for a divergence that predates the Fraser glaciation, whereas the parallel-evolution hypothesis requires postglacial divergence. Since the two hypotheses differ in the amount of time available for divergence, it may be possible to distinguish between the hypotheses at the molecular level.
Pattern of gill innervation in two teleosts, the perch and the trout
Authors: Dunel-Erb Suzanne , Bailly Yannick , Laurent Pierre
Published: July 2008

The distribution of the branchial nerves in the gills of the perch (Perca fluviatilis) and the rainbow trout (Oncorhynchus mykiss) was studied. Two nerve branches supply each gill arch: the first arch receives a posttrematic branch from the glossopharyngeal nerve and a pretrematic branch from the vagus. The second, third, and fourth arches receive a posttrematic and a pretrematic branch from the vagus. Within each arch the posttrematic branch runs on the anterior side and innervates the filaments of the anterior hemibranch. The pretrematic branch runs on the posterior side and innervates the filaments of the posterior hemibranch. In addition, the posttrematic branches innervate the striated muscles and carry the sympathetic fibers for both hemibranchs. The taste buds and gill rakers are supplied by internal branches of both the pretrematic and posttrematic nerves.
Plasticity of age at maturity between two neighbouring populations of the common frog (Rana temporaria L.)
Authors: Augert Dominique , Joly Pierre
Published: July 2008

Maturation and growth were studied in two neighbouring lowland populations of Rana temporaria exhibiting a great difference in body size. This study took place in the southeast of France from 1986 to 1989. In this region, a local harvesting technique ensuring the release of tadpoles after intensive rearing results in regular genetic mixing between populations. Hence, only environmental influence on the growth rate could explain a difference in body size at maturation. The skeletochronological method was used to determine age. Most of the frogs in the two populations lived no longer than 3 years. The difference in body size between populations was reflected by a difference in age at maturity, which varied from 3 years at site 1 (where the frogs were larger) to 2 years at site 2. Newly metamorphosed froglets were larger at site 1 than at site 2. Back-calculated sizes of 1-year-old individuals did not differ between sites. Size was always greater for age-classes 2, 3, and 4 at site 1. We conclude that, relative to size at metamorphosis, faster growth at site 2 enables maturation to occur earlier and at a smaller size than at site 1. The significance of closer lines in bone cross sections as an indication of age at first reproduction is questioned.
Observations on the shape of the lens in the eye of the silver lamprey, Ichthyomyzon unicuspis
Authors: Collin Shaun P. , Fritzsch Bernd
Published: July 2008

The shape of the lens in the eye of the silver lamprey, Ichthyomyzon unicuspis was examined in live, frozen, and fixed material. Contrary to other reports, the lens was found to be nonspherical with a cone-shaped posterior. The egg-shaped lens, which contains horizontal sutures on both the anterior and posterior surfaces, is also asymmetric in the nasotemporal axis. Its equatorial diameter exceeds its axial diameter (thickness) and the radius of curvature of the lens in the dorsoventral axis is greater than the radius of curvature in the anterioposterior axis. The lens is surrounded by a thick basement membrane with the anterior lens surface covered by a single layer of cuboidal epithelial cells. Juxtaposed to the lens capsule is a dense layer of lens fibres, which stain more darkly and surround an ill-defined lens nucleus. The shape of the lens is discussed in relation to that in aquatic gnathostomes and compared with the putative multifocal lenses of some mesopelagic teleosts. It is also hypothesized that the previously reported active focussing ability of the lamprey eye may have been misinterpreted, owing to failure to take into account the nonspherical lens shape, and may reflect measurements taken of the eye and lens at different angles.
Food-niche relationships of sympatric mallards and green-winged teals
Authors: Nummi Petri
Published: July 2008

Diets of juvenile green-winged teals (Anas crecca) and mallards (A. platyrhynchos) in August and September were studied with respect to (i) the proportion of animal and plant matter. (ii) prey size. (iii) prey diversity, and (iv) the vertical distribution of invertebrate prey in the water column. The size distribution of prey in the diets of the ducks was also compared with that in the environment. Teal diets contained a larger and more variable fraction of invertebrates than did mallard diets. Teals used more small food items than did mallards; however, both used a wide spectrum of sizes. Teals ate more invertebrates that live in the water column or above the water surface, whereas mallards ate more benthic animals. These results contradict earlier studies that had classified teals, on the basis of digestive tract morphology, as more herbivorous than mallards. Therefore, inferences about differences in diet based on morphology alone should be made with some caution. I also suggest, contrary to some earlier studies, that both teals and mallards are generalist foragers, the teal being probably even more plastic when different modes of aquatic feeding are considered.
Winter ecology and diet of Ancient Murrelets off Victoria, British Columbia
Authors: Gaston Anthony J. , Carter Harry R. , Sealy Spencer G.
Published: July 2008

We studied Ancient Murrelets (Synthliboramphus antiquus) in coastal areas near Victoria, British Columbia, by means of small-boat transects and collected birds to examine stomach contents and body weights during the winters of 1977–1979. The diet was composed almost entirely of adult Euphausia pacifica, except in November 1978, when herring were also common. Numbers of murrelets recorded on the water per kilometre travelled correlated with tidal amplitude, suggesting that tidal mixing affected prey availability. Body weights were high compared with those of breeding birds, peaking in January, when stomachs contained the maximum number of prey organisms. Dives were brief. Feeding intensity, or food availability, may reach a maximum in midwinter.
Cryoprotectant production capacity of the freeze-tolerant wood frog, Rana sylvatica
Authors: Costanzo Jon P. , Lee Jr. Richard E.
Published: July 2008

Freezing survival of the wood frog (Rana sylvatica) is enhanced by the synthesis of the cryoprotectant glucose, via liver glycogenolysis. Because the quantity of glucose mobilized during freezing bears significantly on the limit of freeze tolerance, we investigated the relationship between the quantity of liver glycogen and the capacity for cryoprotectant synthesis. We successfully augmented natural levels of liver glycogen by injecting cold-conditioned wood frogs with glucose. Groups of 8 frogs having mean liver glycogen concentrations of 554 ± 57 (SE), 940 ± 57, and 1264 ± 66 μmol/g catabolized 98.7, 83.4, and 52.8%, respectively, of their glycogen reserves during 24 h of freezing to −2.5 °C. Glucose concentrations concomitantly increased, reaching 21 ± 3, 102 ± 23, and 119 ± 14 μmol/g, respectively, in the liver, and 15 ± 3, 42 ± 5, and 61 ± 5 μmol/mL, respectively, in the blood. Because the capacity for cryoprotectant synthesis depends on the amount of liver glycogen, the greatest risk of freezing injury likely occurs during spring, when glycogen reserves are minimal. Non-glucose osmolites were important in the wood frog's cryoprotectant system, especially in frogs having low glycogen levels. Presumably the natural variation in cryoprotectant synthesis capacity among individuals and populations of R. sylvatica chiefly reflects differences in glycogen reserves; however, environmental, physiological, and genetic factors likely are also involved.
The ecology of hybrids between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia, Canada
Authors: Aspinwall Nevin , Carpenter Douglas , Bramble Judy
Published: July 2008

Extensive hybridization between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia, provided an opportunity to examine the ecology of hybrid fishes over a 26-year period. Spatial distribution and feeding ecology of the hybrids were compared with those of the parental species. At Stave Lake, M. caurinus was primarily oriented to the limnetic zone at all depths, while R. balteatus was oriented to surface waters in the littoral zone. The hybrids (F1 hybrids and hybrid backcrosses to M. caurinus combined) mimicked the M. caurinus pattern, being significantly more abundant in the limnetic zone. Adult M. caurinus consumed primarily zooplankton with occasional adult insects, while R. balteatus consumed primarily adult insects. The diet of hybrids was not significantly different from that of M. caurinus; they consumed large quantities of zooplankton and some insects.
Fine structure of egg envelopes in some viviparous goodeid fishes, with comments on the relation of envelope thinness to viviparity
Authors: Riehl Rüdiger , Greven Hartmut
Published: July 2008

The egg envelope (zona radiata) of the full-grown oocytes before fertilization was examined by electron microscope in eight viviparous species of Goodeidae (Cyprinodontiformes) from the Mexican plateau. The egg envelope is composed of a homogeneous electron-dense zona radiata perforated mainly by oocyte microvilli. The thickness of the zona radiata ranged from 0.5 μm (Xenoophorus captivus) to 1.5 μm (Ameca splendens). Egg envelopes of Ataeniobius toweri and Ilyodon xantusi appeared to have two layers, tentatively described as a zona radiata interna and a zona radiata externa. The most complex envelope was observed in Girardinichthys multiradiatus, which showed a small filamentous zona radiata interna and an electron-dense zona radiata externa covered by an additional flocculent layer, which is probably the gelatinous coat found in many eggs. The egg envelope of Ameca splendens, Girardinichthys viviparus, and Xenotoca eiseni displayed short external processes resembling attaching filaments, which are known from eggs of substrate-spawning teleosts. The thickness and differentiation of the zona radiata in other viviparous teleosts are compared and discussed with reference to mode of reproduction.
Ecological adaptations of aquatic macroinvertebrates to overwintering in interior Alaska (U.S.A.) subarctic streams
Authors: Irons III John G. , Miller L. Keith , Oswood Mark W.
Published: July 2008

Freshwater invertebrates of northern regions are faced annually with freezing of shallow habitats. Several responses to habitat freezing are possible, including migration to favorable habitats and physiological adaptations such as freeze-avoidance or freeze-tolerance. We thawed sections of frozen stream gravel and identified the live and dead invertebrates present. Chironomidae and Empididae (Diptera) constituted >90% of individuals found in frozen habitats: Empididae showed substantial survival in frozen habitats. We also tested the ability of Alaskan stream invertebrates to survive in habitats that freeze. In a series of laboratory experiments we showed that most taxa found in Alaskan streams do not have the ability to survive even moderately subzero temperatures (e.g., −1.0 °C). When faced with an advancing freezing front, these taxa actively moved away. We suggest that most aquatic invertebrate taxa survive winter by either migrating away from a freezing front or remaining in habitats that do not freeze. Chironomidae and Empididae, however, can overwinter in frozen habitat, and Empididae show high survival upon thawing of frozen stream gravels. Predicted changes in temperature and precipitation patterns at these latitudes due to global climate warming may have effects on the availability of overwintering habitat for stream invertebrates that result in changes in the structure and function of high-latitude stream ecosystems.
Assessment of egg quality in Atlantic salmon, Salmo salar, treated with testosterone: biochemical composition
Authors: Srivastava Rakesh K. , Brown Joseph A.
Published: July 2008

In the present study, eggs were collected from testosterone-treated Atlantic salmon (Salmo salar) and control (sham implanted) fish, and egg-quality parameters were compared. Egg weight and diameter, as well as protein, lipid, carbohydrate, dry matter, and ash contents, of eggs from testosterone-treated fish were significantly less than those of eggs from controls. Intensive utilization of protein energy for metabolism during egg development and predominant utilization of lipid energy after hatching was noted. Polyamines, putrescine, spermidine, and spermine contents in eggs from control and treated fish did not differ. However, embryos and alevins from testosterone-treated fish synthesized more polyamines than did controls during development. There were no significant differences in fertilization and hatching success, or in survival to the eyed stage and first feeding. The development of embryos from treated fish was slower than that of controls, but higher growth rates and greater development of alevins from treated groups were observed after hatching.
Winter survival in northern Peromyscus maniculatus
Authors: Millar John S. , Teferi Taye
Published: July 2008

Winter survival of Peromyscus maniculatus in the Kananaskis Valley, Alberta, was examined in relation to sex, age, population density, size of family groups, body size, and residency status to determine the factors responsible for low winter mortality in northern populations. Young-of-the-year mice survived much better (≈ 50%) than old (> 1 year old) mice (≈ 25%) but no other factor had a significant effect on survival. We conclude that low resource competition may enhance winter survival in northern populations.
Fluid transmission and filtration efficiency of the labral fans of black fly larvae (Diptera: Simuliidae): hydrodynamic, morphological, and behavioural aspects
Authors: Lacoursière Jean O. , Craig Douglas A.
Published: July 2008

Body stance and water flow through the labral fans of suspension-feeding Simulium vittatum Zetterstedt larvae were examined using dead and live larvae. Transmission of flowing water through the fans was determined by means of dye injections. Feeding stance is the outcome of an active feedback process between flow forces and behavioural reactions that maintains the fans in an optimal filtering position. Fans responded to velocity increases through structural reconfiguration, which resulted in an increase in aperture size. As the velocity decreased, an increased fraction of the water directly approaching the fan aperture flowed around its perimeter, with no flow through the fans below 2.5 cm∙s−1. Fluid transmission never exceeded 30–35%, even at velocities up to 50 cm∙s−1. Calculations of suspension-feeding efficiency are reformulated to reflect labral fan transmission and behavioural components of the feeding process. Simulium vittatum larvae are consequently shown to be 4–26 times more efficient in filter feeding than has been previously assessed. The effect of flow on labral fan transmission is discussed in relation to known habitat choices and feeding behaviours of simuliid larvae.
Comparison of mandibular with cemental growth-layer counts for ageing Atlantic walrus (Odobenus rosmarus rosmarus)
Authors: Garlich-Miller J. L. , Stewart R. E. A. , Stewart B. E. , Hiltz E. A.
Published: July 2008

The relationship between the numbers of growth layers counted in the mandible and in the cementum of lower canines from 87 walrus (Odobenus rosmarus rosmarus) was examined. A 1:1 correlation between counts of growth layers in the two tissues was found in males ≤ 19 years old and females ≤ 9 years old. No correlation was found in males with ≥ 21 or in females with ≥ 10 cemental growth layers. In physically mature walrus, mandibular layering was unreliable for age analysis. Resorption and a reduced mandibular growth rate appear to be the main factors limiting mandibular age estimates in mature walrus.
Metazoan parasite communities of yellow eels (Anguilla rostrata) in acidic and limed rivers of Nova Scotia
Authors: Cone D. K. , Marcogliese D. J. , Watt W. D.
Published: July 2008

Metazoan parasite communities of 269 yellow eels (Anguilla rostrata) inhabiting acidic (pH 4.5–5.0) and deacidified (limed to a pH of 6.0–7.0) portions of a watershed in southwest Nova Scotia were compared over 3 years. Paraquimperia tenerrima, Ergasilus celestis, Bothriocephalus claviceps, Proteocephalus macrocephalus, Crepidostomum brevivitellum, and Azygia longa were found. Species richness was greater and there were more multiple infections in the component community in eels from the limed portion of the watershed than in the community in the acidic river. Differential susceptibility of the parasites or their intermediate hosts to acidification appears to be involved in structuring the community. Digeneans were absent from eels in the acidic river. The copepod E. celestis occurred throughout the watershed but was less common in the acidic river. The occurrences of two species, B. claviceps, and P. macrocephalus, were similar at acidified and limed sites. Numbers of infected fish and prevalence of the dominant parasite, P. tenerrima, were highly variable in eels from the acidic region, but were relatively stable at the limed site. It is concluded that the assemblage of metazoan parasites of fish may be useful as environmental indicators, and may also provide information on the dynamics of altered food webs.
Developmental capacity of non-nucleated embryos of coho salmon, Oncorhynchus kisutch, induced by γ-irradiation
Authors: Aoyagi Kazuhiko , Kojima Yutaka , Saneyoshi Mineo
Published: July 2008

The effects of γ-rays on chromosomes and nuclei were examined by observing embryos of coho salmon, Oncorhynchus kisutch, produced using either sperm or eggs that had been exposed to γ-irradiation. These embryos had smaller nuclei than normal control embryos, and half of the normal chromosome number, suggesting that the genomic DNA of the gametes had been inactivated by γ-irradiation. Furthermore, non-nucleated embryos were produced using both sperm and eggs that had been γ-irradiated under the same conditions. In spite of the fact that the fertilized eggs lacked Feulgen-positive material, cleavage was observed in the embryos, and some developed to the blastula stage. These results suggest that the early stages of embryogenesis of fertilized fish eggs may be influenced by the cytoplasm rather than the nucleus.
Androgen levels in a Bornean voiceless frog, Rana blythi
Authors: Emerson Sharon B. , Rowsemitt Carol N. , Hess David L.
Published: July 2008

Male Rana blythi and males of three other species of voiceless frogs from Bornean rain forests lack the suite of secondary sex characteristics typical of most anurans: nuptial pads, vocal sacs, enlarged forearm flexors, and male advertisement calls. At the same time, basal species in the voiceless frog lineage exhibit an extreme type of male parental care: the males carry the tadpoles on their backs. This unusual form of male parental care evolves at the same point in the phylogenetic history of the group as the loss of the secondary sex characteristics. This suggests that these voiceless frogs may have lowered androgen levels. Hormone assays from blood samples of R. blythi show that plasma levels of testosterone, androstenedione, and 5α-dihydrotestosterone are considerably lower in wild-caught R. blythi than those reported for other frog species when similar sample collection methods were employed.
The proximate causes of male-biased natal emigration in Columbian ground squirrels
Authors: Wiggett Darwin R. , Boag David A.
Published: July 2008

The results of this study support the hypothesis that male-biased emigration of yearling male Columbian ground squirrels (Spermophilus columbianus) is socially induced. The likelihood of emigration from both the natal site and the natal colony was correlated with parameters of social structure and behavior. Agonism by the mother and (or) neighboring adult females, in association with parturition and lactation, apparently caused the initial shifts of yearling males away from their natal home ranges. After these shifts, yearling males that lived in areas where the number of neighboring males (both adult and yearling) was high relative to the number of females emigrated to areas within the natal colony that were more female-biased (intracolony emigration), or emigrated from the natal colony (intercolony emigration). Reduced numbers of adult males apparently resulted in lower rates of emigration by yearling males. Among the latter, emigrants appeared to be subordinate to non-emigrants. We discuss these findings in light of current hypotheses concerning the proximate and ultimate causes of emigration in ground-dwelling sciurids.
Roentgenology of myofibrogranuloma in walleye, Stizostedion vitreum
Authors: Holloway Jr. Harry L. , Shoemaker Craig A.
Published: July 2008

Myofibrogranuloma, a muscle degeneration known only in walleye, Stizostedion vitreum, could not until now be recognized without filleting the fish. Muscle in advanced stages of degeneration shows pronounced granuloma formation, and an increase in calcium concentration (X-ray density) compared with normal tissue is associated with such myopathy. Using X-rays and various anatomical combinations of skin, fillet, and vertebral column, myofibrogranuloma could be recognized in several anatomical combinations.
An asymmetric dental formula in a mammal, the São Tomé Island fruit bat Myonycteris brachycephala (Mammalia: Megachiroptera)
Authors: Juste Javier , Ibáñez Carlos
Published: July 2008

The dental formula in heterodont mammals characteristically shows bilateral symmetry. Its expression is likely to be subject to very strong selective pressures, since it is associated with such basic functions as the acquisition and preparation of food. Here we report the exceptional finding of the first asymmetric dental formula in a heterodont mammal observed in the São Tomé Island (West Africa) frugivorous bat Myonycteris brachycephala. The asymmetry results from the absence of a lower internal incisor, occurring variably in the right or left mandible. This morphological innovation is possibly related to a developmental instability associated with the colonization by the island species.
The role of kinship in field interactions among juvenile gray squirrels (Sciurus carolinensis)
Authors: Koprowski John L.
Published: July 2008

Adult eastern gray squirrels influence recruitment into local populations by directing aggression at juveniles and nonresidents. However, the role of juveniles in the social dynamics of squirrel populations is poorly understood. Field interactions among juvenile squirrels were studied between littermates and nonlittermates. Amicable interactions occurred only between littermates, while aggression was directed almost exclusively at nonlittermates. Juveniles within their own natal areas dominated nonresident juveniles. Interactions among juveniles appear to be influenced by kinship and may be important in determining recruitment patterns in squirrel populations.
Significance of wounding to female reproductive success in Hawaiian monk seals (Monachus schauinslandi) at Laysan Island
Authors: Hiruki Lisa M. , Stirling Ian , Gilmartin William G. , Johanos Thea C. , Becker Brenda L.
Published: July 2008

We studied reproductive rate, length of lactation period, pup survival, and mortality of injured and uninjured female Hawaiian monk seals (Monachus schauinslandi) on Laysan Island, northwestern Hawaiian Islands, in 1983 – 1989. The severity and timing of nonfatal injuries were influential in determining their effect on female reproductive success. There was a tendency towards a shorter mean lactation period and lower survival rate of pups for females with major injuries than for uninjured females. Females with minor injuries were similar to uninjured females in terms of reproductive rate, length of lactation, and pup survival. For females injured shortly before the birth of their pup or during lactation, pup survival was lower than for uninjured females, whereas for females injured during the year prior to pupping, measures of reproductive success were not significantly different from those for uninjured females. Immature (aged 4 – 8 years) females entering the reproductive population were injured by adult male seals significantly more often than females aged 0 – 3 years, but at a similar rate to adult females. The major effect of injuries on female reproductive success is an increase in female mortality: 87.5 % of the adult females (n = 16) that died on Laysan Island in 1983 – 1989 sustained injuries from adult male seals.
Weight asymmetry and sequential assessment in convict cichlid contests
Authors: Koops Marten A. , Grant James W. A.
Published: July 2008

We staged contests between pairs of convict cichlids (Cichlasoma nigrofasciatum) that varied in weight ratio (larger/smaller) from 1.02 to 4.86 to test the predictions of the sequential assessment model. As predicted, contests proceeded in a consistent sequence of behaviour (lateral display, biting, mouth wrestling, and circling), the duration of contests was inversely correlated with weight ratio, and the duration of complete phases of behaviour was independent of weight ratio (a phase is complete if the contest escalates to the next behavioural phase). However, there was temporal overlap in the occurrence of different behaviour patterns and variation in the duration of contests that are not explained by the model. Nevertheless, the structure of convict cichlid contests is consistent with the logic of the sequential assessment model.
Calving success of female caribou in relation to body weight
Authors: Cameron Raymond D. , Smith Walter T. , Fancy Steven G. , Gerhart Karen L. , White Robert G.
Published: July 2008

In late September and October 1987–1990 and early July 1988–1991, 66 radio-collared female caribou (Rangifer tarandus granti) of the Central Arctic Herd were captured and weighed 117 times. Caribou were relocated repeatedly during early June 1988–1991; parturition status, calving date, and perinatal calf survival were determined. Mean autumn body weights of subsequently parturient (90.0 kg) and nonparturient (82.5 kg) females differed significantly (P < 0.01). Mean summer weights 4 – 5 weeks after parturition were significantly higher for females that had calved on or before 7 June (82.2 kg) than for those that had calved after 7 June (72.1 kg; P < 0.01), and for females whose calves survived at least 2 days post partum (80.2 kg) than for those whose calves died within 2 days (70.3 kg; P < 0.01). Significant logistic models were generated for relationships between parturition rate and autumn weight (P < 0.01), between the occurrence of early calving and summer weight (P < 0.05), and between calf survival rate and summer weight (P < 0.02). Body weight appears to be a reasonable index of body condition, which in turn is related to reproductive performance. The probability of a successful pregnancy is largely predetermined at breeding, based on autumn condition, whereas calving date and early calf survival appear to be influenced primarily by maternal condition during late pregnancy.
Responses of woodland caribou (Rangifer tarandus caribou) to clear-cutting in east-central Newfoundland
Authors: Chubbs Tony E. , Keith Lloyd B. , Mahoney Shane P. , McGrath Michael J.
Published: July 2008

Movements, sex and age structure, and habitat selection of adult woodland caribou (Rangifer tarandus caribou) were examined in relation to clear-cutting on summer range in east-central Newfoundland during 1987 – 1990. We obtained 2473 locations of 35 radio-collared caribou during at least two consecutive summers. Locations relative to clearcuts were determined for eight males and 27 females. Distances to existing clearcuts were compared with distances to those same geographic points prior to and following the summer in which clear-cutting occurred. Four males and 10 females maintained similar mean distances from clearcuts, 3 males and 12 females were farther away, and 2 females were closer. Three other females and one male were assumed to be too distant to be affected by clear-cutting. Of those found farther away from clearcuts, females were 2 – 3 times farther away than males. Among female caribou that maintained similar mean distances to clearcuts, habitat use during clear-cutting was similar to that before and afterwards. Females displaced by clear-cutting avoided open burns and hardwoods and selected mature black-spruce forest, whereas prior to cutting they used habitats in proportion to their availability. Sex and age ratios indicated that significantly fewer females and calves were present near clearcuts than elsewhere in the study area. Our results demonstrate that clear-cutting mature forests on summer range may affect the movements and distribution of woodland caribou.
Revision of the species of Priolepis possessing a reduced transverse pattern of cheek papillae and no predorsal scales (Teleostei; Gobiidae)
Authors: Winterbottom Richard , Burridge Mary
Published: July 2008

We recognize 10 species in this group of Priolepis, 4 of which are described here. Priolepis ailina n.sp. is known only from Moorea in the Society Islands, Priolepis kappa n.sp. ranges from the Comoro Islands (Comores) to Fiji, Priolepis latifascima n.sp. occurs in Taiwan and Japan, and Priolepis vexilla n.sp. is from Indonesia and the Philippine Islands. Among the previously described species, P. boreus occurs in Taiwan and Japan, P. compita ranges from South Africa to the Marquesas Islands, P. farcimen is restricted to the Hawaiian Islands, P. nocturna ranges from the Comores to the Marquesas, P. nuchifasciatus is found from Australia to Hong Kong and Singapore, and P. semidoliatus is present from the Red Sea to Pitcairn Island. We hypothesize that the clade is monophyletic, based on the loss of predorsal scales, and further, that P. nocturna forms the sister-group of the remaining species, all of which have lost the pectoral fin base scales. Priolepis ailina and P. kappa appear to be sister-species, based on the unique union of the opercular and postocular bars. The presence of at least some unbranched dorsal-fin rays appears to unite the remaining species, although this forces us to postulate a reversal in P. nuchifasciatus, in which the dorsal rays are branched. However, the joining of the bars over the pectoral-fin base and the opercle unites P. compita, P. farcimen, P. latifascima, P. nuchifasciatus, P. semidoliatus, and P. vexilla in a monophyletic group, to the exclusion of P. boreus. Within this clade, P. nuchifasciatus and P. vexilla are sister-species, based on the atavistic presence of a pelvic fraenum.
Ecology and evolution of sympatric sticklebacks (Gasterosteus): origin of the species pairs
Authors: McPhail J. D.
Published: July 2008

Pairs of plankton-feeding and benthos-foraging sticklebacks (Gasterosteus aculeatus) (limnetics and benthics) coexist in six small lakes in southwestern British Columbia. In spite of a persistent low level of hybridization the pairs maintain themselves as distinct genetic and ecological entities; because of this they are viewed as biological species. They appear to be restricted to the central Strait of Georgia region, and the geological history of the area argues that they are of postglacial origin. The pairs occur on three islands (Vancouver, Texada, and Lasqueti), but even on these islands they are not found in all available lakes. Both lake morphometry (size and depth) and altitude appear to influence local distribution. Hypotheses that might explain the origin of the pairs are examined. Neither theory nor data support a sympatric origin, but an allopatric origin through two invasions of marine sticklebacks is consistent with both the geological history of the area and the details of local distribution. An independent but parallel evolution of the pairs on at least two islands (Vancouver and Texada) is implicit in this hypothesis. The hypothesis also assumes that although the initial divergence started in allopatry, competitive interactions in sympatry played a major role in the evolution of reproductive isolation and resource partitioning.