bluuebunny/crossref_metadata_2025 huggingface dataset:
Responses of juvenile largemouth bass to different pH and aluminum levels at overwintering temperatures: effects on gill morphology, electrolyte balance, scale calcium, liver glycogen, and depot fat
Authors: Leino Richard L. , McCormick J. Howard
Published: July 2008

Young-of-the-year largemouth bass were exposed to simulated overwintering conditions, 4 °C for 113 days, in soft ([CaCO3] 48 mg/L, [Ca] 13.4 mg/L) and very soft ([CaCO3] 4.6 mg/L, [Ca] 1.5 mg/L) water. In some treatments pH was reduced to 5.0 and 4.5, with no added Al; in others, a monomeric Al level of 30 μg/L was maintained. In the neutral pH treatments the bass had greatly thickened gill respiratory epithelium and large numbers of chloride cells (compared with bass kept at 20 °C in a prior experiment), and blood osmolalities declined and stabilized at about 260 mosmol/kg. In the acid treatments the bass had thickened respiratory lamellae and chloride cell numbers similar to those found in the neutral pH treatments. In very soft water, mean blood osmolalities declined to 242 and 219 mosmol/kg at pH 5.0 and 4.5, respectively, and did not stabilize. In the acid + Al treatments, respiratory lamellae were frequently obliterated by hyperplasia of the interlamellar epithelium, suggesting markedly compromised respiratory ability. In addition, chloride cell numbers were usually depressed, and those cells that were present were often vacuolated or covered by layers of pavement epithelium; blood osmolalities declined to the lethal and near-lethal level of about 200 mosmol/kg, and heavy mortalities occurred. After 84 days in cold soft water (pH 7.8), scale Ca content declined; this effect was more severe in very soft water (pH 7.0). Acidification did not cause further decline in scale Ca content in the very soft water. At pH 4.5 + Al, scale Ca levels were higher than at pH 4.5 without added Al and higher than at pH 7.0, suggesting that Al may interfere with normal utilization of scale Ca reserves. Substantial lipid reserves persisted throughout the experiment. Mortalities were correlated with pH-associated gill damage and electrolyte losses rather than with duration of exposure to low temperature per se. Modest levels of Al exacerbated gill damage and electrolyte losses. We suggest that overwintering, with only moderate elevation of acid and Al levels, may represent an important critical period for survival to young-of-the-year fish in northern climates, principally by adversely affecting electrolyte balance. The gills of juvenile largemouth bass undergo marked structural changes with prolonged exposure to cold water, possibly to retard electrolyte losses.
Intraclutch egg-size variation and hatching success in the common eider
Authors: Robertson Gregory J. , Cooke Fred
Published: July 2008

Intraclutch egg-size variation and hatching success were studied in a population of Hudson Bay common eiders (Somateria mollissima sedentaria) at La Pérouse Bay, Manitoba (58°24′N, 94°24′W), to test the hypothesis that females allocate more nutrient reserves to eggs that are more likely to hatch. Egg volumes were calculated for 575 known-sequence eggs in 134 complete clutches of 3–6 eggs. In general, the length of eggs decreased linearly with position in the laying sequence, whereas the breadth of eggs followed a curvilinear pattern, the second or third egg being the widest. For all clutch sizes, the last-laid egg was the smallest and the second- or third-laid egg the largest. Hatching success also varied with position in the laying sequence. Pre-incubation failure declined over the laying sequence, whereas hatching failure (dead, infertile, or rotten eggs) increased. In all cases pre-incubation failure was the major cause of egg loss (84% of total loss). Overall, third and fourth eggs were the most successful and first eggs were the least successful. With one exception, successful and unsuccessful eggs were the same size within a laying sequence. We conclude that there is no clear relationship between egg size and hatching success, and that laying sequence per se has a greater effect on hatching success. Female eiders do not appear to allocate more reserves to eggs that are most likely to hatch, and we consider other proximate, physiological mechanisms to explain the observed pattern of intraclutch egg-size variation.
A long-term study of hybridization between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia
Authors: Aspinwall Nevin , McPhail John D. , Larson Allan
Published: July 2008

Hybridizing populations of the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, from Stave Lake, British Columbia, were examined three times over a 26-year interval to determine (i) whether swamping or introgression was occurring, (ii) whether the hybrids were being continually produced, and (iii) whether the composition of the hybrid population was constant. The hybrids were present at all three sampling periods with a rate of hybridization of 5.7% in 1966–1967, 14.1% in 1982, and 6.7% in 1991. F1 hybrids comprised no less than 80% of the hybrids at each sampling period. The remaining hybrids were mostly hybrid backcrosses to M. caurinus. Analysis of mitochondrial DNA (mtDNA) revealed that F1 hybrids were produced by females of both species, although not in equal proportions each year. Hybrid backcrosses to M. caurinus were more abundant as fingerlings than as adults, suggesting that selection is operating against them. After a 26-year interval, no evidence of swamping was detected when diagnostic morphological characters were employed. An analysis of allozyme data suggests that introgression is not occurring. The continued production of the hybrids over the three sampling periods suggests continuity in the environmental factors responsible for hybridization. Likewise, the greater proportion of F1 hybrids than backcrosses over the three sampling periods suggests a continued selective disadvantage of the backcrosses.
Aspects of milk composition and lactation in polar bears
Authors: Derocher Andrew E. , Andriashek Dennis , Arnould John P. Y.
Published: July 2008

Milk samples were collected on 135 occasions from fasting polar bears (Ursus maritimus) on land and from 26 feeding polar bears on the sea ice. Milk specimens were analyzed for fat, protein, carbohydrates, total solids, and gross energy. Fat content of milk from mothers with cubs captured on land declined from 35.8% when they were emerging from dens in spring to 27.5% the following autumn, and to 20.6% one year later when they had yearlings. No changes in milk fat were found for bears captured on the sea ice as offspring age increased. Milk protein levels increased while carbohydrate levels decreased through lactation for both feeding and fasting bears. Total solids ranged between 21.6 and 51.0%. For bears on land, gross energy declined from 16.9 kJ/g for females with 3-month-old cubs to 9.7 kJ/g when offspring were 34 months old. The proportion of females with cubs and yearlings that were lactating declined through the autumn. We suggest that when female polar bears do not have access to food, those with older offspring cease lactating earlier in the autumn and cessation of lactation results in lower milk fat and energy contents. Changes in milk composition may act to conserve maternal energy stores to ensure survival.
Influence of dietary protein on selected measures of humoral and cellular immunity in the cotton rat Sigmodon hispidus
Authors: Vestey M. R. , McMurry S. T. , Lochmiller R. L.
Published: July 2008

Small-mammal populations are subject to unpredictable and often dramatic fluctuations in numbers, but the mechanisms underlying this phenomenon are largely unclear. It has been suggested that protein is an important nutritional factor limiting survival, so we explored the effect of protein intake on the immunocompetence of cotton rats (Sigmodon hipsidus). In vivo and in vitro measures of both humoral and cell-mediated immunity were examined in a series of four protein-feeding trials (with weanlings, juveniles, subadults, and adults), using animals randomly assigned to an isocaloric diet containing either 4 or 16% crude protein. The response of lymphoid organ mass and cellularity to low dietary protein was variable, the spleen being more sensitive to dietary protein than the thymus. The ability of splenic lymphocytes to respond to in vitro stimulation with mitogens was unaffected by dietary protein, while the capacity of weanling and subadult cotton rats fed 4% protein to mount a delayed-type hypersensitivity response was enhanced. Nonspecific immunity (complement activity) was reduced in juveniles fed 4% protein. Dietary protein did not influence the ability of subadults or adults to generate a specific antibody response. These data suggest that cotton rats are less sensitive to dietary protein level than many inbred strains of laboratory rodents, younger animals may be at greater risk, and nutritional history may influence the response of a population to a reduction in available dietary protein.
A key for the identification of guard hairs of some Ontario mammals
Authors: Wallis Robert L.
Published: July 2008

A key is presented for the identification of dorsal guard hairs of 34 species of mammals from central Ontario. The key uses a suite of macroscopic and microscopic morphological features, including cross-sectional shape, medullary pattern, scale pattern, hair dimensions, and coloration.
Additional information on the morphology of the Elaphostrongylinae (Nematoda: Protostrongylidae) of North American Cervidae
Authors: Carreno Ramon A. , Lankester Murray W.
Published: July 2008

The morphology of elaphostrongyline nematodes occurring in North American Cervidae was examined using light and scanning-electron microscopy. The genus Parelaphostrongylus, which includes P. tenuis, P. odocoilei, and P. andersoni, is a morphologically similar group. The shaft of the spicules gives off a dorsal branch that extends to the tip; a membrane spans the shaft and the branch. The corpus of the gubernaculum has a dorsal groove and crurae are present. Protuberances associated with the cloaca of males and a papilliform projection at the tip of the female tail are seen in all three species. The morphology of Elaphostrongylus rangiferi, as described here, agrees with previous studies. Possible functions of the copulatory and associated structures are discussed.
Adaptive rumen function in elk (Cervus elaphus nelsoni) and mule deer (Odocoileus hemionus hemionus)
Authors: Spalinger D. E. , Robbins C. T. , Hanley T. A.
Published: July 2008

We tested the hypothesis that rumen function is adaptive to diet quality and intake rate using ruminally fistulated elk and mule deer. In experiment 1 we measured rumen particle-size distribution, rumen fill, and particle and liquid passage rates of animals fed three diets varying in quality (chopped pea, alfalfa, and wheat hays). In experiment 2, similar measurements were obtained on elk fed alfalfa hay ad libitum or at restricted intake levels. Rumen characteristics and passage rates of particles and liquids were similar for animals consuming alfalfa and pea hays. Intake, rumen dry-matter concentration and fill, and liquid passage rate were significantly lower when animals consumed wheat hay. Few significant differences in rumen characteristics or passage rates were found between animals fed alfalfa ad libitum or at restricted levels. Rumen liquid volume and dry-matter fill were related linearly to intake (r2 = 0.98 for both) in deer and elk fed alfalfa and pea hays. However, liquid volume and dry-matter fill of elk fed wheat hay and alfalfa at restricted levels were higher than the deer–elk interspecific regression, indicating an adaptive ruminal response. We concluded that rumen function was adaptive to both diet quality and availability, but that the response likely was subject to the limitations imposed by food characteristics and the inherent limitations of rumen structure and function.
Seasonal and diel variations of various blood parameters in Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides)
Authors: Audet Céline , Besner Michel , Munro Jean , Dutil Jean-Denis
Published: July 2008

Seasonal and diel variations of different blood variables were studied in Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) subjected to natural fluctuations of salinity and temperature in the St. Lawrence estuary. Significant seasonal fluctuations were found for all the parameters measured (plasma osmolality, Na+, Cl−, K+, glucose, Cortisol, and blood hemoglobin and hematocrit). In cod, the seasonal effect on blood hemoglobin was only detected through its interaction with time of day. In this species, all parameters also varied on an hourly basis, although these changes only represented a small proportion of the variance explained by the statistical model. In plaice, only plasma osmotic composition and blood hematocrit did not show diel variations, while the hour effect was difficult to characterize. In general, though our results indicate that both species acclimated to test conditions, American plaice seemed to cope less efficiently than Atlantic cod with winter conditions. In this respect, the Atlantic cod represents a better candidate for coastal aquaculture in this area.
Fall molt and lipid storage in raccoons (Procyon lotor)
Authors: Hanni Krista D. , Millar John S.
Published: July 2008

Energy storage was examined in relation to the timing of the fall molt in racoons (Procyon lotor) in southwestern Ontario, Canada. Total carcass lipids, corrected for body size, increased curvilinearly over time for juveniles and adults. As well, there were changes in the proportions of the three fall molt categories over time, but these changes were not the same for all four age–sex classes. We suggest that various behavioral and physiological factors are responsible for the differences observed in lipid accumulation and molting over time. Finally, the fall molt had no effect on lipid accumulation by juveniles or adults. For juveniles, lipid stores appeared to have some effect on the start of the fall molt. We suggest that this is due to the need for juveniles to attain a certain level of growth and lipid storage before the fall molt can begin. We conclude that the fall molt and lipid accumulation are occurring simultaneously and that the fall molt is not stressful in adult raccoons. There may be some consequences of growth on the timing of the cycle in juvenile raccoons.
Water balance and food consumption in dehydrated growing jirds (Meriones shawi shawi)
Authors: Sahni Malika , Peignoux-Deville Jacqueline , Lopez Evelyne
Published: July 2008

This study was an investigation of the degree to which water conservation is adapted in jirds (Meriones shawi shawi) when dehydration occurs during growth. During total water deprivation, three different stages became evident. For the first 7 days of total dehydration food intake decreased, then it stabilized over the next 4 weeks, until it approached the initial amounts, and finally increased to twice control levels. Analysis of changes water flux in growing M. s. shawi, with and without a supply of water, revealed that dehydrated animals are able to develop physiological tolerance and performance with respect to their water balance. The excretion of hyperosmotic urine in response to prolonged dehydration is intimately linked to the adaptive morphological kidney changes, i.e., selective hypertrophy, that we observed.
The neuroanatomy of a pharmacophagous insect
Authors: Meierhofer I.
Published: July 2008

The neuroanatomy of the supraoesophageal ganglion and suboesophageal ganglion of larval Creatonotos transiens (Lepidoptera: Arctiidae) was investigated to obtain a three-dimensional model of the brain. Central projections of antennal and maxillary sensory structures were traced using methods of cobalt diffusion. The majority of antennal axons project to the larval antennal centre in the supraoesophageal ganglion, whereas the major region to which the maxillary inputs project lies within the suboesophageal ganglion.
Differences in trapping mortality rates of northern flying squirrels
Authors: Rosenberg Daniel K. , Anthony Robert G.
Published: July 2008

We described trapping mortality rates of northern flying squirrel (Glaucomys sabrinus) populations in western Oregon, U.S.A., and evaluated the effects of sex, age, body mass, and number of times an individual was recaptured on these rates. Although the overall trapping mortality rates were relatively low (7%) during 16–21 day trapping sessions, we observed differential mortality rates among the sex and age cohorts. The order of mortality rates was: juvenile females (32.3%) > juvenile males (11.1%) > adult females (5.1%) = adult males (4.1%). Overall trapping mortality rates were not affected by the number of times an individual was captured. We hypothesize that the differences we found were due to extrinsic factors (weather-related) acting on differential behavioral responses to trapping and thresholds of stress an animal can tolerate.
Size, shape, and surface area of beaver, Castor canadensis, a semiaquatic mammal
Authors: Reynolds P. S.
Published: July 2008

The beaver, Castor canadensis, is a large, herbivorous, semiaquatic rodent. Beaver forage on land as well as in water; thus functional compromise between competing activities should result in a less streamlined body shape than expected for a similarly sized marine mammal. Standard morphometrics and surface areas of 70 Wisconsin beaver ranging in size from 5 to 35 kg were measured. Geometric similarity of surface area was maintained during growth (i.e., area was proportional to body mass raised to the 2/3 power). Scaly-tail area was positively allometric with body mass; hind foot web area was weakly negatively allometric. The surface area of the unfurred extremities (hind feet and scaly tail) comprised 30% of the total surface area of adults and over 50% for younger beaver. The average surface area of 21 adult beaver (mean body mass = 20 kg) was 0.52 m2. This value was significantly lower (P < 0.001) than predicted from the Meeh equation for terrestrial mammals, but similar to that expected for a marine mammal of equivalent mass. Body shape was described by the fineness ratio (a hydrodynamic index of streamlining). The fineness ratio for beaver was 4.8, a value similar to that for phocid seals. Therefore, in spite of expected constraints on body shape imposed by herbivory and the competing demands of terrestrial and aquatic foraging, beaver do not differ significantly in overall shape from other, more aquatic, species. However, shape alone is not a reliable indicator of either hydrodynamic or energetic efficiency. Future comparative studies should incorporate both phylogeny and biomechanical data into evaluations of mammalian morphology.
Acrosome-like structures in the spermatozoa of teleost fishes
Authors: Mattei Xavier , Thiaw Omar Thiom
Published: July 2008

The spermatozoa of teleost fishes lack an acrosome. However, peculiar structures have been described at the front of the nucleus in some species, and these take various forms. One or more vesicles may be placed at the front of the spermatid nucleus and, in some cases, may be retained in the spermatozoon. The anterior nuclear envelope may exhibit densification or intermembraneous differentiation. Stacks of membranes may be apposed to the nuclear envelope. No acrosome has been unambiguously identified to date in the spermatozoon of any teleost. The acrosome has been lost in the Teleostei during evolution, though some species have retained traces of it at the front of the germ cells. Thus, vestiges of acrosomal vesicles remain in Gambusia affinis, Lepadogaster lepadogaster, and Oncorhynchus mykiss. There is also a subacrosomal type of differentiation of the nuclear envelope in some spermatozoa. Similar structures have been described in the Porifera and Cnidaria, groups of primitive Metazoa in which the acrosome first evolved.
Changes in structure of the frontal filament in sequential developmental stages of Caligus elongatus von Nordmann, 1832 (Crustacea, Copepoda, Siphonostomatoida)
Authors: Piasecki W. , MacKinnon B. M.
Published: July 2008

The frontal filament of larval and adult Caligus elongatus was examined using light and electron microscopy. No trace of a frontal filament was evident in eggs, nauplii, or young copepodids. The structure develops in older copepodids in a cuticular pocket in the cephalothorax. Upon infecting a fish, the filament extrudes and attaches permanently to the host. The subsequent chalimus stages inherit the filament. Before moulting, the "frontal organ" produces an extension lobe, which is attached to the old filament by each subsequent chalimus stage during the moult. The structure of the frontal filament is described and illustrated, as well as some details of the frontal organ. Some new terms are proposed for the elements of the filament and the organ. The suggestion is made that the life cycle of C. elongatus includes five, not four, chalimus stages.
Benthic assemblages in Utah headwater streams with and without trout
Authors: Harvey Bret C.
Published: July 2008

In a series of high-gradient streams along the Wasatch Front in northern Utah, perlid stoneflies were more abundant in benthic samples from 14 fishless streams than in 9 similar streams which contained trout. Smaller-bodied perlodid stoneflies were more abundant in samples from streams containing trout. Herbivorous insect abundances varied substantially within groups of streams containing and lacking trout; multivariate analysis of variance using the six most abundant herbivorous taxa indicated no significant difference between the two groups of streams. Similarly, total numbers of invertebrates did not differ between streams with and without fish. Sites above and below the upstream limit of trout in three streams showed patterns in invertebrate abundances similar to that seen at the whole-stream scale. Trout may have no effect on the overall density of stream benthos because of their negative direct effects on invertebrate predators.
Aggression and territoriality among sympatric western plethodontid salamanders
Authors: Ovaska Kristiina
Published: July 2008

Territoriality has been documented among plethodontid salamanders in eastern North America, but aggressive interactions among western plethodontids are largely unknown. I examined the responses of three sympatric western Plethodon species (P. vehiculum, P. dunni, and P. vandykei) toward conspecific and congeneric salamanders in two laboratory experiments. In experiment 1, I investigated intra- and inter-specific aggression by the three species, and in experiment 2, I examined aggression and dispersion of the salamanders when fed either a high or a low level of food. In experiment 1, P. dunni were more aggressive than P. vehiculum and P. vandykei, which rarely bit their opponents. In experiment 2, two different food levels had no detectable effect on the aggressiveness of residents. Resident P. dunni (males, females, and juveniles) were equally likely to bite conspecific and congeneric salamanders introduced into their cages. However, their dispersion under cover objects was uniform (suggesting territoriality) only in pairings between conspecific individuals. In contrast, P. vehiculum showed little aggression and were randomly dispersed under cover objects. The variety of responses exhibited by the three sympatric species toward conspecific and congeneric salamanders suggests that their populations are only superficially similar in ecology and may be subjected to different intensities of intraspecific competition.
Repetition enhances hearing detection thresholds in a harbour seal (Phoca vitulina)
Authors: Turnbull S. D. , Terhune J. M.
Published: July 2008

Pure-tone hearing thresholds of a harbour seal (Phoca vitulina) were measured in air and underwater using behavioural psychophysical techniques. A 50-ms sinusoidal pulse was presented in both white-noise masked and unmasked situations at pulse repetition rates of 1, 2, 4, and 10/s. Test frequencies were 0.5, 1.0, 2.0, 4.0, and 8.0 kHz in air and 2.0, 4.0, 8.0, and 16.0 kHz underwater. Relative to 1 pulse/s, mean threshold shifts were −1, −3, and −5 dB at 2, 4, and 10 pulses/s, respectively. The threshold shifts from 1 to 10 pulses/s were significant (F = 12.457, df = 2,36, p < 0.001) and there was no difference in the threshold shifts between the masked and unmasked situations (F = 2.585; df = 1,50; p > 0.10). Broadband masking caused by meteorological or industrial sources will closely resemble the white-noise situation. At high calling rates, the numerous overlapping calls of some species (e.g., harp seal, Phoca groenlandica) present virtually continous "background noise" which also resembles the broadband white-noise masking situation. An implication of lower detection thresholds is that if a seal regularly repeats short vocalizations, the communication range of that call could be increased significantly (80% at 10 pulses/s). This could have important implications during the breeding season should storms or shipping noises occur or when some pinniped species become increasingly vocal and the background noise of conspecifics increases.
Sex ratio variation in the yuma bat (Myotis yumanensis)
Authors: Milligan Barry N. , Brigham R. Mark
Published: July 2008

Sex allocation theory predicts that monomorphic species should produce natal sex ratios near unity. We measured natal sex ratios in a maternity colony of approximately 1600 yuma bats (Myotis yumanensis) near Squilax, British Columbia, during June and July 1991. Overall, the natal sex ratio did not differ from unity but the sex ratio did vary significantly throughout the summer. Variation appears to be related to an interaction between maternal age and date of birth. This evidence suggests that facultative manipulation of the sex of the offspring by individual females may occur within the population.
Parasites of American shad, Alosa sapidissima (Osteichthyes: Clupeidae), from rivers of the North American Atlantic coast and the Bay of Fundy, Canada
Authors: Hogans W. E. , Dadswell Michael J. , Uhazy Leslie S. , Appy Ralph G.
Published: July 2008

Parasites belonging to a total of 26 taxa were recovered from 695 American shad (Alosa sapidissima) sampled from six rivers and one marine location (Cumberland Basin, Bay of Fundy) on the east coast of North America. Of these, 23 taxa are reported from American shad for the first time. Species identified were predominantly boreal marine forms that have low host specificities and widespread distributions. Two species, Hysterothylacium aduncum and Scolex pleuronectis, were found in American shad from all localities (> 60% prevalence). Relative abundance and diversity indices of the parasite assemblages varied in relation to geographic location and temporally in Cumberland Basin. These data suggest that there is different timing of arrival and departure of shad from individual river populations in Cumberland Basin. High levels of prevalence and incidence of exotic, southern parasite species, such as Genitocotyle atlantica, in shad from Cumberland Basin and most or all river populations indicate that all individual shad spend some portion of their life at or near the southern extent of their reported range.
Functional morphology of laminin, collagen type IV, collagen bundles, elastin, and proteoglycans in the bulbus arteriosus of the white bass, Morone chrysops (Rafinesque)
Authors: Raso Dominic S.
Published: July 2008

Immunolocalization of the basal lamina proteins laminin and collagen type IV, and the distribution of collagen bundles, elastin fibres, and proteoglycans in the bulbus arteriosus of adult white bass, Morone chrysops, were investigated. The bulbus arteriosus consists of three discernible layers: intima, media, and adventitia. The media composes approximately 95% of the bulbus arteriosus volume, and consists of elastin fibres, which allow distensibility, and proteoglycans which may be utilized in dissipating the frictional forces in an actively expanding bulbus arteriosus. Laminin and collagen type IV were co-localized to the luminal and bulbar–ventricular valve subendothelium anchoring the endothelium to the underlying parenchyma. Laminin and collagen IV were also expressed in the adventitia along with prominent collagen bundles which may serve to limit the expansion of the bulbus arteriosus at high intraluminal pressures. Collagen bundles and scattered elastin fibres are longitudinally aligned along the ventricular border of the bulbar–ventricular valve, acting as a semi-stiff border facilitating the timely opening of the valve and buffering the systolic force of inflowing blood. Proteoglycans occupy the bulbar portion of the valve and are most probably involved in absorbing the initial recoil from the front of the valve, thereby decreasing wear and tear upon the valve.
Orientation, passive transport, and sediment erosion features of the sea scallop Placopecten magellanicus in the benthic boundary layer
Authors: Grant Jonathan , Emerson Craig W. , Shumway Sandra E.
Published: July 2008

Passive transport and orientation of sea scallops (Placopecten magellanicus; 27–120 mm shell height) were studied in a laboratory flume to assess flow-mediated control of movement and position on the seabed. Additional experiments were conducted to characterize patterns of sediment transport around the scallop shell in relation to recesses occupied by scallops. The critical shear velocity of scallop transport was not correlated with shell height or other size measures, and most scallops were transported with the ventral shell margin facing downstream. Frontal exposure of scallops to the flow as indicated by fineness (shell height/shell depth) was greater in larger scallops, but when pallial gape was included in fineness (shell height/shell depth + gape)), frontal exposure was not correlated with scallop size. This suggests that variation in the drag component of transport was responsible for the lack of correlation between shell morphometry and critical shear velocity. Sediment transport created a horseshoe-shaped trough around the shell and several smaller erosion–deposition features downstream. The dimensions of sediment transport features were dependent on shell allometry, and it is likely that sediment transport contributes to the formation of scallop recesses typically observed in scallop beds. These results indicate that passive transport of sea scallops has a behavioural component related to gape that is independent of shell size. In contrast, scallop orientation and recessing may be explained by physical processes rather than simply by behaviour. Studies of bivalve hydrodynamics require consideration of living animals in addition to shell specimens and must include conditions of benthic boundary layer flow and sediment transport.
Breeding territoriality and pair formation in the convict cichlid (Cichlasoma nigrofasciatum; Pisces, Cichlidae)
Authors: Mackereth Robert W. , Keenleyside Miles H. A.
Published: July 2008

In many biparental species a sex difference in parental investment in a brood before fertilization, such as establishing a breeding territory or preparing a nest, may be an important component of the overall pattern of parental investment. Prefertilization investment patterns have been described for several species of biparental cichlid fishes, but there are discrepancies in the descriptions for the convict cichlid, Cichlasoma nigrofasciatum. This study describes quantitatively the prespawning behaviour of male and female convict cichlids and examines the influence on their behaviour of limiting the number of available spawning sites. The results indicate that pair formation begins several days before spawning when the female begins to follow a male and chase other females away from him. The pair then begins to spend more time in a smaller area where spawning eventually occurs. The breeding territory is usually established by the pair on the day of spawning. There was little difference in the pattern of prespawning behaviour offish with abundant versus limited spawning sites. It appears that neither sex will establish a territory until the female is ready to spawn and the pair has formed.
Tooth losses and anomalies in the wolf (Canis lupus)
Authors: Vilà C. , Urios V. , Castroviejo J.
Published: July 2008

We observed tooth losses (and subsequent alveolar resorptions) and other cases of anodonty and polydonty and anomalies in the shape and occlusion of the teeth in skulls of wolves from the former Soviet Union. Resorptions increase in number with age, but do not seem to have much of an effect on individual survival (they probably do not affect hunting), and are found in half of individuals over 8 years of age. The highest numbers of resorptions, as well as cases of polydonty and dental anomalies, were in the premolars. This suggests that the premolars are not greatly subject to selective pressure. At least 6.8% of the skulls have malformed teeth or malocclusions.
Effects of temperature and photoperiod on the duration of hatching, swimming, and copepodid survival of the parasitic copepod Salmincola edwardsii
Authors: Conley David C. , Curtis Mark A.
Published: July 2008

We conducted laboratory experiments to test whether various temperature and photoperiod regimes had any effect on the duration of egg hatching, swimming activity, and copepodid survival in the parasitic copepod Salmincola edwardsii, commonly found on brook trout (Salvelinus fontinalis). Pairs of egg sacs were removed from adult female copepods; one of each pair was exposed to a different photoperiod than the other, at the same temperature. Experiments were conducted at 8, 12, 16, and 20 °C. Temperature had a significant effect on the duration of copepodid swimming activity and survival, and the onset of egg sac hatching was directly related to increasing water temperature. However, hatching duration and hatching success were not affected by temperature over the range tested. Photoperiod had no effect on hatching duration, hatching success, swimming activity, or copepodid survival. Our findings indicate that S. edwardsii copepodids can swim and survive for more than 2 weeks; much longer than the 2 days customarily reported in the literature. This must be accounted for in the development of strategies to control transmission.
Activity levels of Marbled Murrelets in different inland habitats in the Queen Charlotte Islands, British Columbia
Authors: Rodway Michael S. , Regehr Heidi M. , Savard Jean-Pierre L.
Published: July 2008

We compared Marbled Murrelet (Brachyramphus marmoratus) activity levels in May, June, and July 1990 in four habitats in the Queen Charlotte Islands, British Columbia: alpine, old-growth forest at high elevation, old-growth forest at low elevation, and second-growth forest. The number of Marbled Murrelet detections was highest in old-growth forests. In alpine areas, small numbers of murrelet detections were mostly of distant birds flying over low-elevation forest. Numbers of detections were higher in low-elevation than in high-elevation old-growth forests in May and July, but not in June. Proportions of detections within smaller radii of survey stations were higher in low elevation forest in all months. The highest activity levels were associated with old-growth forest stands of large Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla). The few detections that occurred in second-growth forests were mostly of distant birds. Stations in second-growth forest close to stands of old-growth forest had more frequent detections than stations with no old-growth forest nearby. Our results support the association of Marbled Murrelets with old-growth forests. Limitations of the survey methodology are discussed.
Diving in ringed seal (Phoca hispida) pups during the nursing period
Authors: Lydersen Christian , Hammill Mike O.
Published: July 2008

In this study, activity and diving performance of nursing ringed seal (Phoca hispida) pups were quantified using time–depth recorders. A total of 1040 h of activity, including 7506 diving cycles, was collected from three female pups. The pups spent 50.3% of their time in the water and 49.7% hauled out on the ice. When the pups were in the water, 20.5% of the time was spent actively diving, while 79.5% of the recorded wet time was spent at the surface. Most of the dives were shallow and of short duration. Mean dive duration was 59.1 ± 63.5 s (SD). Maximum dive durations for the three pups were 5.8, 7.5, and 12 min. Maximum recorded depths were 12, 35, and 89 m. These depths represented the bottom in the area where each pup was situated. The average duration of haul-out sessions where nursing could take place was 6.3 ± 1.6 h, and the time between these sessions was 8.2 ± 3.2 h. The mean number of breathing holes found per pup was 8.7 ± 3.5. The large proportion of time spent in the water, the development of diving skills at an extremely young age, the use of multiple breathing holes, and the prolonged white-coat stage are all interpreted to be evolutionary responses to strong predation pressure, mainly from polar bears.
Bougainvillia aberrans (Cnidaria, Hydrozoa), a new species of hydroid and medusa from the upper bathyal zone off Bermuda
Authors: Calder Dale R.
Published: July 2008

Bougainvillia aberrans n.sp. is described from Bermuda in the western North Atlantic Ocean. Specimens were collected at a depth of 150 fathoms (274 m) from the polypropylene buoy line of a crab trap. The hydroid colony of B. aberrans is erect, with a polysiphonic hydrocaulus, a smooth to somewhat wrinkled perisarc, hydranths having a maximum of about 16 tentacles, and medusa buds arising only from hydranth pedicels. Medusae liberated in the laboratory from these hydroids differ from all other known species of the genus in having a long, spindle-shaped manubrium, lacking oral tentacles, having marginal tentacles reduced to mere stubs, and being very short-lived (surviving for a few hours at most). Gonads develop in medusa buds while they are still attached to the hydroids, and gametes are shed either prior to liberation of the medusae or shortly thereafter. The eggs are surrounded by an envelope bearing nematocysts (heterotrichous microbasic euryteles). The cnidome of both hydroid and medusa stages consists of desmonemes and heterotrichous microbasic euryteles. The diagnosis of the genus Bougainvillia is modified to accommodate this new deep-water species.
Clutch size in eastern phoebes (Sayornis phoebe). I. The cost of nest building
Authors: Conrad Kelvin F. , Robertson Raleigh J.
Published: July 2008

Eastern phoebes (Sayornis phoebe) may build new nests or repair previously built ones. New nests may be of two types: statant (built on supporting ledges) or adherent (plastered to a vertical surface). Repaired nests are statant. Previous workers compared phoebes building new nests to those repairing old nests and found that new nests require more time and effort to build. Similarly, previous workers found that adherent nests took more time and effort to build than statant nests. At the same time, these workers noted that smaller clutches were laid in new and adherent nests than in repaired and statant nests and concluded that the reduction in clutch size was the result of building the former types of nest. This implies that an increase in the demands on parental time and energy just before egg laying can decrease reproductive output proximally. However, the statistical support for this conclusion was weak, and our reanalysis of the previously reported data does not support it. In addition, previous workers used the terms statant and adherent inconsistently. We advise that nest types be carefully defined according to the expected effect of nest type on the bird's behaviour, not just according to the appearance of the nest. We found that building new nests took longer than repairing old ones. However, we failed to find a difference in the time required to build adherent and statant nests. Furthermore, clutch size was apparently unrelated to the type of nest built. We found no relationship of clutch size to female age or clutch initiation date. The type of nest built for the first clutch size of the season also was not related to the probability that there would be a second clutch, the size of the second clutch, or the interval between clutches. More research is required to show conclusively that increased demands on time or energy just before egg laying can reduce the clutch size of small passerines.
Egg-size variation in Yellow Warblers: apportionment of parental investment and the brood-survival hypothesis
Authors: Hébert Percy N. , Sealy Spencer G.
Published: July 2008

It has been hypothesized that in passerine birds the larger size of last-laid eggs is part of a brood-survival strategy. We examined the usefulness of the brood-survival hypothesis in explaining intraclutch variation in egg mass of Yellow Warblers (Dendroica petechia). In 4- and 5-egg clutches, egg mass increased significantly with laying order. Although last-hatched nestlings in broods of 4 had higher survival rates than their counterparts in broods of 5, there were no differences in the absolute or relative mass of last-laid eggs in clutches of 4 and 5 eggs. In addition, the mass of last-laid eggs that hatched but did not produce a fledgling was not significantly different from that of last-laid eggs that did produce a fledgling. Finally, the relative mass of last-laid eggs was also not correlated with hatch spread or with date of clutch initiation. The results of this study do not support the brood-survival hypothesis.
Comparative shell morphology of Dreissena polymorpha, Mytilopsis leucophaeata, and the "quagga" mussel (Bivalvia: Dreissenidae) in North America
Authors: Pathy Diane A. , Mackie Gerald L.
Published: July 2008

Dreissena polymorpha, recently introduced to freshwater habitats of North America, has been confused with Mytilopsis leucophaeata, a related species that is native to brackish and fresh waters of North America. The 1991 discovery of a second exotic dreissenid mussel, the "quagga" mussel, suggests there may be more than one species of Dreissena in the Great Lakes, resulting in even more confusion in identification within the family Dreissenidae. To help distinguish the species, internal and external features, ultrastructure, and composition of D. polymorpha, M. leucophaeata, and quagga mussel shells were determined using stereoscopic, scanning electron microscopic, and X-ray diffraction techniques. The most reliable diagnostic feature is the presence of an apophysis in M. leucophaeata and its absence in D. polymorpha and the quagga mussel. Mytilopsis leucophaeata and quagga mussels also lack the acute shoulder or ridge located ventrolaterally. Dreissena polymorpha, M. leucophaeata, and the quagga mussel all have an outer crossed-lamellar shell structure with an inner complex crossed-lamellar shell structure and a thin, prismatic pallial myostracum between. Microtubules are more prominent in M. leucophaeata than in D. polymorpha. No microtubules were found in the quagga mussels. Shells of D. polymorpha, M. leucophaeata, and the quagga mussel are composed entirely of aragonite crystals.
Systematics and ecology of Adhaesozetes polyphyllos sp.nov. (Acari: Oribatida: Licneremaeoidea), a leaf-inhabiting mite from Australian rainforests
Authors: Walter David Evans , Behan-Pelletier Valerie M.
Published: July 2008

We present the first study of the systematics, ecology, and biogeography of an arboreal oribatid mite from Australia, describe all stages of Adhaesozetes polyphyllos sp.nov., propose new diagnoses for its genus and family, and present a character analysis demonstrating that the family Adhaesozetidae is a member of the Licneremaeoidea. Certain character states, especially the expanded tarsal pulvilli, are interpreted as adaptations to arboreal life. Adhaesozetes polyphyllos grazes on epiphyllic fungi and prefers leaves with smooth surfaces or with closely appressed hairs. It inhabits at least 51 species of trees, shrubs, vines, and ferns in pockets of rainforest in eastern Australia. It is often the most abundant leaf-inhabiting oribatid mite in the cool- to warm-temperate rainforests of Tasmania and Victoria, and inhabits montane subtropical to tropical rainforests at least as far north as Mount Lewis (16°32′S). It appears to be absent from lowland subtropical to tropical rainforests, which suggests an ancient relationship with the Antarctic elements of the Australian flora. Populations are bisexual, with females representing an average of 55% of the adult population. At Wilson's Promontory, populations increase from late winter to midsummer, but all stages are present throughout the year. Females use their ovipositors to lay eggs in protected sites (e.g., insect damage or leaf domatia), often within the cast skins of immature mites.
Seasonal patterns of activity and body mass in the plains vizcacha, Lagostomus maximus (family Chinchillidae)
Authors: Branch Lyn C.
Published: July 2008

Activity patterns of adult male, adult female, and immature plains vizcacha (Lagostomus maximus) were compared throughout the year, and seasonal changes in body mass were documented for adults. All sex–age classes spent more time feeding in winter and less time at the den site (vizcachera) than in other seasons. The pattern was reversed for summer. Seasonal changes in activity budgets for males were associated with an increase in male–male conflicts and territorial displays at the vizcachera. Body mass of males declined in summer, when they were competing for access to areas used by females, and reached a minimum during the fall breeding season. Females spent less time foraging and more time at the den site after parturition in spring. Body mass of females did not change significantly with season. Throughout the year, activity patterns were similar for females and immatures. During all seasons, adult males spent less time foraging and more time at the vizcachera than other sex–age classes did. From a variety of observations, I suggest that the costs of reproduction, including mass loss, shorter feeding time, and short tenure in a social group, are high for male vizcachas.
Use of feeding habitats by breeding Eurasian wigeon
Authors: Jacobsen Odd W.
Published: July 2008

The use of feeding habitats by breeding Eurasian wigeon (Anas penelope) was studied in two lakes in western Norway in 1983 and 1988. During the early and late breeding periods of both years, wigeon preferred to feed on agricultural fields surrounding parts of the lakes. Most individuals preferred to feed among emergent hydrophytes, whereas open water was used less than expected. Beds of floating hydrophytes were not used during the early period but were used in proportion to their availability during the late period. Use of and preference for feeding habitats varied among individuals and lakes and between years. Temporary availability of foods is the most important factor in the birds' selection of terrestrial and aquatic feeding habitats during the breeding season. Because one of the lakes has undergone eutrophication, which has affected the use of feeding habitats by wigeon between years, I suggest that the quality of feeding habitats in this lake can be improved by artificially removing the dense aquatic vegetation that covers much of the surface area. Improvement of the surrounding agricultural fields is another management alternative that could benefit grazing wigeon.
Succès relatif de deux tentatives consécutives de nidification chez l'Hirondelle à front blanc (Hirundo pyrhonotta) à Sherbrooke, Québec
Authors: Gauthier Marc , Thomas Donald W.
Published: July 2008

We report the observation of second nesting attempts by a colony of Cliff Swallows in Sherbrooke (Que.). This represents the most northern record of successful second nesting attempts for this species. Laying periods for the first and second attempts ranged from 19 May to 7 June and from 2 to 28 July 1988, respectively. While the first attempt produced an average of 1.84 ± 0.17 (mean ± SE) fledglings per nest, the second one produced only 0.4 ± 0.17 fledglings. We suggest that the low lipid reserves of parents prior to laying may explain the lower nesting success of the second nesting attempt.