bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective population size and genetic structure of a Piute ground squirrel (Spermophilus mollis) population
Authors: Antolin Michael F , Horne Beatrice Van , Berger, Jr. Michael D , Holloway Alisha K , Roach Jennifer L , Weeks, Jr. Ronald D
Published: April 2011

Piute ground squirrels (Spermophilus mollis) are distributed continuously in habitat dominated by native shrubs and perennial grasses in the Snake River Birds of Prey National Conservation Area in Idaho, U.S.A. This habitat is being fragmented and replaced by exotic annual plants, changing it to a wildfire-dominated system that provides poor habitat for ground squirrels. To assess potential effects of this fragmentation on ground squirrel populations, we combined an estimate of effective population size (Ne) based upon a demographic study with a population genetic analysis. The study area included three subpopulations separated from each other by 813 km. The ratio of effective population size to census number (Ne/N) was 0.57. Combining Ne/N with dispersal distances from a radio-tracking study, we calculated that neighborhood size was 62.2 ha, which included between 204 and 480 individuals. Our population genetic analysis (based on randomly amplified polymorphic DNA (RAPD) and microsatellite markers) showed relatively low levels of genetic differentiation (Qpopulations[Formula: see text] 0.070.10) between subpopulations and no inbreeding within subpopulations (f = 0.0003). These estimates of population subdivision translate into an effective migration rate (Nem) of 2.33.3 per year, which represents a high level of gene flow. Invasion by exotics will reduce the overall productivity of the habitat, and will lead to isolation among subpopulations if favorable habitat patches become isolated.
Differences in key habitat use between dominant and subordinate animals: intraterritorial dominance payoffs in Eurasian badgers?
Authors: Revilla Eloy , Palomares Francisco
Published: April 2011

Group-living territorial animals such as the Eurasian badger, Meles meles L., face the problem of intragroup competition. Badgers are asymmetric in their access to reproduction (dominant individuals being the ones that reproduce), but little information exists about the extent of intragroup trophic competition. We studied badgers' use of a key trophic resource (the European rabbit, Oryctolagus cuniculus), as well as the use of the habitat where this resource is located (key habitat, Mediterranean scrubland) by a low-density group-living population of badgers in Coto del Rey, Doñana, southwestern Spain. During 19951996, there was a 2.2-fold reduction of rabbit density, which was reflected in a significant diminution of rabbit use; despite this, rabbits continued to be the most used trophic resource. Notwithstanding the decrease in rabbit density, subordinate badgers reduced their use of the key habitat, while dominant badgers increased it. These results suggest that in Coto del Rey, badger groups exhibit a fully despotic system, with dominance by some individuals not only in access to reproduction, but also in access to food through unequal use of the key habitat that contains it.
Seasonal changes in glucocorticoid and testosterone concentrations in free-living arctic ground squirrels from the boreal forest of the Yukon
Authors: Boonstra Rudy , Hubbs Anne H , Lacey Eileen A , McColl Carolyn J
Published: April 2011

We examined how glucocorticoid and testosterone concentrations changed from spring to summer by livetrapping free-living populations of arctic ground squirrels (Spermophilus parryii). The primary glucocorticoid was found to be cortisol, with corticosterone below measurable concentrations in most individuals. Livetrapping elicited a strong stress response in both sexes: breeding males and females trapped in spring had free cortisol concentrations 4 and 34 times, respectively, those of base-line animals. The maximum corticosteroid-binding capacity (MCBC) was unaffected by trapping and was about 3 times higher in breeding females than in breeding males. Over the active season, MCBC values were lowest in all male classes (juveniles, nonreproductive adults, and reproductive adults), being less than half those in all female classes; pregnant females had values approximately twice those of juvenile females. However, free cortisol concentrations were similar in all female classes and in juvenile males and about half those in adult males. Livetrapping increased testosterone concentrations in males over those found in samples from base-line males, and testosterone concentrations did not affect MCBC values. Testosterone concentrations in livetrapped animals differed significantly among male classes, with nonreproductive males maintaining concentrations 64% of those in breeding males and 10 times those in juveniles.
Estimating snowshoe hare population density from pellet plots: a further evaluation
Authors: Krebs Charles J , Boonstra Rudy , Nams Vilis , O'Donoghue Mark , Hodges Karen E , Boutin Stan
Published: April 2011

We counted fecal pellets of snowshoe hares (Lepus americanus) once a year in 10 areas in the southwestern Yukon from 1987 to 1996. Pellets in eighty 0.155-m2 quadrats were counted and cleared each June on all areas, and we correlated these counts with estimates of absolute hare density obtained by intensive markrecapture methods in the same areas. There is a strong relationship between pellet counts and population density (r = 0.76), and we present a predictive loglog regression to quantify this relationship, which improves on our previously published 1987 regression, particularly at low hare densities. The precision of density estimates can be improved most easily by increasing the number of sets of quadrats in an area (one set = 80 plots), rather than increasing the number of plots counted within one set. The most important question remaining concerns the generality of this relationship for snowshoe hares living in other habitats in the eastern and southern portions of their geographic range.
Body size, sexual dimorphism, and seasonal mass fluctuations in a larger sika deer subspecies, the Hokkaido sika deer (Cervus nippon yesoensis Heude, 1884)
Authors: Suzuki Masatsugu , Onuma Manabu , Yokoyama Mayumi , Kaji Koich , Yamanaka Masami , Ohtaishi Noriyuki
Published: April 2011

Measurements of shoulder height, body length, hind-foot length, and total body mass were collected from 309 Hokkaido sika deer (Cervus nippon yesoensis Heude, 1884) (115 males and 194 females) and analyzed statistically for sexual dimorphism and seasonal body mass fluctuations. The von Bertalanffy equation was fitted to the growth curves that resulted. Asymptotic shoulder height, body length, and hind-foot length were 106.2, 112.6, and 52.9 cm in males and 94.8, 103.9, and 49.4 cm in females, respectively. Total body mass showed distinct seasonal fluctuations, ranging between 102.8 and 151.0 kg in adult males and 68.0 and 99.8 kg in adult females. Male/female ratios in shoulder height, body length, hind-foot length, and total mass were 1.12, 1.08, 1.07, and 1.51, respectively. These results indicate that the Hokkaido sika deer is one of the largest subspecies, at least in skeleton size. A larger body and longer hind foot would seem to be evolutionary adaptations to Hokkaido's cold, snowy environment.
The effect of interspecific competition on habitat selection by voles: an experimental approach
Authors: Lin Yu-teh K , Batzli George O
Published: April 2011

Both meadow voles (Microtus pennsylvanicus) and prairie voles (Microtus ochrogaster) prefer habitats with high vegetative cover, but in east-central Illinois, meadow voles tend to be associated with higher cover and prairie voles with lower cover. The competition hypothesis proposes that this pattern of habitat segregation reflects the effects of interspecific competition on habitat selection. To test this hypothesis we conducted field experiments that allowed the two species to select from among several habitats when alone and when together. We expected to find a lower proportion of each species in the habitat most associated with the other species, and a negative correlation between the demography and density of each species and the density of the competing species, but this was not the case. Inter specific competition did affect movement patterns of prairie voles. In the presence of meadow voles, net movement (immigration minus emigration) of prairie voles in high-cover habitats decreased and net dispersal of individuals from high- to low-cover habitats increased. Thus, our results indicated only a weak effect of competition on habitat selection. We suggest that other mechanisms, such as differences in habitat preference (or tolerance), differences in dispersal ability, and the advantage of first residency, need to be considered in conjunction with interspecific competition to explain the habitat segregation observed in these species.
Behavior and dispersal of white-tailed deer during the breeding season
Authors: Rosenberry Christopher S , Conner Mark C , Lancia Richard A
Published: April 2011

Sexual competition and aggression by adult females have been hypothesized to prompt dispersal by male white-tailed deer (Odocoileus virginianus). We observed behavioral interactions of 21 yearling males (14 dispersers and 7 nondispersers) at Chesapeake Farms during the early part of the breeding season prior to actual breeding. Interactions with adult males and females constituted a small portion of all interactions and yearling males were similarly subordinate to adults. Dispersers participated in breeding-season behaviors with yearling males more often than nondispersers did (P = 0.005), and tended to be more subordinate than nondispersers (P = 0.095). Behavioral differences related to sexual competition with other yearlings appeared to be correlated with dispersal by yearling males at Chesapeake Farms. We recommend that both sexual competition and aggression by adult females be considered in future attempts to understand the dispersal behavior of white-tailed deer.
Changes in the reproductive behaviour of the endangered Newfoundland marten (Martes americana atrata): implications for captive breeding programs
Authors: Heath Joel P , McKay Donald W , Pitcher Mac O , Storey Anne E
Published: April 2011

Behavioural changes associated with reproduction were studied in captive Newfoundland martens (Martes americana atrata), an endangered species. Patterns of scent-marking and behavioural interactions were recorded before and after a male was introduced to two females. After introduction of the male, marking by the receptive female increased, whereas the nonreceptive female marked less and became less active. Activity and marking bouts were significantly correlated throughout the day for the male and the receptive female, and they often marked in the same locations. The male marked more frequently when the receptive female was active and the female's marking was often associated with behavioural interactions. These findings suggest a major female influence on male marking and activity and suggest that marking may facilitate social interaction. In the spring following this study, the receptive female successfully whelped a litter, the first to be conceived and born in this captive breeding program. The results of this study may help establish successful protocols for captive breeding programs, and thus aid efforts to conserve this endangered species.
REGULAR ARTICLES / ARTICLES RÉGULIERS Whether to reproduce or not: immune suppression and costs of parasites during reproduction in the Arctic charr
Authors: Skarstein Frode , Folstad Ivar , Liljedal Ståle
Published: April 2011

Secondary sexual characters are assumed to be costly to develop, and the costs of parasite infections and immune suppression are currently an active area of research within sexual selection. We investigated differences in parasitic infections and immunological activity between reproductively active and inactive Arctic charr (Salvelinus alpinus). Spawning fish were found to have higher intensities of macroparasite infections than nonspawning or resting fish. The difference in intensity between spawning and resting fish was only observed in males, and can be explained by differences in exposure or susceptibility to parasites. However, there is indirect evidence that the difference in parasite intensities does not stem from varying exposure originating from group differences in consumption of carotenoid-containing intermediate hosts. We show, rather, that spawning males may be more susceptible, since they have a smaller spleen, which is an important lymphocyte-producing organ, than resting males. As these costs of spawning are found predominantly among males, they are unlikely to be the result of energetic investment in gamete production, as gamete production in general is thought to be more energetically demanding in females than in males. Rather, we suggest that the observed costs of reproduction result from immune suppression related to ornamental development and spermatogenesis.
Endocrine and environmental control of reproduction in Polychaeta
Authors: Andries Jean-Claude
Published: April 2011

In Polychaeta, as in many invertebrates, reproduction is controlled by both environmental and endocrine factors. Although the effects of environmental factors on reproductive behaviour are briefly discussed, this review focuses on the endocrinology of reproduction. As Nereidae are the most intensively studied polychaetes, their epigamic monotelic strategy is discussed first in this review. Although a large number of physiological observations have been made, biochemical data have been greatly lacking until recent years, except, however, for the recent isolation of several pheromones. These substances, such as uric acid and L-cysteine gluthathione disulfide, occur widely and must be present at high concentrations in order to exert their physiological effects. Results obtained from iteroparous species are also considered. The stolonization strategy of Syllidae, the control of vitellogenesis in Nephtyidae, Phyllodocidae, Polynoidae, and Cirratulidae, and the regulation of gamete maturation in Arenicolidae and Pectinariidae are discussed. As with Nereidae, our knowledge of endocrine control is mainly based on experimental data, since only sperm-maturation factor in the genus Arenicola has been identified. Therefore, despite numerous interesting experimental studies in which functional roles for polychaete reproductive hormones have been described, their nature, their primary targets, and their mechanism of action are unfortunately still largely unknown.
An overview of glossiphoniid leech development
Authors: Weisblat David A , Huang Françoise Z
Published: April 2011

Dramatic advances in understanding the development of selected "model" organisms, coupled with the realization that genes which regulate development are often conserved between diverse taxa, have renewed interest in comparative development and evolution. Recent molecular phylogenies seem to be converging on a new consensus "tree," according to which higher bilaterians fall into three major groups, Deuterostoma, Ecdysozoa, and Lophotrochozoa. Commonly studied model systems for development fall almost exclusively within the first two of these groups. Glossiphoniid leeches (phylum Annelida) offer certain advantages for descriptive and experimental embryology per se, and can also serve to represent the lophotrochozoan clade. We present an overview of the development of glossiphoniid leeches, highlighting some current research questions and the potential for comparative cellular and molecular studies.
Does mass change of primiparous bighorn ewes reflect reproductive effort?
Authors: Gallant B Y , Réale D , Festa-Bianchet M
Published: April 2011

Reproductive effort during a female's first breeding attempt could affect subsequent fitness, particularly in species that reproduce before completing body growth. We analyzed 26 years of data on marked bighorn (Ovis canadensis) ewes to assess how variation in first reproductive effort affected other life-history traits. We measured reproductive effort as the residual of the regression of mass of primiparous ewes in late lactation on their mass 1 year earlier. Survival of the first-born lamb to weaning reduced maternal mass gain, suggesting a trade-off between reproduction and growth. Mass gain during the year of primiparity therefore appears to reflect reproductive effort. Lower mass gain was associated with lower adult mass and longevity, two important determinants of lifetime reproductive success. Reproductive effort at first parity therefore appears to lower residual reproductive value. Over their lifetime, females with low mass gain as primiparae produced proportionately more daughters than did females with high mass gain. Reproductive effort at first reproduction was not heritable, and may affect the evolutionary potential of adult mass and longevity, two fitness-related traits that are highly heritable in the study population.
Temperature-based variation of rRNA secondary structure models: a case study in the insectDrosophila simulans, the land snailIsabellaria adriani, and the crustaceanDaphnia pulex
Authors: Armbruster Georg FJ
Published: April 2011

The influence of a temperature default on ribosomal RNA (rRNA) secondary structure models was studied with the "Mfold" energy-optimization program. Folding models of the internal transcribed spacer (ITS) 1 rRNA for both Drosophila simulans (Insecta) and Isabellaria adriani (Gastropoda) were generated at two different temperatures. The folding models are compared with the models previously shown for the ITS-1 of D. melanogaster Oregon R strain and I. adriani. A search for phylogenetically informative ITS-1 folding motifs was conducted for D. simulans. In I. adriani, a new approach for ITS-1 secondary structure analyses is suggested. The paper also elucidates results inferred from three energy-optimizing programs (Mfold, GeneBee, and STAR). These three folding programs give different information on the structure and free energy of a ITS-1 rRNA molecule. Furthermore, secondary-structure models of the small subunit (ssu) rRNA of Daphnia pulex (Crustacea: Cladocera) were investigated. The ssu rRNA molecule is usually folded according to alignment information. Here, ssu folding patterns are computed with Mfold using two temperature conditions. The two Mfold models are compared with the alignment model previously suggested for D. pulex. Three cladoceran-specific motifs and a short stem motif within the ssu rRNA of eukaryotes are discussed with respect to structure and phylogenetic information.
Maintenance of androdioecy in the freshwater clam shrimp Eulimnadia texana: longevity of males relative to hermaphrodites
Authors: Zucker Naida , Stafki Brian , Weeks Stephen C
Published: April 2011

The clam shrimp Eulimnadia texana exhibits a rare mixed mating system known as androdioecy. In this ephemeral-pond branchiopod crustacean, males coexist with hermaphrodites, which can outcross with males or self-fertilize. We provide an estimate of the longevity of males relative to hermaphrodites (1  σ), an important parameter of a model that was developed to explain the conditions under which this system would be stable. Under both optimal rearing conditions and various sex-ratio treatments, hermaphrodites from two study populations lived significantly longer than males. Since various aspects of mating have been found to be costly to males and females/hermaphrodites in other taxa, we explored this possibility as well. Hermaphrodites showed no differences in longevity when kept in groups provided with different mating opportunities. Males, however, lived significantly longer when mating opportunities were increased, a result contrary to what we had expected. Behavioral observations, however, suggested that malemale interactions may have been deleterious to males living in groups with little opportunity to mate. This was confirmed by an additional study in which individual males were maintained in the presence and absence of hermaphrodites. Under these conditions we still detected no longevity cost of mating for males.
Intergradation and origins of subspecies of the turtle Chrysemys picta: morphological comparisons
Authors: Ultsch Gordon R , Ward G Milton , LeBerte Chere' M , Kuhajda Bernard R , Stewart E Ray
Published: April 2011

We present morphological data on the four subspecies of painted turtles (Chrysemys picta) from 20 states in the U.S.A. and three provinces in Canada, and from localities within them that are removed from reported zones of intergradation. The characters used are those of Hartman (1958), which have been routinely used in subsequent studies: the extent of plastral patterning (here quantified by image analysis), the degree of misalignment of carapacial scutes, and the width of the light anterior margins of the second lateral scutes. Our purposes are to present descriptive baseline data for each subspecies for use in comparisons with the results of past and future studies of intergradation, and to critique the oft-accepted theory of Bleakney (1958) regarding the evolutionary origins of the current subspecies, particularly C. p. marginata. Data are given for C. p. bellii from 5 states ranging from Minnesota to New Mexico, for C. p. dorsalis from 3 states (Arkansas, Louisiana, and Mississippi), for C. p. marginata from 4 localities (Ontario, Michigan, Indiana, and Ohio), and for C. p. picta from 11 localities from Nova Scotia to Georgia. We find that (i) a "pure" picta does not exist; there is marginata influence throughout picta's range, particularly at the extremes; (ii) similarities exist that group dorsalis with picta; (iii) there is a north-south cline of reduced scute alignment in picta; (iv) there is a north-south cline of increasing extent of the plastral pattern in bellii; (v) the question of which subspecies first reached New England after the Wisconsinan glaciation remains unresolved, but it was likely not picta; (vi) there is no compelling reason to accept or reject Bleakney's theory of the distribution of painted turtle subspecies at the height of the Wisconsinan glaciation or his conjecture that marginata arose as in intergrade of bellii and dorsalis; in fact, it could be argued that if marginata is a hybrid, it could be a hybrid of picta and bellii.
Genetic diversity and population structure among northern bottlenose whales,Hyperoodon ampullatus,in the western North Atlantic Ocean
Authors: Dalebout M L , Hooker S K , Christensen I
Published: April 2011

To assess population structure and genetic diversity among northern bottlenose whales (Hyperoodon ampullatus), we compared mitochondrial DNA control region sequences from three populations in the western North Atlantic Ocean. Skin-biopsy samples were collected from animals in the Gully off Nova Scotia, Canada, in 1996 and 1997 (n = 20), and teeth were obtained from whales taken in Davis Strait off northern Labrador (n = 20) and off northern Iceland (n = 5) between 1967 and 1971 by the historical Norwegian fishery. Only low levels of genetic diversity were found among the 45 animals sampled (three polymorphic sites over 434 base pairs defining four haplotypes; haplotype diversity (h) = 0.57, nucleotide diversity (π) = 0.0015). The cause of this low variability is unclear but may be due to a possible bottleneck event associated with the last glaciation. The distribution of mitochondrial DNA haplotypes between the Gully and Davis Strait populations was suggestive of regional differentiation (FST= 0.118, P = 0.024; ΦST= 0.145, P = 0.007). Animals taken off northern Iceland were not included in statistical analyses of population structure, owing to the small sample size. These data, in conjunction with other information collected to date, indicate that the Gully and Davis Strait populations should be considered separate stocks for management purposes.
Survival of white-tailed deer in intensively farmed areas of Illinois
Authors: Nixon Charles M , Hansen Lonnie P , Brewer Paul A , Chelsvig James E , Esker Terry L , Etter Dwayne , Sullivan Joseph B , Koerkenmeier Robert G , Mankin Philip C
Published: April 2011

Survival of 265 female and 224 male [Formula: see text]1-year-old white-tailed deer (Odocoileus virginianus) marked on 3 study areas in central and northern Illinois was examined. Females lived, on average, 5.5 years and males 2.5 years from birth. Twenty-four of the 265 females lived for at least 10 years from birth, but only 14 males for at least 5 years. The oldest female was 18 years of age and the oldest male 9 years old when killed. For both sexes, deaths were concentrated in the fall, with males more likely to die than females. Males were more likely to die from hunting and females from other causes. Known wounding deaths were 1 for every 3 retrieved deer for archers and 1 for every 8 for firearms hunters. Dispersing male and female yearlings and 2-year-olds suffered greater mortality than did sedentary deer. Annual survival rates of yearling and older females ranged from 0.56 (dispersing 2-year-olds) to 0.92 (8-year-olds). Survival was significantly reduced for 5-year-old females compared with those both older and younger. Annual survival of rates males ranged from 0.35 (dispersing 2-year-olds) to 0.76 (sedentary yearlings).
Repetitive calls of juvenile Richardson's ground squirrels (Spermophilus richardsonii) communicate response urgency
Authors: Warkentin Kurtis J , Keeley Annika TH , Hare James F
Published: April 2011

Richardson's ground squirrels, Spermophilus richardsonii, produce both repetitive and non-repetitive antipredator calls. While many hypotheses have been advanced to explain non-repetitive calls, the function of repetitive calling has received relatively little attention. We presented juvenile Richardson's ground squirrels with a predator model at distances ranging from 1 to 8 m and recorded the subsequent repetitive calls on digital audiotape. The rate of calling was inversely correlated with the distance between the model and the caller, with distance explaining almost 24% of the variation in call rate. To determine whether call recipients use that information, we manipulated the intersyllable latency of a single repetitive call exemplar to form 3 test stimuli varying only in call rate. Across 16 Richardson's ground squirrel colonies to which these calls were broadcast, the proportion of squirrels assuming the highly vigilant, alert posture increased with the rate of the repetitive call presented. Hence, juvenile Richardson's ground squirrels appear to communicate the proximity and presumably the degree of threat posed by potential predators.
Egg morphology and hatching in Mormidea pictiventris (Hemiptera: Pentatomidae)
Authors: Wolf Klaus W , Reid Walton
Published: April 2011

Egg morphology and hatching in the stink bug Mormidea pictiventris (Hemiptera: Pentatomidae) are described with the aid of scanning electron microscopy. In addition, the eggshell is analyzed using transmission electron microscopy and the distribution of follicle cells at the surface of ovarian eggs is studied by epifluorescence microscopy using a DNA-specific fluorescent dye. The surface of the barrel-shaped eggs carries numerous slender processes. Binucleate follicle cells, in most cases arranged in a hexagonal pattern, are responsible for the synthesis of this portion of the eggshell. The rim at the anterior pole of the egg is studded at irregular intervals with short columnar processes, the aero-micropylar processes. Hatching occurs at this pole. The prolarva is wrapped in an embryonic cuticle. Its head portion carries a Y-shaped element, the egg-burster. The major features of the inner face of the eggshell are subtle, radially oriented grooves at the anterior plate and a hexagonal pattern to the surface ornamentation throughout the remainder of the eggshell. Transmission electron microscopy revealed that the processes extending from the surface of the eggshell have a coarse texture, while the eggshell proper is composed of amorphous material. The innermost layer, however, has a trabecular organization. The findings in M. pictiventris are compared with morphological observations on the eggshell in other families of Hemiptera and suggestions are made concerning the meaning of the diverse structures.
Test of character displacement in urban populations of Apodemus sylvaticus
Authors: Mikulová P , Frynta D
Published: April 2011

We studied the wood mouse, Apodemus sylvaticus, inhabiting parks, cemeteries, suburban woods, and other green areas in the city of Prague. To assess the character displacement and (or) release hypothesis we compared seven samples from local populations occurring sympatrically with Apodemus flavicollis with 10 samples from those localities in which A. flavicollis has never been recorded. The analysis included 1410 specimens of A. sylvaticus collected during the years 19801990. Seventeen skull and body characters were measured. Then the data were age- or size-adjusted and treated by principal-component analyses. Factor scores were further subjected to statistical testing. Although the results revealed considerable variation among localities, they did not suggest character displacement and (or) release. Apodemus sylvaticus from populations sympatric with A. flavicollis were morphometrically similar to their conspecifics from other populations collected at the periphery of the city. However, slight but statistically highly significant differences were found between samples from localities in the city centre and those from the periphery. This phenomenon may be interpreted as the effect of urbanisation or isolation by built-up areas.
Sperm-cell ultrastructure of North American sturgeons. IV. The pallid sturgeon (Scaphirhynchus albus Forbes and Richardson, 1905)
Authors: DiLauro Martin N , Walsh Rosemary A , Peiffer Michelle , Bennett Randy M
Published: April 2011

Sperm-cell morphology and ultrastructure in the pallid sturgeon (Scaphirhynchus albus) were examined using transmission and scanning electron microscopy. Metrics and structure were compared with similar metrics obtained from other published descriptions of sturgeon sperm cells. General morphology was found to be similar to that of sperm cells of the white (Acipenser transmontanus), lake (A. fulvescens), stellate (A. stellatus), Chinese (A. sinensis), Russian (A. gueldenstaedti colchicus), and shortnose (A. brevirostrum) sturgeons, which all shared a gradual tapering of the nuclear diameter from posterior to anterior, unlike that of the Atlantic sturgeon (A. oxyrhynchus). The sperm cell of the pallid sturgeon was similar in size to that of the Atlantic sturgeon, being only slightly larger. The sperm cell of the pallid sturgeon differed from those of other sturgeons chiefly in the acrosomal region, where the posterolateral projections (PLP) have the shape of an acute triangle and are arranged in a spiral about the longitudinal axis of the cell. The PLP were longer than those of other sturgeons, being twice the length of those of the Atlantic sturgeon and 58% longer than those of the lake sturgeon. Also, in cross section the acrosome had the shape of a hollow cone rather than the cap of an oak tree acorn, as was found in ultrastructural studies of other sturgeons. In addition, we were able to confirm that the structural arrangement of the distal centriole of the midpiece is identical with that of the proximal centriole: nine sets of microtubular triplets around the periphery of the centriole. This information is of potential use to fishery biologists, forensic biologists, zoologists, reproductive physiologists, taxonomists, evolutionary biologists, and aquaculturists.
Differences in growth and behaviour influence asymmetric predation among early-instar dragonfly larvae
Authors: Suhling Frank , Lepkojus Sigrid
Published: April 2011

Libellulid dragonflies lay large egg clutches. When eggs of two or more species are deposited at the same time and patch, one can expect a high density of early-instar larvae. Thus, interspecific interactions should be evident. We studied the interaction of two species, Sympetrum fonscolombii and Orthetrum cancellatum, which typically co-occur in French rice fields. We experimentally simulated the laying of egg clutches of both species at the same time and site. Survival of O. cancellatum was reduced compared with that of controls without S. fonscolombii and also with that of S. fonscolombii in the two-species treatment. At the end of the experiment, mean head width of S. fonscolombii was greater than that of O. cancellatum, which may be one reason for the differential survival. In a second experiment we observed the behaviour of pairs of early-instar larvae of both species in different size combinations. Small larvae of S. fonscolombii reduced locomotory activity in the presence of larger O. cancellatum. In contrast, small O. cancellatum did not do so in the presence of larger S. fonscolombii. This behavioural difference may also cause asymmetric interspecific predation.
Predation-induced effects on hatchling morphology in the common frog (Rana temporaria)
Authors: Laurila Anssi , Crochet Pierre-André , Merilä Juha
Published: April 2011

As mortality due to predation is often high at early independent life stages in many animals, it can be expected that predation-induced modifications of early life history and morphology will be common when predation risk varies spatially or temporally. However, studies of such effects are still rare. Predation-induced changes in life history and morphology have often been described in amphibian larvae, but the focus has been on older larvae and little is known about responses of hatchlings or very young larvae. We examined whether predator presence influenced timing of hatching and hatchling morphology in the common frog, Rana temporaria. In a paired design, eggs from 10 clutches were allowed to develop from fertilization to hatching, with or without the nonlethal presence of a larva of the large diving beetle Dytiscus marginalis. We found no evidence that predator presence affected timing of hatching. However, hatchlings raised in the presence of the predator had relatively shorter bodies and deeper tail fins than their full-sibs raised in the absence of the predator, indicating that predation induces morphological responses in R. temporaria hatchlings. This is one of the very few studies showing that predators, or chemical cues released during a predation event, can induce a plastic morphological changes in vertebrates at very early life stages.
Influences of weather and moonlight on activity patterns of small mammals: a biogeographical perspective
Authors: Stokes Michael K , Slade Norman A , Blair Susan M
Published: April 2011

We analyzed 15 years of trapping data on prairie voles (Microtus ochrogaster) and cotton rats (Sigmodon hispidus) to elucidate behavioural responses to weather by season and time of day. Use of such a long-term data set is rare and ameliorates many of the problems with short-term data sets typically used for such analysis. The trapping was conducted in the east-central part of Kansas (U.S.A.), near the southern edge of the distribution of prairie voles and the northern edge of the distribution of cotton rats. These distributions provide the framework for differing hypotheses as to responsiveness of individuals of the two species to weather phenomena as indicated by the probability of capture. Probability of capture was statistically significantly affected by weather, most frequently by precipitation and temperature. Effects varied with season and between species, and were generally consistent with hypotheses based on the northern (boreal and temperate) history of prairie voles and southern (subtropical and temperate) history of cotton rats and with predation-avoidance hypotheses. Variation in the probabilities of capture of cotton rats was more associated with weather, especially in the colder seasons, than was variation in the probabilities of capture of prairie voles. In summer, capture rates of prairie voles were more susceptible to weather than were those of cotton rats.
Parasitism patterns and the size-fecundity relationship in the acoustically orienting dipteran parasitoid Ormia ochracea
Authors: Kolluru Gita R , Zuk Marlene
Published: April 2011

Female parasitoids are expected to distribute offspring among hosts in a manner that maximizes fitness. Several theoretical and empirical studies have focussed on clutch-size patterns in hymenopteran parasitoids. In contrast, dipteran parasitoids, which differ from hymenopterans in potentially important ways, have received little attention. The phonotactic tachinid fly Ormia ochracea has been intensively studied for its effects on host crickets, and has recently been the subject of studies of its own reproductive biology. This work suggests a negative relationship between clutch size and progeny fitness (consistent with hymenopterans), but no adjustment of clutch size to host size (different from hymenopterans). However, the repeatability of these patterns and the relationship between fly size and fitness remain to be demonstrated. We examined clutch sizes of O. ochracea larvae in the cricket Teleogryllus oceanicus. Most clutches were smaller than a cricket can support to pupation. Smaller clutches yielded larger offspring and larger wild-caught flies had higher fecundity, supporting the idea that small clutches yield higher fitness. However, although parasitised male crickets were slightly larger than unparasitised males, there was no correlation between cricket size and the number of larvae. Potential reasons for this departure from the patterns found in hymenopteran parasitoids are discussed.
Subsurface and nighttime behaviour of pantropical spotted dolphins in Hawai'i
Authors: Baird Robin W , Ligon Allan D , Hooker Sascha K , Gorgone Antoinette M
Published: April 2011

Pantropical spotted dolphins (Stenella attenuata) are found in both pelagic waters and around oceanic islands. A variety of differences exist between populations in these types of areas, including average group sizes, extent of movements, and frequency of multi-species associations. Diving and nighttime behaviour of pantropical spotted dolphins were studied near the islands of Maui and Lana'i, Hawai'i, in 1999. Suction-cup-attached timedepth recorder/VHF-radio tags were deployed on six dolphins for a total of 29 h. Rates of movements of tagged dolphins were substantially lower than reported in pelagic waters. Average diving depths and durations were shallower and shorter than reported for other similar-sized odontocetes but were similar to those reported in a study of pantropical spotted dolphins in the pelagic waters of the eastern tropical Pacific. Dives (defined as >5 m deep) at night were deeper (mean = 57.0 m, SD = 23.5 m, n = 2 individuals, maximum depth 213 m) than during the day (mean = 12.8 m, SD = 2.1 m, n = 4 individuals, maximum depth 122 m), and swim velocity also increased after dark. These results, together with the series of deep dives recorded immediately after sunset, suggest that pantropical spotted dolphins around Hawai'i feed primarily at night on organisms associated with the deep-scattering layer as it rises up to the surface after dark.
Do land-use patterns influence nest-site selection by burrowing owls (Athene cunicularia hypugaea) in northeastern Colorado?
Authors: Orth Patricia B , Kennedy Patricia L
Published: April 2011

Populations of western burrowing owls (Athene cunicularia hypugaea) are declining. In the Great Plains this decline maybe related to a decline in black-tailed prairie dog (Cynomys ludovicianus) towns that the owls use for nest sites. One potential cause of prairie dog decline is conversion of native prairie to agriculture. We predicted that owl-occupied prairie dog towns would be in less fragmented landscapes that contain more prairie then owl-unoccupied prairie dog towns. To test this prediction, we used a geographic information system and spatial analysis metrics to examine the landscape within 1000 and 2500 m radius circles surrounding prairie dog towns in the shortgrass prairie in northeastern Colorado. We compared landscape features of irrigated cropland, non-irrigated cropland, and shortgrass patches around owl-unoccupied (N = 7) and owl-occupied (N = 15) prairie dog towns at these two spatial scales. Contrary to our predictions, at the 2500-m scale burrowing owls prefer to nest in towns surrounded by a landscape in which shortgrass patches were a smaller percentage of the total landscape, relatively far apart from other shortgrass patches, and more numerous then crop patches. At the 1000-m scale owls nested in towns in which shortgrass patches were a smaller percentage of the total surrounding landscape. In Logan County owls may select nest sites in prairie dog towns in more fragmented landscapes because prey availability maybe higher than in less fragmented landscapes and (or) prairie dog control programs may be more active on shortgrass rangelands than in croplands. In addition, the level of fragmentation in our study area (62% of the study area is occupied by native grassland) may not be high enough to have negative consequences on nest occupancy of burrowing owls. However, it is difficult to generalize about the effects of landscape fragmentation on burrowing owls because any effects are probably a complex function of local habitat structure, landscape structure, and local prey and predator availability.
Sensitivity of ant (Cephalotes) colonies and individuals to antibiotics implies feeding symbiosis with gut microorganisms
Authors: Jaffe Klaus , Caetano Flavio H , Sánchez Pedro , Hernández Jose V , Caraballo Leonardo , Vitelli-Flores Juana , Monsalve Wilmer , Dorta Blas , Lemoine Vidal Rodriguez
Published: April 2011

Ants in the tribe Cephalotini are exceptional in that they maintain microorganisms in their digestive tract. To understand what these microorganisms mean to the ants, we observed the feeding habits of Cephalotes pusillus and Cephalotes atratus, finding that in nature they feed on extrafloral nectars, homopteran secretions, and bird droppings. Feeding the antibiotic kanamycin to colonies of C. pusillus in the laboratory kills them. Ants desiccate or starve rather than feed on liquids to which the antibiotics gentamycin and netilmycin have been added, but feed and survive on liquids containing nystatin, penicillin, and ampicillin. We identified over 10 microorganisms from the intestine of C. pusillus with different antibiotic-resistance patterns. The bacteria are from the genera Corynebacterium, Brevibacterium, Sphingobacterium, Ochrobactrum, Myroides, Brevundimonas, Alcaligenes, Stenotrophomonas, Moraxella, and Pseudomonas. We hypothesize that the microorganisms provide nutrients to the ants by synthesizing amino acids from carbohydrates and nitrates. We do not know whether the ants collect the bacteria from the environment, but they transmit them to their young. They culture them in their digestive tract, eventually feeding on them.
The ability of red squirrels (Tamiasciurus hudsonicus) to discriminate conspecific olfactory signatures
Authors: Vaché Marion , Ferron Jean , Gouat Patrick
Published: April 2011

Using a habituation-dishabituation procedure, we investigated the ability of male red squirrels (Tamiasciurus hudsonicus) to discriminate olfactory signatures of different male conspecifics. Our results indicate that they effectively pay attention to odours from unfamiliar male conspecifics and that they invest more time sniffing litter impregnated with these unfamiliar social odours than control litters. They can also habituate themselves to a given social odour and can discriminate olfactory signatures of different male conspecifics. The role of olfactory communication in this territorial species from the boreal forest is discussed with regard to the "dear enemy" phenomenon and to the fact that these squirrels are known to use vocal communication intensively to advertise their territories.
Sperm-expenditure strategies: the role of mating order, sperm precedence, and non-optimal behavior
Authors: Lance Stacey L , Chao Lin
Published: April 2011

We developed a model to examine the amount of sperm that males should transfer to females under different conditions of sperm precedence. Following a previous model (Parker's), we assume the existence of nonrandom mating roles in which there are males that always mate first and others that always mate second. However, we alter Parker's model by introducing the possibility that males are non-optimal in their sperm allocation (because males make mistakes or are interrupted, or because of phenotypic variation among males). We predicted that when males behave optimally, their sperm expenditures will be equal for most levels of sperm precedence, regardless of whether they mate first or second. However, when the possibility that males behave non-optimally is included, we predicted (i) a positive correlation between the allocations of first and second males when there is second-male precedence, (ii) a negative correlation when there is first-male precedence, and (iii) no correlation when there is no precedence. We discuss these and other predictions and provide supporting evidence from the literature.
Comparison of lake sturgeon (Acipenser fulvescens), Stizostedion spp., Catostomus spp., Moxostoma spp., quillback (Carpiodes cyprinus), and mooneye (Hiodon tergisus) larval drift in Des Prairies River, Quebec
Authors: D'Amours Julie , Thibodeau Stéphanie , Fortin Réjean
Published: April 2011

Several fish species that spawn in lotic habitats have a larval-drift phase which is a major determinant of their reproductive success. The main objective of this study was to compare seasonal, diel, longitudinal, transverse, and vertical variations in rates of lake sturgeon (Acipenser fulvescens), Stizostedion spp., Catostomus spp., Moxostoma spp., quillback (Carpiodes cyprinus), and mooneye (Hiodon tergisus) larval drift in Des Prairies River (DPR) near Montreal (Quebec), which is one of the major lotic spawning habitats of the St. Lawrence River system. Larval sampling was conducted in the spring of 1994 and 1995 for the six taxa, and on a more restricted basis for lake sturgeon in 19961998, using drift nets set at several transects, stations, depths, and periods of the day, along a 19 km long section of river beginning ca. 2 km downstream from the DPR power house. For all taxa except lake sturgeon, peak larval drift occurred ca. 1 week earlier in 1995 than in 1994. The sequence was very similar between years, beginning with Stizostedion spp., followed by Catostomus spp., then lake sturgeon, quillback, and mooneye drifting simultaneously, and finally Moxostoma spp. Generally, for all taxa except quillback, whose multimodal drift pattern suggests intermittent, prolonged spawning, larval-drift profiles showed one major seasonal mode, which was observed simultaneously at all transects. For all taxa except quillback, drift rates peaked between 21:00 and 03:00 and were minimal during daylight hours. Lake sturgeon and Stizostedion spp. larval drift rates decreased radically from the most upstream to the most downstream transect, suggesting that both taxa spawn mostly in the vicinity of the DPR power house. More studies are required to explain this longitudinal decline in drift rates, particularly for lake sturgeon. The other taxa showed longitudinal variation in larval drift rates, suggesting that they spawn near the DPR power house and (or) in the Île de Pierre Rapids, ca. 12 km downstream. At all transects, larval drift rates for the six taxa were generally higher in the right half (Montreal) of the river, suggesting that eggs are deposited mostly in this part of the river at the two major spawning areas and that larvae tend to remain in the same general corridors during downstream migration. For all taxa, though to a lesser extent for lake sturgeon, nocturnal drift rates tend to be higher near the surface than at mid-depth and near the bottom, the reverse situation being observed for diurnal drift rates.