bluuebunny/crossref_metadata_2025 huggingface dataset:
The possible involvement of Arg-Phe-amide immunoreactive neurons during tentacle development and regeneration in the hydromedusa Polyorchis penicillatus
Authors: McFadden Nancy A. , Spencer Andrew N.
Published: July 2008

Descriptions of new neuropeptides are common, yet data on their biological actions are limited. Many act as neurotransmitters and neuromodulators, others appear to have morphogenetic actions, and some probably act as both transmitters and developmental regulators. Ubiquitous within the Cnidaria is a family of neuropeptides having the carboxy-terminus Arg-Xaa-NH2, where Xaa is an aliphatic or aromatic amino acid (usually Phe, Trp, Asn, Ile, Ala, or Pro). Although some of these peptides (here called RXamides) have been shown to have both excitatory and inhibitory actions on muscle and neurons in anthozoans and hydrozoans, the possibility that they have other actions has not been fully investigated. In this study we describe the normal sequence of tentacle development in Polyorchis penicillatus and compare it with the stages in regeneration of tentacles after ablation. Development of tentacles was accompanied by a characteristic sequence of appearance of neurons in the bud that were immunoreactive to antisera raised against Arg-Phe amides (RFamides). Some of these neurons were transitory and may have been giving morphogenic signals. The pattern of development of the RFamide-immunoreactive neuronal system was identical for ontogenetic development and regeneration. When early tentacle buds were treated with hydroxyurea to remove interstitial cells and neurons, the buds failed to develop. Immunocytochemistry showed that RFamide-containing neurons were absent in treated animals. Hydroxyurea treatment also prevented the regeneration of buds at the ablation site. Further studies are needed to establish whether RFamide neurons themselves, or some other neuronal types, are required for tentacle development and regeneration.
A laboratory study of fluid flow and microhabitat selection by larvae of Simulium vittatum (Diptera: Simuliidae)
Authors: Lacoursière Jean O.
Published: July 2008

Microhabitat selection by Simulium vittatum Zetterstedt larvae in a flume was studied at different mainstream velocities on two substrates: a thin flat plate parallel to the flow and a cylinder in cross flow. The results do not support the generally accepted assumptions that simuliid larvae keep within the boundary layer to avoid the direct influence of mainstream current and that they select the fastest velocity available when offered a longitudinal velocity gradient within their tolerance range. Instead, larvae gathered along the zone of boundary layer separation and remained along the stagnation line at the leading point of the cylinder when artificially positioned there. Further, under most conditions, larvae avoided zones of maximum surface shear stress. Larval reaction to hydraulic changes was immediate. It is hypothesized that S. vittatum larvae first scan the velocity profile at the substrate, initially moving toward increasing flow velocity (or water acceleration). They then cue on a steep velocity gradient along the body as part of the processes involved in choosing a location for suspension feeding. Such conditions would maximize particle flux through the labral fans and minimize drag forces on the bulbous posterior abdomen. This study provides the first direct evidence for microhydraulic factors as causative agents in the formation of simuliid larval assemblages.
Behavioural asymmetries and cohesive mother–offspring sociality in bushy-tailed wood rats
Authors: Moses Richard A. , Millar John S.
Published: July 2008

Bushy-tailed wood rats (Neotoma cinerea) are usually confined to highly clumped resource patches (i.e., rock outcrops), and potentially compete for limited den sites within outcrops. Adults may breed on the same outcrop over several years, and philopatric yearlings usually breed in proximity to close kin. We investigated the influence of kinship and reproductive status on the nature and stability of wood rat sociality. Behavioural interactions among mother–offspring and adult female – nonkin dyads from the wild were quantified in a neutral arena during (i) the autumn when offspring were immature subadults, and (ii) the following spring, when all dyad members were reproductively active. Nonkin dyads were characterized almost entirely by agonistic behaviour. Virtually all amicable behaviour was directed toward close kin, and most interactions among kin dyads were amicable. Further, these strong kin-based behavioural asymmetries did not differ between the autumn and the subsequent breeding season, and could not be explained by postweaning familiarity (i.e., residency on a common habitat patch) alone. Wood rat sociality appears to be characterized by two elements: (i) divisive agonism directed toward nonkin, and (ii) stable, cohesive relationships among close kin (mother–offspring). Possible causes and consequences of sociality in bushy-tailed wood rats are discussed.
Methods for photographic identification of bowhead whales, Balaena mysticetus
Authors: Rugh David J. , Braham Howard W. , Miller Gary W.
Published: July 2008

Bowhead whales, Balaena mysticetus, have black skin except for patterns of white along their ventral surface and visible dorsally on their lower jaws, caudal peduncles, and flukes. White scar marks may also be present. These contrasting black and white dorsal patterns were examined in 4871 aerial photographs of bowheads taken from 1976 to 1987 to determine if individual animals could be reidentified when subsequently photographed. The objective of making such reidentifications was to provide important life-history information, such as calving intervals, length-specific growth rates, survival rates, and population abundance. This paper describes procedures developed to categorize whales into 20 file types based on the relative extent of visible white markings. Preliminary analysis of the photographic identification system suggests that it has a high potential for use in population studies but only if whale images are of sufficient quality and quantity to allow for multiple reidentifications. High-quality images are best obtained from aerial photographs taken directly above whales in clear water during good to excellent sea-state conditions without glare. This ensures that sufficient characteristic features, if present, are photographed to permit recognition in subsequent photographs.
Comment—Revised estimates of the bias in the 'minimum number alive' estimator
Authors: Efford Murray
Published: July 2008

The computer simulation results of Hilborn et al. (R. Hilborn, J. A. Redfield, and C. J. Krebs. 1976. Can. J. Zool. 54: 1019–1024) regarding the bias of the 'minimum number alive' estimator of population size are shown to be in error. Minimum numbers alive are approximately twice as biased as estimated by these authors: for five species of Microtus the negative bias is estimated as 24–45% instead of 10–18%. 'Minimum number alive' differs from the Jolly–Seber population estimate in being particularly sensitive to mean trappability when the coefficient of variation of trappability is constant. Both population estimators are highly sensitive to reduced trappability of unmarked animals. The Jolly–Seber estimator remains the method of choice for open populations, especially if the coefficient of variation in trappability can be minimized.
Estimating forage intake and energy requirements of free-ranging wapiti (Cervus elaphus)
Authors: Jiang Z. , Hudson R. J.
Published: July 2008

A single dose marker method was calibrated to estimate intakes of pasture forage by wapiti. Each animal was offered 250 g of alfalfa–barley pellets labeled with chromic oxide (Cr2O3), and freshly voided fecal samples were collected before and for 6–7 days after administration. Dry fecal output was calculated by dividing the marker dosage by the average fecal marker concentration. Feed intake was then calculated from fecal output and feed digestibility as determined by total fecal collection or the ratio of acid-insoluble ash in feed and feces. The concordance of the marker estimate with measured feed intake was tested on penned wapiti fed alfalfa–barley pellets or herbage. On pasture, the marker method was compared with intakes estimated by the bite-count method. As an additional check, data from pen and field studies were pooled to establish the relationship between metabolizable energy intake and body-weight gain. The single dose marker method provided a practical way to assess feed intake of free-ranging animals. Metabolizable energy requirements for maintenance of live weight were 572 kJ/W0.75 for penned wapiti in winter and 936 kJ/W0.75 for wapiti on summer pasture. Tissues mobilized during winter provided 26 kJ/g, and metabolizable energy requirement per unit liveweight gain was 39 kJ/g on summer pasture.
Phylogeny, historical biogeography, and ecology of Anophryocephalus spp. (Eucestoda: Tetrabothriidae) among pinnipeds of the Holarctic during the late Tertiary and Pleistocene
Authors: Hoberg E. P. , Adams A. M.
Published: July 2008

Phylogenetic systematic analyses of Anophryocephalus spp. resulted in a single most-parsimonious cladogram (consistency index: 80%). Cladograms for pinniped hosts (phocids and otariids) and Anophryocephalus spp. were highly incongruent, corroborating a hypothesis for colonization as a dominant determinant of parasite diversification. Phoca (Pusa) spp. in the Atlantic basin are postulated as the initial hosts; range expansion for hosts and parasites into the Pacific basin through the Arctic (ca. 3.0–2.5 million years ago) was followed by radiation of Anophryocephalus spp. among Phoca spp. and subsequent colonization of otariids (Eumetopias jubatus as typical hosts; ca. 2.0 million years ago). Host phylogeny and historical biogeography in conjunction with host distributions of these cestodes indicate evolution of Anophryocephalus was associated with dispersal and radiation of Phoca spp. in the Holarctic during the Late Pliocene and Pleistocene. Isolation in regional refugia and vicariance (during stadials) and subsequent range expansion and sequential colonization (interstadials) are postulated as the primary determinants of host–parasite diversification in the North Pacific during the late Tertiary and Quaternary. Colonization is regarded as a central theme in the development of cestode faunas among marine homeotherms.
Maximal enzyme activities of energy production pathways in the heart, hepatopancreas, and white muscle of the giant scallop (Placopecten magellanicus) and lobster (Homarus americanus)
Authors: Stewart John M. , Brass Molly E. , Carlin Robert C. , Black Heather
Published: July 2008

The maximal activities of enzymes in energy pathways were measured in the ventricle, hepatopancreas, and white muscle of lobster (Homarus americanus; abdominal flexor) and giant scallop (Placopecten magellanicus; phasic adductor). Both animals show an energy metabolism based upon the utilization of carbohydrate. Carnitine palmitoyltransferase activity was not detected, and this was interpreted as an incapacity for mitochondrial β-oxidation of fatty acids; the absence of 3-hydroxybutyrate dehydrogenase and D-3-hydroxybutyrate indicated that ketone bodies were not a significant energy source. The levels of hexokinase, phosphofructokinase I, citrate synthase, and cytochrome c oxidase in the myocardia of both animals suggest a dependence on the aerobic processing of both blood-borne and glycogen-derived glucose. The significance of the enzyme activity data in the hepatopancreas of both animals was not immediately apparent. The abdominal flexor muscle of the lobster and the phasic adductor of the scallop showed enzyme profiles that suggest a reliance on glycolysis to fuel rapid bursts of activity. In the lobster flexor the presence of hexokinase and phosphofructokinase I along with low levels of citrate synthase and cytochrome c oxidase indicated that this tissue can utilize blood-borne and glycogenic glucose anaerobically. The absence of hexokinase, the low levels of citrate synthase and cytochrome c oxidase, and the presence of phosphofructokinase I in the scallop adductor suggested a reliance upon glycogen-fueled glycolysis to power burst activity. 3-Hydroxyacyl-CoA dehydrogenase was found in all tissues except the lobster flexor, which was curious in light of the undetectable activity of carnitine palmitoyltransferase.
Locomotor correlates of ecomorph designation in Anolis: an examination of three sympatric species from Jamaica
Authors: Powell G. Lawrence , Russell Anthony P.
Published: July 2008

Scaling of locomotor structures (limb length, scansor area, and intergirdle distance) in three Jamaican Anolis species (A. garmani, A. grahami, and A. opalinus) is examined. Reference to structural-niche use patterns and partitionings typical of these three species is made. Each species represents a separate Anolis ecomorph, differing from the others in adult size, shape, and structural niche. All are part of a single intra-island phyletic radiation. Allometric models indicate that intra- and inter-specific differences in proportion of locomotor structures are not necessarily ontogenetically invariant, but that all three species ontogenetically arrive at, or have attained, the differences in proportion typical of their adult sizes. Differences in adult proportion between two species are not functions of body size alone but are the products of different scaling trajectories. No intraspecific differences in structural-niche use are documented, but interspecific differences are well defined: the greater the number of differences in locomotor scaling between two species, the greater the structural-niche partitioning. We suggest that the locomotor structure scaling patterns observed in these three species are typical of the ecomorphs that they represent. Analogous ontogenetic patterns of development should be displayed by independently derived representatives of these ecomorphs from other Greater Antilles islands.
Étude démographique d'une population de salamandres (Ambystoma maculatum) à l'aide de la méthode squeletto-chronologique
Authors: Flageole Sylvie , Leclair Jr Raymond
Published: July 2008

Two hundred and twelve (212) adults of the yellow-spotted salamander, Ambystoma maculatum, were caught in the springs of 1989 and 1990 with unbaited minnow traps in two adjacent temporary ponds located in a deciduous forest in Trois-Rivières (Quebec). The sex ratio was approximately 2:1 in favor of males. Snout–vent length (SVL) was significantly higher in females (90.2 ± 6.3 mm) than in males (82.9 ± 5.5 mm). Age was determined in cross sections of phalanges by counting the number of growth lines in the bone. Most of the salamanders were between 2 and 18 years of age, with a major peak distribution at 7 in both sexes and a secondary peak at 15 in males. The oldest animal was 32 years old. The study shows that most females are mature by the age of 7 at SVL > 78 mm, but many males reach maturity between the ages of 2 and 6 at SVL > 63 mm. Back calculation of growth curves reveals that females are already longer than males at 3 years old. Differences in age at maturity, reproductive frequency, and survival explain the observed sex ratio. Sexual dimorphism in body length is due to the rapid growth of females and their delayed maturity, not to a difference in longevity.
Classification and phylogeny of the Holarctic water strider genus Limnoporus Stål (Hemiptera, Gerridae)
Authors: Andersen N. Møller , Spence John R.
Published: July 2008

The Holarctic water strider genus Limnoporus Stål is redescribed, a key and diagnoses are provided for the six species described, and their distributions are documented. The geographic variation of the Palearctic and northwestern Nearctic L. rufoscutellatus (Latreille) is surveyed. Male specimens from Fairbanks, Alaska, and the Yukon Territory (described as Gerris nearcticus Kelton, syn.nov.), cannot be separated from L. rufoscutellatus from Europe or the former Asian USSR. Limnoporus genitalis (Miyamoto), stat.nov., was originally described as an insular subspecies (from Hokkaido, the Kurile Islands, and Sakhalin) of L. rufoscutellatus but is clearly diagnosable and deserves specific status. The boreal Nearctic L. dissortis (Drake and Harris) and the western Nearctic L. notabilis (Drake and Hottes) are very similar to each other, but males of the two species show practically no overlap in size, L. notabilis being distinctly larger than L. dissortis. However, males, and more especially females, can be difficult to identify in areas where the two species hybridize. The two species of Limnoporus with smaller body size, the eastern Nearctic L. canaliculars (Say) and the east Asian L. esakii (Miyamoto), are more distinct from each other than are the remaining four species of the genus. A cladistic analysis of relationships between species was conducted, mainly on the basis of the structural characteristics of adults, and with species of Aquarius and Gerris as out-groups. The reconstructed phylogeny is discussed in relation to previous standard as well as molecular taxonomic work about species relationships and previous ambiguities are resolved. The phylogeny is further used to infer evolutionary sequences in habitat preference, wing polymorphism, and phenology, and to discuss the geographical distribution and historical zoogeography of Limnoporus species.
Swim speed in a female northern elephant seal: metabolic and foraging implications
Authors: Boeuf Burney J. Le , Naito Yasuhiko , Asaga Tomohiro , Crocker Daniel , Costa Daniel P.
Published: July 2008

The swim speed and dive pattern of an 8-year-old female northern elephant seal (Mirounga angustirostris) were recorded during the postlactation period at sea. A swim speed – distance meter and a time–depth recorder attached to the animal's back recorded the following synchronously and continuously for 29 days: swim speed, distance, depth, and duration of free-ranging dives. Mean swim speeds calculated as a function of time and distance ranged from 0.91 to 1.66 m/s. Mean descent velocities were 27% greater than ascent velocities and velocities at depth. Minimum and maximum speeds ranged from 0.4 to 3.0 m/s for most segments of all dives. There was no surface swimming. Angles of descent were less steep (30–56°) than angles of ascent (52–82°). Mean total horizontal distance traveled per dive ranged from 0.6 to 1.3 km, depending on dive type. From the above data and related information, each of four dive types, which accounted for the majority of dives in the record, were hypothesized to have one of the following principal functions: transit, foraging (pelagic and benthic), and process (serving rest, food processing, or anaerobic metabolite clearance).
Variation saisonnière dans la répartition des ressources alimentaires entre cinq espèces de poissons en fonction de la disponibilité des proies
Authors: Harnois Élyse , Couture Richard , Magnan Pierre
Published: July 2008

We observed that yellow perch, Perca flavescens, golden shiner, Notemigonus crysoleucas, spottail shiner, Notropis hudsonius, and log perch, Percina caprodes, partitioned food resources in relation to resource abundance in a small bay of Lake Saint-Pierre, Quebec. When the abundance of benthic resources was at its lowest, in May 1988, the fish showed a very low overlap in their diet. In contrast, when these resources were most abundant, in August 1988, the four species had a high degree of food overlap. Two other sampling periods, in June and July, revealed intermediate situations. A fifth species, the silvery minnow, Hybognathus nuchalis, was phytophagous and, therefore, did not compete with the other species for food resources. An ecomorphological analysis of the first four species suggests that these partition food resources according to their functional morphology. Our results support Schoener's hypothesis, which states that the intensity of interspecific competition, in terms of resource partitioning, varies according to the abundance of these resources.
Tissue distribution of fish antifreeze protein mRNAs
Authors: Gong Zhiyuan , Fletcher Garth L. , Hew Choy L.
Published: July 2008

The presence of fish antifreeze protein (AFP) mRNA was examined in a variety of tissues from the winter flounder (Pseudopleuronectes americanus), sea raven (Hemitripterus americanus), and ocean pout (Macrozoarces americanus), each of which contains one of the three known AFP types. Northern blot analysis indicates that whereas the AFP mRNA is restricted to liver in sea raven (type II AFP), significant amounts of mRNA are present in many other tissues in both winter flounder (type I) and ocean pout (type III). These results indicate that in sea raven, antifreeze protein synthesis only occurs in the liver, whereas in the ocean pout and winter flounder, synthesis occurs in many tissues throughout the body. These investigations are relevant to understanding the mode of action of these polypeptides.
The fine structure of the multiporous sensilla on the antenna of the diving beetle Graphoderus occidentalis Horn (Coleoptera: Dytiscidae)
Authors: Jensen J. C. , Zacharuk R. Y.
Published: July 2008

The antenna of the diving beetle Graphoderus occidentalis Horn has a cluster of multiporous (MP) sensilla on the antero-medial aspect of each flagellomere. These sensilla are modified basiconic pegs that are sunk in longitudinal sockets and flattened to a platelike surface externally. On the terminal flagellomere, approximately 15 multiporous pitted sensilla (MPp) have a pitted external surface and each is innervated by one or two morphologically similar neurons. In addition, eight multiporous grooved sensilla (MPg) have longitudinal surface grooves with pores opening at the bottom of each groove; each sensillum is innervated by two neurons that differ in electron density. In both sensillar types the pores open into channels that traverse the sensory cuticle. The branched dendritic terminations in the underlying chamber are bathed in an electron-dense sensillar liquor that extends into the channels leading to the surface pores. The neuronal perikarya in both types, and the proximal portion of the dendrites in the MPg, are unsheathed and exposed to the hemolymph. The putative function of these sensilla as odor detectors is discussed.
Inositol pentaphosphate in the erythrocytes of an Amazonian fish, the pirarucu (Arapaima gigas)
Authors: Val Adalberto Luís , Affonso Elizabeth Gusmão , Salvo Souza Roberto Huet de , Almeida-Val Vera Maria Fonseca de , Moura Marcia Alves Ferreira de
Published: July 2008

During the Alpha Helix expeditions to the rivers of the Amazon basin, inositol pentaphosphate (IPP) was detected in the erythrocytes of Arapaima gigas. We analyzed the intraerythrocytic phosphate levels of A. gigas specimens during the first year of life in captivity. IPP increased slowly during the first year, stabilizing at around 7 mM when the animals reached 1–1.5 m in length. ATP and GTP concentrations decreased in parallel. Wild animals within the same size range showed similar intraerythrocytic IPP levels. These changes represent qualitative and quantitative adjustments of the principal modulators of haemoglobin–oxygen affinity in the erythrocytes of A. gigas. These temporal changes seem to play an important physiological role, since this species changes its respiratory habit from aquatic respiration to obligatory air breathing, when it uses a modified swim bladder.
Immunocytochemical identification of peptidergic neurons in compartment 4 of the supraesophageal ganglion of the leech Theromyzon tessulatum (O.F.M.)
Authors: Verger-Bocquet M. , Wattez C. , Salzet M. , Malecha J.
Published: July 2008

The use of polyclonal antibodies directed against mammalian peptide hormones and of monoclonal antibodies raised against molecules of supraesophageal ganglion neurons of the leech Theromyzon tessulatum has led to the identification of more than half of the 30 neurons present in compartment 4 of the supraesophageal ganglion. Six cellular types were characterized at stage 3B of the life cycle: (1) a group of four or five large angiotensin II and γ-melanocyte stimulating hormone (γ-MSH) immunopositive cells also immunoreactive with monoclonal antibodies Tt-7 and Tt-159 (cells of class I), (2) a group of five small growth hormone releasing factor (GRF) positive cells, (3) three motilin-positive cells, (4) one met-enkephalin-positive cell, (5) one oxytocin-positive cell that also immunoreacts with monoclonal antibody Tt-1, and (6) one vasopressin-positive cell immunoreactive with monoclonal antibody Tt-9. This study shows the heterogeneity of the neurons constituting compartment 4 and demonstrates that most of them have secretions of a peptidergic nature. The co-localization of epitopes recognized by anti-γ-MSH and anti-angiotensin II is demonstrated in cells of class I. The number of immunoreactive cells found in compartment 4 is not always constant and can vary for the following reasons: (i) changes in the physiological status of the leech, as is the case with anti-GRF and anti-motilin, (ii) individual variations for some cellular types (cells of class I), (iii) variability in the situation of the connective-tissue septum separating compartments 4 and 5.
Biologie et étude ultrastructurale des spermatozoïdes du cnidaire Clytia hemispherica (Leptomedusae): mise en évidence d'un processus acrosomal
Authors: Carré Danièle , Carré Claude
Published: July 2008

Mature sperm of Clytia hemispherica were studied by electron microscopy in the gonads, at their exit from the gonads, and at fertilization. The presence of an acrosomal complex at their anterior pole, which has long been a subject of controversy in cnidarians, was demonstrated. A chemoattractant and an inductor of the acrosomal reaction, both released at the animal pole of the eggs, were responsible for the accumulation of spermatozoons and the formation of the acrosomal process. A striated rootlet extending from the pericentriolar region to the plasma membrane was described, and its possible relationship to positive chemotaxis discussed. Ultrastructural modifications of the testes induced by light, a factor controlling spermiation, were investigated.
Magnetic particles in chum salmon (Oncorhynchus keta): extraction and transmission electron microscopy
Authors: Ogura Miki , Kato Mamoru , Arai Naru , Sasada Takeshi , Sakaki Yo
Published: July 2008

Magnetic material was extracted from the head and an area covering the lateral line of chum salmon. Although magnetic material was distributed widely in the head, it was more often extracted from the posterior part of the skull. The material was black in coloration. Crystalline particles were observed with a transmission electron microscope. These particles were covered by a thin film and ranged in diameter from 15 to 196 nm. The major element of these particles was iron, and we conclude that they are biogenic magnetite.
Distribution of ringed seals in the southeastern Beaufort Sea during late summer
Authors: Harwood Lois A. , Stirling Ian
Published: July 2008

The distribution and relative abundance of ringed seals (Phoca hispida) in the southeastern Beaufort Sea were examined through systematic aerial surveys in August–September of 1982 and 1984–1986. All data analyzed were collected by the same observer when sea state was ≤ 2 on the Beaufort Scale and when there was no forward glare. In late summer and early fall of 1982, 1984, and 1986, ringed seals occurred singly and in groups, to an observed maximum of 21 seals. Groups of seals were clumped into large areas of aggregation which appeared to persist for several weeks. Densities in aggregation areas ranged from 121 to 326 seals/100 km2, approximately 6–13 times greater than regional mean densities. The geographic extent of aggregation areas (350–2800 km2) and the numbers (1 in 1984, 2 in 1982, 3 in 1986) and locations of aggregations varied among years. Ringed seals tended to aggregate most frequently and in greatest numbers in waters north of the Tuktoyaktuk Peninsula, in the general area where the Cape Bathurst polynya occurs in winter. The relative abundance of ringed seals varied among the years of the study, reaching a maximum in 1982 (42.20 seals/100 km2), declining through 1984 (14.73/100 km2) and 1985 (7.92/100 km2), and increasing again in 1986 (19.35/100 km2).
Indirect calorimetry measurements of behavioral thermoregulation in a semiaquatic social rodent, Myocastor coypus
Authors: Moinard Christine , Doncaster C. Patrick , Barré Hervé
Published: July 2008

The role of behavior is quantified in the maintenance of thermic homeostasis by a semiaquatic rodent, the coypu (Myocastor coypus). Indirect calorimetry measurements showed that huddling behavior is responsible for a 20% drop in resting metabolic rate at temperatures below the thermoneutral zone. Different associations of males and females in groups of two and three resulted in significant differences in decreases of resting metabolic rate. In a cold environment (Ta = −5 °C), males used a ball-like posture significantly more often than females. When presented with a choice of substrates (air versus water) at different temperatures, females tended to reduce their time spent in cold water but males did not, despite a greater loss of energy in water compared with air. These results appear to express a conflict between social and thermoregulatory behaviors, contributing to male-biased mortality in winter.
Distribution and behaviour of male sperm whales on the Scotian Shelf, Canada
Authors: Whitehead Hal , Brennan Sebastian , Grover David
Published: July 2008

Studies of mature male sperm whales (Physeter macrocephalus) were carried out on the Scotian Shelf during the summers of 1986, 1988, 1989, and 1990. Sperm whales were found principally along the edge of the Shelf, although there were some encounters in water less than 100 m deep. Within the Gully, a prominent submarine canyon, sperm whales showed a consistent pattern of distribution between years, distinct from that of northern bottlenose whales (Hyperoodon ampullatus). Some male sperm whales were individually identified in the Gully after periods of 2–47 days, and in one case, after 2 years. The male sperm whales showed little evidence of social organization and rarely performed aerial behaviour. However, their diving behaviour was similar to that observed from female sperm whales in the tropics. On one occasion a group of presumed female and immature sperm whales entered the Gully, attracting the attention of resident mature males.
Diving behaviour of lactating Antarctic fur seals
Authors: Boyd I. L. , Croxall J. P.
Published: July 2008

The diving behaviour of 11 lactating female Antarctic fur seals (Arctocephalus gazella) was recorded for a total of 254 animal-days at sea. Median and maximum dive depths for individuals varied from 8 to 19 m and from 82 to 181 m, respectively, and median and maximum dive durations from 0.75 to 1.17 min and from 2.8–10.0 min, respectively. Theoretical aerobic diving limits were exceeded on < 1% of dives. Dives were mainly V-shaped. Sixty percent of dives were to less than 20 m depth, and these dives were distinguished from deep dives (> 20 m) by having slower rates of descent and ascent and by being confined to the mixed layer at the ocean surface, as judged by records of sea temperature obtained concurrently with records of depth. Dives were grouped into bouts, defined by inflexion points observed in the cumulative probability distribution of surface interval after probit transformation. Bouts (defined by preceding and succeeding surface intervals lasting 13–24 min) occurred within a diel pattern of diving activity, with 74–85% of dives occurring at night. The pattern of diving, in terms of division into bouts, showed greater differences between individual seals than did dive depth and duration. Dives tended to be shorter and shallower later in lactation. Most variation in diving behaviour between individuals was in terms of the proportion of available time spent foraging, bout frequency, and bout duration. The foraging strategy in the Antarctic fur seal is geared to exploiting prey within the surface mixed layer.
Seasonal mountain lion predation on a feral horse population
Authors: Turner Jr. John W. , Wolfe Michael L. , Kirkpatrick Jay F.
Published: July 2008

A population of feral horses (Equus caballus) was studied from 1986 to 1991 to determine the demographic impact of predation by the mountain lion (Felis concolor). The population, inhabiting a 600-km2 area on the central California – Nevada border comprised approximately 162 individuals > 1 year old, with an average of 9 yearlings, 8 two-year-olds, and 144 adults. Numbers of horses varied by only 4–8% and showed no consistent trend. The parturition peak spanned May and June, when 80% of foaling occurred. One-third of the average annual cohort of 33 foals was missing by July and only half of the cohort remained by October. The mean first-year survival rate estimated from the differential incidence of foals and yearlings in successive years was 0.27, which was less than one-third of the foal survival rate reported for other feral horse populations. A minimum of four adult mountain lions used the study area each year between May and October. Of 28 foal carcasses located from May to mid-July, at least 82% were the result of mountain lion kills. No evidence of predation on older horses was observed, but mountain lions preyed on mule deer (Odocoileus hemionus) during winter. We conclude that the growth of this horse population is limited by predation.
The locomotory response of the egg parasitoid Trichogramma evanescens Westwood to hexane extracts of eastern spruce budworm scales (Choristoneura fumiferana (Clemens))
Authors: Schmidt J. M. , Carter M. H.
Published: July 2008

The response of Trichogramma evanescens Westwood to various concentrations of hexane extracts from the scales of one of its hosts, the spruce budworm moth (Choristoneura fumiferana (Clemens)), was investigated. When placed on filter papers treated with hexane extracts of the moth scales, the wasps responded with two distinct phases of intensified searching behaviours. The first was characterized by a rapidly induced, transient klinokinetic response (decreased walking speed) lasting 10–20 s. This response had an abrupt threshold at scale extract concentrations between 0.05 and 0.5 mg/mL. After 15 s of exposure walking speeds subsequently recovered to rates similar to those of wasps walking on areas treated with hexane only (control). The second behaviour consisted of a persistent orthokinetic response (increased number of abrupt turns, greater than 70°), which resulted in the wasps remaining longer in the test arena. This increased retention on the patch was observed for extract concentrations below 0.05 mg/mL and appeared to be at least partially independent of changes in wasp velocity. Several parameters evaluated, including mean velocity, mean angular change, and fractal dimension, were highly variable within and between treatment groups, and showed no consistent pattern of response with dosage. In contrast, time spent on the patch and total distance travelled on the test area showed a significant correspondence to the dosage-dependent orthokinetic response of the wasps.
Factors that possibly influence variation in the calling song of field crickets: temperature, time, and male size, age, and wing morphology
Authors: Souroukis Konstantine , Cade William H. , Rowell Gareth
Published: July 2008

The structure of the calling song of the Texas field cricket, Gryllus integer, was studied. Pulse rates, percentage of missed pulses within a trill, numbers of pulses per trill or trill lengths, and intertrill intervals were measured for males singing in the field and in the laboratory. All song parameters were variable and were distributed normally. Intertrill intervals were longer in the laboratory, but all other parameters were similar in laboratory and field populations. Pulse rates varied in a linear fashion with ambient temperature in the laboratory and field. The percentage of missed pulses in a trill decreased with increasing temperature in the field and in the laboratory; intertrill intervals varied inversely with temperature only in the field. In field populations, immediately before and after sunrise male songs had fewer pulses per trill and a greater frequency of missed pulses than songs produced for a few hours following sunset. Song structure did not vary with age, weight, or hind-wing dimorphism. Most song parameters were correlated with each other. The data are discussed in terms of female choice and attraction to male song, male competition by way of acoustical interaction, and underlying genetic variation in G. integer.
Stability of white-tailed doe parturition ranges on a refuge in east-central Illinois
Authors: Nixon Charles M. , Hansen Lonnie P. , Brewer Paul A. , Chelsvig James E.
Published: July 2008

Stability and retention of parturition sites were examined for 17 white-tailed does (Odocoileus virginianus) radio-marked on an 800-ha forested area in Piatt County, east-central Illinois. Pre- and post-natal home range sizes were not significantly correlated with density of females, age of doe, litter size (postnatal range only), or sex of litter. As females aged, parturition sites moved closer to prenatal centers of home range activity (P < 0.02), and overlap of both pre- and post-natal home range boundaries increased in consecutive years (P < 0.001). Postnatal core areas of related females evidenced considerable overlap, whereas those of unrelated does were discrete. Breeding does used upland successional forests (< 60 years old) more than expected and bottomland forests less than expected (P < 0.05) as sites for parturition. Through seasonal movements, including migratory and dispersal behaviors, does in east-central Illinois, where forests are scarce, use all available sites suitable for parturition. Selection and retention of these parturition sites promote the development of matriarchal social groups, which ensures continued use of these sites by related females.
Comparative evolutionary genetics of trematode parasites (Plagiorchiidae) and their anuran hosts
Authors: Rannala B. H.
Published: July 2008

A study of five trematode species of the genera Glypthelmins and Haplometrana inhabiting anurans produced allozyme-based estimates of Nei's (1978) genetic distance ranging from 0.126 to 1.867. An estimate of trematode phylogeny is in agreement with earlier morphologically based phylogenetic hypotheses and is similar to the phylogeny for associated host ranid and hylid frogs based on rDNA and morphology. A comparison of the genetic distances observed among trematodes with those of their respective hosts suggests that host and parasite genetic distances are not significantly correlated. This is counter to expectations based on a molecular clock for protein evolution in hosts and parasites. These results may reflect (i) the effects of sampling error on genetic distance estimates, (ii) a non-clocklike rate of protein evolution in hosts and (or) parasites, (iii) temporally independent speciation events in associated host and parasite lineages, or (iv) the effects of host hybridization.
Cephalopod prey of the southern elephant seal, Mirounga leonina L.
Authors: Rodhouse P. G. , Arnbom T. R. , Fedak M. A. , Yeatman J. , Murray A. W. A.
Published: July 2008

In the austral summers of 1986 and 1988–1989, 51 southern elephant seals (Mirounga leonina) at Husvik, South Georgia (54°10′S; 36°43′W), were stomach lavaged after chemical immobilization. Only cephalopod remains were retrieved, including 1070 lower beaks that were identified and measured. In total these were estimated to represent a wet weight of 187.8 kg. Fourteen species of squid from 11 families and 2 species of octopod from 1 family were present. The most important species overall were the squids Psychroteuthis glacialis in terms of numerical abundance (33.7%) and Moroteuthis knipovitchi in terms of estimated biomass (31.2%). The remaining biomass was mainly comprised of the five large muscular squids, Kondakovia longimana (24.0%), P. glacialis (15.4%), Martialia hyadesi (11.2%), Alluroteuthis antarcticus (10.8%), and Gonatus antarcticus (3.6%). Larger seals of both sexes fed on a wider variety of cephalopod species than smaller seals, with large males taking the greatest diversity. Between the two summers of the study there were some changes in the relative importance of the various cephalopod species consumed; in particular, in 1988–1989 M. knipovitchi and M. hyadesi were less important and P. glacialis was more important. The taxa and size of cephalopods taken by southern elephant seals at South Georgia are almost identical to those taken by the grey-headed albatross (Diomedea chrysostoma), but the relative proportions are quite different. The biogeography of the cephalopods eaten suggests that southern elephant seals sampled at South Georgia do not forage to the north of the Antarctic Polar Front but probably travel southwards towards the Antarctic continent or Peninsula.
Size divergence and dietary partitioning enhance coexistence of two herbivorous species of Diaptomus (Copepoda: Calanoida) in some shallow Quebec lakes
Authors: Chow-Fraser Patricia , Maly Edward J.
Published: July 2008

We examined the vertical and horizontal distribution patterns of Diaptomus minutus Lilljeborg and Diaptomus oregonensis Forbes in several shallow Quebec lakes where they occurred allopatrically and sympatrically within a small geographic region. Both species overlapped extensively in their vertical and temporal distributions and were found to be positively associated within and among lakes. Although size displacement could not be detected when body lengths of sympatric and allopatric populations were compared, in lakes where there was a reduction in size overlap between species, the two species coexisted at relatively high densities. This contrasted with situations where convergence in size between species was accompanied by a limited abundance of one or both diaptomids. We conducted stomach-content analyses on the sympatric populations of two of these lakes to determine if diet preference was related to copepod size divergence, and if algae were selected as a function of copepod size. We found that D. minutus, the smaller copepod, preferentially ingested a number of small algal particles (< 10 μm), whereas D. oregonensis, the larger copepod, tended to ingest a greater number of larger particles. Although preference for small algae (Selenastrum and small blue–green algae) was negatively correlated with prosome length, preference for larger algal taxa (Planktosphaerium, centric diatoms such as Melosira, and Achnanthes) was positively correlated with diaptomid size. There were, however, differences with respect to the degree of diet overlap between species in the two lakes, which was reflected in a significant negative correlation between dietary and size overlap. These observations are consistent with the hypothesis that reduction in size overlap has resulted in reduced exploitative competition, and that divergence in size and diet may be the mechanism that allows D. minutus and D. oregonensis to coexist when food becomes limiting.
Heat increment of feeding and partitioning of dietary energy in yearling Black Brant
Authors: Sedinger James S. , White Robert G. , Hauer William E.
Published: July 2008

We examined daily energy expenditure and energy balance by making simultaneous measurements of gaseous exchange and apparent metabolizable energy (AME) intake in four captive Black Brant (Branta bernicla nigricans) that ate alfalfa pellets. Daily energy expenditure was positively correlated with AME intake in all four individuals. The slope of this relationship represented an estimate of the heat increment of feeding, which averaged 0.20 for individuals in positive energy balance. Maintenance AME intake under experimental conditions was estimated at 451–646 kJ∙d−1∙kg−1. Individuals in positive energy balance retained AME at an efficiency of 81%, which is amongst the highest recorded for birds. Thirty-five percent of the apparent net energy for production was accounted for by protein deposition, but the ratio of protein to lipid produced increased from late winter through spring.
Threespine stickleback aggregations create a potential predation refuge for sockeye salmon fry
Authors: Ruggerone Gregory T.
Published: July 2008

Coho salmon (Oncorhynchus kisutch) frequently consume sockeye salmon (Oncorhynchus nerka) fry in Chignik Lake, Alaska, but have never been observed to consume threespine sticklebacks (Gasterosteus aculeatus), which are often closely associated with sockeye fry. Because coho salmon are visual predators and appear to avoid sticklebacks, a series of experiments was conducted in net pens to determine whether juvenile sockeye associated with threespine sticklebacks experienced less prédation than sockeye without sticklebacks and whether prey size affected prédation rates. Significantly fewer sockeye fry by coho were consumed in the pen containing 60 sticklebacks [Formula: see text] than in the 30-stickleback (4.7 fry/day) and 0-stickleback (4.4 fry/day) pens. An identical experiment with large, yearling sockeye (rather than sticklebacks) did not reveal a significant effect (p = 0.28), although there was a tendency for fewer large fry to be consumed when yearlings were abundant. A third experiment demonstrated predation rates on fry that were 45% lower in the presence of sticklebacks (1.2 fry/day) than in the presence of yearling sockeye (2.2 fry/day). Large sockeye fry (37–44 mm) consumed by coho declined steadily from about 36 to 29 to 22% of the total number of fry eaten as the number of sticklebacks or yearling sockeye increased from 0 to 30 to 60, respectively. These data suggest that the presence of threespine sticklebacks may reduce predation by coho on juvenile sockeye, especially those sockeye similar in size to sticklebacks.
Field observations on the reproductive biology of a newly discovered stickleback (Gasterosteus)
Authors: Jamieson I. G. , Blouw D. M. , Colgan P. W.
Published: July 2008

Field observations on a newly discovered form of stickleback, termed the white stickleback, were conducted at three sites in Bras d'Or Lake on Cape Breton Island, Nova Scotia. The white stickleback is sympatric with but reproductively isolated from the threespine stickleback (Gasterosteus aculeatus). White males nest above the substrate in filamentous algae, whereas threespine males nest on the substrate away from algae. At one of our sites, however, a few males of both sticklebacks were found nesting in similar habitat, namely on top of alga-covered rocks. Nevertheless, there was microhabitat separation of the two sticklebacks, because white males consistently nest farther from the shore than threespine males. Hence, there is little interaction between the two forms during courtship of females. In areas where territories were adjacent, white males attracted gravid threespine females to their nest, but courtship broke off at that point. Observations indicated positive assortative mating, as found in earlier laboratory work, and suggest that the two sticklebacks may be good biological species. However, the previously reported association between white sticklebacks and dense growth of filamentous algae is not perfect, since white males at one site had built their nests and were actively courting females before the filamentous algae bloomed. Some white males vacated their nest sites during the day, whereas threespine males never did. It is not clear why white males do this, where they go, or for how long, but the departures may be related to the high levels of activity shown by white males while on their territories.