bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural requirements for stimulation by thyrotropin-releasing hormone of α-MSH release from rainbow trout (Oncorhynchus mykiss) pituitary fragments in vitro
Authors: Schwartzentruber R. Steven , Vaudry Hubert , Omeljaniuk Robert J.
Published: January 2008

Juvenile rainbow trout (Oncorhynchus mykiss) pituitary glands were isolated and the neurointermediate lobes (NILs) were removed from the partes distalis. NILs were surgically fragmented, pooled, and superfused in vitro with culture media, then treated with 3-min pulses of native thyrotropin-releasing hormone (TRH) or TRH analog; 10-min fractions were collected and stored (−20 °C) for subsequent analysis of α-melanocyte-stimulating hormone (α-MSH) content by specific radioimmunoassay. After 1–2 h of superfusion, α-MSH release from the NIL remained relatively constant; α-MSH-like immunoreactivity was not detected in eluate from the partes distalis in a series of parallel experiments. Native TRH stimulated acute releases of α-MSH from the NILs with a minimum effective dose of 10−9 M and an estimated ED50 of 1.73 × 10−9 M on the basis of increasing dose–response experiments; decreasing dose–response data provide an estimated minimum effective dose and ED50 of 10−9 and 1.57 × 10−9 M, respectively. No up- or down-regulatory effect was observed when NIL fragments were treated with repeated large (10−6 M) doses of TRH. By comparison, increasing pulse concentrations of pGlu-3-Me-His-Pro-NH2 (MeTRH) stimulated α-MSH release with a minimum effective dose of 10−10 M and an estimated ED50 of 1.56 × 10−9 M. Substitution of the histidine residue with phenylalanine decreased the stimulatory actions of TRH so that the minimum effective dose was 10−6 M. Substitution at either the amino terminus ([Glu1]TRH and [1-Me-(S)-dihydroorotyl1]TRH) or carboxy terminus (pGlu-His and TRH-Gly) resulted in near complete loss of bioactivity. To the best of our knowledge, this is the first investigation of the structural requirements for TRH biological activity in the teleost pituitary. Our data indicate that the structural criteria for TRH stimulation of α-MSH from the teleost pituitary are highly conservative; modification of TRH beyond the methylation of the histidine residue results in massive loss of biological activity. These data are consistent with our previous demonstrations of highly conservative structural requirements for TRH-receptor recognition in the trout pituitary and hypothalamus.
Ecology of young-of-the-year fishes in Severn Sound, Lake Huron
Authors: Leslie John K. , Timmins Charles A.
Published: January 2008

Seasonal occurrence, distribution, density, and size were estimated for young-of-the-year fishes collected in altered and unaltered littoral areas of eastern Severn Sound, Lake Huron, a Great Lakes "Area of Concern." Fishes were sampled with nets and seines (0.3-mm mesh) in open water and at the shore from May to October, 1989, 1990, and 1991. The highly diverse young-of-the-year fish community reflects unfragmented heterogeneous habitats that range from exposed rock and sand shores to densely vegetated embayments and marshes. Fishes (89 000 specimens) were represented by 9 reproductive guilds, 16 families, and 38 taxa. Cyprinids, centrarchids, and percids dominated collections; common and abundant species included Perca flavescens (56% of total catch), Lepomis gibbosus (18%), and Alosa pseudoharengus (8%). Generally, fewer species at lower mean densities occurred in unaltered habitats than in altered areas. Large spatial and temporal differences were observed in peak density and mean total lengths of most species collected on the same date at several sites. Fish species diversity and abundance were consistently highest in mixed submersed plants and lowest in open water and on exposed shores.
Occurrence, population composition, and habitat use of humpback whales in Samana Bay, Dominican Republic
Authors: Mattila David K. , Clapham Phillip J. , Vásquez Oswaldo , Bowman Robert S.
Published: January 2008

A study of humpback whales (Megaptera novaeangliae) was conducted between 1988 and 1991 in Samana Bay, Dominican Republic. Humpbacks were observed as early as the earliest survey (3 January) and as late as the latest (16 March). Local abundance varied from 0 whales per hour to a maximum of 3.2 whales per hour (mean = 1.70, SD = 0.79), and densities calculated from track surveys ranged from 0.09 to 0.82 whales per square nautical mile (mean = 0.31). Abundance generally peaked in February, but variation was observed both within a season and between years. Almost all whales were observed in the eastern part of the bay, towards or at its mouth. In all, 397 individuals were photographically identified during the study period. Of these, 18 were observed in more than 1 year (17 in 2 years, 1 in 3 years). A total of 15.8% of identified individuals were observed on more than 1 day in a year (maximum 5 days), with mothers representing 33.3% of all resightings. Observed occupancies of resighted animals ranged from 1 to 33 days (mean = 6.3 days, SD = 7.14). The mean group size was 1.95 (range = 1–15, SD = 1.30, n = 652 groups). Ninety-nine groups contained a calf, and all groups larger than three (n = 45) were competitive in nature. Comparisons of fluke photographs with the North Atlantic Humpback Whale Catalogue revealed 141 matches of 118 individuals to other areas. Of these, 76 were to high-latitude feeding grounds (including the Gulf of Maine, Newfoundland, Labrador, the Gulf of St. Lawrence, and west Greenland), while the remaining 65 were to other areas of the West Indies (Silver Bank, Navidad Bank, Puerto Rico, Virgin Bank, or Anguilla Bank) or to Bermuda. We suggest that Samana Bay is one of the most important winter habitats in the West Indies for humpback whales from all over the western North Atlantic, although whaling records suggest that the abundance of whales in this area may be a relatively recent phenomenon. Sightings of other marine mammal species in Samana Bay are summarized.
Food and space: resources defended by territorial parous female Columbian ground squirrels
Authors: Boag David A. , Wiggett Darwin R.
Published: January 2008

The importance of food and space, as resources defended by parous female Columbian ground squirrels (Spermophilus columbianus), was studied by manipulating one of these resources, that is increasing the quality of forage (through urine fertilization) on small plots within territories. Use of these fertilized plots by ground squirrels increased more than 100-fold when averaged over 2 years after manipulation. This increase, however, was not equal for each sex and age class: parous females used the fertilized plots relatively more, and nonparous females less, than either yearling or adult males. The number of parous females with territories overlapping the experimental plots also increased after fertilization, but the size of their territories declined only slightly, by less than 10%. Parous females with access to the fertilized plots, relative to those without such access, had greater body mass and larger litters that both weighed more at birth and gained body mass subsequently more rapidly. Parous females on territories with fertilized plots showed higher levels of agonism than those on territories lacking such plots. Most of the agonism was centered on the experimental plots and more of it was directed at young of other females than at their own young. Such differential treatment of kin, however, did not extend to their offspring of the previous year. We suggest that for parous females of this ground squirrel, both food and space (at least that normally needed to supply sufficient forage) are important resources to defend, and both may have played a significant role in the evolution of territoriality in females of this species.
Infections of Diphyllobothrium dendriticum, D. ditremum (Cestoda), and Cystidicola farionis (Nematoda) in a north Norwegian population of Arctic charr (Salvelinus alpinus) during winter
Authors: Knudsen Rune , Klemetsen Anders
Published: January 2008

Infections of the parasites Diphyllobothrium dendriticum, Diphyllobothrium ditremum, and Cystidicola farionis in Arctic charr (Salvelinus alpinus) from Takvatn, northern Norway, were followed throughout a 9-month overwintering period. The relative density of all three parasite species increased with the age of the host in response to ontogenetic shifts in habitat and food of Arctic charr in the lake. Our results indicate that some recruitment of the three parasite species, particularly D. ditremum, takes place during the winter. However, winter parasite recruitment was lower than in the ice-free season. In spite of high parasite infection in some individuals, no strong indications of parasite-induced host winter mortality were found for any of the three species. Low overwintering mortality of heavily parasitized charr may be connected with a stock-reduction program in the lake that has improved the conditions of the fish, and the residual stock is probably less affected by parasites.
Genetic and epigenetic variation in suitability of a Drosophila host to three parasitoid species
Authors: Delpuech J.-M. , Frey F. , Carton Y.
Published: January 2008

The genetic and epigenetic variability in suitability of a host, Drosophila melanogaster Meigen, for the development of three parasitoid species (Leptopilina boulardi (Barbotin, Carton, and Kelmer-Pillault), Leptopilina heterotoma (Thompson), and Pachycrepoideus dubius Ashmead) was analyzed. The Drosophila population came from an oasis in central Tunisia, where it is infested by the three wasp species. The genetic variability of the host was analyzed by the technique of using isofemale lines. The host population exhibited no genetic variability in the degree of infestation except in the case of L. heterotoma. It did, however, show a high level of genetic variability concerning its suitability for development of the three parasitoids. The experimental conditions had a significant effect on infestation by two of the parasitoids (L. boulardi, L. heterotoma). The rates of successful parasitism were correlated only in the case of the two eucoilid parasitoids. Therefore, a single host genotype was not suitable for all three parasitoid species concomitantly. Under pressure from the three parasitoids, the host population maintained genetic variability of its response to parasitoid development.
Diurnal habitat use of American woodcock wintering along the Atlantic coast
Authors: Krementz David G. , Pendleton Grey W.
Published: January 2008

The long-term decline of the American woodcock (Scolopax minor) population led us to investigate diurnal habitat use with radiotelemetry on the wintering grounds. Sites included the coastal plain of Georgia (1989–1991), South Carolina (1988–1989), and Virginia (1991–1992). Habitat use was not explained by age, sex, or date during the winter, but individuals used habitat differently (P < 0.05). Only shrubland was preferred at all sites in all years. Pine plantations of various ages were used according to availability, but usually less often than expected, while bottomland hardwoods and pine–hardwoods were used more often than expected.
Chromosomal NOR phenotypes in North American pikes and pickerels, genus Esox, with notes on the Umbridae (Euteleostei: Esocae)
Authors: Ráb P. , Crossman E. J.
Published: January 2008

A comparison was made of the localization of nucleolar organizer region (NOR) sites in the karyotypes of the North American pikes and pickerels Esox lucius, E. masquinongy, E. niger, and the two subspecies of E. americanus (Esocidae). NORs were located by silver staining or chromomycin A3 fluorescence. The study revealed that the position of chromosomal NORs in all Esox taxa examined was the same: the pericentromeric region of one middle-sized chromosome pair. The same NOR phenotype was found previously in a related European species, Umbra krameri (Umbridae), and in U. pygmaea, one of the two North American representatives of the genus. The NOR phenotype of the remaining North American species (U. limi) is different. It is hypothesized that this kind of NOR phenotype, shared by two phyletic lineages in the Esocae, represents an ancestral character for the members of that group.
Foraging behavior of Black-backed and Three-toed woodpeckers during spring and summer in a Canadian boreal forest
Authors: Villard Pascal
Published: January 2008

During one spring to summer study in a Canadian boreal forest, Black-backed Woodpeckers (Picoides arcticus) were found to excavate mainly on logs and at the base of large-diameter tree trunks. In contrast, Three-toed Woodpeckers (Picoides tridactylus) preferred higher strata and smaller diameter trunks. The predominant foraging technique used by Three-toed Woodpeckers was bark scaling. Canadian Three-toed Woodpeckers showed foraging behavior similar to that found in European woodpeckers, but in the Nearctic range they have not fully developed the sap-licking behavior that is typical of the Three-toed Woodpeckers of the western Palearctic range.
Growth in bumble bee larvae: relation between development time, mass, and amount of pollen ingested
Authors: Ribeiro M. F.
Published: January 2008

The development of worker, male, and queen larvae of Bombus terrestris was analysed by measuring their mass and the amount of pollen they had ingested. The three kinds of larvae grew significantly differently. Workers and queens differed strongly in their growth from the beginning of the larval stage. On the other hand, males and queens were more similar in their development. Furthermore, during the later stages, pollen played a less important role in the increase of the queens' mass, which indicates that a different mechanism is probably involved in their growth. Two hypotheses are discussed: either there is a difference in the queens' metabolism or they receive a different diet, which improves their growth.
Geographical ecology of a Neotropical lizard: Ameiva ameiva (Teiidae) in Brazil
Authors: Vitt Laurie J. , Colli Guarino R.
Published: January 2008

The large-bodied teiid lizard Ameiva ameiva was studied at eight different sites in four major South American habitats of Brazil: caatinga, cerrado, Amazonian rain forest, and Amazonian savanna. We found striking similarity in ecological attributes of this lizard among very different habitats. Activity is concentrated in late morning and early afternoon; active body temperatures average 37.9 ± 0.09 °C and vary little among sites or throughout the day; the diet consists of a variety of vertebrates and invertebrates but is dominated by grasshoppers, roaches, beetles, spiders, and insect larvae; and niche breadths for prey are similar among study sites but the actual composition of the diets varies. There is minimal morphological variation among sites (mostly size); the most striking morphological variation is between the sexes. Males reach larger body sizes and have relatively larger heads than females. Juveniles have relatively larger heads than would be predicted on the basis of body size alone. Sexual selection may explain the sexual differences in head size of adults, whereas the relatively large heads of juveniles may be associated with food competition with sympatric teiid lizards. Clutch size varies from 1 to 11 eggs, is related to female body size (snout–vent length), and varied among study sites. Similar variation among sites occurs in egg size but not in relative clutch mass. An interesting positive relationship was found between body size and relative clutch mass. In a population from the state of Rondônia egg dry mass was correlated with female size, indicating that individual offspring size is, to some extent, a consequence of female size. The reproductive season is extended for all populations and it appears that predictability of rainfall may regulate the season length. Reasons for the apparent success of A. ameiva in a diversity of habitats on a large geographic scale include its large body size, foraging mode, and preferred microhabitat (ecotones and disturbed areas).
Respiratory gill surface area of a facultative air-breathing loricariid fish, Rhinelepis strigosa
Authors: Santos C. T. C. , Fernandes M. N. , Severi W.
Published: January 2008

The respiratory surface area of the gill in relation to body mass of the facultative air-breathing loricariid fish Rhinelepis strigosa was analyzed using logarithmic transformation (log Y = log a + b log W) of the equation Y = aWb. The data revealed differences in growth pattern for each gill element. The increase in gill surface area was not isometric with body mass (b = 0.76). The total number of secondary lamellae (b = 0.38) and the average bilateral surface area of the secondary lamellae (b = 0.46) contributed most to the rate of development of the gill surface area (total area of the secondary lamellae) with increase in body mass. Gill filament length (b = 0.339) was more important than the frequency (number/mm) of secondary lamellae in determining the increase in the total number of secondary lamellae. The number of gill filaments showed the lowest b value, 0.072. Rhinelepis strigosa has a larger gill surface area than most other air-breathing fish, indicating that it is better adapted for breathing in water than in air.
Ultrastructure of the uniporous sensilla on the galea of larval Mamestra configurata (Walker) (Lepidoptera: Noctuidae)
Authors: Shields Vonnie D. C.
Published: January 2008

The structure and innervation of sensilla on the galea of fifth-instar Bertha armyworms, Mamestra configurata, were examined using bright-field light, scanning electron, and transmission electron microscopy. Four sensillar types were identified. The galea bears two uniporous styloconic sensilla, one aporous spire-shaped basiconic sensillum, two aporous basiconic sensilla, and one campaniform sensillum. The uniporous styloconic sensillum consists of a small socketed peg inserted into a large cone or style. Each styloconic sensillum is innervated by five bipolar neurons and associated with three sheath cells. Four distal dendrites end in the peg at various levels beneath the pore and the fifth ends in a tubular body at the base of the peg. The intermediate and outer sheath cells enclose a very large liquor-filled sensillar sinus. The inner sheath cell forms a nonlapped cylindrical sleeve around the neurons. These sensilla exhibit features of contact chemosensilla.
Omnivory of the larval phantom midge (Chaoborus spp.) and its potential significance for freshwater planktonic food webs
Authors: Moore Marianne V. , Yan Norman D. , Pawson Trevor
Published: January 2008

Developmental and seasonal changes in the preferred prey and the diet composition of the invertebrate predator Chaoborus punctipennis were determined in Plastic Lake, an acidified (pH 5.6) lake in south-central Ontario, Canada. All instars consumed rotifers (mainly Keratella cochlearis, Ploesoma sp., and Asplanchna priodonta), and instars III and IV fed preferentially on crustaceans (mainly bosminids and copepods). Phytoflagellates (Peridinium sp. and Dinobryon sp.), however, numerically dominated the diet of all instars examined (II–IV), and were consumed by instar II larvae in excess of their relative availability. On 40 and 20% of the sampling dates, instars III and IV, respectively, consumed phytoflagellates in accordance with their relative abundance in the lake. Although the contribution of phytoflagellates to the biomass-based diet of C. punctipennis was low, on one occasion phytoflagellates formed almost half of the diet biomass of instar II larvae. A review of the literature shows that in lakes where phytoflagellate densities are high (≥ 100–200/mL), phytoflagellates contribute ≥ 50% of the diet biomass of all instars of Chaoborus spp. These findings indicate that Chaoborus spp. are omnivores that frequently feed on phytoflagellates even when alternative animal prey are abundant. Consumption of phagotrophic phytoflagellates by Chaoborus spp. and other large invertebrate omnivores, such as Mysis spp., Epischura spp., and cyclopoid copepods, may increase the transfer efficiency of organic carbon from the microbial food web to the upper trophic levels in fresh waters. In acidified lakes, consumption of large dinoflagellates by Chaoborus spp. and other invertebrate omnivores may ameliorate the hypothesized bottleneck impeding the flow of carbon between phytoplankton and zooplankton.
Cytochrome b sequence variation and a molecular phylogeny of the live-bearing fish genus Gambusia (Cyprinodontiformes: Poeciliidae)
Authors: Lydeard Charles , Wooten Michael C. , Meyer Axel
Published: January 2008

Nucleotide sequences for a 402-base segment of the mitochondrial cytochrome b gene were determined from 25 species of live-bearing fishes. A total of 34 sequences representing 24 species of the genus Gambusia and 1 species of Belonesox were generated via the polymerase chain reaction. The levels of overall variation were consistent with those from other genera of fishes. In total, 137 of 402 (34.1%) nucleotides exhibited variation within or among the species. Observed differences at 24 (17.9%) of the 134 cytochrome b codons would result in amino acid replacements. Phylogenetic analyses employing various weighting schemes resulted in several clades representing traditionally recognized taxonomic groups. However, precise relationships among species-groups remained uncertain. Randomization tests indicated that these topologies contained significant nonrandom phylogenetic information. As with other fishes, the overall rate of divergence appeared to be slower than that of other vertebrates and the overall replacement/substitution pattern was suggestive of nonrandom evolutionary input.
Seasonal changes in gut capacity in the white-footed mouse (Peromyscus leucopus) and meadow vole (Microtus pennsylvanicus)
Authors: Derting Terry L. , Noakes III Edward B.
Published: January 2008

Changes in gut capacity may be important for a species adapting to increased energy requirements or decreased food quality in a seasonal environment. We conducted a comparative study of seasonal changes in gut capacity in two rodent species with diets of different types. Although the lengths and masses of gut organs differed between species within a season, the species did not differ in the types of gut changes that occurred from summer to winter. All organs except the colon had significantly heavier wet and dry masses in winter than in summer. No significant differences in organ lengths, volumes, or surface areas occurred with season. Increased mass of the small intestine was due to large increases in the mass of the mucosa and smaller increases in the mass of the serosa. In winter, Microtus pennsylvanicus had significantly lower body mass than in summer. Peromyscus leucopus had no change in body mass in winter but may have used torpor as an energy-conservation mechanism. Energy-conservation adaptations in each species may have minimized the need for large changes in the gut organs.
Nesting success of ducks on the central Yukon Flats, Alaska
Authors: Grand James Barry
Published: January 2008

Nesting success was studied at Canvasback Lake and Mallard Lake on the Yukon Flats in interior Alaska in 1989–1991. Simple estimates of nesting success were computed using two techniques that assume a constant daily survival rate (DSR). Maximum-likelihood estimates of nesting success for all ducks, assuming constant DSR, ranged among years and sites from near zero to 12%. However, DSRs were not constant but increased with nest age and initiation date (R2 = 0.42, P = 0.0001). Nesting success was near zero for nests initiated 1–10 May and increased to 100% for nests initiated after 30 June. Therefore, species nesting in early to mid season, such as Mallard (Anas platyrhynchos), Northern Pintail (A. acuta), and Northern Shoveler (A. clypeata), had lower success than later nesting species such as Green-winged Teal (A. crecca) and Lesser Scaup (Aythya affinis). In 1990 and 1991, combined nesting success of all species, allowing for variation in DSR with nest initiation date and age of nest, was 12.50%.
Comparative fine structure of sperm of Heterodera schachtii and Punctodera chalcoensis, with phylogenetic implications for Heteroderinae (Nemata: Heteroderidae)
Authors: Cares J. E. , Baldwin J. G.
Published: January 2008

The fine structure of sperm of Heterodera schachtii and Punctodera chalcoensis demonstrates a high degree of interspecific morphological and developmental diversity, particularly in comparison with previously examined Heteroderinae that develop cysts, including Globodera tabacum, as well as out-groups that lack cysts, including species of Verutus, Meloidodera, and Ekphymatodera. Sperm of P. chalcoensis are much smaller and have fewer filopodia than those of species of Heterodera and Globodera. However, the distribution of filopodia on only part of the body, the smooth surface of the filopodia, and the presence of cortical microtubules are traits shared by the three genera with cysts. Unique features shared by P. chalcoensis and Globodera species include the short persistence of fibrous bodies after spermiogenesis and the lack of sperm polarization in the female genital tract. These traits are absent in Heterodera species. Conversely, chromatin remains unchanged with respect to condensation during sperm development in P. chalcoensis and species of Heterodera but not in Globodera. Patterns of evolution of sperm may be useful for testing hypotheses of the phylogeny of Heteroderinae, but the diversity is so great that character coding will be required for a large number of representative species.
Reproductive isolating mechanisms between the peamouth, Mylocheilus caurinus, and the redside shiner, Richardsonius balteatus, at Stave Lake, British Columbia, Canada
Authors: Aspinwall Nevin , McPhail John D.
Published: January 2008

Since at least 1952, the peamouth, Mylocheilus caurinus and the redside shiner, Richardsonius balteatus, have engaged in extensive hybridization (5.7–14.1% of the combined gene pools) in Stave Lake, British Columbia. A research project initiated in 1966 and continued to 1991 demonstrated that genetic swamping of the two species has not occurred. A study was conducted to determine the strength of premating and postmating isolating mechanisms between these two species. Temporal isolation is weak because both species had spawning periods in Devils Creek that overlapped by approximately 1.5 months. Also, both species spawned at night, and only on nights preceded by a sunny day. Both species were group spawners and both spawned on the first riffle of Devils Creek. Hybrid sterility is not well developed. While male F1 hybrids have low fertility, female F1 hybrids are as fertile as females of either species and would allow swamping if other postmating mechanisms were not operating. Hybrid inferiority was examined by laboratory experiments in which we measured survival of fingerling hybrids. While F1 hybrids displayed survival equal to that of M. caurinus, hybrid backcrosses to M. caurinus showed a 20% lower survival rate than M. caurinus. Also, hybrid backcrosses to M. caurinus included a significant proportion (8.4%) of deformed individuals.
Variation in growth and reproduction of walleye (Stizostedion vitreum) in three Manitoba lakes
Authors: Craig J. F. , Babaluk J. A. , Stevenson S. G. , Williams P. C.
Published: January 2008

Growth, lifetime egg production and biomass, and lipid accumulation in three female populations of walleye (Stizostedion vitreum) were studied. Two populations inhabit large, heavily exploited Canadian prairie lakes and the third inhabits a smaller, cooler, unexploited boreal lake in the Canadian Shield. Fish in the unexploited population grew more slowly and to a smaller asymptotic size than those in the other two populations. Although annual reproductive output per individual was less for this population, the reproductive life-span was greater. Lifetime egg production and ovary lipid biomass per recruit appeared to be similar (within 13%) for female walleye in the three different populations. The significance of energy allocation in the life history of these populations is discussed.
Flow patterns around gills of pupal net-winged midges (Diptera: Blephariceridae): possible implications for respiration
Authors: Pommen Gregory D. W. , Craig Douglas A.
Published: January 2008

Dye studies of water flow around pupae of species of Blephariceridae show that the pupa and gills act as a "bluff body" and produce matched pairs of vortices, or regions of low pressure, downstream of the gills. Solenoidal vortices are also produced at the bases of the gills, as is reversed flow between the two gills. Bubbles of air produced from the gill plastron of live pupae are considered to be the result of decreased solubility of air in water in the low-pressure regions associated with the gills. We conclude that the pupal gills of Blephariceridae, Simuliidae, and probably other aquatic insects are designed to make use of regions of low pressure for respiratory purposes.
Communal nesting in prairie voles (Microtus ochrogaster): an evaluation of costs and benefits based on patterns of dispersal and settlement
Authors: McGuire Betty , Getz Lowell L.
Published: January 2008

We evaluated costs and benefits of group nesting in prairie voles (Microtus ochrogaster) by examining dispersal from communal nests. Nests at which dispersal occurred did not differ in size from those at which no dispersal was recorded, and most animals did not exhibit declines in body mass prior to dispersal. Of those animals which left communal groups that contained at least one potential mate, half left groups at which level of competition for mates was judged to be low as opposed to medium or high. Our data do not support competition for food or mates as important costs of group nesting. One probable cost to individuals living in family groups is lack of mating opportunity; about one-third of all dispersers were from groups composed solely of family members. Several of our findings suggest that energy conservation is not the primary reason for communal nesting in prairie voles. Reductions in winter group size typically did not precipitate dispersal, and most dispersers that settled into a nest in winter joined groups which were smaller than the groups they had left. Dispersal did not increase during snow cover. Benefits of group nesting in natural populations of prairie voles remain to be identified.
Effects of sex and reproductive status on the diets of breeding Ring-necked Ducks (Aythya collaris) in north-central Minnesota
Authors: Eberhardt Robert T. , Riggs Mike
Published: January 2008

We analyzed the diets of 83 Ring-necked Ducks (Aythya collaris) collected on breeding areas in Beltrami County, Minnesota. Larval Trichoptera, Odonata, and Diptera, adult Hirudinea, and seeds from three plant genera, Zizania, Nuphar, and Potamogeton, formed most of the diets of hens during the breeding season. Males differed from females in the amounts and proportions of animal taxa consumed and in their diversity. Differences between the sexes increased during the breeding season. Consumption of animals by females increased significantly between prelaying and laying periods, while consumption by males changed little. We suggest that temporal diet shifts of female Ring-necked Ducks relative to males are a result of the higher protein requirements of females during prelaying and laying periods.
Absence of naturally occurring hybridization between the quagga mussel (Dreissena bugensis) and the zebra mussel (D. polymorpha) in the lower Great Lakes
Authors: Spidle Adrian P. , Mills Edward L. , May Bernie
Published: January 2008

The coexistence of two dreissenids, the quagga mussel (Dreissena bugensis) and the zebra mussel (D. polymorpha), in a new environment raises the possibility of natural hybridization and possible introgression. Animals of both species were collected in areas where they occur sympatrically (25–39% were quagga mussels) and screened at two protein-coding loci believed to differentiate between the two species. The occurrence of alleles diagnostic for both species in an individual would demonstrate hybridization between the species. No hybrid individuals were observed in a survey of 750 animals from four sites in Lake Ontario and one site in Lake Erie. Successful hybridization between these two genetically disparate species seems unlikely in the Great Lakes.
A method of culturing coronary artery explants for measuring vascular smooth muscle proliferation in rainbow trout
Authors: Gong Bang Q. , Farrell Anthony P.
Published: January 2008

A standardized method of in vitro [3H]thymidine incorporation during the S phase of cell division was developed to study vascular smooth muscle proliferation in the coronary artery of rainbow trout (Oncorhynchus mykiss). We established a reliable medium system, an optimum [3H]thymidine dose, and optimum incubation conditions. Incorporation of the radiolabel into vascular smooth muscle nuclei was confirmed with autoradiography. To test the sensitivity of the assay system, the coronary artery was surgically exposed and gently rubbed in anesthetized rainbow trout. Following either a 1-, 2-, or 3-day recovery period, fish were sacrificed and the coronary artery explants were cultured with [3H]thymidine. Gentle rubbing of the coronary artery in vivo resulted in a significant increase in [3H]thymidine incorporation into the coronary artery explant compared with sham-operated and untreated control groups of fish. Peak incorporation of [3H]thymidine occurred at day 2 in the treated group, when incorporation was three times that in the sham-operated group. This technique has potential application in the study of coronary arteriosclerosis in salmonids, where vascular smooth muscle proliferation is a primary event.
Pseudonitzschia species found in digestive tracts of northern anchovies [Engraulis mordax)
Authors: McGinness Kellie L. , McEachran John D. , Fryxell Greta A.
Published: January 2008

The diatom species Pseudonitzschia australis Frenguelli has been implicated as the source of the domoic acid that contaminated anchovy species in Monterey Bay, California, during 1991. In other geographic areas, as well as in laboratory cultures of isolates obtained from various geographic areas, other Pseudonitzschia species have been shown to produce domoic acid. The stomach contents of anchovies caught in Monterey Bay during the following summer were analyzed to identify and determine the abundance of each of the Pseudonitzschia species present. Pseudonitzschia species present in net-tow samples taken at the same time from Monterey Bay were also recorded. In the stomach samples, nine different Pseudonitzschia species were found, including four that have produced domoic acid either under natural or laboratory conditions. These findings illustrate the risk of possible neurotoxin accumulation inherent in the diets of the anchovies studied. The planktophagous diet of the anchovies reflected the plankton composition of the surrounding water and also demonstrates the anchovies' ability to filter pennate diatoms from the near-surface seawater.
Summer foraging by lactating female New Zealand fur seals (Arctocephalus forsteri) off Otago Peninsula, New Zealand
Authors: Harcourt Robert G. , Schulman Andrew M. , Davis Lloyd S. , Trillmich Fritz
Published: January 2008

The behaviour of female New Zealand fur seals (Arctocephalus forsteri) at sea and on land at the rookery of Fuchsia Gully, Otago Peninsula, New Zealand (45 °52′S, 170 °44′E), was examined during the early stages of lactation in the 1993 – 1994 breeding season. The attendance patterns of 19 females were investigated using daily observation at the rookery. Trips to sea to forage ranged from 3.4 h up to 8 days (mean 3.26 ± 1.1 days), and attendance periods at the rookery ranged from 1 to 13 days (mean 3.09 ± 1.63 days). At sea, the behaviour of four females was examined by deploying time–depth recorders. Females showed a nocturnal pattern of diving, 88.8–97.3% of dives being made during the hours of darkness. For all females and each night of foraging, the deepest dives were completed around dawn and dusk. The deepest dive recorded was 163 m and all females dove over 100 m deep on at least one dive. The overall median dive depth was considerably less than this, as around 24:00–03:00, females undertook many shallow dives, and during this time the median dive depth ranged from 5 to 10 m for the four females. Dives occurred in bouts, but bout duration varied significantly with time of day. Bouts were short during the day and longer at night, 55% of night bouts lasting throughout the night. Maximum dive durations ranged from 3.17 to 6.17 min and mean dive durations from 0.67 to 1.18 min for individual females. Dive depth was significantly related to dive duration for all four females. Two of the females also carried satellite transmitters, and at sea location was determined on three separate nights of foraging. Females were found to be foraging up to 78 km from the rookery, but always over the continental shelf (in water shallower than the 200 m depth contour).
Prédation on red squirrels during a snowshoe hare decline
Authors: Stuart-Smith A. Kari , Boutin Stan
Published: January 2008

We examined the extent and impact of predation on red squirrels (Tamiasciurus hudsonicus) during a cyclic decline of snowshoe hares in the southwestern Yukon, Canada. We monitored survival of squirrels on three control grids and a predator exclosure from March 1991 through August 1993. On controls, adult survival during the breeding season decreased from 1991, when snowshoe hare populations were high, to 1992, when hare populations declined rapidly. Survival increased slightly in 1993, when hare and predator populations were very low. Similarly, adult survival during winter was lower in 1992 – 1993 than in 1991 – 1992. Adult survival on the exclosure remained similar in each breeding season but declined during winter 1992 – 1993. Adult survival was similar on the controls and the exclosure in each year except during winter 1991–1992 and the 1992 breeding season, when it was lower on the controls. There was no difference in juvenile survival between the controls and the exclosure. Despite the decrease in adult survival due to predation, there was no population decline on any of the control grids. We conclude that predation did not have a measurable impact on red squirrel densities at Kluane and that it is unlikely red squirrels show 10-year population cycles in conjunction with snowshoe hares.
Air breathing in the armoured catfish (Hoplosternum littorale) as an adaptation to hypoxic, acidic, and hydrogen sulphide rich waters
Authors: Brauner C. J. , Ballantyne C. L. , Randall D. J. , Val A. L.
Published: January 2008

The armoured catfish (Hoplosternum littorale) from the Amazon River system is a facultative air breather that is tolerant to both acidic and hydrogen sulphide rich waters. Facultative air breathing in fishes is known to be an important strategy for surviving hypoxia, but its importance for surviving in acidic and hydrogen sulphide rich waters has not previously been investigated. Air-breathing frequency in H. littorale increased from 2 to 28 breaths/h as the partial pressure of oxygen [Formula: see text] in the water was reduced from 137 to 105 mmHg (1 mmHg = 133.322 Pa). Further reduction in [Formula: see text] to 55 mmHg resulted in a reduction in air-breathing frequency and depression of the metabolic rate. During exposure to acidic water (pH 2.8, [Formula: see text] = 155 mmHg), air-breathing frequency was 28 breaths/h, and during exposure to hydrogen sulphide in water buffered to pH 5.6 (700 μM, [Formula: see text] = 155 mmHg), air-breathing frequency was 40 breaths/h. In fish denied access to air, 200 μM hydrogen sulphide is lethal. Thus, in the armoured catfish, air breathing may be more important for surviving in hydrogen sulphide rich and acidic waters than for surviving in mild hypoxia.
Black flies (Diptera: Simuliidae) of the Marquesas Islands, French Polynesia: redescriptions and new species
Authors: Craig D. A. , Fossati O. , Séchan Y.
Published: January 2008

All stages of Simulium buissoni Roubaud, 1906 are redescribed. Larvae, pupae, and males of S. gallinum Edwards, 1932 are associated with the female holotype and all are fully described. Simulium adamsoni Edwards, 1932, the males of which have enlarged cerci, gonocoxae fused medially, and an enlarged keel-like ventral plate, is similarly redescribed. The female holotype and two paratypes of S. mumfordi Edwards, 1932 are fully redescribed. Males and females of S. hukaense Séchan, 1983 are associated with the pupae and larvae and described. Since all type material of this species is lost, a neotype is designated. Simulium uaense Séchan, 1983 is briefly mentioned. Three new species are described: S. pichoni Craig, Fossati, and Séchan, S. rivierei Craig, Fossati, and Séchan, and S. sechani Craig and Fossati. Brief comments are made concerning the bionomics and the relationships of the species.
The visual pigments of wild white sturgeon (Acipenser transmontanus)
Authors: Sillman A. J. , Sorsky M. E. , Loew E. R.
Published: January 2008

The visual pigments of the anadromous white sturgeon (Acipenser transmontanus) taken from relatively saline estuarine water were characterized by means of in situ microspectrophotometry and partial bleaching analysis of a digitonin extract. The three cone pigments (λmax = 605, 539, and ca. 460 nm) and one rod pigment (λmax = 541 nm) of the wild sturgeon are the same as those of cultured sturgeon that spend their entire lives in fresh water. All the visual pigments incorporate a chromophore based on vitamin A2. Unlike other anadromous fishes during the "saline phase," the white sturgeon shows no evidence of the presence of any vitamin A1 based visual pigment in the retina.
Denervation and concomitant amputation of advanced forelimb regenerative outgrowths in adult Xenopus laevis
Authors: Liversage Richard A. , Tsilfidis Catherine
Published: January 2008

The current investigation was undertaken to determine whether year-old regenerative outgrowths of adult Xenopus laevis respond to forelimb denervation and concomitant amputation through the distal one-third of the regenerate in the same manner as younger regenerates of postmetamorphic X. laevis froglets. Following limb amputation, our innervated and sham-denervated adult frogs regenerated typical spike-like outgrowths by 63 weeks. However, denervation of 60-week-old regenerates and denervation concomitant with amputation through the regenerative outgrowths of the mature frogs in series III and VI, respectively, resulted in no significant regression (resorption) or further growth of the regenerates 3 weeks later. Therefore, 60-week-old experimental regenerates can be considered mature appendages, as they maintained morphological stability for an additional 3 weeks in the absence of innervation. Our results are in contrast with the regression of regenerate tissues previously reported in delayed-denervated younger forelimb regenerates, as well as concomitantly denervated and amputated regenerates of X. laevis froglets.
Patch occupancy and dispersal of spruce grouse on the edge of its range in Maine
Authors: Whitcomb Scott D. , Servello Frederick A. , O'connell Jr. Allan F.
Published: January 2008

We surveyed 18 habitat patches (black spruce (Picea marinana) – tamarack (Larix larcina) wetlands) for spruce grouse (Dendragapus canadensis canadensis) on Mount Desert Island, Maine, during April–May in 1992 and 1993 to determine patch occupancy relative to patch area. We also equipped nine juvenile grouse with radio transmitters to determine movement and habitat use outside of patches during autumn dispersal. The 2 large patches (77 and 269 ha), 5 of 6 medium-sized (11–26 ha) patches and 1 of 10 small (4–8 ha) patches were occupied. Spruce grouse occupied smaller habitat patches than previously reported and occupied patches were closer (P < 0.05) to the nearest occupied patch ([Formula: see text] = 1.2 km) than were unoccupied patches ([Formula: see text] = 2.5 km). Eight of nine juvenile grouse left their natal habitat patch during autumn dispersal and net dispersal distance ([Formula: see text] = 2.3 km) was greater than that reported for grouse in areas with more contiguous habitat. Dispersing juveniles used all major forest types and 33% of relocations were in deciduous forest. Thus, deciduous forest was not an absolute dispersal barrier.
The unique intertidal subterranean habitat and filtering system of a limpet-like brachiopod, Discinisca sparselineata
Authors: Kato Makoto
Published: January 2008

Living limpet-like brachiopods, Discinisca sparselineata (Inarticulate), were found in a unique intertidal subterranean habitat in the Seto Inland Sea, Japan. They were attached beneath boulders that were deeply buried in coarse sand in the middle intertidal zone, and were accompanied by a characteristic sessile epifauna. The habitat was protected from ultraviolet light, desiccation, turbidity, physical turbulence by harsh waves, disturbance by rock-scraping epiphyte-grazers, and from predation by carnivorous snails, seastars, and fishes. The filter-feeding mechanism is unusual in that water enters the mantle cavity frontally and exits laterally through lateral filaments and dorsally through ventrally directed spires as in D. strigata, which is distributed on the Pacific coast of Central America. However, D. sparselineata inhabits more protected habitats and has less capacity for spatial competition than D. strigata.
Lack of specialization in trophic morphology between genetically differentiated dwarf and normal forms of lake whitefish (Coregonus clupeaformisMitchill) in Lac de l'Est, Quebec
Authors: Chouinard Angelo , Pigeon Dany , Bernatchez Louis
Published: January 2008

We recently observed a bimodal distribution in size of sexually maturing lake whitefish (Coregonus clupeaformis Mitchill) in Lac de L'Est, Quebec. The objective of this study was to test the hypothesis that these two spawning size classes represent genetically distinct ecotypes, potentially adapted in morphology for occupying different trophic niches. This was accomplished by quantifying the extent of genetic (mitochondrial DNA (mtDNA) and enzyme loci) and morphological differences. Significant differences in haplotype and allele frequency distributions confirmed the hypothesis that whitefish maturing at small (dwarf) and normal sizes are structured into two distinct gene pools. However, low Fstvalues at mtDNA and enzyme loci, coupled with the apparent lack of spatial and temporal spawning segregation, suggest that reproductive isolation is incomplete and that gene flow is still occurring between the two forms. Patterns of mtDNA diversity favoured the origin of genetically distinct dwarf and normal-size lake whitefish forms in Lac de l'Est through sympatric divergence. However, a lack of differences in morphological traits potentially related to trophic ecology did not support the hypothesis that the two forms represent ecotypes which are morphologically specialized in trophic niches. This study established that sympatric dwarf and normal-size spawning groups of lake whitefish in Lac de l'Est represent two genetically distinct populations despite the potential for gene flow between them. This, coupled with their low level of morphological diversification, suggests that they represent an early stage of population divergence, and therefore makes them of particular interest for understanding the gene–environment processes involved in the early steps of speciation events.