bluuebunny/crossref_metadata_2025 huggingface dataset:
Dolomitization of the Lower Ordovician Aguathuna Formation carbonates, Port au Port Peninsula, western Newfoundland, Canada: implications for a hydrocarbon reservoir
Authors: Azmy Karem , Lavoie Denis , Knight Ian , Chi Guoxiang
Published: August 2008

The Lower Ordovician Aguathuna Formation (∼100 m thick) is formed of shallow-marine carbonates, which constitute the uppermost part of the St. George Group of western Newfoundland. Sedimentation was paused by a major subaerial exposure (St. George Unconformity), which likely developed a significant pore system in the underlying carbonates by meteoric dissolution. The sequence has been affected by multiphase dolomitization that caused complex changes in the rock porosity. The Aguathuna dolomites are classified into three main generations ranging in crystal size between ∼4 µm and 2 mm. The occurrence of fabric-retentive dolomicrites implies that dolomitization likely started during the early stages of diagenesis. Although dolomitization is pervasive in the upper part of the formation and significantly occludes the pores, some intervals in the lower part have higher porosity. The development of lower permeable layers overlain by an impermeable (seal) cap suggests a possible potential diagenetic trap. Unlike sabkha deposits, the Aguathuna carbonates do not have evaporite interlayers. Furthermore, the low Sr contents (∼96 ppm) and the δ18O values of earlier dolomites (–3.3‰ to –6.9‰ VPDB (Vienna Pee Dee Belemnite)) are also difficult to reconcile with a brine origin. The Sr/Ca molar ratios (0.0067–0.0009), calculated for the earliest dolomitizing fluid, suggest a modified seawater origin, likely mixed sea and meteoric waters. The least radiogenic 87Sr/86Sr values of the earliest dolomite are consistent with those of early Ordovician seawater, which supports an early-stage diagenesis. Petrography, geochemistry, and fluid inclusions of the late dolomites suggest precipitation at higher temperatures (∼73–95 °C) in deeper burial environments from hydrothermal solutions.
Classification of the Late Cambrian (Steptoean) trilobite genera Cheilocephalus Berkey, 1898 and Oligometopus Resser, 1936 from Laurentia
Authors: Westrop Stephen R. , Eoff Jennifer D. , Ng Tin-Wai , Dengler Alyce A. , Adrain Jonathan M.
Published: August 2008

All recent work has assigned the genera Cheilocephalus Berkey, 1898 and Oligometopus Resser, 1936 to the family Cheilocephalidae Shaw, 1956, a small group of largely Laurentian trilobites from the Late Cambrian Steptoean Stage. New data from Nevada and Newfoundland indicate that the Cheilocephalidae is polyphyletic and that Cheilocephalus and Oligometopus are allied with different superfamilies. The Cheilocephalidae, which includes Cheilocephalus and Pseudokingstonia Palmer, 1965, is assigned to the Dameselloidea Kobayashi, 1935, and a pygidium from the Cow Head Group of Newfoundland indicates that Cheilocephalus first appears in the late Marjuman. The Dameselloidea disappeared on other continents at an extinction interval at the end of the Marjuman, but Cheilocephalus survived and underwent modest diversification in Laurentia in the succeeding Steptoean Stage. Oligometopus is transferred to the leiostegioidean family Leiostegiidae Bradley, 1925. The genus shows closest affinities with such Gondwanan genera as Idamea Whitehouse, 1939, and its appearance in mid-Steptoean strata records immigration of the Leiostegoidea into shelf-margin environments of Laurentia.
Mercury Uptake by Lake Trout, Salvelinus namaycush, Relative to Age, Growth, and Diet in Tadenac Lake with Comparative Data from Other PreCambrian Shield Lakes
Authors: MacCrimmon Hugh R. , Wren Christopher D. , Gots Barra L.
Published: August 2008

Lake trout, Salvelinus namaycush, released into Tadenac Lake as juveniles, show a pronounced acceleration in growth rate, following a change in diet from benthic invertebrates to rainbow smelt, Osmerus mordax, beginning at age 6 (> 30 cm). An abrupt increase in the rate of mercury accumulation in white muscle of these fish occurs at the same time. Mercury levels in lake trout ([Formula: see text] = 0.24–3.44 μg/g) and coresident smelt ([Formula: see text] = 0.06–0.48 μg/g) from Tadenac and eight neighboring lakes reveal maximum levels reaching 10.0 and 0.84 μg/g, respectively. Mercury levels in lake trout from Tadenac Lake, an undisturbed PreCambrian Shield ecosystem without detected indigenous sources, exceed the "safe" level (0.5 μg/g) at sexual maturity and at a size less than generally acceptable for human utilization. Mercury accumulation by the trout is correlated with length (r = 0.92) in each lake population examined, but substantial among-lake differences occur in fish of comparable ages. As the growth rates are similar in various waters, differences in extent of mercury accumulation is attributed to differences in mercury availability among lakes. In view of a strong correlation (r = 0.96) between mercury levels in smelt and trout calculated at standardized length, it is proposed that the smelt is an appropriate indicator species for the ranking of cold-water lakes relative to the availability of mercury for uptake by lake trout and other living aquatic organisms.Key words: mercury uptake, lake trout, rainbow smelt, growth rate, diet
Predicting the Movements of Juvenile Atlantic Herring (Clupea harengus harengus) in the SW Bay of Fundy Using Computer Simulation Techniques
Authors: Jovellanos Cesario L. , Gaskin David E.
Published: August 2008

A simulation model of Atlantic herring (Clupea harengus harengus) locomotion was used to predict the movements and distribution of 2-yr-old juveniles during the summer within the Quoddy region of the southwestern Bay of Fundy. The model assumed herring (i) swim at speeds of 1–2 body lengths per second, (ii) exhibit positive rheotaxis, and (iii) display cross-current movements whose frequency varies inversely with the speed of the current. Independent sets of simulated fish schools were introduced into a computer model of the study area at two sites (Letete approaches, Head Harbor approaches) and tide phases (slack low water, slack high water). Only those simulated schools entering through the Letete approaches at slack low water yielded the spatial pattern showing significant concordance with catch-by-weir records, acoustic survey data, and the distribution of foraging flocks of common terns (Sterna hirundo). The simulation indicated high mortality due to the weir fishery and the possibility of size-segregation in Quoddy herring.Key words: acoustics, Bay of Fundy, distribution, herring, locomotion, model, movements, Quoddy region, simulation, weir fishery
Optimal Fisheries Investment: Comparative Dynamics for a Deterministic Seasonal Fishery
Authors: Charles Anthony T.
Published: August 2008

A dynamic fisheries model is developed to simultaneously optimize investment in the resource stock (the fish) and investment in the capital stock (the fleet). Each of these investment problems faces a major complication; investment in the resource is constrained by the natural population dynamics, while investment in the physical capital stock tends to be irreversible because capital used in natural resource industries is often nonmalleable. The model assumes a seasonal fishery in which annual escapement and capital investment levels can be controlled. A dynamic programming approach is used to analyze the model heuristically and numerically. The comparative dynamics of optimal investment strategies are studied, with regard to (i) delays in investment, (ii) population dynamics parameters, (iii) fish price, (iv) capital cost, (v) depreciation rate, and (vi) discount rate. In particular, the depreciation rate and the ratio of unit capital costs to unit operating costs play interesting and complex roles in determining optimal investment levels.
Production of Juvenile Atlantic Salmon (Salmo salar) in Two Acidic Rivers of Nova Scotia
Authors: Lacroix Gilles L.
Published: August 2008

Densities, growth, and production of juvenile Atlantic salmon (Salmo salar) were estimated at sites in two acidic rivers of different pH, the Westfield and North rivers, in Nova Scotia, Canada, from 1982 to 1984. Annual production was significantly lower in the more acidic Westfield River (< 0.4 g∙m−2∙yr−1 at pH 4.7–5.4) than in the North River (1.4 g∙m−2∙yr−1 at pH 5.6–6.3). Low production rates in the more acidic river were attributable to the lower densities and poorer survival of juveniles at the lower pH levels. Low densities of parr in the more acidic river were a function of the high initial mortality of postemergent fry, and the mortality of parr during periods of pH minima such as over winter. Marking and recapture information and trapping at a weir for counting migrating fishes indicated that there was little emigration of parr other than in the spring when some movements occurred preceding and during smoltification. Average potential yield of 2-yr smolts was 0.8 smolt/100 m2 in the Westfield River and in the range of 2.7–6.6 smolts/100 m2 at higher pH levels in the North River. Growth was not limiting to production at the lower pH levels. After the first winter, 1-yr-old parr were much larger at the lower pH than they were at less acidic pH levels, the faster growth possibly resulting from the lower density of parr at the lowest pH. A temperature-related biphasic growth of 1-yr-old parr with periods of maximum growth in spring and autumn was recorded. Reduced production, a result of deleterious effects of low pH on survival and density in the Westfield River was probably sufficient to prevent the continued maintenance of a naturally produced salmon population in that river, whereas production at higher pH levels in the North River was comparable to that in near-neutral waters of other areas.
Food supplementation experiments with terrestrial vertebrates: patterns, problems, and the future
Authors: Boutin Stan
Published: August 2008

I reviewed 138 cases in which terrestrial vertebrates received supplemental food under field conditions. These cases are strongly biased toward small-bodied herbivores in north temperate environments. Most studies address population level questions and have supplied food over a short term (< 1 year) and on a small spatial scale (to less than 50 individuals). Individuals receiving supplemental food usually had smaller home ranges, higher body weights, and advanced breeding relative to those on control areas. The typical population response to food supplementation was two- to three-fold increase in density, but no change in the pattern of population dynamics. In particular, food addition did not prevent major declines in fluctuating populations. Researchers have failed to examine behaviour of individuals under conditions of supplemental food when addressing questions of population regulation. This review points to the need for researchers to conduct food supplementation experiments in tropical environments, on a larger scale, and over longer periods of time.
Blood rheology of captive and free-ranging northern elephant seals and sea otters
Authors: Wickham L. L. , Costa D. P. , Elsner R.
Published: August 2008

Hematologic and rheologie characteristics of blood from captive and free-ranging sea otters, Enhydra lutris, and northern elephant seals, Mirounga angustirostris, were studied to evaluate short- and long-term responses to captivity. Red blood cell counts, white blood cell counts, hemoglobin concentrations, hematocrits, total plasma proteins, and mean corpuscular volume measurements were made on anticoagulated venous blood samples. Mean corpuscular hemoglobin concentrations were calculated. Viscosity measurements were made at shear rates from 11.5 to 230.4 s−1 on a Wells–Brookfield cone-plate viscometer. A capillary viscometer (radius, 500 μm) provided additional viscometric measurements. Comparisons of hematologic and rheologic data revealed only minor differences between captive and free-ranging seals and sea otters. Although hematologic variables were within the ranges reported in earlier wild vs. captive studies of these species, no evidence of short- (3 weeks) or long-term (> 6 months) acclimatization to captive exposure was found in the hemorheology of these marine mammals.
Fine structure of the pecten oculi of the mallard (Anas platyrhynchos)
Authors: Braekevelt Charlie R.
Published: August 2008

The pecten oculi of the mallard duck (Anas platyrhynchos) has been examined by light and electron microscopy. In this species, the pecten is of the pleated type and 12–14 accordion folds are joined apically by a heavily pigmented bridge of tissue which holds the pecten in a fanlike shape, widest at the base. It is situated over the optic nerve head and extends out into the vitreous. The entire pecten is enclosed by a fine basal lamina and hyalocytes are often present on its outer surface. Within each fold are numerous capillaries, larger blood vessels, and melanocytes. The capillaries are surrounded by thick fibrillar basal laminae which often contain pericytes. These capillaries display extensive microfolds on both the luminal and abluminal borders. The endothelial cell bodies are extremely thin, with most organelles present in a paranuclear location. The melanocytes, which are most plentiful in the bridge region, form an incomplete sheath around the capillaries and other blood vessels. The morphology of the pecten in the mallard is indicative of a heavy involvement in the transport of materials.
Correlations between pituitary and testis in sexually maturing male rainbow trout, Oncorhynchus mykiss, during spermatogenesis
Authors: Ruby Sylvia M. , Bryant Simon
Published: August 2008

Histological changes in the pituitary of sexually maturing male rainbow trout, Oncorhynchus mykiss, were correlated with spermatogenesis in the testes. Granular basophils in the pituitary appeared simultaneously with the development of spermatogonial cysts in the testis. There was no histological evidence that basophils released their granules during spermatogonial cyst formation. A coefficient of correlation was calculated to test the interaction between the numbers of granular basophils and cysts of spermatogonia. The correlation was not significant. These findings suggest that granules from pituitary basophils do not play a significant role in the development of spermatogonial cysts. Histological sections revealed that basophils degranulated rapidly with the appearance of cysts of spermatocytes. A significant correlation (r = −96) between basophils and cysts of spermatocytes occurred when the interaction between these two variables was tested. The negative correlation indicated that pituitary basophils decreased in number as cysts of spermatocytes in the testes increased. These findings provide support for the hypothesis that basophils may play a significant role in the development of spermatocyte cysts in rainbow trout testes. A second nongranular basophil observed in the pituitaries of fish in this study had no apparent correlation with any of the stages of spermatogenesis. While previous investigators have reported the appearance of granular basophils in the pituitary concurrent with the process of spermatogenesis, this marks the first study that compares histological changes in the testis directly with those in the pituitary in sexually maturing rainbow trout. In addition, it reports for the first time a significant correlation between basophils and a specific stage in the cycle of spermatogenesis.
Effect of externally applied bunker fuel on body mass and temperature, plasma concentration, and water flux of Glaucous-winged Gulls, Larus glaucescens
Authors: Hughes Maryanne R. , Kasserra Claudia , Thomas Barbara R.
Published: August 2008

The effects of externally applied bunker fuel on food intake, body mass, water flux, body temperature, and plasma concentration were determined in 5-month-old Glaucous-winged Gulls, Larus glaucescens. Food intake, body mass, water flux, body temperature, plasma sodium, and chloride concentrations were lower (P < 0.001) in gulls coated with bunker fuel for 4–5 days than in unoiled gulls. Plasma potassium concentration was transiently increased on day 2 in unoiled, oiled, and sham-oiled gulls (P < 0.01). Water flux was not affected by sham oiling but was significantly (P < 0.001) lowered by application of bunker fuel oil to the feathers and by washing with detergent.
Étude comparative de la membrane coquillère chez les souches ovipare et vivipare du lézard Lacerta vivipara
Authors: Heulin Benoît
Published: August 2008

Evolution of viviparity in reptiles has resulted in more or less complete regression of the eggshell membrane. Such a regression has been studied in a lizard, Lacerta vivipara, which has both oviparous and viviparous populations. In oviparous reproduction, eggs laid have parchmentlike eggshells with a mean thickness of 36 μm. These eggshell membranes are composed of fibrils and of calcite, which is distributed over the outer surface and in the interfibrillar matrix. In viviparous reproduction, a transparent eggshell membrane remains between the embryonic and maternal tissues throughout pregnancy. This membrane consists mainly of fibrils and has only minor traces of calcite. Its mean thickness is only 9 μm. Reduction of thickness and of calcification is thought to be an adaptation that allows better respiratory exchanges at the end of pregnancy, when embryos require more oxygen. The author emphasizes that species with bimodality of reproduction (oviparity and viviparity) are of considerable interest in research investigating the evolution of viviparity in reptiles.
Effects of body size, sibship, and tail injury on the susceptibility of tadpoles to dragonfly predation
Authors: Semlitsch Raymond D.
Published: August 2008

The effect of tadpole body size, sibship, and tail injury on the survival of treefrog tadpoles (Hyla chrysoscelis) in the presence of dragonfly larvae (Tramea lacerata) was examined in a three-way factorial experiment. Tadpole body size had a dramatic effect on survival; large tadpoles had higher survival than medium-sized or small tadpoles. The presence of tail injury simulating an unsuccessful predation attempt significantly reduced survival. Survival of control tadpoles without tail injury in the presence of a predator was almost twice as high as that of tadpoles with 75% tail loss. Tadpole sibship had no effect on survival and indicated that genetic differences in antipredator behavior or production of alarm substances and allelochemicals, independent of body size, were not apparent. There were no significant interactions between tail injury and body size or tail injury and sibship. These results indicate that increasing body size is an effective mechanism for reducing predation and that injury from an unsuccessful predation attempt reduces subsequent survival by increasing the risk of future predation.
Distribution and morphological variation of the slimy sculpin (Cottus cognatus) in the north central United States
Authors: Lyons John
Published: August 2008

Slimy sculpins (Cottus cognatus) in the north central United States are found primarily in three areas: Lake Superior and its tributaries, Lake Michigan, and small cold streams in the "Driftless Area" of southwestern Wisconsin, northeastern Iowa, and southeastern Minnesota. In the region between the Driftless Area and the Great Lakes, populations exist only in a few small streams and two small deep lakes, Trout and Big Green. Slimy sculpins from the north central United States display extensive within-population morphological variation. Males and females appear to differ in morphometry (shape) but not in meristics. Patterns of morphological variation among populations have little correspondence to patterns from other parts of the species' range, and do not match predictions based on the likely degree of reproductive isolation among populations. Some morphometric differences are evident among populations in different habitats, primarily because of the distinctiveness of slimy sculpins from Trout and Big Green lakes. Slight clinal differences exist in meristic variables from Great Lakes to Driftless Area populations, although Big Green Lake deviates from the cline. Hybridization with the mottled sculpin (C. bairdi) may contribute to morphological variation within some populations.
Retinometra albeolae n.sp. (Cestoda: Hymenolepididae) from the bufflehead duck, Bucephala albeola L.
Authors: Ewart Michael J. , McLaughlin J. Daniel
Published: August 2008

Retinometra albeolae n.sp. is described from bufflehead ducks (Bucephala albeola L.) from Manitoba, Canada. It is armed with eight skrjabinoid rostellar hooks 69–75 μm long, and has a cirrus sac 240–480 μm long that extends to approximately the midline of mature proglottids, a trilobed ovary, and a lobed vitelline gland. Staphylepis indica and Staphylepis meggitti, currently included in the genus Retinometra, are returned to Staphylepis on the basis of proglottid morphology and the apparent lack of a cirrus stylet in both species.
Découverte d'une nouvelle espèce du genre Ptilocrinus (Échinodermes, Crinoïdes pédonculés) au large de Terre-Neuve
Authors: Roux Michel
Published: August 2008

Ptilocrinus atlanticus sp. nov. belongs to the family Hyocrinidae (Echinodermata, stalked Crinoidea). That new species is the first record of the genus Ptilocrinus in the Atlantic Ocean. Skeletal organization of the arms suggests that it has a taxonomic place halfway between the genus Ptilocrinus (especially Ptilocrinus pinnatus from N.-E. Pacific) and the genus Anachalypsicrinus, only recorded from N.-E. Atlantic. Such a discovery confirms the phylogenic affinities between large hyocrinids of the eastern Pacific and those of the northern Atlantic. Geographic isolation of these two deep-sea provinces since the Uppermost Cretaceous took place after the differentiation of the two genera Ptilocrinus and Anachalypsicrinus.
Patterns of geographic variation in the skull of Nearctic Ermine (Mustela erminea)
Authors: Eger Judith L.
Published: August 2008

A. H. Macpherson suggested that much of the current geographic diversity in species and species groups of arctic mammals resulted from isolation in glacial refugia during the Wisconsin glacial stage. The present study evaluates this refugium hypothesis using a statistical assessment of geographic variation in 13 craniometric characters of Nearctic Mustela erminea. There is significant geographic variation among samples of North American ermine. Most of the skull character variance in this species reflects differences in size and is clinal. Variation in skull size is better explained by temperature and precipitation variables than by geographic distance, suggesting that environmentally ordered selection for size has been superimposed on any size differentiation that occurred during isolation in refugia. Variation in skull shape shows a relatively low correlation with climatic variables, and partitioning tests on shape variation reveal discontinuities consistent with the refugium hypothesis. Distinctive groups of samples reflect possible refugial populations in Eastern Beringia, in periglacial refugia south of the Wisconsin ice in eastern North America, and in one or more western North American refugia.
Distribution patterns of vertebrate and invertebrate planktivores in Newfoundland lakes with evidence of predator–prey and competitive interactions
Authors: Campbell Christine E. , Knoechel Roy
Published: August 2008

The vertebrate Gasterosteus aculeatus, the threespine stickleback, and the invertebrates Chaoborus punctipennis, Chaoborus trivittatus, and Leptodora kindtii are the major predators of zooplankton in lakes on the Avalon Peninsula, Newfoundland. Predator–prey and competitive interactions among these planktivores are potentially strong. Low faunal diversity in the lakes limits the number of interacting species, which may increase the intensity of the interactions, while the low habitat heterogeneity of the lakes decreases the probability of spatial separation of species to increase rates of species encounters. Analyses of distributional patterns (presence or absence data) of the planktivores in 15 Avalon lakes indicated that the distributions of both Chaoborus spp. were significantly and negatively related to the distribution of sticklebacks. Chaoborus densities were significantly higher in the lakes without sticklebacks. Sticklebacks were observed to eat third and fourth instars of both Chaoborus species in laboratory experiments and hence, through predation, may be able to exclude these species from some lakes. There was no significant relationship between the distributions of Leptodora and sticklebacks or between Leptodora and C. punctipennis, however the distributions of Leptodora and C. trivittatus were significantly and negatively related, indicating a possible competitive interaction. Environmental factors also influence planktivore distribution and abundance: a principal components factor derived from planktivore density data was significantly correlated with cyclopoid copepod biomass, lake SO4 levels, and lake surface area (multiple linear regression, r2 = 0.71).
Killer whales (Orcinus orca) attack and kill a Bryde's whale (Balaenoptera edeni)
Authors: Silber Gregory K. , Newcomer Michael W. , M. Héctor Pérez-Cortés
Published: August 2008

On 3 May 1988, we observed a group of killer whales that pursued, killed, and partially consumed a Bryde's whale in the northern Gulf of California, Mexico (31°01′N, 114°15′W). The attack was observed from 06:54 to 08:53 while circling in a single-engine aircraft at an altitude of 160 m. The group comprised about 15 killer whales, including two adult males and at least two calves. Females and (or) subadult males pressed the attack most intently. The killer whales tore skin and blubber from the right flank of the Bryde's whale, and on 11 occasions the killer whales swam onto the head or back of the Bryde's whale, which hindered its breathing. The respiration intervals of the Bryde's whale were short and irregular, and blow rates differed significantly from those of undisturbed Bryde's whales. Fatiguing the whale may have facilitated an easier kill by asphyxiation. After the death of the Bryde's whale, the two adult male killer whales surfaced slowly about 200–300 m away from the remainder of the group, which presumably fed on the submerged Bryde's whale carcass. Two days later, the drifting Bryde's whale carcass was located. A large wound was visible on the abdomen, and sections of the lower jaw had been removed. Like those of canids and some felids that hunt cooperatively when preying on ungulates, attacks by Orcinus orca exhibit coordination of activities and efficiency in dispatching prey.
Digestive and metabolic efficiencies of grizzly and black bears
Authors: Pritchard Geoffrey T. , Robbins Charles T.
Published: August 2008

Digestive and metabolic efficiencies of black bears (Ursus americanus) and grizzly bears (Ursus arctos) were determined in 7-day total collection trials using seven single foods and four mixed diets. No significant interspecific differences in digestive or metabolic efficiencies were observed. Dry matter and energy digestibilities were inversely related to the dietary fiber content, whereas digestible protein was directly correlated with dietary protein content. Mean retention time for hair in a meat diet was 13 h, whereas the retention time for clover was 7 h and did not differ between species. Giant pandas (Ailuropoda melanoleuca), grizzly bears, and black bears appear to have very similar digestive efficiencies and passage rates. The relationships between diet composition and digestive efficiency can be used to begin evaluating the nutritional quality of diets consumed by free-ranging bears.
Divergence and speciation as viewed from an insect hybrid zone
Authors: Hewitt Godfrey M.
Published: August 2008

Hybridism is examined both from Darwin's point of view and in light of current views on the species concept. It seems that many of the relevant concepts of population genetics and speciation are inherent in primitive molecular evolution and may be useful in explaining divergent evolution from the earliest life forms. When divergent genomes meet they may hybridize and, in many cases, form a hybrid zone. Work on insect hybrid zones is used to exemplify the factors and processes involved. Many such zones are the result of postglacial secondary contact and involve some form of hybrid unfitness. They usually comprise multigenic differences and each gene may have different properties. Two grasshoppers, Podisma pedestris and Chorthippus parallelus, are used as case studies. In the case of P. pedestris, as a result of vegetation analysis, it is possible to be fairly sure that the zone is not environmentally determined but rather the result of heterozygous disadvantage at many loci. In the other species, in which two divergent mate recognition systems meet, there is no evidence of their reinforcement toward speciation, despite the F1 hybrids showing severe testis dysfunction and providing another example of Haldane's rule. A scenario for the postglacial contact and hybridization is proferred in an attempt to explain differences between disjunct sections of the zone. It is argued that gene flow occurs over only very small distances in hybrid zones and that the zones themselves will not move far because they fall in low density traps. Compound hybrid zones may be formed by cycles of range contraction and expansion and the substructure of a species will be determined by its life style. Hybrid zones provide a demonstration that divergence occurs in various characters at different rates and divergence brings with it hybrid disadvantage and frequency dependence. Speciation is seen as some way down this path, but occasional transfers of genetic material may still occur.
Definition of a new genus of glossiphoniid leech and a redescription of the type species, Clepsine picta Verrill, 1872
Authors: Barta John R. , Sawyer Roy T.
Published: August 2008

A new genus, Desserobdella, is described to accommodate the leech Clepsine picta Verrill, 1872 which feeds exclusively on amphibians of northern and central North America. This leech belongs to the subfamily Glossiphoniinae and therefore deposits cocoons directly onto the substrate. The genus Desserobdella n.gen. has the following diagnostic characteristics: (i) two pairs of coalesced eyes; (ii) one pair of diffuse salivary glands; and (iii) a single pair of saccular mycetomes containing prokaryotic endosymbionts. Members of the new genus are distinguished from species of the closely related genus Placobdella Blanchard, 1893 on the basis of their salivary gland structure; Placobdella species have two pairs of compact salivary glands versus the single pair of diffuse salivary glands of the genus Desserobdella n.gen. Congenitors of the new genus are Desserobdella cryptobranchii (Johnson and Klemm, 1977) n.comb., Desserobdella michiganensis (Sawyer, 1972) n.comb., and Desserobdella phalera (Graf, 1899) Jones and Woo, 1990. Desserobdella picta n.gen. et comb. exhibited a stereotypical sequence of feeding behaviours on Rana catesbeiana tadpoles which involved picking at the site of proboscis insertion prior to probing, probing, and finally blood-feeding with the posterior sucker released.
Gastropod intermediate hosts of lungworms (Nematoda: Protostrongylidae) on a bighorn sheep winter range: aspects of transmission
Authors: Robb L. A. , Samuel W. M.
Published: August 2008

A study of the gastropod intermediate hosts of the lungworms Protostrongylus stilesi and Protostrongylus rushi was conducted on a bighorn sheep (Ovis canadensis canadensis) winter range in southwestern Alberta, 1984–1985. Over 7000 gastropods were examined. Seven gastropod species were infected with Protostrongylus-type larvae: the predominant intermediate hosts were Euconulus fulvus (6.8% infected), Vertigo gouldi (5.6%), and Vertigo modesta (3.2%). Prevalence of third-stage (infective) larvae was highest in September and April, coinciding with use of the winter range by bighorn sheep. An index of lungworm availability to sheep was highest in autumn in the margins of aspen copses and in spring in the grassy openings. Copses were used extensively by sheep in autumn, and open areas were used in the spring. Presence of a mule deer (Odocoileus h. hemionus) lungworm, Orthostrongylus macrotis, was an inherent problem.
Étude morphofonctionnelle comparative des structures osseuses impliquées dans le fouissage d'Arvicola terrestris scherman (Rodentia, Arvicolidae)
Authors: Laville Élisabeth
Published: August 2008

An analysis of Arvicola terrestris scherman burrowing cinetics was used to draw a functional interpretation of its morphology. This morphofunctional study was conducted using a comparative series of rodents that show a range of affinity to subterranean biotopes. This analysis revealed functional equivalences, which are not necessarily homologies, with other burrowers: great resistance moments of cervical vertebrae, more anterior cranial insertion of the temporalis muscle, etc. Comparison with other Arvicolidae shows the morphofunctional predisposition of the family to use the head in burrowing. However, A. t. scherman is distinguishable from its congeners by discrete adaptations, which may be the result of morphogenetic remodelling.
Tannage quinonique de la capsule ovigère de la Roussette Scyliorhinus canicula (Linné)
Authors: Rusaouën-Innocent Marguerite
Published: August 2008

Histochemical and histoenzymological investigations performed on sections of the capsule wall have led to the localisation of the substances involved in the process of quinone tanning. Ultrastructural autoradiography and cytochemical and cytoenzymological techniques applied to the nidamental gland have helped to clarify previous histochemical results and to establish a link between gland secretions and the different capsule layers; a hypothesis concerning the capsule secretion process and its hardening is presented.
Reproductive effort of male northern elephant seals: estimates from mass loss
Authors: Deutsch Charles J. , Haley Michael P. , Le Boeuf Burney J.
Published: August 2008

The energetic component of reproductive effort of male northern elephant seals, Mirounga angustirostris, was estimated from mass loss over the breeding season and correlated with dominance rank and age. Fifty-four unrestrained bulls were weighed on a platform scale by luring them with a model of a female seal or moving them with a tarpaulin and using playback of male aggressive vocalizations. Adult males weighed up to 2300 kg upon arrival at the breeding rookery. Mean rate of mass loss during the breeding season was 7.1 ± 1.5 (SD) and 4.6 ± 0.8 kg per day for 17 adults and 13 subadults, respectively. Rate of mass loss was positively correlated with body size (mass or length) for both age-classes. Mass-specific rate of mass loss did not differ between age-classes but increased with increasing dominance rank among adult males. Reproductive effort, expressed as percentage of body mass lost over the 3-month breeding season, was greater for high-ranking bulls (mean 41.4%) than for low-ranking adults (33.8%), but was not related to age-class or body size. High-ranking males experienced higher mating success and expended more energy than subordinate males. Comparison with a previous study on conspecific females indicates that mass-specific energetic investment in reproduction is similar for both sexes, despite marked sex differences in reproductive strategy and duration of effort.
Albionella kabatai sp.nov. (Lernaeopodidae: Siphonostomatoida), a copepod parasite of the spatulasnout cat shark (Apristurus platyrhynchus (Tanaka, 1909) from the Sea of Kumano
Authors: Benz George W. , Izawa Kunihiko
Published: August 2008

Albionella kabatai sp.nov. (Lernaeopodidae: Siphonostomatoida) is described from a single ovigerous female found on a fin of the spatulasnout cat shark (Apristurus platyrhynchus) in the Sea of Kumano (Pacific side of middle Japan). Albionella kabatai sp.nov. is uniquely distinguished from its five congeners by its relatively small caudal rami, each with three relatively long spiniform setae and by its mandibular tooth formula (P1, S1, P1, S1, P1 S1, B3).
Variations de la densité et de la croissance des recrues de l'annélide polychète Nereis virens (Sars) en zone intertidale
Authors: Desrosiers Gaston , Olivier Marc , Vincent Bruno
Published: August 2008

Weekly samples were taken in the intertidal zone at l'Anse à l'Orignal (in the St. Lawrence River estuary) to evaluate changes in density, growth, and mortality of Nereis virens recruits in three different types of sediments. Egg laying, which started on 14 May 1986, lasted 10 days and this spacing out probably explains the staggered arrival of larvae at the three sites. We have studied the increase in the number of segments in field specimens, from the nectochaete stage (3 segments) to the 13-segment stage. Random dispersal takes place in the upper part of the intertidal zone and recruits of N. virens do not seem to prefer any particular type of sediment. All three substrates are relatively rich in organic matter and can provide the abundance of food necessary for the growth of the young recruits. Growth rates are virtually identical in fine sand substrates and in gravelly, silty sands. Concave survivorship curves show that mortality rates are higher among the young stages and that life expectancy increases with age; this type of pattern is very common in species with high fecundity, such as the polychaete N. virens.[Translated by the journal]
Redescription of Lernaeopoda oviformis Shiino, 1956 (Copepoda: Lernaeopodidae), a parasite of the shortspine spurdog (Squalus mitsukurii Jordan and Snyder, 1903), and hitherto covert member of Albionella Kabata, 1979
Authors: Benz George W.
Published: August 2008

Lernaeopoda oviformis Shiino, 1956 (Lernaeopodidae: Siphonostomatoida: Copepoda), a parasite of the shortspine spurdog (Squalus mitsukurii Jordan and Snyder, 1903), is redescribed from the holotype. Based on the presence of a maxilliped claw with one secondary denticle and a first maxilla exopod bearing three setae, the species is transferred to the genus Albionella Kabata, 1979.
The anatomy of the pharynx of two predatory aquatic oligochaetes
Authors: Brinkhurst R. O. , McKey-Fender D.
Published: August 2008

The genera Haplotaxis (Haplotaxidae) and Phagodrilus (Lumbriculidae) have convergent modifications of the pharynx that are adaptations for ingesting prey, especially other oligochaetes. Neither these taxa nor the predatory lumbriculid Agriodrilus (which is not closely related to Phagodrilus within that family) need be considered to be directly related to the leeches or branchiobdellidans simply because of these modifications. The commensal and predatory life style has evolved quite independently in several oligochaetes. Haplotaxis does not have a furrow across the prostomium as previously described. The prostomium consists of a very short bulb on the end of a peristomium, which is elongate dorsally and divided by the first obvious external transverse groove. In the Oligochaeta the peristomium is considered by convention to be segment I, but in the Polychaeta segment numbers begin with the first setiger (regarded as II in Oligochaea). In leeches the prostomium is counted as I.
On the taxonomy of giant sheep (Ovis ammon Linnaeus, 1766)
Authors: Geist Valerius
Published: August 2008

Giant sheep or argalis (Ovis ammon Linnaeus, 1766) were classified into subspecies according to the nuptial coat of large males. Seven subspecies are recognized: nigrimontana, hodgsoni, jubata, darwini, ammon, polii, and karelini; kozlovi is a possible subspecies. The occurrence of dwarf argalis in Mongolia suggests that other subspecies may be described. This review corrects errors in earlier taxonomic studies based on inadequate understanding of seasonal and age-related pelages, invalid taxonomic criteria (morphometry without correction for allometry and the effects of muscular work), body size (without evidence for heritability), geographic location (not part of the specimen, and unverifiable), misunderstandings due to language barriers, and mislabelled or altered specimens and data. A key is included. New insights concerning argali biology emerged.
Effects of saline acclimation and cecal ligation on body water and water flux in male and female Pekin ducks
Authors: Hughes Maryanne R. , Zenteno-Savin Tania , Kojwang David
Published: August 2008

Total body water, mean daily water flux, and plasma ionic and osmotic concentrations were determined in sham-operated and cecally ligated male and female Pekin ducks, Anas platyrhynchos, drinking fresh water and after acclimation to 0.3 M NaCl. Body mass, hematocrit, plasma sodium concentration, and osmolality were unaffected by saline acclimation or cecal ligation. Total body water of ducks acclimated to fresh water was about 63% of body mass and increased to 73% of body mass in all groups acclimated to 0.3 M NaCl except ligated females. Mean daily water flux of male and female ducks acclimated to fresh water was the same and was not affected by cecal ligation. Drinking 0.3 M NaCl increased mean daily water flux by 70% in both sham-operated male (P < 0.05) and female ducks (P < 0.01), and 135% (P < 0.001) in cecally ligated males, but did not affect cecally ligated females. Thus, following saline acclimation, mean daily water flux was greater (P < 0.05) in cecally ligated males than in females.
Design and evaluation of a bottom-closing net used to capture mysids and other suprabenthic fauna
Authors: Lasenby David C. , Sherman R. K.
Published: August 2008

A simple and easily constructed bottom-closing drop net was designed for capturing mysids during the day or at night. During the day, when mysids are epibenthic and (or) suprabenthic and difficult to sample quantitatively, the bottom-closing drop net captures more mysids per unit area than vertical hauls with a plankton net. The net works well on both hard and soft substrates and is useful for obtaining density estimates and delineating population distribution.
Enzyme polymorphism in Glossina longipennis (Diptera: Glossinidae)
Authors: Nesbitt S. A. Tarimo
Published: August 2008

Adult Glossina longipennis Cortie, collected at Nguruman, Kenya, were examined electrophoretically for variation in esterase, octanol dehydrogenase, malate dehydrogenase, manganese-stimulated malate dehydrogenase, arginine Phosphokinase, and hexokinase. Variation was found in the first two enzymes, and the banding patterns indicated that the loci for these enzymes are on autosomes. The mean heterozygosity per locus was 4.5%.
An evaluation of the usefulness of mammalian keratin in systematic analyses
Authors: Jong Constantinus G. van Zyll de , Wright Shelagh A.
Published: August 2008

Hair proteins of 114 species and subspecies representing 10 orders of the class Mammalia were compared after isoelectric focusing and densitometric scanning of the isoelectric focusing gels, to evaluate their usefulness in systematic analyses. Results show that keratin profiles within a species vary very little, but interspecific comparisons at all taxonomic levels show that relationships derived from similarities among keratins are not congruent with currently accepted phylogenetic relationships based on morphological and other characters. This lack of correlation imposes strong limitations on isoelectric focusing of keratins for use in systematic analyses.
Factors affecting wing molt chronology of female mallards
Authors: Leafloor James O. , Ankney C. Davison
Published: August 2008

We manipulated nest success of captive mallards (Anas platyrhynchos) during two breeding seasons to determine the effects of different breeding events on the timing of wing molt initiation in females. We also studied the effect of different social environments during the postbreeding period on female wing molt chronology. Late (renesting) brood hens molted their remiges later than did early brood hens in both years of the study. Unsuccessful nesters showed a late, asynchronous wing molt when they molted solitarily, but an early, synchronous wing molt when they were placed together during the postbreeding period. There was a positive relationship between the last date of incubation and the date of wing molt initiation when birds were placed in a group after the breeding period. Social environment appeared to influence the timing of wing molt, particularly among unsuccessful nesters. We discuss the implications of these results in terms of postbreeding mortality factors and potential fall banding bias.
Melatonin increases the ratio of 5-hydroxyindoleacetic acid to serotonin in the hypothalamus and brainstem concurrently with gonadal involution in male Syrian hamsters
Authors: Vriend J.
Published: August 2008

Gonadal involution, with reduced serum levels of luteinizing hormone and prolactin, was induced in male Syrian hamsters by daily injections of melatonin, given in the evening. Highly significant increases in daytime concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and in the ratio of 5-HIAA to serotonin (5-HT) were noted in extracts of mediobasal hypothalamus of melatonin-treated hamsters. An increase in the 5-HIAA/5-HT ratio, with decreased 5-HT concentrations, was found in brainstem extracts of hamsters treated with melatonin. The increase in the 5-HIAA/5-HT ratio was not prevented by inhibition of catecholamine synthesis with α-methyl-p-tyrosine, which suggests that the melatonin-induced increase in the 5-HIAA/5-HT ratio was not due to changes in catecholamine turnover. These results are consistent with the view that serotonergic neurons terminating in the hypothalamus mediate the melatonin-induced inhibition of luteinizing hormone, prolactin, and thyroid hormones accompanying gonadal involution.
Endogenous activity rhythms in tomcod (Microgadus tomcod) post-yolk-sac larvae
Authors: Massicotte Bernard , Dodson Julian J.
Published: August 2008

Post-yolk-sac tomcod (Microgadus tomcod) larvae were caught in a spawning river. They were held in the laboratory under three different environmental conditions: (i) constant conditions; (ii) exposure to a simulated tidal cycle; and (iii) exposure to simulated tidal and diel cycles. Swimming activity determinations made under constant conditions revealed significant endogenous rhythms in each group. Chronobiological flexibility affected by simulation of the basic cycles of the estuarine habit was demonstrated. Groups of larvae exposed to simulated tidal signals demonstrated modified rhythmic patterns relative to control groups held under constant conditions. Rhythms of groups exposed to both tidal and diel light signals included a low-frequency component in the 20-h region. Examination of the metabolic effects of feeding on endogenous activity patterns revealed lower activity levels when larvae were deprived of food. However, control groups exhibited the same period length whether fed or unfed, and entrained groups did not show consistent trends in period change related to feeding. This is not consistent with the hypothesis that metabolic conflict between digestion and aerobic swimming should modify the period length of endogenous activity rhythms.
Further observations on the sporogony of Eimeria sardinae in the testis of the herring Clupea harengus L.
Authors: Morrison Carol M.
Published: August 2008

Sporocyst formation commences with division of the sporoblast nucleus, after which two sporozoites develop, one at each end of the sporoblast. A thickening beneath the limiting unit membrane of the sporoblast is the first indication of the sporozoite pellicle forming. This subsequently develops into a cone-shaped structure, which becomes the anterior end of the sporozoite as it separates from the sporocyst residuum. The sporozoites elongate as they mature, and the sporocyst residuum, containing amylopectin and refractile granules, becomes smaller. A typical apical complex is present at the blunt anterior end of the sporozoite. A homogeneous area containing paracrystals is present in both the sporoblast and the sporozoite. There are no refractile granules in the sporozoite. The sporocyst wall is thin and contains no mechanism for releasing the sporozoite, such as a Stieda body or suture.