bluuebunny/crossref_metadata_2025 huggingface dataset:
Yersinia pestisIS1541Transposition Provides for Escape from Plague Immunity
Authors: Cornelius Claire A. , Quenee Lauriane E. , Elli Derek , Ciletti Nancy A. , Schneewind Olaf
Published: February 2009

Yersinia pestisis perhaps the most feared infectious agent due to its ability to cause epidemic outbreaks of plague disease in animals and humans with high mortality. Plague infections elicit strong humoral immune responses against the capsular antigen (fraction 1 [F1]) ofY. pestis, and F1-specific antibodies provide protective immunity. Here we asked whetherY. pestisgenerates mutations that enable bacterial escape from protective immunity and isolated a variant with an IS1541insertion incaf1Aencoding the F1 outer membrane usher. Thecaf1A::IS1541insertion prevented assembly of F1 pili and provided escape from plague immunity via F1-specific antibodies without a reduction in virulence in mouse models of bubonic or pneumonic plague. F1-specific antibodies interfere withY. pestistype III transport of effector proteins into host cells, an inhibitory effect that was overcome by thecaf1A::IS1541insertion. These findings suggest a model in which IS1541insertion intocaf1Aprovides for reversible changes in envelope structure, enablingY. pestisto escape from adaptive immune responses and plague immunity.
Characterization and Studies of the Cellular Interaction of Native Colonization Factor CS6 Purified from a Clinical Isolate of Enterotoxigenic
Escherichia coli
Authors: Ghosal Abhisek , Bhowmick Rudra , Banerjee Rajat , Ganguly Sandipan , Yamasaki S. , Ramamurthy T. , Hamabata T. , Chatterjee Nabendu Sekhar
Published: February 2009

CS6 is a widely expressed colonization factor of enterotoxigenic
Escherichia coli
(ETEC). To date, CS6 has not been well characterized in its native state. Here, we purified CS6 for the first time from an ETEC clinical isolate. Purified CS6 was composed of two structural subunits, CssA and CssB, which were present in equal amounts and tightly linked through noncovalent, detergent-stable association. The CssA subunit was poorly immunogenic, whereas CssB was highly immunogenic. Although the predicted molecular mass of CssA is 15 kDa, the purified CssA has an effective molecular mass of 18.5 kDa due to fatty acid modification. When purified CS6 was screened for its ability to bind with different extracellular matrix proteins, fibronectin (Fn) was found to interact with CS6 as well as CssA in a dose-dependent and saturable manner. This interaction was inhibited both by a synthetic peptide corresponding to the C-terminal hydrophilic, surface-exposed region of CssA (positions 112 to 126) and by the antibody derived against this region. Enzyme-linked immunosorbent assay results showed that CssA interacted with the 70-kDa N-terminal domain of Fn. The modifications on CssA probably do not play a role in Fn binding. Preincubation of INT 407 cells with CssA, but not CssB, inhibited ETEC binding to these cells. The results suggested that CS6-expressing ETEC binds to Fn of INT 407 cells through the C-terminal region of CssA. Purified CS6 was found to colocalize with Fn along the junctions of INT 407 cells. Based on the results obtained, we propose that CS6-expressing ETEC binds to the intestinal cells through Fn for colonization.
Francisella tularensisPhagosomal Escape Does Not Require Acidification of the Phagosome
Authors: Clemens Daniel L. , Lee Bai-Yu , Horwitz Marcus A.
Published: February 2009

Following uptake,Francisella tularensisenters a phagosome that acquires limited amounts of lysosome-associated membrane glycoproteins and does not acquire cathepsin D or markers of secondary lysosomes. With additional time after uptake,F. tularensisdisrupts its phagosomal membrane and escapes into the cytoplasm. To assess the role of phagosome acidification in phagosome escape, we followed acidification using the vital stain LysoTracker red and acquisition of the proton vacuolar ATPase (vATPase) using immunofluorescence within the first 3 h after uptake of live or killedF. tularensissubsp.holarcticalive vaccine strain (LVS) by human macrophages. Whereas 90% of the phagosomes containing killed LVS stained intensely for the vATPase and were acidified, only 20 to 30% of phagosomes containing live LVS stained intensely for the vATPase and were acidified. To determine whether transient acidification might be required for phagosome escape, we assessed the impact on phagosome permeabilization of the proton pump inhibitor bafilomycin A. Using electron microscopy and an adenylate cyclase reporter system, we found that bafilomycin A did not prevent phagosomal permeabilization byF. tularensisLVS or virulent type A strains (F. tularensissubsp.tularensisstrain Schu S4 and a recent clinical isolate) or by “F. tularensissubsp.novicida,” indicating thatF. tularensisdisrupts its phagosomal membrane by a mechanism that does not require acidification.
Development of Multiplex PCR Assays for Detection of Enterotoxigenic
Escherichia coli
Colonization Factors and Toxins
Authors: Rodas Claudia , Iniguez Volga , Qadri Firdausi , Wiklund Gudrun , Svennerholm Ann-Mari , Sjöling Åsa
Published: February 2009

Four multiplex PCR assays for detection of 19 enterotoxigenic
Escherichia coli
(ETEC) colonization factors and an improved ETEC toxin multiplex PCR were developed and tested on Bangladeshi and Bolivian ETEC strain collections. The assays will be useful for surveillance of ETEC infections in diagnostic laboratories that have access to PCR.
Predicting Clearance of Colonization with Vancomycin-Resistant Enterococci and Methicillin-Resistant
Staphylococcus aureus
by Use of Weekly Surveillance Cultures
Authors: Huckabee Charmaine M. , Huskins W. Charles , Murray Patrick R.
Published: February 2009

We analyzed surveillance cultures for vancomycin-resistant enterococci (VRE) and methicillin-resistant
Staphylococcus aureus
(MRSA) collected during a multicenter trial to determine if three negative cultures collected at weekly intervals would predict clearance of VRE or MRSA from colonized patients. Seventy-two percent of VRE-colonized patients and 94% of MRSA-colonized patients were culture negative after three consecutive negative cultures.
Search for secondary osteoporosis: are Z scores useful predictors?
Authors: Swaminathan K , Flynn R , Garton M , Paterson C , Leese G
Published: February 2009

Aim

To determine whether Z scores can be used to predict the likelihood of patients having a secondary cause of low bone mineral density.

Methods

A retrospective cross sectional study was conducted among 136 consecutive patients with osteoporosis at Ninewells Hospital, Dundee, UK, between 1998–2002.

Results

20.5% of female patients in this study were identified with previously unrecognised contributors to the low bone mineral density. In women, at a Z score cut-off of −1, the sensitivity of detecting a secondary cause for osteoporosis is 87.5% with a positive predictive value of 29.2%.

Conclusion

In women, a Z score of −1 would identify a majority of patients with a secondary cause for low bone mineral density and identifies patients who would especially benefit from a thorough history and clinical examination.
Changing practice to improve pain control for renal patients
Authors: Salisbury E M , Game D S , Al-Shakarchi I , Chan M , Fishman L , Tookman L , Brown E A
Published: February 2009

Pain is a common symptom described by patients with end-stage kidney disease (ESKD) but remains ineffectively managed. The aim of this audit was to determine what proportion of these patients report pain, then introduce the use of an analgesic ladder adapted specifically for ESKD, and finally re-evaluate the prevalence of pain symptoms, looking for an improvement. A cohort of inpatients on the renal wards of a West London teaching hospital was studied. The number of patients reporting pain and the severity of their pain on a scale of 1–10 were recorded. A considerable number of patients were barred from participating because of a language barrier. Interpreters were introduced, and the phase was repeated. The World Health Organization (WHO) three-step analgesic ladder was adapted for patients with ESKD and introduced to medical staff on the renal wards. The number of patients reporting pain and the severity of their pain were re-recorded. There was a significant reduction in the number of patients reporting pain and the severity of their pain. Pain control in patients with ESKD is improved through the use of an adapted version of the WHO analgesic ladder. Strategies must be in place for effective communication with foreign patients.
Current controversies in the management of Warthin tumour
Authors: Thangarajah T , Reddy V M , Castellanos-Arango F , Panarese A
Published: February 2009

Warthin tumour is the second most common benign neoplasm of the parotid gland. It has a low rate of growth and exhibits malignant transformation in 0.3% of cases. Although its aggressiveness has not been a concern, surgical resection remains the most common treatment modality. This entails the risk of a general anaesthetic and those pertaining to the procedure itself, most notably permanent facial nerve damage. This has led some authors to use conservative management, albeit rarely. There are those who condemn such a policy despite the encouraging results reported thus far. To understand the rationale underpinning non-operative management, it is imperative that one has a comprehensive understanding of the pathogenesis, clinical presentation and diagnosis of Warthin tumour. The aim of this review therefore is to detail these elements and clarify the current controversies in managing this lesion.
Infiltrative ophthalmopathy and primary hypothyroidism: a rare clinical manifestation of a common disease
Authors: Rajput R , Dhingra A , Kumar K , Sen J
Published: February 2009

The association of infiltrative ophthalmopathy with primary hypothyroidism is uncommon. We describe two such cases manifesting at different times during the course of primary hypothyroidism. The successful outcome of the present cases suggests that the timely addition of levothyroxine treatment alone or in combination with steroids is useful and effective in the management of hypothyroid Graves’ ophthalmopathy.
What killed Socrates? Toxicological considerations and questions
Authors: Dayan A D
Published: February 2009

The death of Socrates in 399 BCE, as reported by Plato in the Phaedo, is usually attributed to poisoning with common hemlock. His progressive centripetal paralysis is characteristic of that poison. Socrates is said to have had a prominent loss of sensation extending centrally from his legs, which is not a feature of hemlock poisoning, and he seems not to have had the unpleasant taste or common gastrointestinal effects of that poison. It is suggested that Plato gave a modified account of the death of Socrates for political and other reasons by describing a more “noble” death.
Yolk Absorption, Yolk Sac Constrictions, Mortality, and Growth During First Feeding of Atlantic Salmon (Salmo salar) Incubated on Astro-turf
Authors: Hansen T. J. , Møller D.
Published: February 2009

Groups of pooled Atlantic salmon (Salmo salar) eggs were incubated in a "California" incubation system with and without astro-turf, an artificial substrate, and later transferred to separate feeding units. Alevins reared in astro-turf absorbed their yolk sac faster and more efficiently than alevins reared on a flat screen. Alevins reared on the flat screen developed yolk sac constrictions probably due to the backward and lateral force created by the high swimming activity. No such malformations were found on the yolk sacs of the astro-turf reared alevins. The fry hatched without astro-turf grew faster than the fry hatched with astro-turf during the initial feeding period, but later this was reversed. Mortality of alevins and fry hatched with astro-turf was lower during incubation and during first feeding.
Biology of the Bathylagid Fish, Leuroglossus schmidti, in the Strait of Georgia, British Columbia, Canada
Authors: Mason J. C. , Phillips A. C.
Published: February 2009

The northern smoothtongue (Leuroglossus schmidti), a deep-sea smelt, coexists with Pacific hake (Merluccius productus) and walleye pollock (Theragra chalcogramma) in the Strait of Georgia, British Columbia. Their eggs and larvae rank third in abundance, and these three pelagic stocks show marked spatial and temporal overlap in deeper waters, especially during reproduction. Development to hatching occurs in the spring at depths > 150 m. Smelt larvae metamorphose at 22 mm standard length (SL), some 90 d from hatching, and juveniles join the adults at depths > 200 m by autumn. Larger juveniles mature as 2-yr-olds > 50 mm SL. Males seldom live beyond 3 yr or exceed 60 mm SL but females may live[Formula: see text] and attain 100 mm SL. Adult sex ratio is 2:3 in favor of females. Larger females are multibatch spawners, 2 batches/yr, with a mean fecundity of 100 eggs∙g−1∙batch−1. Larval diet includes eggs and early stages of crustaceans dominated by Copepoda. juveniles and adults fed mainly of polychaetes, amphipods, euphausiids, and calanoid copepods found at depths > 100 m. Except for the postlarval and early juvenile stages lasting some 3 mo, the life cycle is pursued at depths > 150 m. Their bathypelagic existence in the Strait emphasizes predator avoidance coupled with low fecundity, slow growth, and short life span.
Recent Changes in the Inshore Forage Fish of Lake Michigan
Authors: Jude David J. , Tesar Frank J.
Published: February 2009

Concerns have been expressed that increasing predatory pressure by salmonids may change the forage fish community of Lake Michigan. A decline in alewife (Alosa pseudoharengus), the major forage fish, would be a forewarning of such a change. Our 1973–82 surveys showed that alewife declined 86% in 1980–82; concurrently, rainbow smelt (Osmerus mordax) and yellow perch (Perca flavescens) increased threefold and fivefold, respectively. Spottail shiner (Notropis hudsonius) and trout-perch (Percopsis omiscomaycus) showed no long-term changes. Bloater (Coregonus hoyi) increased 24-fold since commercial fishing was prohibited in 1976. These trends imply that (1) alewife declined from predatory pressure, (2) alewife suppressed rainbow smelt and yellow perch, presumably by preying on their pelagic larvae, (3) alewife did not substantially affect spottail shiner and trout-perch, presumably because their demersal larvae escaped alewife predation, and (4) overfishing, more than the alewife, suppressed bloater.
Organic Nitrogen Compounds in Atmospheric Precipitation: Their Chemistry and Availability to Phytoplankton
Authors: Timperley M. H. , Vigor-Brown R. J. , Kawashima M. , Ishigami M.
Published: February 2009

Urea accounted for 30, 36, and 56%, respectively, of the water-soluble organic nitrogen (DON) compounds deposited from the atmosphere at two sites in New Zealand and one site in japan. The other DON compounds were not identified but they were all of low molecular size, apparently anionic, and did not include detectable quantities of amino acids or uric acid. In axenic culture, Chlorella spp. grew successfully using DON from New Zealand precipitation as its only source of N; Pediastrum biwae, a phytoplankton endemic to Lake Biwa in Japan, also achieved successful growth using DON separated from Japanese precipitation. Ammonium-N and DON were deposited from the atmosphere in the absence of rain or snow, and we suggest that particulate matter, possibly soil, is a major source of these N compounds in atmospheric precipitation.
Predicting the Vertical Distribution of Fish Populations: Analysis of Cisco, Coregonus artedii, and Yellow Perch, Perca flavescens
Authors: Rudstam Lars G. , Magnuson John J.
Published: February 2009

We develop a model based on fish behavior in temperature and oxygen gradients that yields quantitative predictions of the vertical distribution of a fish population throughout the water column. The model was tested against observed vertical distributions of cisco, Coregonus artedii, and yellow perch, Perca flavescens, in 1981 and 1982 from five Wisconsin lakes. In some cases, the model seemed adequate for cisco, but in most cases, they occupied a temperature lower than their final preferendum. Occupation of lower temperature is consistent with a response to less than ad libitum food rations expected in these oligotrophy to mesotrophic lakes. In Lake Mendota, which is eutrophic with an anaerobic hypolimnion, cisco occupied temperatures higher than predicted by the model. For perch distributions, avoidance of high light intensities appears important. We did not observe effects of interspecific segregation between cisco and perch in their vertical distributions beyond that expected from differences in their preferred temperatures. Deviations of actual distributions from predictions of our relatively simplistic two-factor model can be used to help identify and evaluate other important physical and biotic factors influencing vertical distributions.
Fish Production in Warmwater Streams in Poland and Ontario
Authors: Mahon Robin , Balon Eugene K.
Published: February 2009

Density (numbers per hectare), biomass (kilograms per hectare), and annual production (kilograms per hectare per year) of entire stream fish taxocenes were significantly higher at localities in Ontario (n = 11) than in Poland (n = 14). The production/biomass ratio and the mean size of individuals did not differ significantly between the two sets of localities. The average stream size at the localities studied in Poland was significantly smaller than in Ontario. Production and biomass in Poland showed a significant negative association with stream size, whereas in Ontario these relationships were not significant; therefore, the differences in these variables between Poland and Ontario may even be underestimated. Differences in fluvial fish taxocene richness might explain the observed differences in production if the streams in Poland are less saturated than those in Ontario. However, the possibility of more basic differences in productivity at lower trophic levels cannot be ruled out.
Phytoplankton Response to Freshwater Runoff: The Diversion of the Eastmain River, James Bay
Authors: Ingram R. Grant , Legendre Louis , Simard Yvan , Lepage Serge
Published: February 2009

Phytoplankton, nutrients, and hydrodynamic conditions were regularly sampled in the estuary of the Eastmain River (Québec) and offshore in James Bay, before and after the diversion of the river for hydroelectric development on 19 July 1980. In the estuary, mean flow decreased by over 90% and the semidiurnal tidal amplitude increased significantly over a 5-d period. The most dramatic event was a major phytoplankton bloom in the river mouth, during a 10-d period of higher water column stability in late August; the cells then remained and bloomed in the thin photic layer. This stresses the role of hydrodynamics (as determined here by the freshwater runoff) in the timing of phytoplankton blooms.
The Retention of Coho Salmon (Oncorhynchus kisutch) Carcasses by Organic Debris in Small Streams
Authors: Cederholm C J. , Peterson N. P.
Published: February 2009

Twenty marked coho salmon (Oncorhynchus kisutch) carcasses were placed in each of nine small streams on the Olympic Peninsula of Washington during the fall–winter spawning period. Distribution of the carcasses in 500 m of stream below each release site was followed for 4 wk. One week after placement, 78 of the 180 carcasses were found in the nine study reaches; 80% were found in the first 200 m downstream of the release sites. A general positive trend was observed between the number of carcasses retained and the amount of debris in the stream channel (r = 0.61). Terrestrial animals rapidly consumed carcasses during the experiment, and removed many of them to the riparian zone.
Stock Definition, Recruitment Variability, and Larval Recruitment Processes in the American Lobster, Homarus americanus: A Review
Authors: Ennis G. P.
Published: February 2009

A review of the literature pertaining to stock definition, causes of variability in recruitment to standing stocks, and larval recruitment processes in the American lobster, Homarus americanus, is presented. Several stocks can be identified but their boundaries are indistinct. The areas are too large for consideration of any of the stocks as a single management unit. The bulk of annual landings is composed of recruitment to standing stocks since the preceding fishing season. Landings for all areas fluctuate and there is considerable variability in patterns of fluctuations between areas. Suggested causes of variability in recruitment include variation in temperature, variation in annual river discharge, fishery induced variability in egg production, man-made interruption in larval supply, and ecosystem change. Mechanisms that determine where larvae that originate in a given area eventually settle are uncertain. Literature on larval recruitment processes contains theories based on passive transport of larvae by surface currents and others based on interacting behavioral and hydrographic mechanisms that may enable larvae to maintain position near parental grounds.
Review of the Fishery for and Biology of the Cape Rock Lobster Jasus lalandii with Notes on Larval Recruitment
Authors: Pollock David E.
Published: February 2009

The South African fishery for the rock lobster Jasus lalandii currently yields about 3800 metric tons (8.4 million animals) of which more than 90% are males. Males grow much faster than females, and a size limit which is fairly large in relation to the size and age at maturity protects females from exploitation for most of their lifespans, thereby ensuring a high level of larval production from the population. Exploitation rates in the fishery are controlled by means of quotas on fishing companies, as well as catch limits on individual fishing grounds. Quotas are reassessed annually to maintain instantaneous fishing mortality rates of approximately 0.3 on all grounds. Catch rates on most grounds have been increasing since area catch limits were introduced in 1980, and seasonal averages now vary between 4 and 12 kg∙trap-day−1. Although annual indices of puerulus larval recruitment are not available, and the stock–recruitment relationship is unknown, it appears that relatively stable yields can be maintained despite fluctuations in puerulus recruitment. Density-dependent regulatory mechanisms operative in juvenile and young adult stages tend to dampen large variations in the numbers of adults entering the fishable size range each year. Variations in puerulus recruitment are likely to result from changes in the paths and velocities of extensive offshore currents which eventually return larvae toward the coast of South Africa after many months of pelagic existence.
Prediction of Commercial Catches of the Western Rock Lobster Panulirus cygnus
Authors: Phillips B. F.
Published: February 2009

Predictions of the size of the Western Australian commercial catch of the western rock lobster Panulirus cygnus have been successfully made 4 yr ahead. The predictive system, which has operated for 9 yr has been recognized by industry and government as an important tool in the management of Australia's most valuable single-species fishery. The accurate prediction depends on demonstrated relationships between the number of rock lobsters at the puerulus stage of their development (the last stage of its pelagic existence) and the level of recruitment to the fishery, and the total catch of the fishery, 4 yr after settlement. Since 1980, predictions of the catches have been based on settlement data from a single site, Seven Mile Beach, which is near the centre of the distribution of the species. The catches of the fishery from 1961–62 to 1983–84 ranged from 6.8 × 106 kg in 1973–74 to 12.4 × 106 kg in 1982–83. Based on a regression of total catches from 1969 to 1979 on puerulus settlement, and allowing for a trend of increasing catch with time, the total catch is predicted to fall to about 7.72 × 106 kg in 1986–87 because of the low level of puerulus settlement in 1982–83. However, increased settlement in 1983–84 and the highest settlement ever recorded in 1984–85 indicate that catches should increase for the 1987–88 fishing season. Similar relationships between life history stages can be discerned for other crustacean species, provided accurate, long-term data are available.
Application of Laboratory Studies of Larval Behavior to Fisheries Problems
Authors: Sulkin Stephen D.
Published: February 2009

An evaluation of the utility and constraints of an experimental approach to study of larval behavior is presented. Properly designed laboratory studies can provide a description of species-specific traits that contribute to vertical distribution and thus influence dispersal and recruitment. Results from such studies are most effectively applied to fisheries problems when field studies alone cannot provide sufficient information. Fisheries problems that require an understanding of the mechanistic basis of larval dispersal may also require the rigor and control provided by laboratory-based studies of larval behavior. A conceptual model of the physical and behavioral components determining vertical position of a plankter in the water column is presented as the basis for developing specific experiments that test for the direction and speed of passive and active movement. Data from these experiments permit development of hypotheses regarding larval dispersal and survival.
Relative Egg Production and Abundance of Berried Lobsters, Homarus americanus, in the Bay of Fundy and off Southwestern Nova Scotia
Authors: Campbell A. , Pezzack D. S.
Published: February 2009

The relative abundance of berried female lobsters, Homarus americanus, and their contribution to total egg production in various areas of the Bay of Fundy and off southwestern Nova Scotia are estimated from sampling commercial and research cruise catches from traps. Concentrations of berried females occurred on Browns Bank, Georges Bank, and the New Brunswick side of the Bay of Fundy. To a lesser extent, berried females occurred in the coastal areas of southwestern Nova Scotia. Using a range of mortality values, a variety of population sizes were estimated from 1983 landings from which relative egg production values were calculated for each area. Lobsters from coastal waters of southwestern Nova Scotia combined with the Bay of Fundy were estimated to produce between 23 and 53% and those from the offshore Brown and eastern Georges Banks to produce between 47 and 77% of the region's total egg production. The results suggest that lobsters in each area are capable of producing large numbers of eggs. Where the resulting planktonic larvae settle as benthic juveniles is unclear.
Recruitment of Packhorse Rock Lobster Jasus verreauxi in New Zealand
Authors: Booth John D.
Published: February 2009

The main breeding population of packhorse rock lobster Jasus verreauxi around mainland New Zealand is in the extreme north, near Cape Reinga. Some larvae from this area (and possibly some from Australia) are carried southeastward in the East Auckland Current along the east coast of North Island, and settlement occurs as far south as Cook Strait. Recapture of tagged animals shows that most juveniles migrate toward Cape Reinga where they mature and breed. The single major breeding population and migratory pathway may mean that the species is particularly vulnerable to overfishing. New Zealand and Australian stocks may be linked by larval transport across the north Tasman Sea.
Conservation of Recruitment of the Western Rock Lobster (Panulirus cygnus) by Improving Survival and Growth of Undersize Rock Lobsters Captured and Returned by Fishermen to the Sea
Authors: Brown R. S. , Caputi N.
Published: February 2009

The western rock lobster (Panulirus cygnus) fishery is one of the largest rock lobster fisheries in the world with an average catch (1974–75 to 1983–84) of 10 million kg. On average, 18 million undersize rock lobsters (sublegal size) are caught, handled, and returned to the sea each season despite the release of many through mandatory escape gaps in traps. Depending on the handling procedure, undersize rock lobsters experience various degrees of exposure, displacement, and damage which adversely affect their survival and growth. Laboratory, field, and tagging experiments showed that handling produced a mortality of 14.6% that costs the industry in excess of $A13 million per season (1984–85 values). An education programme has resulted in improved handling of undersize rock lobsters, and trials have shown that by increasing the size of the escape gap, the number of undersize rock lobsters handled can be reduced by 40–60%. This would result in a significant enhancement of recruitment to the fishery.
Competition for Shelter Between Lobsters (Homarus americanus) and Jonah Crabs (Cancer borealis): Effects of Relative Size
Authors: Richards R. Anne , Cobb J. Stanley
Published: February 2009

American lobsters (Homarus americanus) and Jonah crabs (Cancer borealis) inhabit rocky subtidal areas where they take shelter in crevices or burrows. In previous studies, lobsters dominated crabs of equivalent size in competition for shelter; however, we predicted that large crabs could dominate small lobsters. SCUBA surveys revealed a broad overlap in size of lobsters and Jonah crabs cooccurring in Narragansett Bay, Rhode Island; thus, opportunity exists for interaction between animals disparate in size. In laboratory experiments, relative size did not affect the outcome of competition for shelter: lobsters were competitively superior to crabs of all sizes. However, some crabs excluded lobsters from shelter. Fish predation on lobsters increased significantly when shelter was limited, but predation on crabs did not. Crabs were able to escape predation by rapid burrowing, while lobsters were dependent on locating preexisting refuges. Differential vulnerability to predation may explain the lack of size effect in competition between lobsters and crabs. The cost of not obtaining shelter is lower for crabs than for lobsters; thus, crabs utilize alternatives rather than compete with lobsters.
Environmental Influence on Recruitment of the American LobsterHomarus americanus: A Perspective
Authors: Aiken D. E. , Waddy S. L.
Published: February 2009

Heredity determines the biological limits within which an organism can function, and environment determines whether those biological limits will be reached. When they are, biological processes essential to the recruitment cycle begin to fail, and recruitment to subsequent life stages is adversely affected. The American lobster, Homarus americanus, experiences a spectrum of environmental forces within its natural range. The most important among these are temperature and disease. These, plus anthropogenic changes, fishing pressure, and several factors with local or short-term impact, can cause stress, which is cumulative and debilitating. These factors combine to influence spawning, egg attachment, incubation success, hatching, larval development, growth, maturity, reproductive capability, and geographic distribution of the animal—major elements of the recruitment cycle.
Crustacean Endocrinology, A Review
Authors: Quackenbush L. Scott
Published: February 2009

Crustacean endocrinology has benefited from the recent advances in peptide chemistry and immunoassay. Current research has focused on the isolation of peptides and the measurement of steroids. Terpenoid hormones, long known from insects, are now believed to be present and active in crustaceans. The role of biogenic amines as neuromodulators and neurohormones in crustaceans is also being examined. Details of crustacean regulatory physiology suggest a similarity to well-known insect patterns. This brief review will examine some examples from each of these areas.
Review of Sexual Selection and Chemical Communication in the Lobster, Homarus americanus
Authors: Atema Jelle
Published: February 2009

Field and laboratory observations have shown that female lobsters, Homarus americanus, are the active searching partner in courtship, choosing locally dominant males. The attractive features of the male are suspected to be intrasexual aggressive behavior and chemical cues. Size-based dominance is an important factor allowing males to secure a suitable mating shelter. In nature, male and female lobsters often approach and check shelters of other lobsters. This behavior may allow the animals to monitor the observed daily and seasonal changes in their physical and social environment. Premolt females approach the dominant male's shelter frequently in the weeks before the female's molt. Indirect evidence indicates that the female then "blows" a urine-related sex pheromone into the male shelter. One to several days before molting, a female enters the male shelter. Female intrasexual competition increases the premolt, but not the postmolt, cohabitation period. During cohabitation, males fan with their pleopods blowing a strong current through the shelter and into the environment. This chemical advertisement attracts other females, including future mating partners, to his shelter entrance. Females spent 1–2 wk in the male shelter. Mating takes place 30 min after the female molts. Another female may start cohabitation with the male immediately. In one 10-wk period a dominant male in the laboratory cohabited and mated with five females in sequence; females ignored a second male of equal size. Theoretically, by allowing a female to spend time in his shelter the male foregoes other mating opportunities, but this is balanced—and hence a stable strategy—by his protection of a vulnerable postmolt female who carries his offspring. Females must choose males who can protect them efficiently from prédation and, perhaps more importantly, from competing lobsters.
Variation in the Competitive Abilities of Fishermen and its Influence on the Spatial Distribution of the British Columbia Salmon Troll Fleet
Authors: Abrahams M. V. , Healey M. C.
Published: February 2009

We estimated the catch rates of individual fishing vessels within the British Columbia salmon troll fleet from the data of a 7-yr log book program. Catch rates varied considerably among vessels. A portion of the variation could be attributed to environmental variation. However, there were also significant differences in competitive ability among vessels. The top ranked vessels had a catch rate 3.6 times that of the lowest ranked vessels. Top ranked vessels distributed their fishing effort among more fishing areas than bottom ranked vessels, but were also more successful at catching fish when fishing in the same areas as bottom ranked vessels. This information, through an application of the ideal free distribution theory, can be used to develop a model that will describe the expected relationship between vessel distribution, vessel catch rate, and fish distribution, potentially allowing vessel distributions to be used as a tool for assessing fish stocks.
Denitrifïcations in Sediments from the Hyporheic Zone Adjacent to a Small Forested Stream
Authors: Duff John H. , Triska Frank J.
Published: February 2009

Denitrification was assayed by the acetylene blockage technique in hyporheic sediments. Samples were obtained along transects perpendicular to the stream at two sites: (1) the base of a slope dominated by old-growth redwood and (2) the base of a slope dominated by alder regenerating from a clearcut in 1965. Denitrification was evident at in situ nitrate concentrations at all locations tested. Activity was stimulated by nitrate but nitrate plus glucose had no additional effect. Denitrifying potentials increased with increasing distance from the stream channel. Dissolved oxygen was 100% of the concentration expected in equilibrium with the atmosphere in water obtained from monitoring wells immediately adjacent to the stream but was as low as 7% of the expected value in water 11.4 m inland. Both nitrate and dissolved organic carbon decreased over summer in wells at the base of the alder-forested slope. A 48-h injection of nitrate-amended stream water into hyporheic water 8.4 m inland stimulated nitrous oxide production in the presence of acetylene. Nitrous oxide was generated as nitrate and acetylene were co-transported to a well 13 m down-gradient. The acetylene-block experiments coupled with the chemistry data suggest that denitrification can modify the chemistry of water during passage through the hyporheic zone.
Regulation of Pigment Sedimentation by Photo-Oxidation and Herbivore Grazing
Authors: Leavitt P. R. , Carpenter S. R.
Published: February 2009

Reversed-phase high pressure liquid chromatography was used to show that algal carotenoid sedimentation is regulated by photo-oxidation and herbivore grazing in three unproductive, north-temperate lakes. Comparison of algal carotenoid and biovolume standing stocks revealed that carotenoid concentrations in epilimnetic waters were influenced by nonplanktonic inputs of pigments as well as phytoplankton community composition. Sediment traps did not record weekly events in the water column. Pigments that were incorporated in zooplankton feces and sank rapidly (e.g. alioxanthm and pheophorbide a) were overrepresented in trap material relative to epilimnetic pigment standing stocks. Differential decay of pigments in traps could not account for this observed bias. Chlorophyll mass–balance budgets corroborated the important influence of grazing by large-bodied zooplankton on pigment sedimentation. Interannual differences in pigment sedimentation were caused by changes in zooplankton community structure and the vertical zonation of phytoplankton communities. In the absence of fecal transportation, photo-oxidation destroyed carotenoids prior to their sedimentation from the photic zone. Therefore, sedimentary carotenoid composition is regulated by loss processes as well as changes in algal community composition.
Thermal Structure of a Multibasin Lake: Influence of Morphometry, Interbasin Exchange, and Groundwater
Authors: Robertson Dale M. , Ragotzkie Robert A.
Published: February 2009

Interbasin differences which develop below the upper mixed layer in small multibasin lakes provide the unique opportunity to examine how a lake's morphometry affects the rates of certain processes and the distribution of certain physical, chemical, and biological parameters without the confounding inter-lake dissimilarities encountered when examining different lakes. To determine if the variability in basin morphometry can be the primary factor causing interbasin differences, we examined the thermal structure of Trout Lake, Wisconsin, during summer and winter stratification and quantitatively explained the observed differences in temperature among basins. Differences in hypolimnetic temperature during summer stratification and differences in the temperature of the entire water column in the winter were primarily due to the morphometric differences among basins. During winter, variations in the temperature among basins were also influenced by interbasin exchange and differences in groundwater inputs. Therefore, this multibasin lake can provide the opportunity to test for morphometric affects without the confounding inter-lake dissimilarities encountered when examining different lakes.
Performance of Tripfoid Pacific Oysters, Crassostrea gigas: Gametogenesis
Authors: Allen Jr. Standish K. , Downing Sandra L.
Published: February 2009

Triploid Pacific oysters, Crassostrea gigas, were produced by treating newly fertilized eggs with cytochalasin B. After a year of growth, diploid and triploid oysters were sampled throughout the reproductive season to determine the effect of triploidy on gamete formation and sexual expression. Relative to diploids, gametogenesis in triploids was retarded but not absent: both male and female triploids produced some gonad. Gametogenesis in most triploid males resulted in spermatid production; all triploid males produced numerous spermatocytes. Oocyte formation in most triploid females was severely retarded, although some triploid females produced numerous eggs. Hermaphroditism in the triploid population was markedly higher than in diploids: 29 versus 1%, respectively. The ratio of males:females was the same in diploids and triploids.
Bioenergetics and PCB, DDE, and Mercury Dynamics in Lake Ontario Lake Trout (Salvelinus namaycush): A Model based on Surveillance Data
Authors: Borgmann U. , Whittle D. M.
Published: February 2009

Lake trout (Salvelinus namaycush) ingestion rates in a bioenergetics and contaminant dynamics model were estimated directly from contaminant concentrations in lake trout and their prey, rather than from the sum of growth and predicted metabolism. Elimination rates for PCB and DDE, but not for mercury, were dependent on either body mass or lipid content. Concentrations in lake trout responded rapidly to changes in concentration of their prey. This was due primarily to growth dilution and not contaminant elimination, especially for DDE and PCB. Changes in lipid concentrations, therefore, have only minor effects on final concentrations in lake trout, and it is not appropriate to lipid normalize PCB or DDE concentrations when examining trends in whole-body concentrations for this species. Concentrations of PCBs and lipids have declined in lake trout from 1977 to 1988. The drop in PCB concentrations is probably not caused primarily by the lowered lipid concentrations but is the result of either a reduction in feeding rates and improved growth efficiencies, a reduction in PCB concentrations in alewife (Alosa pseudoharengus), or an undocumented change in prey selection. Models based on chemical kinetics across the gastrointestinal tract are more consistent with observed data than models based on a constant contaminant assimilation rate and direct excretion.
Seawater Adaptability in Baltic Salmon (Salmo salar): A Bimodal Smoltification Pattern in Previously Mature Males
Authors: Berglund Ingemar , Schmitz Monika , Lundqvist Hans
Published: February 2009

In three years, maximum seawater adaptability in 2-yr-old Baltic salmon (Salmo salar) was found during a period of about 2 wk in late May – early June. At this time the previously mature males developed in one of two directions. One group (8–44%) developed a seawater adaptability comparable with that of immature fish whereas the other did not. Previously mature males that did not adapt to seawater had larger gonadosomatic indices than males with good performance in seawater. Individually tagged previously mature males and immature fish released into the river in spring had a total adult recapture rate of 1.6 and 11.6%, respectively. In both groups the recapture rate was highest for fish released about 2 wk before the time of optimal seawater adaptability. The effect of size on recapture rate was more pronounced among previously mature males than among immature fish, with a particularly low recapture rate of small previously mature males. It is suggested that previously mature male parr can either mature sexually again or complete smoltification in spring and that the probability for smoltification and seaward migration is affected by body size and the conditions for growth during the previous autumn–winter.
Variability of Diel Vertical Migration in the Marine Planktonic Copepod Pseudocalanus newmani in Relation to Its Predators
Authors: Frost Bruce W. , Bollens Stephen M.
Published: February 2009

We report results of a 3-yr field study of the vertical distributions and diel vertical migration (DVM) of Pseudocalanus newmani in the central basin of Dabob Bay, Washington, USA. Our results include two novel findings. First, a statistically significant relationship exists between strength of DVM in P. newmani and the potential predation impact of its planktonic invertebrate predators. Second, a strong "normal" DVM (up at night, down during the day), unique for P. newmani in 5 yr of sampling at this locale, occurred at a time when the zooplanktivorous fish Ammodytes hexapterus was unusually abundant and preying on the copepod; this DVM may have been induced by the fish. DVM behavior of P. newmani was highly variable, with changes in behavior commonly occurring on a time scale of weeks; in one case the copepod switched from a normal migration pattern to a reverse migration pattern (down at night, up during the day) in less than 5 wk. These observations, combined with those of previous research, indicate that P. newmani has an exceptionally diverse repertoire of migration behavior, any particular expression of which is most likely manifested by individual copepods exercising phenotypic behavioral plasticity in response to potential predation.
Seasonal Variation in the Physiological Response of Atlantic Cod (Gadus morhua) to Low Salinity
Authors: Dutil J.-D. , Munro J. , Audet C. , Besner M.
Published: February 2009

Plasma Na+, Cl−, K+, osmotic pressure, Cortisol, glucose, and protein, blood hemoglobin and hematocrit, and water content of skeletal muscle were measured at regular intervals during a 28-d period following the transfer of Atlantic cod (Gadus morhua) to waters of 7, 14, 21, and 28‰ (control) salinity. These experiments were repeated four times at 3-mo intervals under natural photoperiod and temperatures (0–10 °C). Exposure to 7‰ salinity caused large decreases in plasma Na+ in winter (25 mmol/L over 14 d) and in spring (32 mmol/L over 7 d) when the lowest value for the year was reached (156 mmol/L). Transfer to 14 and 21‰ salinity resulted in a slight decrease (maximum 4%) in plasma Na+ which was much smaller than the seasonal variation (14%) observed in controls. Hydration of skeletal muscle occurred only at 7‰ (2.3% maximum), but these changes were small compared with the seasonal variation (3.9%) observed in the controls. Principal components and clustering analyses showed that all ionic and osmotic variables measured were highly correlated while being only weakly associated with the condition or reproductive status of the fish. There were no indications that acclimation to low salinity was stressful for cod.
Physiological Effects of Brief Air Exposure in Exhaustively Exercised Rainbow Trout (Oncorhynchus mykiss): Implications for "Catch and Release" Fisheries
Authors: Ferguson R. A. , Tufts B. L.
Published: February 2009

Rainbow trout (Oncorhynchus mykiss) which were air exposed for 60 s after exhaustive exercise initially had a much larger extracellular acidosis than trout which were only exercised. In both groups, however, plasma pH returned to normal by 4 h. Blood lactate concentrations were also greater in the air-exposed fish and continued to increase throughout the experiment. During air exposure, there was retention of carbon dioxide in the blood, and oxygen tension (Po2) and hemoglobin:oxygen carriage (Hb:O2) both fell by over 80%. After 30 min of recovery, however, blood gases resembled those in fish which were only exercised. Finally, survival after 12 h was 10% in control fish and 88% in the exercised fish but fell to 62 and 28% in fish which were air exposed for 30 and 60 s, respectively, after exercise. These results indicate that the brief period of air exposure which occurs in many "catch and release" fisheries is a significant additional stress which may ultimately influence whether a released fish survives.
Relationship between Diatom Assemblages and Trophic Variables: A Comparison of Old and New Approaches
Authors: Agbeti Michael D.
Published: February 2009

Diatoms have been used as indicators of trophic status, and many ad hoc diatom indices have been developed. Although many of these indices have been useful, more direct methods for inferring trophic status are now available. Weighted-averaging regression and calibration was found to be a superior method for assessing lake trophic status from diatom assemblages when compared with a multiple linear regression index developed from a set of 30 Canadian Lakes.