Larval settlement and epidemiology of Lepeophtheirus salmonis Kroyer, 1837 (Copepoda; Caligidae)

This study has been carried out to investigate the biological and environmental parameters influencing the settlement and post-settlement survival of the infective stages of Lepeophtheirus salmonis Kroyer 1837. The abiotic factors investigated were temperature and salinity. Temperature was found to have a significant effect on the settlement success of the copepodids with an inverse relationship between temperature and settlement. Survival of the louse at 10 days post infection showed a decrease at the reduced temperature. Temperature was also shown to have a direct relationship on lice development; higher seawater temperatures resulted in faster development. Regression analysis of temperature and settlement shows a significant correlation. A constant reduced salinity, 24%, resulted in a reduced ability of the copepodid to infect its host compared with 34%. Post-settlement survival in 24%, at approximately 13°C resulted in 5.8% survival of lice to day 10 post-infection compared to 79% in 34% salinity. When this experiment was repeated but with elevated seawater temperatures of up to 18°C, survival at the reduced salinity was found to be 75.3%, higher than the ambient control group. The developmental rate at day 10 post-infection of L.salmonis larva at 24% was shown to be slower than development at 34%o. Distribution of the L.salmonis copepodid on its host showed the highest settlement on the gills and on the fins, particularly the pectoral and dorsal fins. Examination of L.salmonis survival at day 10 post-infection indicated the highest losses on the gills and the pelvic, caudal and dorsal fins. Settlement on the pectoral fins showed the highest settlement and the greatest survival. The infective copepodid has a reduced ability to infect its host after 7 days following the moult from nauplius 2, compared to copepodids aged 1 and 3 days following the nauplius 2 moult. For copepodids of all ages, once settlement had been achieved, survival at 10 days post-infection was approximately 50% in all groups. Copepodids of all ages did not show any difference in the development rate at 10 days post infection. Highest settlement was found to be on the gills and pectoral and dorsal fins. The effects of varying dose rates of copepodids, has shown that a finite percentage of lice settle and survive the first five days post-infection. Settlement distribution was found to be highest on the body, gills and pectoral and dorsal fins. In serial infections of fish there was a reduced settlement count with second infections, possibly through intraspecific competition. Experiments using different host stocking densities showed that with an increased number of hosts the intensity of the infection of individual fish was reduced. Smaller fish appear more susceptible to settlement of L.salmonis than larger fish, and this is associated with the relatively greater fin area of those fish compared to larger fish. L.salmonis exhibits a preference for the fins as an area of settlement in all sizes of fish. Comparison of copepodid settlement on salmon and sea trout showed that in single populations of fish salmon had the highest intensities of infection whilst in mixed populations of fish sea trout had a higher intensity. Settlement distribution of L.salmonis on salmon showed greatest settlement on the body, pectoral and dorsal fins, whilst on sea trout settlement was highest on the body, pectoral, pelvic, caudal and dorsal fins. The comparative development of L.salmonis between the two species of host fish showed an increased rate of development on salmon. The calculated energy levels for L.salmonis larval stages show a decrease in available energy within each developmental stage. After 6 days from the nauplius 2 moult the copepodid starts to show a sharp decline in energy levels which coincides with the reduced ability of the copepodid to infect the host. Post-settlement energy levels remain constant even though the copepodid is actively feeding, as seen by SEM examination at 2 days postinfection. The principal lipid class found within L.salmonis larval stages as energy reserve is triacylgylcerol (37.6% of the total lipid). A preliminary epidemiological model for sea lice population dynamics is proposed. This is a differential equation compartmental model that has been designed to examine the flow of L.salmonis developmental stages on the host. The model was able to predict the timing of the maximum number of pre-adult 1 lice stages to within one day. The difference between the observed data and the model output is probably due to the considerable variability in the parameters used in the model construction

The impact of inflation on selected wage and salary groups in the Richmond area

One of the greatest economic problems existing in the United States today is inflation. This problem is magnified because our population is still growing, there are changes taking place in methods of production, and property and wealth are being re-distributed. Americans continually want more things which are bigger and better and they are willing to go in debt to have them. They want more and bigger automobiles, highways, more services, better schools, and more leisure time. The effective demand sometimes has a way of getting ahead of the capacity to produce. With this demand for goods, prices continue to rise and a unit of currency buys less and less. Prices climb when there is an increase in effective demand relative to available supplies. Rising prices tend to stimulate production and discourage demand. Prices are the automatic regulators that keep production and consumption in balance. When prices go up, it is not because things are worth more but because the dollar is worth less

Aquaculture Potential for Hornyhead Chubs

The hornyhead chub (Nocomis biguttatus) is one of the most valuable baitfish species in Minnesota. Culturing hornyhead chub supplies valuable baitfish to anglers and generates income for fish farmers and baitshop owners in Minnesota and other northern states. Hornyhead chubs can be reared in aquaculture facilities and sold through baitshops to anglers, who are often willing to pay $5 to$6 per dozen. Because it is illegal to import baitfish into Minnesota, such prices put harvesting pressure on wild populations. Culturing hornyhead chubs relieves pressure on wild populations while keeping the market adequately supplied with this desirable bait. This technical bulletin describes how to spawn and grow hornyhead chubs produced in an outdoor spawning system and an indoor over-winter growout facility

Effects of polyploidy on female call preference in gray treefrogs, Hyla chrysoscelis

Abstract only availableThe gray treefrog complex consists of two cryptic species; Hyla versicolor is a tetraploid (N=48) species that arose from the polyploidization of its diploid counter-part, H. chrysoscelis (N=24) and two other extinct treefrog species. Speciation via polyploidy is almost instantaneous because polyploid species are isolated reproductively from their non-polyploid ancestors. However, the establishment of newly arisen polyploid lineages requires assortative mating between polyploids. Genome duplication has been shown to affect the quality of the male's species-specific mate-attraction signal, thus polyploids could be reproductively isolated from their diploid ancestors through the action of female mating preferences. Autopolyploid individuals I generated last summer (polyploidy was verified by initial karyotyping) are currently reaching sexual maturity. Once sexually mature, the acoustic mate-choice preferences of female polyploids will be tested using playback experiments. The experimental tests will compare preferences for call traits that vary between the two species, including frequency, pulse shape, and pulse rate. We hypothesize that these changes in the communication system result from ploidy-induced changes in tissue and cellular dimensions. Thus, as a related experiment, we will also look for effects of larval density on blood cell size, male calls and female preferences. We expect to find that polyploidy affects the advertisement-call preferences of female H. chrysoscelis treefrogs, independent of other factors. Preliminary results indicate that autopolyploid individuals are able to reach sexual maturity and that there is an effect of polyploidy on blood cell size.Life Sciences Undergraduate Research Opportunity Progra

Cardiomyocyte proliferation in zebrafish and mammals: lessons for human disease

Cardiomyocytes proliferate profusely during early development and for a brief period after birth in mammals. Within a month after birth, this proliferative capability is dramatically reduced in mammals unlike lower vertebrates where it persists into adult life. The zebrafish, for example, retains the ability to regenerate the apex of the heart following resection by a mechanism predominantly driven by cardiomyocyte proliferation. Differences in proliferative capacity of cardiomyocytes in adulthood between mammals and lower vertebrates are closely liked to ontogenetic or phylogenetic factors. Elucidation of these factors has the potential to provide enormous benefits if they lead to the development of therapeutic strategies that facilitate cardiomyocyte proliferation. In this review, we highlight the differences between Mammalian and Zebrafish cardiomyocytes, which could explain at least in part the different proliferative capacities in these two species. We discuss the advantages of the zebrafish as a model of cardiomyocyte proliferation, particularly at the embryonic stage. We also identify a number of key molecular pathways with potential to reveal key steps in switching cardiomyocytes from a quiescent to a proliferative phenotype. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00018-016-2404-x) contains supplementary material, which is available to authorized users

Systolic and diastolic ventricular function in zebrafish embryos: Influence of norepenephrine, MS-222 and temperature

<p>Abstract</p> <p>Background</p> <p>Zebrafish are increasingly used to study the influences of gene mutation and manipulation on cardiac development, structure and function. In this study, a video edge detection system was used to characterise, continuously, cardiac ventricle function in 2–5 days old zebrafish embryos embedded in 0.6% agar and examined under light microscopy at room temperature (22°C). Using video edge detection software (IonOptix Inc), the motion of a small region of the cardiac ventricle wall was converted to a continuous chart trace allowing analysis of wall motion amplitude (WMA) and myocardial wall velocity during systole (MWVs) and diastole (MWVd).</p> <p>Results</p> <p>Cardiac wall motion characteristics changed progressively from day 2 to 5 (WMA, 2-days, 17.6 ± 4.4 μm vs 5-days, 24.6 ± 4.7 μm, p < 0.01). MWVd was more rapid than MWVs at all developmental time points. Embryonic hearts were also assessed after increasing concentrations of norepenephrine (NE) and the anaesthetic agent MS222 (tricaine) were added to the bathing water. In response to NE, WMA increased significantly more in 4 day embryos compared with 2 day embryos (change in WMA,13.6 ± 8.2 μm vs 4.0 ± 8.8 μm, p = 0.01, respectively) while the decrease in WMA in response to MS222 was similar in both 2 and 4-day embryos. Heart rate, MWVs and MWVd were significantly higher at 28°C compared with 22°C. No differences in cardiac function were observed between AB and Golden strains.</p> <p>Conclusion</p> <p>Video edge detection appears sufficiently sensitive to detect subtle changes in diastolic and systolic cardiac function during development and changes resulting from pharmacological and environmental interventions. Such measurements could be valuable in assessment of altered cardiac function after genetic manipulation.</p

The effect of certain packaging and storage treatments on the acceptability of frozen beef

Digitized 2007 AES.Includes bibliographical references (pages 31-32)

The Adirondack Chronology

The Adirondack Chronology is intended to be a useful resource for researchers and others interested in the Adirondacks and Adirondack history.https://digitalworks.union.edu/arlpublications/1000/thumbnail.jp

Spatial distribution and cluster analysis of risky sexual behaviours and STDs reported by Chinese adults in Guangzhou, China: a representative population-based study

To assess associations between residences location, risky sexual behaviours and sexually transmitted diseases (STDs) among adults living in Guangzhou, China