Ecdysial rhythms in megalopae and first instars of the Dungeness crab Cancer magister

Diel molting cycles of megalopae and first instar Dungeness crabs Cancer magister Dana captured in the Grays Harbor estuary (46° 55N; 124° 05 W) in May 1991 were studied under laboratory conditions. Sixtyone percent of the megalopae and 76% of the first instar crabs molted during periods of ambient darkness under a normal light — dark diel regime, and molting pattern was not affected by changes in the photoperiod (24 h daylight or 24 h darkness). Time until metamorphic molt increased as conspecific density increased. Habitat type (shell or mud) did not affect time until molt of megalopae and first instar crabs, nor did it affect daily molting rhythm of first instars. We hypothesize that nightly ecdysis of megalopae and first instar Dungeness crabs and density-dependent molting may be an adaptive response to predation and cannibalism among young-of-the-year.Contribution No. 875 from the School of Fisheries, WH-10, University of Washington, Seattle, Washington     

Prenatal diagnosis of 45,X/46,XY mosaicism in a fetus with asymmetric gonadal dysgenesis

An 18 week abortus had been prenatally diagnosed as a 45,X/46,XY mosaic. The fetus was a phenotypic male with glandular hypospadias, a horseshoe kidney and asymmetric gonadal dysgenesis. This case represents a rare instance of prenatally diagnosed 45,X/46,XY mosaicism with an abnormal phenotype.     

Effects of the insecticide sevin and its first hydrolytic product, 1-naphthol,on some early developmental stages of the bay mussel Mytilus edulis

Six developmental stages of the bay mussel Mutilus edulis, from fertilization to 32 h after fertilization, and also unfertilized eggs, were exposed for 1 h to different concentrations of the insecticide Sevin and its first hydrolytic product, 1-naphthol. After exposure, the larvae or eggs were separated from the pesticide solution and returned to clean water. At 48 h after fertilization, the numbers of normal and abnormal larvae were determined and 1-h EC₅₀ values (the effective concentrations that caused anomalous development of 50% of the test animals) were calculated. The most sensitive developmental stage was the one that occurred shortly after fertilization at the time of appearance of the first polar body. Thereafter, sensitivity decreased as age increased. The EC₅₀ of Sevin for the first polar body stage and 32-h stage were 5.3 and 24.0 mg/l of Sevin, respectively. The EC₅₀ of l-naphthol for the first polar body stage was 5.2 mg/l. Effects of the toxicants on development were characterized by disjunction of blastomeres, a reduction in the rate of development, and asynchronous and unaligned cleavages.     

Human impact on the Falkland Islands environment

Summary A historic analysis of human-initiated influences on the Falkland Islands ecologies is presented. Ecosystems were extensively altered by the destruction of seal and penguin communities in the late eighteenth and nineteenth centuries; and by the introduction of domesticated animals and exotic plants, the proliferation of fires, and the hunting to extinction, or near extinction, of certain animals. The harsh Falklands climate has permitted only limited recovery from some of these ravages. No island ecosystems, however remote, are spared the effects of economic and political changes influencing the rest of the world.He has published a previous article on island ecologies inThe Environmentalist (1992).     

An Experiment Testing whether Condition and Survival are Limited by Food Supply in a Reintroduced Hihi Population

Abstract: The Hihi (Stitchbird, Notiomystis cincta ) is an endemic New Zealand honeyeater that after European colonization survived on only one offshore island. Attempts to reintroduce Hihi to other islands have been unsuccessful, with populations slowly declining. The main hypothesis for these declines was an inadequate year-round supply of carbohydrate food (nectar and fruit) due to human impacts on the forest habitat. When Hihi were reintroduced to Mokoia, another island with regenerating forest, we tested whether survival was limited by carbohydrate food in the year after release. We conducted an "on-off" experiment in which ad libitum sugar water was available to birds for 2 out of every 4 weeks. We compared the masses of individual birds at the end of on and off periods to identify times when birds lost condition with no supplementary food and would be likely to starve. We also used mark-recapture analysis of resighting data to test whether mortality rates were higher when supplementary food was unavailable. The only effect of the supplementary food was that Hihi spent less time foraging for nectar and fruit and more time foraging for invertebrates. There was no time of year when birds lost mass when the food was taken away, and survival rates were not significantly lower when supplementary food was absent. The low (38%) annual survival rate could not be accounted for by shortage of carbohydrate food, and population viability analysis suggests that the population is likely to slowly decline. Our experiment shows that declines of reintroduced Hihi populations may be unrelated to food supply and that alternative hypotheses should be developed and tested. Our results also show the importance of using experimental methods, when possible, to test hypotheses about factors thought to be limiting reintroduced populations.     

Workshop report on the extraction of foetal DNA from maternal plasma

Objective Cell free foetal DNA (cff DNA) extracted from maternal plasma is now recognized as a potential source for prenatal diagnosis but the methodology is currently not well standardized. To evaluate different manual and automated DNA extraction methods with a view to developing standards, an International Workshop was performed. Methods Three plasma pools from RhD-negative pregnant women, a DNA standard, real-time-PCR protocol, primers and probes for RHD were sent to 12 laboratories and also to one company (Qiagen, Hilden, Germany). In pre-tests, pool 3 showed a low cff DNA concentration, pool 1 showed a higher concentration and pool 2 an intermediate concentration. Results The QIAamp DSP Virus Kit, the High Pure PCR Template Preparation Kit, an in-house protocol using the QIAamp DNA Blood Mini Kit, the CST genomic DNA purification kit, the Magna Pure LC, the MDx, the M48, the EZ1 and an in-house protocol using magnetic beads for manual and automated extraction were the methods that were able to reliably detect foetal RHD. The best results were obtained with the QIAamp DSP Virus Kit. The QIAamp DNA Blood Mini Kit showed very comparable results in laboratories that followed the manufacturer's protocol and started with ≥ 500 µL plasma. One participant using the QIAamp DNA Blood Midi Kit failed to detect reliably RHD in pool 3. Conclusions This workshop initiated a standardization process for extraction of cff DNA in maternal plasma. The highest yield was obtained by the QIAamp DSP Virus Kit, a result that will be evaluated in more detail in future studies. Copyright © 2007 John Wiley & Sons, Ltd.     

Spatio-temporal variability in the distribution of epi- and meso-pelagic acoustic backscatter in the Irminger Sea,North Atlantic,with implications for predation on<Emphasis Type="Italic"> Calanus finmarchicus</Emphasis>

The deep scattering layers of the North Atlantic, including the Irminger Sea, contain many predators of the key copepod species Calanus finmarchicus. Previous seasonally restricted studies have described the deep acoustic scattering layers of the Irminger Sea as ubiquitous. They have shown that the intensity of the acoustic backscatter varies across the region, and so, by implication, the potential predation pressure on C. finmarchicus also varies spatially. This paper reports observations of the distribution of epi-pelagic (0–200 m) and meso-pelagic (200–1,000 m) acoustic backscatter in the Irminger Sea, made using a scientific echosounder operating at 38 kHz during four seasonal (winter, spring and summer) cruises. Our study demonstrates that the intensity of the backscatter varies seasonally in regionally distinct ways across the Irminger Sea. The mean acoustic backscatter, both in the upper 800 m and upper 200 m of the water column, varied significantly between the northern, central and southern areas of the central basin (open ocean), and within each area between the Greenland shelf slope, open ocean and Mid-Atlantic Ridge subregions. Different patterns of seasonal change in the acoustic backscatter between the upper 800 m and upper 200 m were also seen, indicating both persistent differences in the underlying amount of backscatter in each area, and varying patterns of seasonal increase in the near surface backscatter in the different areas and subregions. These observations could be related to the different oceanographic regimes encountered in each location, and are discussed in terms of their implications for potential predation pressure on C. finmarchicus.Communicated by J.P. Thorpe, Port Erin     

THE BUREAU OF RECLAMATION'S ROLE IN AMERICA'S GROWTH1

ABSTRACT. The Bureau of Reclamation was created to implement the Reclamation Act of 1902 and subsequent legislation to conserve and develop the water resources of the western states for maximum efficient use. This has been accomplished by the planning and construction of major multiple use projects which now supply water to approximately eight million acres of land which annually produce 52 million tons of food and fiber with a gross crop value of approximately $2 billion. Fifteen million people are served with municipal and industrial water supplies and hydroelectric power from Bureau projects now returns $160 million annually to the Treasury. Flood control, recreation, and fish and wildlife enhancement are other major benefits. The Bureau of Reclamation is now undertaking a Westwide Survey of water resources and of the needs of the future which is more far-reaching than anything heretofore accomplished. The information accumulated during this ten-year survey will determine whether there is a necessity for consideration of major interbasin transfer of water supply.     

Using experimental reintroductions to resolve the roles of habitat quality and metapopulation dynamics on patch occupancy in fragmented landscapes

Declines of species in fragmented landscapes can potentially be reversed either by restoring connectivity or restoring local habitat quality. Models fitted to snapshot occupancy data can be used to predict the effectiveness of these actions. However, such inferences can be misleading if the reliability of the habitat and landscape metrics used is unknown. The only way to unambiguously resolve the roles of habitat quality and metapopulation dynamics is to conduct experimental reintroductions to unoccupied patches so that habitat quality can be measured directly from data on vital rates. We, therefore, conducted a 15-year study that involved reintroducing a threatened New Zealand bird to unoccupied forest fragments to obtain reliable data on their habitat quality and reassess initial inferences made by modeling occupancy against habitat and landscape metrics. Although reproductive rates were similar among fragments, subtle differences in adult survival rates resulted in λ (finite rate of increase) estimations of <0.9 for 9 of the 12 fragments that were previously unoccupied. This was the case for only 1 of 14 naturally occupied fragments. This variation in λ largely explained the original occupancy pattern, reversing our original conclusion from occupancy modeling that this occupancy pattern was isolation driven and suggesting that it would be detrimental to increase connectivity without improving local habitat quality. These results illustrate that inferences from snapshot occupancy should be treated with caution and subjected to testing through experimental reintroductions in selected model systems.