Chemical aspects of mass spawning in corals. II. (-)-Epi-thunbergol,the sperm attractant in the eggs of the soft coral Lobophytum crassum (Cnidaria: Octocorallia)

Sea turtles migrate between feeding and nesting areas that are often geographically separated by hundreds or thousands of kilometers. Observations of their aggregations at sea and at nesting beaches have led to the hypothesis that sea turtles migrate in socially structured groups. While this migratory strategy is common to many marine vertebrates, socially facilitated behavior is not well documented in testudines. In 1990 and 1991, we attached satellite transmitters to olive ridleys (Lepidochelys olivacea Eschscholtz) found ovipositing together during a mass nesting at Nancite Beach, Costa Rica, to determine whether they migrate independently or in groups after they leave the nesting beach. Results showed that the turtles were not spatially associated during the internesting period, were capable of re-establishing themselves as a group during a subsequent nesting emergence, and were not spatially associated during their postnesting migrations to oceanic feeding areas. We suggested that what appear to be socially structured groups of L. olivacea are in fact individual turtles simultaneously using the same habitat.     

Simulating the effects of Glen Canyon Dam releases on Grand Canyon river trips

The Shechter-Lucas wilderness use simulation model (WUSM) has been modified to quantify the effects of fluctuating Glen Canyon Dam releases on Grand Canyon river trips. The model now simulates changes in flow as predicted by the Streamflow Synthesis and Reservoir Regulation computer model for the Colorado River. This revised WUSM provides data on several flow-related effects, including delays at rapids, encounters with other parties, and the time available for visiting attraction sites. Nine flow alternatives are evaluated and compared. Analysis of these outputs provides useful information to the Bureau of Reclamation on how the operation of Glen Canyon Dam effects river trips through Grand Canyon National Park.     

Chorionic villus culture for first trimester diagnosis of chromosome defects: Evaluation by two london centres

The maceration technique for the culture of chorionic villi has been applied by St Mary's Hospital and King's College Hospital, to a total of 225 villus aspirates of which 100 were from diagnostic cases. Two hundred and eighteen (96·8 per cent) of these were successfully karyotyped, and chromosome abnormalities were detected in 15 cases. Of the cases with a normal karyotype, 113 were male and 90 were female. Sixty-nine (77 per cent) of the female cultures were demonstrated to be fetal and a further two of these may be verified at delivery. The use of Chang medium was found to accelerate cell growth thereby reducing the interval between sampling and reporting to less than 2 weeks. An unlimited quantity of metaphase spreads was obtained suitable for the application of routine banding techniques, and comparable to those obtained from amniotic fluid culture. Experience with diagnostic cases reinforced our view that culture should always back up direct analysis and this is discussed with particular reference to the occurrence of mosaicism in the trophoblast.     

Spatial and covariate-varying relationships among dominant tree species in Utah

Environmental and Ecological Statistics - The presence and establishment of a tree species at a particular spatial location is influenced by multiple physiological and environmental filters such as...     

The wilderness use simulation model applied to Colorado River boating in Grand Canyon National Park,USA

A modification of the Shechter-Lucas Wilderness Use Simulation Model (WUSM) for peak season boating on the Colorado River through Grand Canyon National Park, USA, is evaluated as a tool for making management decisions. A new microcomputer program to select trip itineraries for inclusion in the WUSM that was developed as part of this study is presented. This program simplifies user input and expands the WUSM's usefulness as a tool for management decisions by randomizing itinerary schedules based on probabilities developed from actual use of sites by canyon visitors. Model usefulness is demonstrated by simulating various management changes and comparing use levels of attraction sites and campgrounds as well as numbers of encounters between parties. The WUSM is being used as part of an ongoing study, to reflect the impact of fluctuating flow regimes through the turbines at Glen Canyon Dam on river trips.