Optimization of Weaning Elvers in a Closed Cycle System: Preliminary-Results

Replicated tests to study the best combination of environmental conditions were carried out with a total of about 200 kg of glass eels of the Thyrrenian sea. Conditions tested were; stocking density, feed formulation, form of feed, grading frequency, cage and tank dimensions and protection of rearing units. Production and survival rates are reported, as well the size — class distribution at the beginning and at the end of the rearing period and the component chart of percentages of different size classes.     

A predatory land snail invades central-western Argentina

The pulmonate land snail, Rumina decollata, is a highly invasive gastropod adapted to arid conditions, and native from the Mediterranean area. It was recorded for the first time in Argentina in 1988, in the northeastern Pampas of the Buenos Aires Province, a region characterized by a humid mesothermal climate with no water deficit. In the present contribution, we report the finding of populations of this species in the semiarid region of La Pampa and Mendoza provinces in central-western Argentina. The present findings extend the invasive distributional range of R. decollata westwards through more than 1000 km from the site where it was detected in 1988. Although no damages to agricultural areas have been reported to the moment in Argentina, the presence of R. decollata in semiarid areas warns us about its potential as an important plague in the future.     

Evaluation of honey residues from Iron Age hill-top sites in southwestern Germany: Implications for local and regional land use and vegetation dynamics

Organic contents of bronze vessels from royal burial sites dating to the Iron Age in southern Germany were investigated by pollen analysis. All pollen assemblages observed were dominated by non-arboreal pollen of non-wind pollinated species, a characteristic feature of honey. On the basis of investigations on recent honey, estimates of the original amounts of honey present were made. It is suggested that two of the vessels were filled with a freshly prepared, highly concentrated mead, while a third contained possibly a mead or a beverage sweetened by honey. The high diversity of the pollen assemblages differs from recent honeys and points to a high biodiversity in the Iron Age landscapes, but also to the use of honey mixtures that originate from a large area that included the surrounding uplands. Records for several exotic pollen also support this hypothesis. At the Glauberg site, a honey-source area of more than 50-km radius is probable. This corresponds quite well with the average distance between known Celtic centres in central Europe, which is ca. 100 km.     

Circadian rhythms and photic entrainment of swimming activity in cave-dwelling fish Astyanax mexicanus (Actinopterygii: Characidae), from El Sotano La Tinaja,San Luis Potosi,Mexico

Circadian regulation has a profound adaptive meaning in timing the best performance of biological functions in a cyclic niche. However, in cave-dwelling animals (troglobitic), a lack of photic cyclic environment may represent a disadvantage for persistence of circadian rhythms. There are different populations of cave-dwelling fish Astyanax mexicanus in caves of the Sierra El Abra, Mexico, with different evolutive history. In the present work, we report that fish collected from El Sótano la Tinaja show circadian rhythms of swimming activity in laboratory conditions. Rhythms observed in some of the organisms entrain to either continuous light–dark cycles or discrete skeleton photoperiods tested. Our results indicate that circadian rhythm of swimming activity and their ability to entrain in discrete and continuous photoperiods persist in some organisms that might represent one of the oldest populations of cave-dwelling A. mexicanus in the Sierra El Abra.     

The Invasive Woody Weed Ligustrum robustum subsp. walkeri Threatens Native Forests on La Réunion

One of the last primitive island ecosystems in the Indian Ocean has been invaded since 1969 by the Sri Lankan privet, Ligustrum robustum. L. robustum is still spreading in the forests of La Réunion Island, where only 30% of the original vegetation remains, but where 98% of the primary native vegetation of the Mascarene Islands still exists. On Mauritius, where L. robustum was introduced about 1895, it now forms dense, impenetrable thickets, and its presence has been correlated with the inability of native vegetation to re-establish. We assessed the potential impacts of L. robustum invasion on the native ecosystems of La Réunion and identified the factors of invasibility. We determined the degree of invasion in 12 plots of 156 m² and followed native flora and privet recruitment for 3 years in 12 seedling plots of 39 m². The data show that monocultural L. robustum stands now exist in human-disturbed primary forest patches (3.3 individuals/m² and 80% of total individuals) and high seedling densities (0.3–0.6/m²) occur in the least disturbed patches. L. robustum's rapid growth, high shade tolerance and seed production, bird-assisted seed dispersal and high seedling recruitment contribute to its invasiveness in intact forests. The conservation of the original ecosystems of La Réunion depends on the setting up of a long-term and immediate global control strategy. This revised version was published online in July 2006 with corrections to the Cover Date.