Fitness consequences of sexual cannibalism in female<Emphasis Type="Italic"> Argiope bruennichi</Emphasis>

The evolution of sexual cannibalism as the most extreme form of nuptial feeding is still poorly understood. Although increasing evidence suggests that female aggressiveness is related to other aspects of foraging behaviour, it is not clear whether the nutritional value of a male is sufficient to provide an adaptive significance for sexual cannibalism. A widely cited though rarely tested explanation is based on a paternal investment model, and predicts that consumption of a male results in increased female fecundity. The available evidence is either correlational or restricted to species with relatively large and potentially nutritious males, and different studies have come to different conclusions. Here we present a test of the paternal investment hypothesis using the very cannibalistic and highly size-dimorphic spider Argiope bruennichi. After a preset schedule, we had females consume none, one or two males independent of the female's cannibalistic behaviour. Consumption of male bodies did not result in any detectable fitness benefit for the female: neither the number of clutches, nor clutch size or hatching success were affected by consumption of males. The frequency of cannibalism was around 80%, independent of the female mating status. We did not observe male complicity, but cannibalism was associated with prolonged copulation. This suggests a sexually selected benefit of cannibalism for males. We conclude that the paternal investment hypothesis does not explain the existence of sexual cannibalism in A. bruennichi and probably not in other spider species with a pronounced sexual size dimorphism.Communicated by L. Simmons     

Relationships between effects of environmental temperature and seston on growth and mortality of Mytilus edulis in a temperate northern estuary

The growth and mortality of experimentally-rafted Mytilus edulis L. of known age at 7 locations in a northern estuary (Damariscotta River, Maine, USA) were related to environmental temperatures and to the presence or absence of various potential food sources. All particles were regarded as potential food substrates. Growth decreased appreciably at sites where water temperatures exceeded 20°C, but mussels survived a wide range of elevated temperature exposures, ranging from 0 to 149 degree-days in excess of 20°C. The maximum temperature was 25°C. Mortalities of mussels at all sites but did affect the extent of mortality, which increased abruptly in late summer, when water temperatures were declining. Differences in degree-days of exposure to elevated temperatures did not influence the timing of mortality, which occurred synchronously at all times, but did affect the extent of mortality, which ranged from 35 to 90%. The period of high mortality was preceded by a rapid decline in phytoplankton standing crop. Total particle concentrations decreased during this period, but the shift toward larger particles suggests that there was little, if any, decrease in total volume of material in the seston, at least through August. It is suggested that living phytoplankton provided the critical energy source for these mussels, and that the mortalities were caused by rapidly reduced ration at a time of metabolic stress. The role of temperature and the possible role of the gametogenic cycle are discussed. In addition, the feeding efficiency of M. edulis may have decreased during this period due to an increase in mean particle diameter. Chlorophyll was divided into a nannoplankton fraction (<-20 m) and a larger fraction (>20 m). A smaller size criterion for this distinction is proposed for future studies. The importance of nannoplankton to the primary production of this estuary and the role of nannoplankton and nannoplankton-sized particles in the diet of mussels in nature are discussed.     

Teil III: Die Verkehrsbilanz der Universität Osnabrück

One central aspect of the environmental management system for universities developed in Osnabrück is the environmental audit of universities, realized by an ecobalance. This article deals with modelling the material and energy flows caused by the University’s commuters (staff and students), and by the business trips of employees, using the software Umberto^®. The result is the University’s traffic balance. 10,000 MWh of energy are consumed yearly by the University’s traffic. 94% of the consumption is caused by commuters (1,300 employees and 11,500 students) and only 6% by business trips. Compared with the whole energy consumption of the University, the traffic’s share is 32% and therefore lies between the electricity’s share (25%) and that of heat (43%). Similarly related are the CO₂ emissions, caused by traffic (3,160 tons per anno). Compared with the whole CO₂ emissions of the University the traffic’s share is 31%, thus putting it between the heat’s share (27%) and that of electricity (42%). Although the average weekly distance the University’s commuters drive (79 km/student and 84 km/employer) is at the bottom of the range for other comparable universities, a transportation demand management for a further reduction of the traffic-caused CO₂ emissions should be implemented.     

Trace Metal Studies on the Starfish Asterias rubens L. From the Western Baltic Sea

In 1984, 115 samples of the starfish Asterias rubens L. collected in the south-eastern part of Cadet Trench (Mecklenburg Bay/Western Baltic Sea) were analyzed for their contents of a few major (calcium, magnesium) and trace elements (cadmium, copper, iron, mercury, manganese, nickel, lead, selenium and zinc). Distinct differences were found between starfish from different stations, and these are attributed to the composition of the sediments acting as a substrate for their prey (mussels, snails). Except for cadmium, the concentrations of the elements studied all correlated negatively with the diameter and weight of the starfish.

Parallel analyses of starfish arms and the central discs of the same animals showed that iron, zinc, copper and mercury levels were 16 to 30% higher, and selenium, manganese, magnesium, calcium and lead were 4 to 9% higher in the arms. Cadmium concentrations were 20% higher in the central discs than in the arms.

Stock estimations (about 52,000 tons fresh weight) show that starfish play a significant role in the benthic ecosystem of the western Baltic Sea. They can consume up to 200,000 tons of mussels and clams (Mytilus edulis, Macoma baltica) a year and may therefore represent a notable factor in the trace metal balance of the region.     

Integrated relief design for gas-generating reactions: predicted vessel pressure course in dependence on the phase separation model

Pressure relief of a hydrogen peroxide decomposition in a top-vented vessel is simulated numerically using six phase separation models. The results lead to the conclusion that generally a parameter study will be required for relief design by simulation when a gas-generating reaction is considered. None of the phase separation models can be expected to be always conservative in contrast to the case of tempered systems.     

Fostering sustainability through sourcing from small businesses: public sector perspectives

This article examines the opportunities for fostering sustainable development through public sector sourcing from small- and medium-sized enterprises (SMEs). Buying from small businesses can make such contributions in a variety of forms, ranging from a contribution to local economic development through providing innovative green products and services, particularly in the food sector, to helping the public sector organisation to better align its operations with its community. Sourcing from small businesses also has implications for the governance of sourcing processes and can benefit from a partnership approach. Barriers to public sector sourcing from small businesses are discussed and suggestions made on how these can be overcome.