Feeding behavior in sexual and clonal strains of Poeciliopsis

Summary Sexual and clonal fish of the genus Poeciliopsis occur together in desert streams of Sonora, Mexico. Their coexistence has been explained in terms of niche partitioning for food and space. We examined predatory behavior that might influence niche relationships, and found significant differences among two coexisting sperm-dependent clonal strains and their two sexual progenitors. Handling time and prey manipulation of free-swimming (Artemia) and benthic (chironomid larvae) prey differed significantly among sexual and clonal strains. Analyses of gut contents from field-collected fish revealed that the laboratory estimates of predatory efficiency were related to their feeding behavior in nature. Behavior differences, such as those described herein, contribute to our understanding of the mechanisms of unisexual/bisexual coexistence in Poeciliopsis. Offprint requests to: R.C. Vrijenhoek     

Zur Kritik des Hooker-Forbes-Tests (HFT)

The Science of Nature -     

Quecksilbergasfeinreinigung mittels metall- und salzpartikelbelegter Trägermaterialien (G/S-Reaktor) Ökotoxizität von Quecksilber und seiner Verbindungen

Waste and process gases from thermal power and metallurgical plants or such products from alkali-chloride industries contain metallic, inorganic and organic mercury. Widespread processes applied to remove the greatest amount of mercury are absorption and adsorption. Caused by the lowering of the emission limit from 200 to 50 μg/m³ [STP] by national and European legislators, considerable efforts have been made to enhance the efficiency of the main separation units of flue gas cleaning plants by applying the appropriate technological measures. This article is focused on the removal of mercury from waste gases. The state of engineering is described, especially with regard to enhancing the efficiency of separation in the raw gas, in wet, dry and quasi-dry processes as well as in tail-end process units. Specially impregnated ceramic carriers can be used for the selective separation of metallic, inorganic and organic mercury. Amalgamation has been investigated as a possible separation mechanism both experimentally and in theory. Using the ceramic reactor, removal rates for gaseous mercury and its compounds can be achieved which are even lower than 50 μg/m³ [STP]. The technology, the separation mechanisms and the ecological advantages through the use of ceramic reactors are presented in the article as well.     

Chitinolytic enzymes in the integument and midgut-gland of the shrimpPalaemon serratus during the moulting cycle

Chitinase andN-acetyl--D-glucosaminidase activity were quantified inPalaemon serratus (Pennant) integument and midgut gland during the moulting cycle. Studies were performed on specimens collected near Concarneau, France, in July 1989. The changes in specific activity are different in the two organs: in the midgut gland enzymatic activity is high throughout the whole moulting cycle with a weak peak at the early premoult Stage D1, whereas in the integument the activity of both enzymes is very low throughout post- and intermoult stages and rises only after premoult Stage D1. The highest specific activity is reached in D1 for chitinase and somewhat earlier (D1) forN-acetyl--D-glucosaminidase. The increase in specific chitinolytic activity coincides with an increase in ecdysteroids.