Umbra pygmaea, an acid-tolerant fish

Prolactin cell activity and sodium balance in the acid-tolerant mudminnow Umbra pygmaea in acid and neutral water.

In East-American mudminnows, obtained from lakes and bogs of different water pH levels, prolactin cell size and ultrastructure reflect higher secretory activity in neutral water than in water of pH 3.5-6.5. This contrasts with observations on other species in which prolactin cell activity is higher at low water pH. Laboratory experiments involving acute exposure of mudminnows from pH 5.5 for 48...

Sodium Balance in the Acid Resistant East American Mudminnow, Umbra Pygmaea (de Kay)

Effects of Acid Stress on the Distribution and Reproductive Success of Freshwater Fish in Dutch Soft Waters

The distribution and reproductive success of fish were examined in Dutch soft waters of varying pH. In total, 20 fish species were encoun­ tered. The lowest pH-values at which fish species were observed varied remarkably. Umbra pygmaea and Tinea tinea appeared to be extremely acid tolerant and occurred in waters with pH-values below 4.0. Abramis brarna, Cyprinus carpio, E’sox iucius, Misgumus f...

Generating Shadows with an Umbra and Penumbra

An algorithm for generating shadows with an umbra and penumbra due to distributed light sources is presented. The method used is based on the inclusion of the shadow volumes in the object data processed by a depth-buffer visible surface computation. The standard depth-buffer data structure is modified to allow the handling of shadows with a depth-buffer hidden surface algorithm. The algorithm i...

Umbra, an Object-Oriented Simulation and Integration Framework

This paper describes a modeling, simulation, and integration framework developed at Sandia National Laboratories with support from ORION International Technologies, Inc. This framework, called Umbra, increases the efficiency for developing new applications and for integrating new and/or existing applications. A process for rapidly and effectively developing new modeling and simulation applicati...