The relationship between pH and community structure of invertebrates in streams of the Shenandoah National Park, Virginia, U.S.A.

1. A replicated natural experiment was used to assess the influence of pH and low alkalinity on abundance and richness of invertebrate families in streams draining catchments that receive acid deposition. Individual streams were used as the unit of replication, allowing conclusions to refer to a class of streams rather than to particular streams. 2. We also controlled for several factors other than pH and alkalinity, including flow and temperature, that are recognized as determinants of invertebrate distribution. Samples were from indigenous rocks, standardized for size, surface area, and geology. 3. Repeated measures analyses of variance (ANOVA) revealed that invertebrate abundance and richness were significantly lower at pH 5.8 than at pH 7.1 for the total community. Thirty per cent of the forty-seven families exhibited significantly lower abundance at pH 5.8; thirteen families were absent at pH 5.8. Differences were greatest for Ephemeroptera: species richness was significantly lower at pH 5.8, and 71% of the twenty-four species were either absent (seven) or found in reduced abundance (ten) in the acidic streams. 4. Stream alkalinity is projected to continue to decrease with continued acid deposition in the Shenandoah National Park. Concurrent decreases in pH may lead to the absence or continued numerical decline of certain Ephemeroptera species in streams that acidify to less than pH 6.0 and/or 50μEql^?1 alkalinity.     

Long-range Perspectives on Neurobiology and Behavior

This essay is part of the seventh presentation of a yearly educationalproject of the American Society of Zoologists. The purpose isto provide background materials for those who teach the first-yearbiology courses in colleges and universities. The Science asa Way of Knowing project emphasizes the conceptual frameworkof the biological sciences, shows how scientific informationis obtained and validated, and relates science to human concerns.The topic for consideration this year is Neurobiology and Behavior.The introductory essay is concerned mainly with the conceptualframework of neurobiology, as developed over the ages, and afew examples of behavioral studies which can be related to neurobiologyor which are of special interest through links to human considerationsand problems.     

Insect responses to plant water deficits. II. Effect of water deficits in soybean plants on the growth and survival of Mexican bean beetle larvae

Abstract. 1. We examined the effect of water deficits in soybean, Glycine max [L.] Merr., on the growth and survival of Mexican bean beetle larvae, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae).
2. Larvae were reared under growth chamber, glasshouse, and field conditions on foliage from plants that were either well-watered or subjected to water deficits.
3. Larval survival, growth rate and pupal weight were reduced, and development time was increased when larvae were reared on foliage from plants subjected to water deficits. These results are contrary to White's (1974) hypothesis that water deficits in plants cause increased growth and survival of herbivorous insects.
4. Changes in foliage chemistry caused by water deficits, possibly in the concentration of free amino acids, are the most likely causes of the observed effects on growth rate and development time. However, under glasshouse and field conditions, physical changes in foliage and/or the foliage's environment that accompany water deficits are also important.     

Hormonal Control of Behavior: Amines as Gain-setting Elements that Bias Behavioral Output in Lobsters

Hormones and neurohormones act on the nervous system to produceimportant changes in behavior. This article uses studies ofamine actions in the lobster nervous system and their possiblerelationship to aggressive behavior in lobsters to explore howsuch changes might come about.