Predator-prey interactions have historically been studied to explain patterns of organization observed in populations and communities. They have also been important in understanding the evolution of antipredator responses in prey and counterstrategies in predators. Despite the breadth of knowledge that exists for heterospecific interactions, relatively few studies have investigated the...
The causes of the global biodiversity crisis are varied and complex. Anthropogenic threats may act in isolation, or interact additively or synergistically with each other or with natural stressors to affect sensitive taxa. The recent emergence of many infectious diseases in wildlife has brought attention to the role of disease...
In the past decade, declines in amphibian populations have captured scientific and popular interest. The causes of the declines are likely to be complex and involve interactions between several environmental stressors. Using multifactorial experiments, I investigated the combined effects of several anthropogenic stressors on developing amphibians in Oregon, USA. In...
The feeding ecology of a common temperate mesoherbivore, the oligophagous sea slug Placida dendritica (Gastropoda: Opisthobranchia: Ascoglossa), was examined from April 1985 to June 1989. Along the central coast of Oregon, Placida consumed three host species: the low intertidal green algae Codium setchellii, C. fragile, and Bryopsis corticulans. Individual slugs...
The influence of large-scale processes on natural communities has become one of the central issues of modern ecology. I combined field and laboratory studies to investigate the effects of variation in coastal upwelling on rocky intertidal communities along the central Oregon coast. I examined whether the growth of intertidal barnacles...
The lack of a suitable demembranated cell model has hindered the
study of the mechanisms responsible for the regulation of ciliary
waveform and coordination. In this study procedures for the
isolation of ciliated cells from the newt, Taricha granulosa, by
trypsin dissociation, and their subsequent demembranation with Triton
X-100 and...
The spermiogenesis of Mytilus edulis (a marine mussel) has
been studied, employing techniques of light and electron microscopy
and cytochemical preparations. The observations trace the development
of the acrosomal complex, the nucleus, the mitochondrial
middle-piece, and the flagellum.
In early spermatids numerous membrane-bounded proacrosomal
vesicles arise from several Golgi complexes...
Callianassa californiensis (Dana), a burrowing crustacean
inhabitant of estuarine mudflats along the Pacific coast, is subjected
to severely hypoxic interstitial water twice each tidal
cycle.
A preliminary approach was made to understanding the metabolic
mechanisms employed by Callianassa during periods of anoxic stress.
Percent glycogen in the hepatopancreas and chela...
Primary monolayer cultures of chick renal epithelial cells
grown on plastic coverslips were reversibly dissociated with the
chelating agent ethylenediaminetetraacetic acid (EDTA). The cellular
responses during dissociation and reaggregation in Hank's balanced
salt solution (BSS) were observed with phase optics and recorded
by time-lapse cinemicrography.
The epithelial cells grow as...
I examined two amphibian communities to assess factors
that may impact amphibian biodiversity. The results suggest
that the potential factors which influence the maintenance
of amphibian biodiversity are multi-faceted and thus,
attempts to understand these factors must reflect these
complexities.
I investigated factors that influenced the susceptibility
of western toad...