Collin H. Johnson

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Chlamydomonas reinhardtii expresses a well-documented circadian rhythm of phototaxis, which peaks in the subjective daytime. We find that vegetative cells also express circadian rhythms of chemotaxis to ammonium and ammonium uptake (as gauged by uptake of [(14)C]methylammonium). The chemotaxis rhythm peaks in the subjective night. Methylammonium uptake is(More)
The uptake and utilization of dissolved organic matter (DOM) by marine invertebrates is a field that has received significant attention over the past 100 years. Although it is well established that DOM is taken up by marine invertebrates, the extent to which it contributes to an animal's survival, growth, and reproduction (that is, the ecological benefits)(More)
For nearly a century researchers have inves­ tigated the uptake and utilization of dissolved organic matter (DOM) by marine invertebrates, but its contribu­ tion to their growth, reproduction, and survival remains unclear. Here, the beneWt of DOM uptake was assessed for the marine bryozoan Bugula neritina (Linnaeus 1758) through performance comparisons of(More)
Intracellular pH (pH(i)) was measured during the circadian cycle of Neurospora. Internal pH of Neurospora cultures in liquid medium was assayed by the 5,5-dimethyl-2,4-oxazolidinedione method and gave values for pH(i) which were similar to those previously obtained by other workers using pH-microelectrodes with agar-grown cultures. Cytoplasmic pH changed in(More)
Conspecific aggregations in terrestrial and aquatic organisms can have a significant effect on an individual's survival, growth and reproductive fitness, particularly if these aggregations are composed of closely related individuals. Such aggregations can form passively, as a consequence of dispersal, or actively, as a consequence of kin recognition. In(More)
Understanding the consequences of selfing in simultaneous hermaphrodites requires investigating potential deleterious effects on fitness at all stages of life. In this study, I examined the effects of selfing throughout the life cycle of the marine bryozoan Bugula stolonifera, a colonial simultaneous hermaphrodite. In 2008, larvae from field-collected(More)
For sessile invertebrates, the degree to which dispersal mechanisms transport individuals away from their natal grounds can have significant ecological implications. Even though the larvae of the marine bryozoan Bugula stolonifera have limited dispersal potential, high levels of genetic mixing have been found within their conspecific aggregations. In this(More)
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