David D. Hof

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In most pollination systems, animals transfer pollen among plants of a given species. Pollinator visitations do not come without cost, so plants usually offer a reward. However, the flowers of some plant species, mostly orchids, lack rewards and deceive animals into visiting their flowers. Deceptive species are thought to have high levels of variation in(More)
Rival conspecifics often produce stereotyped sequences of signals as agonistic interactions escalate. Successive signals in sequence are thought to convey increasingly pronounced levels of aggressive motivation. Here, we propose and test a model of aggressive escalation in black-throated blue warblers, presenting subjects with two sequential and(More)
Voltage-clamp recordings of INa in squid axons dialysed with Cs or TMA, and bathed in low Na choline seawater, showed that, except close to threshold, the initial peak of fast-inactivating current was invariably decreased by TMA, whereas the non-inactivating current in the steady state was simultaneously increased. The results suggest that although TMA does(More)
The modification of the ultraviolet blocking of sodium channels and of the ultraviolet-induced potential shift of the gating parameters by means of the sulfhydryl compoundsl-cysteine and 2-mercaptoethanol was investigated in the node of Ranvier under voltage-clamp conditions. The UV wavelength was 280 nm. The radiation-induced potential shift of the(More)
The effects of ultraviolet (UV) radiation at various intermediate states of excitation of the frog nerve membrane were measured under voltage-clamp conditions. By synchronizing a UV flash source (flash duration: 10 μsec) with the stimulating voltage-clamp pulses it was possible to irradiate the membrane at any state of excitation. The resulting UV(More)
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