Temporal patterns in the vibratory courtship signals of the wandering spider Cupiennius salei Keys.

Summary The vibratory courtship signal generated by abdominal and leg movements of male Cupiennius salei on plants consists of impulses, which in groups of about ten form syllables. A syllable together with the preceding silent pause is called a sequence. Up to 50 sequences chained together form a series. A series together with the preceding silent period is called an interseries. A complete courtship is built up from a row of successive interseries. An additional signal produced by palpal drumming only occurs between syllables. Females respond to ca. 40% of the male signal series with a single irregular signal produced by leg oscillations and lasting for 113–1790 ms. Their response reduces the duration of the male interseries significantly from an average of 27.9 s to 20.6 s. The female signal follows a male signal series within a narrow time frame of 0.89±0.53 s. Analysis over long periods of time and of complete courtships showed the male signalling to be highly structured in the time domain and to contain many cues potentially usable by the female for both such precise timing and conspecific recognition: (1) On average, the interval between the last two syllables is significantly longer than the preceding ones. (2) During the course of a series, syllable durations increase nearly linearly from 93 ms to 123 ms. (3) The twelfth sequence (T-12) prior to the final one (T) is outstanding since here, roughly 4 s before the end of a series, the duration of sequences and pauses, the signal amplitudes and the occurrence of palpal drumming abruptly start to increase. Also, the frequencies contained in the syllables shift to higher values. (4) Between sequences T-4 and T-6 pause duration and sequence duration reach their minimum whereas the values for signal acceleration and the occurrence of palpal drumming are highest.     

The use of the tergal gland defensive secretion in male intrasexual aggression of the rove beetle,Aleochara curtula (Coleoptera: Staphylinidae), measured by closed-loop-stripping-analyses and tandem bioassay — mass fragmentography

Summary 2-methyl-1,4-benzoquinone as a target compound of the tergal gland secretion of the rove beetle,Aleochara curtula, was quantified from the reservoirs of individual beetles. Males store less secretion than females, and they evaporate more of the secretion as measured by adsorption from the air (closed-loop-stripping-analysis). The amount of emitted quinone is increased during aggressive interactions of rival males. The pulsed emission of the secretion during aggression is demonstrated by a novel technique combining observation of behavior with the on-line measurement of target fragment ions by mass-spectrometry (tandem bioassay — mass fragmentography). The emission of the secretion is used as a weapon in combats between males and may result in the repulsion of subordinate males from the mating site, but may also serve to mimic females chemically in order to avoid aggressive encounters.     

Forest ecosystems and the changing patterns of nitrogen input and acid deposition today and in the future based on a scenario

A global assessment of the impact of the anthropogenic perturbation of the nitrogen and sulfur cycles on forest ecosystems is carried out for both the present-day [1980-1990] and for a projection into the future [2040-2050] under a scenario of economic development which represents a medium path of development according to expert guess [IPCC IS92a]. Results show that forest soils will receive considerably increasing loads of nitrogen and acid deposition and that deposition patterns are likely to change. The regions which are most prone to depletion of soils buffering capacity and supercritical nitrogen deposition are identified in the subtropical and tropical regions of South America and Southeast Asia apart from the well known 'hotspots' North-Eastern America and Central Europe. The forest areas likely to meet these two risks are still a minor fraction of the global forest ecosystems, though. But the bias between eutrophication and acidification will become greater and an enhanced growth triggered by the fertilizing effects of increasing nitrogen input cannot be balanced by the forest soils nutrient pools. Results show increasing loads into forest ecosystems which are likely to account for 46% higher acid loads and 36% higher nitrogen loads in relation to the 1980-1990 situation. Global background deposition of up to 5 kg N ha-1 a-1 will be exceeded at more than 25% of global forest ecosystems and at more than 50% of forest ecosystems on acid sensitive soils. More than 33% of forest ecosystems on acid sensitive soils will receive acid loads which exceeds their buffering capacity. About 25% of forest areas with exceeded acid loads will receive critical nitrogen loads.