Die Sukzession der Testaceen-Assoziationen (Protozoa,Rhizopoda) im rezenten und subfossilen Sphagnum des Obersees bei Lunz (Niederösterreich)

The Succession of Testacea-Associations (Protozoa, Rhizopoda) in Recent and Subfossil Sphagnum from the Obersee near Lunz (Austria). The present paper deals with the Testacean micro-distribution and succession on Sphagnum plants and in a peat profile from the Sphagnum bog of the Obersee near Lunz (Austria). The vertical distribution of living Testacea on Sphagnum plants from the Sphagnum bog of the Obersee near Lunz (Austria) was studied as well as the succession of the Testacean nekrocoenoses in a peat profile (0–100 cm). In the green portion of Sphagnum species possessing Zoochlorellae (Amphitrema flavum, Heleopera sphagni, Hyalosphenia papilio) and Centropyxis aculeata are living. The remaining species are distributed in the lower (dead brown) zone. Active animals were seen to a depth of 18 cm. Some Testacea individuals were able to keep alive again to a depth of 45 cm. Certain species of the Forest Moss Type (Trinema lineare, T. enchelys, Euglypha laevis) dominated in recent Sphagnum and in the peat profile to 12 cm depth. In this time the number of specimens increased. At a depth of 18 cm several typical sediment species of the genus Difflugia (amphora, corona, acuminata, lebes) appeared and the populations of Centropyxis aculeata showed characteristics of sediment-inhabiting individuals (tests covered with mineral particles and vaulted, no spines).     

The distribution of acetylcholinesterase in the cyclostome brain

In the brain of the hagfish Myxine glutinosa the distribution of acetylcholinesterase has been studied in serial cryostat sections. High activity was found in the motor column of the brain stem, in the pars ventralis thalami and in the primordium hippocampi. In the hemispheres and the olfactory bulb the ACHE-content is low.     

Nachweis eines Pharynxbulbus bei Polychaeten aus der Familie Flabelligeridae

The fore-gut of the flabelligerid polychaetesFlabelligera diplochaitus andStylarioides monolifer was investigated histologically. In contrast toDales (1962, 1963) a buccal bulb was found. Important parts of the stomodeum in flabelligerids are a blindly-ending, separate pharynx sac (stomodeal sac) whose epithelium consists of cylindrical and vacuolized cells and is provided with a cuticle, a buccal bulb comprising muscles and vacuolized cells, a sagittal muscle system (investing muscles of the bulb), and a retractor muscle of the bulb. A comparison with the stomodeum of other polychaetes shows that detailed investigations, which might provide a basis for phylogenetic studies, are still lacking.     

Waveform tuning of electroreceptor cells in the weakly electric fish, Gnathonemus petersii

Electroreceptive afferents from A- and B-electroreceptor cells of mormyromasts and Knollenorgans were tested for their sensitivity to different stimulus waveforms in the weakly electric fish Gnathonemus petersii. Both A- and B-mormyromast cells had their lowest sensitivity to a waveform similar to the self-generated electric organ discharge (EOD) (around 0° phase-shift). Highest sensitivities, i.e. lowest response thresholds, in both A- and B-cells were measured at phase shifts of +135°. Thus, both cell types were inversely waveform tuned. The sensitivity of B-cells increased sharply with increasing waveform distortions. Their tuning curves had a sharp minimum of sensitivity at +7° phase shift. A-cells had a much broader waveform tuning with a plateau level of low sensitivity from +24° to −15°. Across a 360° cycle of phase-shifts, the range of thresholds was 16 dB for individual B-cells and 4.5 dB for individual A-cells. Knollenorgan afferents were tuned to 0° phase-shifted EODs and had a dynamic range of 12 dB. Lowest sensitivities were measured at a phase shift of +165°. Experiments with computer-generated stimuli revealed that the strong sensitivity of mormyromast B-cells of EOD waveform distortions cannot be attributed to any of the seven waveform parameters tested. In addition, EOD stimuli must have the correct duration for B-cells to respond to waveform distortions. Thus, waveform tuning appears to be based on the specific combination of several waveform parameters that occur only with natural EODs. Accepted: 28 April 1997     

Wind-sensitive interneurones in the spider CNS (Cupiennius salei ): directional information processing of sensory inputs from trichobothria on the walking legs

Spiders can use air particle movements to localize moving prey. We studied the responses of 32 wind-sensitive interneurones in the hunting spider Cupiennius salei to prey stimuli. Stimulation with a tethered flying fly or with artificial air pulses activated plurisegmental interneurones that responded to changes in air movement velocity and were thus well suited to represent the highly fluctuating air stream typical of prey stimuli. In most interneurones (n = 18) the responses to the stimulation of different legs were not significantly different from each other. Different interneurones had different response characteristics and their latencies largely overlapped suggesting that there is parallel processing of the signals by populations of interneurones with different response characteristics. In two interneurones the number of spikes and the spiking pattern elicited by stimulation of each of the eight legs markedly differed depending on the leg stimulated. These neurones may play an important role in directional information processing. Stimulation of the adjacent legs from front to back or from back to front revealed two interneurones sensitive to the direction of successive stimulation of the legs. These neurones may be able to detect the motion of an air movement source in a preferred direction and thus act as nearfield motion detectors to localize a moving prey item. Accepted: 28 September 1996     

A review of the Nearctic digger‐wasp genus Microstictia Gillaspy, 1963, with description of two new species from Arizona and Florida (Hymenoptera: Apoidea: Crabronidae)

The genus Microstictia is characterized, its species are diagnosed and keyed; their distribution and collecting period summarized; and their taxonomic status discussed. Photographs of selected important characters are provided. Two new species are described, Microstictia pimensis from Arizona (in the rufescens species group) and M. eos from Florida (in the femorata species group). This is the first unambiguous record of Microstictia from the eastern USA. Based on this finding, M. femorata may actually have originated from Florida, which is frequently questioned. Microstictia minutula (described in Monedula), currently misinterpreted, is a valid name for M. texensis Gillaspy, new synonym. This new synonymy is largely based on female colour characters, whose significance is discussed. The species hitherto known as M. minutula is actually M. exigua (W. Fox), with M. divergens (J. Parker) as a new junior synonym.