The ultrastructure of the cuticle of Nematoda

 The ultrastructure of the body cuticle in species of six of seven representative genera of Stilbonematinae (Eubostrichus, Catanema, Laxus, Robbea, Leptonemella, and Stilbonema) was investigated using SEM and TEM techniques. Additionally, one species of Spirinia (Spiriniinae) and one of Desmodora (Desmodorinae) were studied for outgroup comparison. The body cuticle of all investigated stilbonematids shows a consistent pattern composed of specific elements in a characteristic arrangement to each other. This pattern does not occur in Stilbonematinae alone, but also in Desmodorinae and Spiriniinae. Furthermore, a comparison within the Desmodorida reveals that this cuticular pattern apparently is present in the cuticle of representatives of Monoposthiidae, Epsilonematidae, and Draconematidae. The present results lead to the following conclusions: (1) the cuticle of Stilbonematinae contains no autapomorphic characters for this taxon, (2) there is a common cuticular pattern within the Desmodorida, and (3) this pattern is an autapomorphic character for the order Desmodorida. Accepted: 4 February 1996     

Behavioural and morphological changes in ciliates induced by the predator Amoeba proteus

The predator Amoeba proteus induced behavioural and morphological changes in ciliates of the genus Euplotes. The frequency of avoidance behaviour in E. octocarinatus increased from 16±5% to 84±5% (SD) after 14 h of coexistence with the predator. The ciliate's width increased from 59±3 μm to 77±4 μm (SDM) within 48 h. Similar behavioural, but not morphological, change was induced in E. daidaleos, but neither morphological nor behavioural responses occurred in E. aediculatus. E. octocarinatus and E. daidaleos populations survived in the presence of A. proteus, whereas E. aediculatus populations became extinct by predation. Induced behavioural response seemed to be the reason for the low predation risk of E. octocarinatus and E. daidaleos. The results suggest that Euplotes ciliates have evolved specific defence mechanisms to various predators. Defensive changes are induced by a chemical substance released from A. proteus. This “kairomone” has a molecular weight between 5000 and 10000 Da. Proteolytic digestion of its activity indicated that the avoidance-inducing substance is a peptide. After the turbellarian Stenostomum sphagnetorum had induced a defensive morphology in E. octocarinatus or E. aediculatus, neither of these ciliates immediately avoided Amoeba proteus. Thus, Euplotes ciliates with a defensive morphology do not have behavioural defences in reaction to all predators.     

‘Absolute steepness’ of ramps as an essential cue for auditory pattern recognition by a grasshopper (Orthoptera; Acrididae; Chorthippus biguttulus L.)

Male grasshoppers of the species Chorthippus biguttulus react to female songs with a characteristic turn towards the female. The probability of turning towards female song models was used to evaluate those parameters which are essential for a signal to be interpreted as female song.

1. The shape of sound pulses turned out to be most decisive; pulses with ramps rising gradually over 3 and more ms were efficient (Figs. 2, 3), whereas rectangularly modulated pulses evoked only weak responses and only when pulse intervals were between 3 and 5 ms (Fig. 2). The decline of a pulse did not influence its efficiency (Fig. 3). In particular, pulses with sudden onsets and gradual declines were as weakly effective as rectangularly modulated ones and thus remarkably less effective than pulses with ramp-like onsets (Fig. 4).
2. Intensity tuning curves suggest, that the absolute steepness of ramps (expressed as μbar/ms) is detected by the grasshopper nervous system (Figs. 6, 7), possibly by processing the delay in excitation onset of at least two receptor types differing in threshold sensitivity.
3. The sawtooth shape of pulses in female signals is suggested to be adaptive with respect to directional hearing.

     

Vibratory communication in spiders

We analyzed the response of the vibration sensitive lyriform organ on the metatarsus of female spiders (Cupiennius salei) to dummies of male courtship vibrations. One of the two representative slits studied is sharply tuned to 500 Hz. Only the other slit is sensitive enough at lower frequencies to represent the parameters contained in the behaviourally effective dummies:

1. Amplitude. The physiological threshold is similar to the behavioural threshold. The stimulus acceleration amplitudes leading to a good synchronization between response and temporal stimulus pattern coincide with those effectively eliciting a behavioural response. The most frequent spike intervals remain nearly constant in this range. At acceleration amplitudes above the natural range, syllable and pause durations are misrepresented by the receptor response.
2. Frequency. Varying the carrier frequency between 35–500 Hz changes the most frequent spike intervals. Interval histograms resulting from behaviourally effective stimuli (50–200 Hz), however, are similr for carrier frequencies differing by a factor of 2.
3. Temporal pattern. Response duration reflects the temporal parameters of the stimulus. The most frequent spike interval only changes with temporal stimulus characteristics far off the natural range. The number of spikes during a syllable decreases in ongoing stimulus series. The quality of copying the temporal stimulus pattern remains unchanged, however.

     

Morphological effects of tributyltin (TBT) in vitro on the genital system of the mesogastropodaLittorina littorea (Prosobranchia)

This ultrastructural study investigates the pathological changes in the penial, the sperm groove and the glandular cushion epithelium in maleLittorina littorea (Mesogastropoda) related to TBT (tributyltin) contamination. The results are compared with those onOcinebrina aciculata (Neogastropoda), which shows a wide range of cell changes in the penis epithelia of male and imposex affected females. The investigation of the different penis epithelia ofL. littorea revealed that the cells analysed show a low sensibility towards TBT. The cells display normal metabolism. Certain atypical structures like swelling microvilli and cristae which tend to lie parallel to the long axis in the mitochondria, were detected as pathological effects.