Ecomorphology of retinal structures in zooplanktivorous haplochromine cichlids (Pisces) from Lake Victoria

Synopsis Before the decline of the species flock of haplochromine cichlids of Lake Victoria due to the Nile perch upsurge, there were many co-existing haploehromine species such as the taxonomically and ecologically well-studied zooplanktivores of the Mwanza Gulf. In spite of the scarcely separated niches of some of these species, no sign of competition for space or food could be demonstrated. As is argued in this paper, optical differentiation could well be an aspect of adaptive radiation of these zooplanktivores, particularly among the highly sympatric species. Our hypothesis is based on the morphological modifications of retinal structures in nine zooplanktivorous species. Interspecific variation was observed in composition, size and density of the photoreceptors and ganglion cells. The analyses included the intraretinal variation and size dependency of some of the structural parameters. The optical functions deduced from retinal structure indicate distinct interspecific differences in sensitivity thresholds and a slight differentiation in visual resolution. These functions correlate poorly with the photic conditions of the species-specific habitats. The optical properties can, on the other hand, be connected with the more subtle differentiation in food items and feeding behaviour among these species. It is our concluding hypothesis, that the optical differentiation among the haplochromine zooplanktivores primarily served resource partitioning by different modes of visual prey detection rather than niche partitioning by habitat.     

Diapause detection and monitoring in the Mediterranean corn stalk borer

Abstract. Sesamia nonagrioides Lefebvre diapauses as mature larvae. Once diapause is induced, larvae continue to grow and moult with no apparent changes, so distinction between non-diapausing and diapausing larvae is difficult. In the present work two physiological markers of diapause induction are obtained and their efficacy in detecting diapause onset and in monitoring diapause development in field populations is evaluated. The first marker is based on the differential capacity of two photoregimes, LD 0:24 h and LD 16:8 h, to reverse diapause induction. When larvae of the first and second stadia were subjected to the diapause-inducing LD 12:12 h light cycle and then transferred to LD 0:24 h, larvae pupated after a development duration significantly higher than that of the larvae transferred to LD 168 h. This criterion was used to monitor diapause development in overwintering larvae until field-collected larvae submitted to LD 0:24 h pupated synchronously with those submitted to LD 16:8 h. This occurred between late January and early March. The second marker refers to development of imaginal wing discs. A relative index of the tracheal mass area divided by the total disc area diminishes steadily during development in non-diapausing sixth-instar larvae until it becomes zero just before pupation, whereas it remains constant in diapausing larvae. Though wing disc development was blocked in diapausing sixth-instar larvae, the disc continued to grow and, consequently, the total area of the disc was not a suitable marker of diapause induction. When the constancy of the relative area index was used to monitor diapause development and termination in overwintering larvae, the results agreed with those obtained using the first criterion and with previous field observations.     

Morphology,physiology and in vivo activity of cuticular stress detector afferents in crayfish

Cuticular Stress Detector afferents (CSD1 and CSD2) in the 5th walking legs of crayfish (Pacifastacus leniusculus, Procambarus clarkii) have been studied in an in vitro preparation allowing intracellular recordings to be made from the central terminals of primary afferent fibres during mechanical stimulation of the sense organs. Biocytin anterograde fills and transverse sections of the sensory nerves showed CSD1 to comprise fewer and more heterogeneous fibres than CSD2. Lucifer yellow filling of single fibres showed branching patterns compatible with monosynaptic projections to some motorneuronal groups. Whole nerve recordings during sinusoidal or ramp stimuli showed an important contribution from units with phasic properties. The intracellular recordings identified three features unique to CSD1: 1. Many on-off units have a phasic response to both increases and decreases of force. 2. Many high threshold units respond only to high amplitude vibratory stimuli. 3. A few sensory fibres have a main branch projecting rostrally within the interganglionic connectives, possibly as far as the brain. In vivo recordings of CSD1 activity during forward locomotion on a treadmill showed a discharge occurring in advance of, as well as during, the power stroke. It is therefore suggested that at least some CSD1 fibres encode active as well as passive force during locomotion.Abbreviations AEP Anterior extreme position of a leg during walking - CSDs (CSD1 and CSD2) Cuticular stress detector organs - PEP Posterior extreme position of a leg during walking - VNC Ventral nerve cord     

中国对虾两种球状病毒的免疫检测

以江苏、河北某虾场病虾组织中提取的对虾的两种球状病毒作为抗原,制备出特异性强、效价较高的抗血清,用对流免疫电泳,酶联免疫吸附,免疫电镜技术对五个不同地区的病虾材料进行检测,结果表明：江苏、青岛、河北地区的病虾组织中均含有相应的球状病毒病原。     

Predictive optimality criterion for idealization of ion channel data and exact Akaike's criterion

Different statistical or low-pass filters may be used for the idealization of ion channel data. We address the problem of predicting optimal filter parameters, represented by a threshold test-value for statistical filters and by a cut-off frequency for low-pass filters. Optimal idealization is understood in the sense of maximal similarity between recovered and real signals. Special procedures are suggested to quantitatively characterize the difference between the recovered and the real signals, the latter being known for simulated data. These procedures, called objective criteria, play the role of referees in estimating the performance of different predictive optimality criteria. We have tested standard Akaike's AIC and its modification by Rissanen, MDL. Both gave unsatisfactory results. We have shown analytically, that the Akaike-type criterion, based on the use of a certain penalty for the log likelihood function per transition, indicates the correct optimum point only if the penalty is set equal to half the optimal threshold. As the latter varies significantly for different data sets, this criterion is not particularly helpful. A new universal predictive optimality criterion, valid for real data and any idealization method, is suggested. It is formally similar to AIC, but instead of log likelihood it uses the doubled number of false transitions. The predictive power of the new criterion is demonstrated with different types of data for Hinkley and 50% amplitude methods. Received: 23 July 1996 / Accepted: 9 May 1997     

Unidirectionality of floral colour changes

Many angiosperms have arranged their flowers in inflorescences forming a distinct signalling unit to flower visitors. In some species, the flowers of inflorescences undergo a temporal colour change corresponding exactly to a change in the reward status. Based on information obtained from the spectral reflection curves of pre-change and postchage colours of flower corollas and/or floral guides, it was possible to demonstrate that the colour phase associated with reward closely corresponds to the visual stimuli which trigger behavioural responses of inexperienced flower visitors, and that the colour phase associated with less reward corresponds to visual stimuli less attractive to naïve flower visitors. Reciprocal colour changes were not observed. It is to be assumed that the unidirectionality of floral colour changes is an adaptation of angiosperms aimed at the guidance of first-time flower visitors. Signalling reward to inexperienced flower visitors is an additional function of floral colour changes. The main function of floral colour changes, however, is to provide cues with which the flower visitors can learn to associate one colour phase with reward.     

膜片钳技术与其它技术的结合在神经科学中的应用

膜片钳技术作为一种先进的电生理技术,在生命科学研究中不仅已得到了广泛的应用,而且已与其它许多技术如Ｆｕｒａ－２显微荧光测钙技术、碳纤电极局部电化学微量检测技术以及单细胞逆转录多聚酶链式反应技术等进行了有机的结合。本文仅就此技术与其它技术的结合及在解决神经生物学跨膜信号转导问题中的应用情况作一综述。     

Object detection in the fly during simulated translatory flight

Translatory movement of an animal in its environment induces optic flow that contains information about the three-dimensional layout of the surroundings: as a rule, images of objects that are closer to the animal move faster across the retina than those of more distant objects. Such relative motion cues are used by flies to detect objects in front of a structured background. We confronted flying flies, tethered to a torque meter, with front-to-back motion of patterns displayed on two CRT screens, thereby simulating translatory motion of the background as experienced by an animal during straight flight. The torque meter measured the instantaneous turning responses of the fly around its vertical body axis. During short time intervals, object motion was superimposed on background pattern motion. The average turning response towards such an object depends on both object and background velocity in a characteristic way: (1) in order to elicit significant responses object motion has to be faster than background motion; (2) background motion within a certain range of velocities improves object detection. These properties can be interpreted as adaptations to situations as they occur in natural free flight. We confirmed that the measured responses were mediated mainly by a control system specialized for the detection of objects rather than by the compensatory optomotor system responsible for course stabilization. Accepted: 20 March 1997     

Identification of hemorphins in a cathepsin D bovine hemoglobin hydrolysate by radioimmunoassay and photodiode array detections

Morphinomimetic peptides have been purified fromhemoglobin enzymatic hydrolysates and a significantamount of evidence has been accumulated indicatingthat the generation of these peptides (hemorphins)might occur in vivo. In order to investigatetheir putative physiological role and processing fromhemoglobin in vivo, two methods were developed:a specific radioimmunoassay and a UV spectracomparison analysis. These methods were applied to acathepsin D bovine hemoglobin hydrolysate and allowedthe detection of two hemorphin-7 peptides. Thisobservation supports the putative implication ofcathepsin D in the in vivo release ofhemorphins. Among the two methods used in this study,the immunological approach exhibits highersensitivity and represents a useful method toinvestigate the in vivo role and physiologicalprocessing of hemorphins.