Ontogeny and phylogeny of the trunk lateral line system in cichlid fishes

An examination of the ontogeny of the lateral line trunk canal and the diversity of adult trunk canal patterns among cichlids indicates that bidirectional canal formation is a general ontogenetic pattern in the Cichlidae with the exception of Cichla and those few species with a complete trunk canal pattern. In addition to the tubed scales which make up the trunk canal, some lateral line scales have pits containing superficial neuromasts. These are recognized as components of the lateral line system of the trunk in adult cichlids for the first time. Eight trunk canal patterns that are variations on a simple disjunct pattern are defined among the 17 cichlid genera examined. Using bidirectional canal formation as a developmental model, these patterns can be placed along an ontogenetic spectrum. This suggests that heterochrony (alterations in the timing of development) is an important mechanism of evolutionary change in the lateral line system of the trunk in cichlid fishes.     

Morphology and innervation of the lateral line system inSarotherodon niloticus (L.) (cichlidae,teleostei)

Summary Topography, morphology, and innervation of superficial neuromasts and canal neuromast in adult bony fishes ofSarotherodon niloticus (L.) were studied and compared by light and electron microscopical methods. Apart from certain other morphological differences the two neuromast types also differ in innervation. They can be distinguished by the number, course, and ending of the myelin sheath of their corresponding nerve fibers. All superficial neuromasts arranged in one row are interconnected by a so-called connecting strand. This tissue, unlike the epidermis, consists of tightly packed cells the external membranes of which are considerably meshed. The tissue of the connecting strand does not contain neuronal structures. Supported by a grant from the Universit?t Bielefeld     

Innate sound production in the cichlid Oreochromis niloticus

The mouthbrooding cichlid Oreochromis niloticus is one of the world's best-studied fish and is raised extensively for aquaculture. Although it is a common behavioural model, its acoustic communication has been neglected. Because of extensive parental care, the species is a good candidate for vocal learning. In male O. niloticus , we investigated for the first time sound production in agonistic interactions during nest construction. Males produce short-duration (250–400 ms), often double-pulse sounds. Most energy is below 200 Hz and includes three main low-frequency peaks although energy extends beyond 1 kHz. Males (separated as eggs and raised in isolation) produce similar sounds in the same context as parental fish, indicating that the ability to produce sounds and the basic properties of the sounds are innate.     

Developmental pattern of NADPH-diaphorase activity in the peripheral nervous system of the cichlid fish Tilapia mariae

The distribution of NADPH-diaphorase activity was studied in the cichlid fish Tilapia mariae, during the first developmental stages by means of the tetrazolium salt technique. The reaction product was first found, 48 hours after fertilization (stage 10), in the cells of the olfactory placodes and in the superficial neuromasts. A faint positivity was seen in some hair cells of the otic vesicles. The epithelial cells of the most caudal part of the intestinal tract showed a strong labeling. At stage 12 (hatch), the reaction product was in addition detected in scattered enteric neurons surrounding the digestive tract. At stage 13 (4.5 days after spawning), the reaction product was also found in the putative sympathetic trunk, which supplies the gill arches and digestive tract. The epithelial cells of the gastrointestinal canal showed a more strong positive labeling and two large clusters of cells near the pronephritic tubules (the putative adrenomedullar tissue) were also labeled. The present results indicate an early activity of NADPH-diaphorase during the development of the peripheral nervous system of Tilapia and reveal a gradual maturation of NADPH-diaphorase positive structures.     

Single unit activity in the mesencephalon of Sternarchus

Action potentials evoked in a phase-locked 1 : 1 relationship by natural electric organ discharges (EOD) were recorded extracellularly and intracellularly from single mesencephalic magnocellular nucleus units in the high frequency electric fish Sternarchus albifrons (Gymnotidae). This activity has been shown to be the result of an extrinsic feedback of the electrosensory system and is probably important for the socalled jamming avoidance response triggered artificial electric pulses when delivered into the water in a 1 : 1 relationship at intensities higher than the EOD. In the same way, artificial pulses of frequency near EOD could either drive or, due to beats, greatly disturb the regular firing of the units. More insight into the neural mechanism was yielded by single EOD-triggered shocks provoking a failure in firing of certain action potentials of the series and causing long-lasting (10-20 ms) accelerations and decelerations of the regular EOD-evoked firing (transient disturbance). Intracellular stimulations show similar effects. The biological significance of this neural mechanism for the fish's electroperception and JAR is discussed.     

Mhc class I genes of the cichlid fish Oreochromis niloticus

In terms of number of species, perciform (perch-like) fishes are one of the most diversified groups of modern vertebrates. Within this group, the family Cichlidae is best known for its spectacular adaptive radiation in the great lakes of East Africa. The molecular tool kit used in the study of this radiation includes the major histocompatibility complex (Mhc) genes. To refine this tool, information about the organization of the Mhc regions is badly needed. In this study, the first step was taken toward providing such information for the Mhc class one regions of Oreochromis niloticus, a representative species of the tilapiine branch of the Cichlidae, for which good bacterial artificial chromosome library is available. Screening of the library with class I gene probes led to the identification and isolation of 31 class-I-positive clones. Sequencing of one of these clones and partial characterization of the remaining clones for the presence of class I exons resulted in the construction of two contigs representing the class I region of this species as well as identification of seven additional class-I-positive singleton clones. The O. niloticus genome was shown to contain at least 28 class I genes or gene fragments. The shorter of the two contigs was approximately 330 kb long and contained eight class I genes/gene fragments; the longer contig encompassed 1,200 kb of sequence and contained minimally 17 class I genes/gene fragments; three additional class I genes were found to be borne by a clone that might be part of the shorter contig. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. This work had been carried out in part at the Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Germany (A.S., R.D., N.T., S.S., and J.K.). The sequences reported in this paper have been deposited in the GenBank database (accession nos. AB270803–AB270897).     

Building the posterior lateral line system in zebrafish

The posterior lateral line (pLL) in zebrafish has emerged as an excellent system to study how a sensory organ system develops. Here we review recent studies that illustrate how interactions between multiple signaling pathways coordinate cell fate,morphogenesis, and collective migration of cells in the posterior lateral line primordium. These studies also illustrate how the pLL system is contributing much more broadly to our understanding of mechanisms operating during the growth, regeneration, and self-organization of other organ systems during development and disease.     

Analysis of unit activity in the cat lateral geniculate body

Spontaneous and evoked single unit activity of lateral geniculate body neurons was recorded extracellularly in acute experiments on cats. Eight groups of neurons differing in the durations of the minimal and mean interspike intervals of spontaneous unit activity, and in the latent period and duration of the first volley of spikes of evoked activity, were distinguished by analysis of the data. On the basis of this classification a scheme for interaction between neurons of the lateral geniculate body is suggested.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 30–37, January–February, 1978.     

Single unit activity in the guinea-pig cochlear nucleus during sleep and wakefulness.

The effects of waking and sleep on the response properties of auditory units in the ventral cochlear nucleus (CN) were explored by using extracellular recordings in chronic guinea-pigs. Significant increases and decreases in firing rate were detected in two neuronal groups, a) the "sound-responding" and b) the "spontaneous" (units that do not show responses to any acoustic stimuli controlled by the experimenter). The "spontaneous" may be considered as belonging to the auditory system because the corresponding units showed a suppression of their discharge when the receptor was destroyed. The auditory CN units were characterized by their PSTH in response to tones at their characteristic frequency and also by the changes in firing rate and probability of discharge evaluated during periods of waking, slow wave and paradoxical sleep. The CNS performs functions dependent on sensory inputs during wakefulness and sleep phases. By studying the auditory input at the level of the ventral CN with constant sound stimuli, it was shown that, in addition to the firing rate shifts, some units presented changes in the temporal probability of discharge, implying central actions on the corresponding neurons. The mean latency of the responses, however, did not show significant changes throughout the sleep-waking cycle. The auditory efferent pathways are postulated to modulate the auditory input at CN level during different animal states. The probability of firing and the changes in the temporal pattern, as shown by the PSTH, are thus dependent on both the auditory input and the functional brain state related to the sleep-waking cycle.     

Transformation of peripheral inputs by the first-order lateral line brainstem nucleus

Extracellular recording techniques were used to record the responses of medial nucleus cells and posterior lateral line nerve fibers in mottled sculpin, Cottus bairdi, and goldfish, Carassius auratus, to a 50-Hz dipole source (vibrating sphere). Responses were characterized in terms of (1) receptive fields that relate responsiveness (spike rate and phase-locking) to the location of the source along the length of the fish, (2) input-output functions that relate responsiveness to vibration amplitude for a fixed source location, and (3) peri-stimulus time histograms that relate responsiveness to time during a sustained period of vibration. Relative to posterior lateral line nerve fibers, medial nucleus cells in both species were similar in showing (1) lower spontaneous and evoked rates of spike activity, (2) greater degrees of adaptation, (3) greater heterogeneity in all response characteristics, and (4) evidence for inhibitory/excitatory interactions. Whereas receptive fields of nerve fibers in both species faithfully reflect both pressure gradient amplitudes (with rate changes) and directions (with phase-angle changes) in the stimulus field, receptive fields of medial nucleus were more difficult to relate to the stimulus field. Some, but not all, receptive fields could be modeled with excitatory center/inhibitory surround and inhibitory center/excitatory surround organizations. Accepted: 26 November 1997     

Hydrodynamic image formation by the peripheral lateral line system of the Lake Michigan mottled sculpin, Cottus bairdi

Lake Michigan mottled sculpin (Cottus bairdi) have a lateral-line-mediated prey-capture behaviour that consists of an initial orientation towards the prey, a sequence of approach movements, and a final strike at the prey. This unconditioned behaviour can be elicited from blinded sculpin in the laboratory by both real and artificial (vibrating sphere) prey. In order to visualize what Lake Michigan mottled sculpin might perceive through their lateral line when approaching prey, we have combined anatomical, neurophysiological, behavioural and computational modelling techniques to produce three-dimensional maps of how excitation patterns along the lateral line sensory surface change as sculpin approach a vibrating sphere. Changes in the excitation patterns and the information they contain about source location are consistent with behavioural performance, including the approach pathways taken by sculpin to the sphere, the maximum distances at which approaches can be elicited, distances from which strikes are launched, and strike success. Information content is generally higher for laterally located sources than for frontally located sources and this may explain exceptional performance (e.g. successful strikes from unusually long distances) in response to lateral sources and poor performance (e.g. unsuccessful strikes) to frontal sources.     

Effect of extracellular polarization on unit activity in the lateral geniculate bodies

Unit responses of the lateral geniculate bodies (LGB) to polarization of the cells through the recording microelectrode were investigated in acute experiments on cats anesthetized with Nembutal. Under the influence of anodic polarization the firing rate of the LGB cells clearly increased. Complete adaptation of the cells to the polarizing current was not observed during the time intervals investigated (5–10 min). Cathodic polarization by a current of 5–50 nA induced inhibitory effects; neurons with a single type of spontaneous activity under these circumstances generated volleys of 2–5 spikes. Off-responses were recorded in 75–85% of neurons. It is postulated that complex changes in unit activity produced by polarization may be due to the structural characteristics of the functional connections of the LGB neurons investigated. The change to grouped activity on the part of many of the neurons under the influence of cathodic polarization is evidently explained by the specific functional pattern of the synaptic system of the LGB cells.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 130–140, March–April, 1972.     

Single unit activity of dopaminergic neurons in freely moving cats

Single unit activity was recorded from the area of the substantia nigra in freely moving cats. A sub-population of these neurons had the following characteristics: long action potential durations (2–4 msec); relatively slow discharge rates (2–6 spikes/sec); firing as single spikes along with periods of bursting activity in which spike amplitude successively decreased; suppression of unit activity by systemic injection of apomorphine and increased activity after systemic injection of haloperidol. These characteristics are similar to those of identified dopamine neurons recorded in chloral hydrate anesthetized or peripherally paralyzed rats. Therefore, based upon these physiological and pharmacological similarities, this study represents the first systematic report providing evidence for recording the activity of dopaminergic neurons in freely moving cats. In addition, when these cells were studied across the sleep-waking cycle they displayed little variation in firing rates between waking, slow wave sleep and REM sleep.     

Single motor unit activity in the diaphragm of cat during pressure breathing

In this study we analyzed the breath-by-breath activity of single motor units in the diaphragm slip of allobarbital-anesthetized cats during quiet breathing and during continuous positive- and negative-pressure breathing. Our objective was to determine whether single motor units, on the basis of their activities, can be separated into discrete subpopulations or whether they fall on a continuum analogous to that of motor units of hindlimb muscles. The firing profiles of each unit were characterized for each pressure level by the onset and peak firing frequencies, onset latency, duration of firing, number of impulses per breath, and minimal frequency, when appropriate. Units with shorter onset latencies had higher peak frequencies, longer firing durations, and increased firing frequencies than did units with longer onset latencies. These comparative relationships persisted even though the activity of every motor unit was altered during pressure breathing. During positive-pressure breathing onset latencies were lengthened, and durations of firing were shortened with little change in onset or peak frequencies. Late units might be silenced. During negative-pressure breathing onset latencies were shortened, and durations of firing were lengthened, sufficiently in some cases to fill the expiratory pause. In addition, previously inactive units were recruited late in inspiration for short, relatively high frequency bursts during inspiration. The results support the concept that the phrenic motoneuron pool is comprised of three discrete subpopulations.     

Stress-induced water permeability changes in the tropical cichlid, Oreochromis niloticus (Trewavas)

The effect of short-term, experimentally-induced stress on the branchial water permeability of Oreochromis niloticus was studied. Both handling and thermal stress increased water permeability but apparently by different mechanisms. The enhancement of water permeability by acclimation temperatures and acute temperature changes had Q ₁₀ of 3.52 and 2.24 respectively. Environmental sodium concentration and acute hypoxia had no effect while hypercapnia and mild anaesthesia decreased water permeability. Both hypercapnia and mild anaesthesia probably elevated arterial pCO₂ with a concomitant reduction of metabolism.     

Pattern formation in the lateral line of zebrafish.

The lateral line of fish and amphibians is a sensory system that comprises a number of individual sense organs, the neuromasts, arranged in a defined pattern on the surface of the body. A conspicuous part of the system is a line of organs that extends along each flank (and which gave the system its name). At the end of zebrafish embryogenesis, this line comprises 7-8 neuromasts regularly spaced between the ear and the tip of the tail. The neuromasts are deposited by a migrating primordium that originates from the otic region. Here, we follow the development of this pattern and show that heterogeneities within the migrating primordium prefigure neuromast formation.