Assessment of the Multispecies Freshwater Biomonitor (MFB) in a marine context: the Green crab (Carcinus maenas) as an early warning indicator.

The Multispecies Freshwater Biomonitor is an online continuous biomonitor which utilises impedance conversion to quantitatively record behavioural responses of vertebrates and invertebrates to environmental change. Here, we extend the use of the MFB into the marine aquaculture environment using the Green crab (Carcinus maenas) as a biological monitor. As a ubiquitous and abundant species, C. maenas can be used in applications such as aquaculture and monitoring of diffuse and point source marine pollution. Four experiments were undertaken to establish: (1) if the electrical field generated by the apparatus had any effect on C. maenas; (2) if the behaviour of C. maenas was altered by the presence of ammonia; (3) if the behaviour of C. maenas was affected by the electrical field when ammonia was present and (4) if defined behaviours could be detected by the MFB. There was no significant effect of the current on C. maenas in the MFB. There was a significant difference in overall expression of behaviour in response to an increasing gradient of ammonia and activity of the chamber. Five behaviours, 'walking', 'climbing', 'leg stretch', 'cleaning' and 'inactivity' were detected by the MFB. C. maenas appears to be a suitable candidate for use in the MFB in a marine context. Further testing of the biomonitor and C. maenas is required using other toxicants to establish alarm thresholds that could be used in situ for water quality monitoring.

Behavioural responses to electrical and visual stimulation of the toad tectum.

Slow potential shifts in brain structures have been recorded and correlated with motivational state in several species. Previous studies have also found that application of an electrical current to the surface of brain tissue generates such slow potential shifts. The present study was conducted to examine if imposed dc shifts to the brain influenced motivation in the toad (Bufo bufo). Toads (B. bufo) had stimulating electrodes implanted on the surface of each optic tectum. After 1 day of recovery combined dc stimuli and a prey-like visual stimulus were presented to the animal. A current-dependent increase in prey-catching activities occurred with dc currents from 0.1 to 500 micro A and in avoidance behaviours from 50 to 500 micro A. There is also evidence of additivity of dc and visually induced negativity increasing some behaviours. The dc current was applied in order to start a movement of ions through the brain structure but more specifically through radial glia. The resulting flux of ions is thought to be responsible for the recorded slow potential shift associated with motivation and these experiments hopefully shed further light on the possible neuromodulatory role played by radial glia through the spatial buffering of potassium and the associated slow potential shifts.

Suitability of Crangonyx pseudogracilis (Crustacea: Amphipoda) as an early warning indicator in the multispecies freshwater biomonitor.

BACKGROUND: Biological monitors are increasingly important in 'Biological Early Warning Systems' (BEWS) for monitoring water quality. This study examines the freshwater amphipod Crangonyx pseudogracilis as a potential new indicator species when used in the Multispecies Freshwater Biomonitor (MFB). The MFB is an online continuous biomonitor which uses impedance conversion to record behavioural responses of vertebrates and invertebrates. METHODS: Four experiments were undertaken to establish: (1) if the electrical field generated by the MFB affected the organisms' behaviour, (2) if defined behaviours and their response to a gradient of ammonium chloride could be detected by the MFB, (3) if there was variation in the behaviour of C. pseudogracilis over a diel cycle, and (4) if behaviour changed significantly in response to a pulse of ammonium chloride. RESULTS AND DISCUSSION: Results showed no significant effect of the MFB's current on behaviour of C. pseudogracilis. Four behaviours; swimming, walking, grooming and inactivity, were observed and identified in the MFB. In the MFB, each behaviour changed significantly in response to an increasing gradient of ammonium chloride exposure. The MFB also detected increases in nocturnal activity by C. pseudogracilis. The MFB also detected a significant increase in activity after a pulse of ammonium chloride. CONCLUSION: The range of behaviours exhibited by Crangonyx pseudogracilis, together with its ease of culture, suggest future potential of this species as an indicator species for the Multispecies Freshwater Biomonitor. RECOMMENDATIONS AND OUTLOOK: Further testing is required over a range of toxicants and concentration gradients to establish threshold responses and the full compliment of behaviours that could be useful in online biomonitoring.

Mechanoreceptive and nociceptive responses in the central nervous system of goldfish (Carassius auratus) and trout (Oncorhynchus mykiss).

UNLABELLED: Nociceptive responses to a repetitive pin-prod stimulus in goldfish and trout were assessed. Single unit recordings were taken from the spinal cord, cerebellum, tectum, and telencephalon. Neuronal responses were elicited in all these regions of the central nervous system in both species of fish during brush (mechanoceptive) and pin-prod (nociceptive) stimuli. In addition, in trout, a heated prod stimulus was used. Mechanoreceptive and nociceptive neuronal responses to various stimuli were elicited in all regions, and responses were detected as far as the telencephalon in both species. In goldfish, a noxious stimulus produced greater neuronal activity than a mechanoreceptive stimulus. This was not found in trout. The accurate setting of timed prods allowed the latency of the response to be calculated in all regions. From these data, conduction velocities suggested that A delta and C fibers were activated; both fiber groups previously have been shown to be involved in nociception in fish. This study has shown that there is neuronal activity in all brain areas including the telencephalon, suggesting a nociceptive pathway from the periphery to the higher central nervous system of fish. PERSPECTIVE: This study presents novel data on telencephalic activity in fish after noxious stimulation and demonstrates the potential for pain perception in lower vertebrates. Not only is this of an evolutionary significance, but it also adds to the controversial argument about whether fish perceive pain.

Behaviour of the three-spined stickleback, Gasterosteous aculeatus (Gasterosteidae, Teleostei) in the multispecies freshwater biomonitor: a validation of automated recordings at three levels of ammonia pollution.

The validity of using an automated online biomonitoring system, the multispecies freshwater biomonitor (MFB), in recording the physiological and behavioural activities of the three-spined stickleback Gasterosteous aculeatus, is assessed. The direct impact of the alternating electrical current generated by the impedance converter on fish activity was measured using a repeated measures design, machine on/machine off. Twelve subjects were used in each of three experimental groups: (1). standard hard water environment (control), (2). 0.1mM NH(4)Cl and (3). 10mM NH(4)Cl. Impedance generated waves were compared to corresponding manually recorded behavioural observations in an attempt to calibrate the MFB, assigning particular behaviours to a particular frequency and amplitude range. Data analysis suggests that the MFB current did not affect fish behaviour at any of the three contamination levels studied. Furthermore, analysis of the frequency with which behavioural activity changed (activity phases classified as inactive or active) showed that MFB behavioural data was not significantly different from that recorded manually. This suggested that the MFB recorded the behaviours that were concurrently observed. The feasibility of using the MFB as an effective behavioural early warning system in an aquacultural environment and as a scientific tool for toxicity testing is discussed.

DC electrical stimulation of the pretectal thalamus and its effects on the feeding behavior of the toad (Bufo bufo).

The feeding motivation of the common European common toad (Bufo bufo) can be quantified by the feeding sequence of arousal-orientation-approach-fixate-snap. Previous work has found that the optic tectum is an important structure responsible for the mediation of feeding behaviors, and combined electrical and visual stimulation of the optic tectum was found to increase the animals feeding behaviors. However, the pretectal thalamus has an inhibitory influence upon the optic tectum and its lesion results in disinhibited feeding behaviors. This suggests that feeding behavior of anurans is also subject to influence from the pretectal thalamus. Previous studies involving the application of DC stimulation to brain tissue has generated slow potential shifts and these shifts have been implicated in the modulation of the neural mechanisms associated with behavior. The current study investigated the application of DC stimulation to the diencephalon surface dorsal to the lateral posterodorsal pretectal thalamic nucleus in Bufo bufo, in order to assess effects on feeding motivation. The application of DC stimulation increased the incidence of avoidance behaviors to a visual prey stimulus while reducing the prey catching behavior component of approach, suggesting that the DC current applied to the pretectum increased the inhibition upon the feeding elements of the optic tectum. This can be explained by the generation of slow potential shifts.

Neuronal responses are differentially affected by the polarity of tectal DC stimulation in the toad Bufo bufo.

Male toads were tested behaviourally for their prey catching responses to worm-like stimuli before being prepared for visual unit and slow potential shift (SPS) recording from the optic tectum. The neuronal responses of toads to a prey-like visual stimulus reflected their motivational tendency prior to operations. One second of DC stimulation to the tectum was followed by an SPS of reversed polarity during which time a visual prey-like stimulus was presented. A negative SPS following positive DC stimulation was associated with enhanced neuronal responses to a visual stimulus. The positive SPS that followed negative stimulation was associated with a decline in neural responses below background when a visual stimulus was additionally given. The SPS was largely a result of DC stimulation that interacted with the motivational tendency to produce enhanced neuronal responses, while the potential was negative and vice versa.

Tectal responses to potassium loads and subsequent visual stimuli in the toad, Bufo bufo.

Calling male toads were tested behaviourally for their prey catching responses to wormlike stimuli and assigned to groups of non-hungry and hungry depending on their prey catching motivation before being prepared for visual unit, massed unit and slow potential shift (SPS) recording from the optic tectum. Control recordings to visual stimuli were made before recording the effects of application of isotonic solutions containing concentrations of 0-41 mM K(+). Application of solution was followed by presentation of the visual stimulus while the solution still bathed the tectum. The best tectal responses were made to large square visual stimuli in the non-hungry toads, perhaps because recordings were made in the breeding season. Responses of the tectum to solution addition were significant in the concentration range of 7-17 mM K(+). Hungry toads showed an earlier, smaller response than non-hungry (sexually motivated) animals. When the visual stimulus was presented, there were unit and massed unit responses at all bathing solution concentrations, which were larger in non-hungry animals. These experiments revealed that toads motivated to feed respond earlier than non-hungry toads to application of artificial CSF to the tectum, though non-hungry toads responded best to the subsequent visual stimulus.