Session B9: How Fish Use and Process Flow Information

Abstract: Fish use the mechanosensory lateral line and the acoustic system for the processing of hydrodynamic information. With their lateral line fish perceive the amplitude, direction and frequency content of water motions relative to their body and tail fin surface as well as local pressure gradients across their head and trunk. With the acoustic system fish detect the particle displacement component and the pressure amplitude of a sound wave. Both, the lateral line and acoustic system, play an important role in many fish behaviors, including schooling, predator avoidance, intraspecific communication and prey detection. With the acoustic system fish not only can discriminate multiple sound sources but in addition can determine the direction and distance to these sources. Rheophilic fish even use lateral line (and acoustic?) information to save energy while swimming in turbulent flow. The smallest sensory unit of the lateral line is the neuromast. The lateral line neuromasts occur freestanding on the surface of a fish or they are embedded in lateral line canals. Inner ear receptors relevant for the processing of sound information are the hair cells of the utricle, sacculus and lagena. Hydrodynamic stimuli are received and transduced into neuronal signals by the lateral line neuromasts and the inner ear receptors. Lateral line and acoustic information is conveyed by afferent nerve fibres to the fish’s brain and processed by higher order neurons in distinct nuclei. In my talk I will introduce the peripheral morphology of the lateral line and acoustic system of fish, describe behavioral and physiological work, thereby focusing on recent studies that have investigated how fish behave in unsteady flow, what kind of sensory information is provided by the flow and how fish use and process this information

The role of pinna movement for the localization of vertical and horizontal wire obstacles in the greater horseshoe bat, Rhinolopus ferrumequinum

Six Rhinolophus ferrumequinum were trained to fly through an array of vertical or horizontal wires. Obstacle avoidance performance was measured as the percentage of flights in which the bats did not touch the wires (successful flights). Bats with normal mobile pinnae scored between 70% and 90% successful flights both with vertical and horizontal wires. After surgically immobilizing the pinnae by cutting motor nerves and ear muscles, avoidance performance with vertical wires (horizontal target localization) was unchanged but the percentage of successful flights with horizontal wires (vertical target localization) decreased significantly. This demonstrates the importance of pinna movements for target localization in the vertical plane and supports the hypothesis that scanning movements with pinnae are used by Rhinolophus ferrumequinum for determination of target angle

Neurobiology of the Fish Lateral Line: Adaptations for the Detection of Hydrodynamic Stimuli in Running Water

Mogdans J, Kröther S, Engelmann J. Neurobiology of the Fish Lateral Line: Adaptations for the Detection of Hydrodynamic Stimuli in Running Water. In: The Senses of Fish. Dordrecht: Springer Nature; 2011: 265-287

Responses of brainstem lateral line units to different stimulus source locations and vibration directions

Künzel S, Bleckmann H, Mogdans J. Responses of brainstem lateral line units to different stimulus source locations and vibration directions. Journal of Comparative Physiology A. 2011;197(7):773-787.We recorded responses of lateral line units in the medial octavolateralis nucleus in the brainstem of goldfish, Carassius auratus, to a 50 Hz vibrating sphere and studied how responses were affected by placing the sphere at various locations alongside the fish and by different directions of vibration. In most units (88%), stimulation with the sphere from one or more spatial locations caused an increase and/or decrease in discharge rate. In few units (10%), discharge rate was increased by stimulation from one location and decreased by stimulation from an adjacent location in space. In a minority of the units (2%), changing sphere location did not affect discharge rates but caused a change in phase coupling. Units sensitive to a distinct sphere vibration direction were not found. The data also show that the responses of most brainstem units differ from those of primary afferent nerve fibers. Whereas primary afferents represent the pressure gradient pattern generated by the sphere and thus encode location and vibration direction of a vibrating sphere, most brainstem units do not. This information may be represented in the brainstem by a population code or in higher centers of the ascending lateral line pathway

Responses of Medullary Lateral Line Units of the Goldfish, Carassius auratus, to Amplitude-Modulated Sinusoidal Wave Stimuli

This paper describes the responses of brainstem lateral line units in goldfish, Carassius auratus, to constant-amplitude and to amplitude-modulated sinusoidal water motions. If stimulated with constant-amplitude sinusoidal water motions, units responded with phasic (50%) or with sustained (50%) increases in dicharge rate. Based on isodisplacement curves, units preferred low (33 Hz, 12.5%), mid (50 Hz, 10% and 100 Hz, 30%) or high (200 Hz, 47.5%) frequencies. In most units, responses were weakly phase locked to the carrier frequency. However, at a carrier frequency of 50 Hz or 100 Hz, a substantial proportion of the units exhibited strong phase locking. If stimulated with amplitude-modulated water motions, units responded with a burst of discharge to each modulation cycle, that is, units phase locked to the amplitude modulation frequency. Response properties of brainstem units were in many respects comparable to those of midbrain units, suggesting that they emerge first in the lateral line brainstem

Effects of running water on lateral line responses to moving objects

Engelmann J, Kröther S, Bleckmann H, Mogdans J. Effects of running water on lateral line responses to moving objects. Brain, behavior and evolution. 2003;61(4):195-212.We investigated in goldfish, Carassius auratus, and trout, Oncorhynchus mykiss, how running water affects the responses of afferent fibers in the posterior lateral line nerve and of lateral line units in the brainstem medial octavolateralis nucleus to an object that is moved from anterior to posterior or opposite along the side of the fish. In still water, nerve fibers in both species responded to the moving object with alternating periods of increased and decreased firing rate. Most fibers in goldfish but none in trout discharged bursts of spikes in response to the object's wake. Responses of brainstem units were more variable and less distinct than nerve fiber responses. Bursting activity in response to the object's wake was found in only one brainstem unit. In running water, responses of goldfish nerve fibers were weaker than in still water. This effect was independent of object motion direction. Responses of trout fibers were weaker when the object was moved with the flow but were slightly stronger when the object was moved against the flow. In general, running water affected the responses of goldfish nerve fibers more strongly than the responses of trout fibers. Compared to still water, brainstem units in both species responded more weakly when the object was moved with the flow. When the object was moved against the flow, brainstem responses were on average comparable to those in still water. Measurements of changes in pressure and water velocity caused by the moving object indicate that the observed effects can largely be explained by peripheral hydrodynamic effects. However, physiological differences between goldfish and trout units indicate that the lateral line systems in these two species are adapted to different hydrodynamic conditions

Flow Sensing in Air and WaterBehavioral, Neural and Engineering Principles of Operation /

XIII, 562 p. 200 illus., 77 illus. in color.onlin

Wie Fische Wasser fühlen: Das Seitenliniensystem

Bleckmann H, Mogdans J, Engelmann J, Kröther S, Hanke W. Wie Fische Wasser fühlen: Das Seitenliniensystem. Biologie in unserer Zeit. 2004;34(6):358-365