Rheotropism in Fishes

Abstract

Summary (1) The fluid properties of air and water enable animals to orientate to flow and this behaviour in water is termed rheotaxis. Fish, however, have a wide range of responses to currents, extending beyond simple orientation, and the term rheotropism is therefore used as a ‘portmanteau’ word to describe all such reactions. (2) Fish detect currents directly by flow over the body surface or indirectly by other stimuli. Indirect responses are more common and occur in response to visual, tactile and inertial stimuli resulting from displacement of the fish by the current. Reactions to displacement of visual images are called optomotor reactions. The lateral line is not involved except in the detection of small localized jets of water. It has not been demonstrated that any fish can detect the current by electrical stimuli, although it is theoretically possible for some to do so. (3) In the basic form of rhotaxis the fish heads upstream and maintains station by stemming the current. Current detection thresholds fall within the range 0.4 to 10 cm/s for tactile stimuli but may be as low as 0.03 cm/s for visual stimuli. (4) Visual responses have been studied by simulating displacement by the current in optomotor apparatus. Fish respond to a rotating black‐and‐white‐striped background by compensatory movements of the head and eyes ‐ optokinetic nystagmus ‐ or by the optomotor reaction, in which the fish swims with the background. (5) Fish show an orthokinesis in optomotor apparatus, their mean swimming speed increasing with the speed of rotation of the background. The precise form of the relationship varies between species and there is also considerable individual variation in performance. Fish accelerate and decelerate relative to the background, fixating on a particular stripe for short periods. (6) Factors limiting the appearance of the optomotor response are contrast, illuminance, acuity, critical flicker fusion frequency and spectral sensitivity. (7) Fish tolerate retinal image movements equivalent to those received when they are carried forwards by the current but not to those received when they are carried backwards. There are ganglion cells in the optic tectum which are sensitive to the direction of movement of targets across the visual field. In the goldfish there are significantly more units sensitive to movements in the temporo‐nasal than in the opposite direction. (8) There are close parallels between the behaviour of fish in schools and in an optomotor apparatus. The optomotor response is apparently innate, occurring in newly hatched fry. (9) Physical and chemical factors can modify rheotaxis. Temperature and olfactory stimuli affect both the sign of the taxis and the kinetic component of the behaviour. (10) Thyroid hormones which are involved in the control of migration have been shown to affect the kinetic component of rheotaxis. (11) Fish show a number of hydrodynamic adaptations to life in currents. Morphological modifications are greatest in fish from torrential streams, which show extreme dorsoventra...

Bacterial rheotaxis

“…In larger organisms like fish (11,12) and aquatic invertebrates (20) rheotaxis is active, as these organisms are able to measure shear and behaviorally respond to it. Shear-sensing mechanisms include the lateral line in fish (12), the setae on copepods' antennae (18), and changes in the membrane's electrical potential in protists (33).…”

“…Rheotaxis refers to changes in organism movement patterns due to shear. Rheotaxis is common in fish (11,12), which actively sense shear and respond by either turning into the flow or fleeing high-flow regions. Certain insects use rheotaxis to escape droughts by swimming upstream in desert rivers (13).…”

Fish navigation of large dams emerges from their modulation of flow field experience

“…In the real world, fish swimming works in context with many factors, including light and vision (16,24,30), sound (16), social interactions (49), feeding, predators, water quality, chemical cues, fish size and age, and hydraulics at scales smaller than considered here. Differences between modeled and actual environments could have implications on what we infer about fish behavior (50); however, at minimum, our study suggests that abstractions of the real world from hydraulic and behavioral modeling may inform how engineered features function with the cue responses that fish have naturally evolved.…”

“…Our approach is based on the simple notion that animals sensitive to gravity are generally also sensitive to other acceleratory and inertial stimuli (22). Decades of work have identified fish sensitivity to relative water velocity and acceleration fields over short ranges, as well as inertial stimuli (17,(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). To explore how water acceleration may shape fish movement and identify why fish avoid some flow field regions, we need descriptions of water velocity and acceleration throughout the environment.…”

Lateral line-mediated rheotactic behavior in tadpoles of the African clawed frog (Xenopus laevis)

“…Initially, visual cues were believed to be paramount in rheotaxis, as orientation of some species of pelagic fish was more accurate when a fixed visual external reference point was provided (Arnold 1974). More recent research using benthic, semipelagic, and cryopelagic species and conducted in the absence of visual cues (Montgomery et al 1997;Baker and Montgomery 1999) suggest that the lateral line system is also crucial for providing information on the direction of water currents.…”