(Positive) Rheotaxis is a form of

taxis A taxis (; ) is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism (turning response, often growth towards or away from a stim ...

seen in many aquatic organisms, e.g.,

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

, whereby they will (generally) turn to face into an oncoming

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

. In a flowing stream, this behavior leads them to hold their position rather than being swept downstream by the current. Rheotaxis has been noted in

zebrafish The zebrafish (''Danio rerio'') is a freshwater fish belonging to the minnow family (Cyprinidae) of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often ca ...

and other species, and is found in most major

aquatic invertebrate Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evo ...

groups. Rheotaxis is important for animal survival because the positioning of an animal in the water can increase its chance of accessing food and lower the amount of energy it spends, especially when it remains stationary. Some organisms such as eels will exhibit negative rheotaxis where they will turn away from and avoid oncoming currents. This action is a part of their tendency to want to migrate. Some

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

also exhibit positive or negative rheotaxis. In fish, the

lateral line system The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

is used to determine changes in the oncoming flow pattern of a body of water, and the corresponding orientation of the animal toward or away from the current. The lateral line sensory system consists of mechanosensory hair cells that detect the movement of water. Animals can also use rheotaxis in conjunction with other methods to orient themselves in the water. For example,

sea lamprey The sea lamprey (''Petromyzon marinus'') is a parasitic lamprey native to the Northern Hemisphere. It is sometimes referred to as the "vampire fish". Description The sea lamprey has an eel-like body without paired fins. Its mouth is jawless, ...

will use the flow of the current to identify upstream chemical stimuli, and position themselves towards the direction of the signal. Rheotaxis is also a phenomenon seen in small scale artificial systems. Recently, it was observed that certain

self-propelled particles Self-propelled particles (SPP), also referred to as self-driven particles, are terms used by physicists to describe autonomous agents, which convert energy from the environment into directed or persistent motion. Natural systems which have insp ...

(gold-platinum nanorods) will rheotax and reorient themselves against the flow in small microfluidic channels.

References

Ichthyology Aquatic ecology Taxes (biology) {{biology-stub