Hairs Detect Changes in Water Current

Biological Strategy

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Sense Motion

Perceiving motion is important for a living system to sense where it is in relation to a moving environment, which is critical in locating resources or wayfinding. This applies whether the environment itself is in motion (such as water movement coming from a nearby fish) or the living system is moving within a stationary environment (such as a bird flying through the air). Because motion dampens over distance and the cost of missing those motion signals is high, living systems must be quite sensitive to these signals. For example, fast-flying big brown bats have microscopic, stiff, domed hairs on their wing membranes that act as a sensor array to monitor flight speed and airflow conditions.

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Crustaceans

Subphylum Crustacea (“crust”): Crabs, barnacles, shrimp, pillbugs

Some crustaceans, like pillpugs and woodlice, live on land, but most are found in the ocean. Their heads are distinctive among the arthropods: they have two pairs of antennae and three pairs of feeding appendages that help them hold and crunch food. Crustaceans also have a unique larval stage called the nauplius (named after the son of Poseidon) which has three pairs of legs and one eye. Most crustaceans are in class Malacostraca, which contains a wide range of species that live in mostly marine environments, like krill, lobster, and mantis shrimp.

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The antennae of Euchaeta rimana, a copepod, detect changes in the smooth water current (created by the shrimp's mouthparts) via motion-sensitive hairs.

“One tiny crustacean, Euchaeta rimana, combines elements of the fish’s sensitive skin and the spider’s motion-sensitive hairs. The shrimp moves its mouthparts to create a smooth water current that it can detect through sensory hairs on its antennae. As creatures swim by, they create ruffles in this current, creating a ripple ‘fingerprint’ that the little shellfish can instantly recognize as food or foe.” (Shuker 2001:36)

Last Updated August 18, 2016

References

Book

The Hidden Powers of Animals: Uncovering the Secrets of Nature

26/02/2021 | Dr. Karl P. N. Shuker

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